Content of Reaction & Separation in our journal

Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For Selected: Download Citations EndNote Ris BibTeX Toggle Thumbnails Select Extraction of vanadium and zinc by sulfuric acid leaching from descloizite Kelun ZHANG Bo LI Yonggang WEI Hongao XU The Chinese Journal of Process Engineering    2021, 21 (11): 1297-1303.   DOI: 10.12034/j.issn.1009-606X.220376 Abstract （389）      PDF （1180KB）（153）       Knowledge map    Save Vanadium lead zinc ore contains a variety of valuable metals with high V grade and high economic value. In this work, vanadium and zinc were extracted from the mine by sulfuric acid leaching method, and the thermodynamics of the leaching process was analyzed. The effects of sulfuric acid concentration, liquid-solid ratio, leaching time, stirring rate and leaching temperature on the leaching rate of vanadium, lead and zinc were studied through conditional experiments. The results showed that the hydrolysis of V in the leaching solution and hydrolysis products containing V remained in the leaching residue at high pH and higher temperatures, which affected the leaching rate of V. The optimum leaching conditions were as follows: sulfuric acid concentration 200 g/L, liquid-solid ratio 3:1, leaching time 30 min, stirring rate 200 r/min and leaching temperature 30℃. Under the optimum conditions, the V leaching rate was 97.90%, the Zn leaching rate was 97.11%, the Fe leaching rate was less than 1%, and the Pb leaching rate was less than 0.01%. The results of kinetic analysis showed that the reaction rate of leaching process was controlled by diffusion process. In the acid leaching process, V and Zn entered the leaching solution, and Pb and Fe remained in the leaching residue. The resulting leaching solution can be separated by ion exchange or extraction. The leaching residue contained 0.41wt% vanadium, 0.61wt% zinc, 15.50wt% iron and 47.70wt% lead. The main components were PbSO 4 and FeO(OH), which can be returned to the pyrometallurgical lead smelting system. Related Articles | Metrics Select The simultaneous recovery of lead and tin in zinc oxide dust by carbothermic reduction Foguang LEI Minting LI Chang WEI Zhigan DENG Xingbin LI Gang FAN The Chinese Journal of Process Engineering    2021, 21 (11): 1304-1314.   DOI: 10.12034/j.issn.1009-606X.220399 Abstract （262）      PDF （1510KB）（109）       Knowledge map    Save A carbothermic reduction peocess was used to achieve the simultaneous separation and recovery of lead, tin and zinc in zinc oxide dust. The effects of pretreatment to remove fluorine, chlorine and sulfur (Na2CO3-alkali washing and calcination) and adding additives (CaO and bentonite) on the volatilization rate of lead and tin in carbothermic reduction process were investigated. The results show that the volatilization rate of lead and tin were 78.58% and 95.97% respectively when the dust was not pretreated and the conditions were the temperature of 1300℃, the reductant dosage of 14.04% and the holding time of 120min. Under the same conditions, alkali washing and calcination could reduce the volatilization rate of lead and tin. After alkali washing, the volatilization rate of lead and tin reduced to 12.97% and 16.99% respectively. After calcination, the volatilization rate of lead and tin reduced to 30.46% and 57.83% respectively. Increasing the dosage of CaO is beneficial to reduce the volatilization rate of lead and tin. When the dosage of CaO was 5%, the volatilization rate of lead and tin drops to 32.16% and 57.7% respectively. Increasing the dosage of bentonite promotes the volatilization of lead, but has no obvious effect on volatilization of tin. When the dosage of bentonite was 5%, the volatilization rate of lead and tin drops to 37.44% and 83.25% respectively. Using this process, lead-tin alloy (Pb＞70%，Sn＞5%) and crude zinc (Zn＞63%，Pb＞9%) are finally obtained at the same time. Related Articles | Metrics Select Optimization of preparation of cassava alcohol sludge-based activated carbon by response surface methodology and its adsorption properties for gallic acid Zhilin ZHANG, Lei DING, Qiang ZHOU, Jian YU, Changjin GUO, Dewei ZHANG The Chinese Journal of Process Engineering    2021, 21 (7): 794-806.   DOI: 10.12034/j.issn.1009-606X.220204 Abstract （340）   HTML （4）    PDF （1377KB）（114）       Knowledge map    Save The dewatered sludge from the production process of cassava alcohol plant was used as raw material. Response surface methodology was applied to optimize the preparation of cassava alcohol sludge activated carbon. At the same time, a series of characterization analysis was carried out for the optimal product, which was applied to the treatment of gallic acid wastewater. The results showed that the optimal preparation conditions were: activation temperature of 489℃, impregnation time of 14 h, activation time of 51 min, zinc chloride concentration of 21.53%, the adsorption iodine value under this condition was 521.64 mg/g. The results of characterization to CASAC suggested that the BET surface was found as 441.86 m2/g and the average pore diameter as 2.50 nm. It was full of different sizes of small pores on the carbon surface. The activated carbon owned a low metal content but more oxygen-containing functional group after activation process. The effects of carbon dosage, pH, contact time and solution temperature on the removal of gallic acid from water were investigated. It is suggested that the sample carbon could remove gallic acid efficiently, and the removal rate of gallic acid increased with the increase of carbon dosage and the decrease of pH value. The adsorption of gallic acid by cassava alcohol sludgy-based activated carbon was in line with pseudo second-order kinetics model as well as Freundlich isothermal model. The maximum adsorption capacity was 126.72 mg/g. The diffusion mechanism showed that the adsorption process was influenced by the diffusion of liquid film in addition to the diffusion within particles. Thermodynamic analysis indicated that the adsorption of gallic acid was a spontaneous process of heat absorption and entropy increase. This study provided a theoretical basis for the preparation of high-performance activated sludge and the application of high concentration of natural organic wastewater treatment. Table and Figures | Reference | Related Articles | Metrics Select Effects of hydrophilicity/hydrophobicity of humic acid components on the removal of bromide adsorbed on magnetic ion exchange resin LI Ling, Lei DING, Gang XUE, Yunhan JIA, Meiying ZHONG, Dewei ZHANG The Chinese Journal of Process Engineering    2021, 21 (7): 807-816.   DOI: 10.12034/j.issn.1009-606X.220217 Abstract （300）   HTML （5）    PDF （957KB）（76）       Knowledge map    Save The effect of different hydrophilic/hydrophobic humic acid on the removal of bromide adsorbed on magnetic ion exchange resin was studied. When the pH value of the solution was 7.0, the presence of four humic acid components (very hydrophobicity, slightly hydrophobicity, polar hydrophilicity, neutral hydrophilicity) reduced the removal efficiency of bromide. In contrast, the hydrophobic components of humic acid had the most significant adverse effect on the removal efficiency of bromide. Humic acid weakened the pH dependence of the adsorption process of bromide on resin. The fractions of humic acid can accelerate the adsorption rate of bromide. The adsorption equilibrium was attained quickly. With or without the fractions of humic acid, the kinetic processes of bromide adsorbed on resin agreed with the pseudo-second-order model. Because of the competitive adsorption, the humic acid fractions reduced significantly the equilibrium adsorption capacity of resin for bromide. The adsorption equilibrium can be simulated by Langmuir and Freundlich isotherm model. The existence of HA components can reduce the spontaneity of adsorption system, and the very hydrophobicity component had more significant effect. The results of this investigation were of great significance for the effective control of bromide in water sources. Table and Figures | Reference | Related Articles | Metrics Select Study on the comprehensive recovery of zinc from tailings of a lead-zinc ores from Yunnan province Bo YANG Xiong TONG Xiao WANG Yonggang XIE Xian XIE The Chinese Journal of Process Engineering    2021, 21 (6): 704-712.   DOI: 10.12034/j.issn.1009-606X.220177 Abstract （284）      PDF （871KB）（104）       Knowledge map    Save Tailings of Pb–Zn ores from Yunnan province of China are of high sulfur content and contains the Pb 0.84% and the Zn 3.67% respectively, it is economic to comprehensive recovery these valuable minerals from the tailings. The results from processing mineralogy of these tailings, the Pb-containing minerals existed mainly as galena and cerusite and the Zn-containing minerals as sphalerite and smithsonite. The laboratory-scale flotation experiment indicated that the valuable minerals were effectively recovered by the differential flotation of sulfide minerals, followed by the desliming and flotation of smithsonite. It is also found that the recovery and grade of Zn concentrate are significantly improved by using the amine collector with the different chain lengths during the roughing and scavenging flotation stage of zinc oxide minerals. Besides, these problems such as a large amount of foam and the difficulty in defoaming existed in the flotation of smithsonite were avoided by using the different chain lengths amine collector. The recovery rate and grade of zinc sulfide concentrates were 23.46% and 13.04%, and the recovery rate and grade of zinc oxide concentrates were 27.86% and 51.69% respectively. The total recovery rate of Zn concentrates was 64.73%. The “Sulphide Ore Priority Flotation-Floating Sulfur Tailings Desliming-Zinc Oxide Flotation” process successfully realized the efficient recovery of lead and zinc minerals in the tailings. In addition, organic amine salts with different carbon chain lengths are used as collectors in the roughing and sweeping stages of zinc oxide, which successfully solves the problems of defoaming difficulties and low concentrate grades that are common in the zinc oxide flotation process. It realizes the efficient recovery of valuable minerals in the tailings, and provides an important basis for the reutilization of this tailings. Related Articles | Metrics Select Dynamic adsorption of low concentration gallium ion by LX-92 resin in sulfuric acid system Chaolu WEN Zhenhua SUN Shaopeng LI Zhibin MA Huiquan LI The Chinese Journal of Process Engineering    2021, 21 (5): 567-578.   DOI: 10.12034/j.issn.1009-606X.220142 Abstract （286）      PDF （607KB）（61）       Knowledge map    Save The dynamic adsorption-desorption behavior of gallium in simulated sulfuric acid leach solution of fly ash on polystyrene resin (LX-92) was investigated by fixed bed device. The dynamic adsorption process was analyzed by Thomas, Yoon-Nelson, and Adam-Bohart empirical models. The results showed that decreasing the flow rate (Fad) and the initial concentration of gallium(III) (C0), increasing the bed height (Z) were conducive to improve the fixed bed adsorption efficiency and equilibrium adsorption capacity. According to experiments data, the optimum conditions for dynamic adsorption process was as follow: Fad=5.0 mL/min, C0=260 mg/L and T=55℃, and the maximum adsorption capacity was 56.65 mg/g. The elution rate of gallium could reach 94.40% at the conditions of 3.0 mol/L H2SO4 and 1.0 mL/min flow rate. After the process of adsorption and desorption, the concentration of gallium ions could be enriched more than 10 times. The dynamic adsorption behavior of gallium by the resin was well fitted by the Yoon-Nelson dynamic adsorption model. The corresponding equations of the dynamic adsorption rate constant KYN and the half-through time τ value constant with the initial Ga(III) ion concentration, flow rate, and bed height were established. The dynamic adsorption results would be used for engineering purpose of the of low-concentration gallium ions recovery. Related Articles | Metrics Select Factors affecting the critical flux in a forward osmosis membrane process Ye YANG Rui TANG Yuzhu SUN Xingfu SONG Jianguo YU The Chinese Journal of Process Engineering    2021, 21 (5): 579-586.   DOI: 10.12034/j.issn.1009-606X.220134 Abstract （375）      PDF （851KB）（210）       Knowledge map    Save Critical flux is an important concept in fouling control for membrane-based processes. Operation below the critical flux can maintain the membrane flux and reduce the maintenance cost which is associated with membrane cleaning and replacement in forward osmosis (FO) processes. In this research, the effects of foulant type, binding ions concentration, and cross-flow velocity on the critical flux in FO processes were investigated using a draw solution concentration stepping method. The results showed that the draw solution concentration stepping was feasible for the critical flux determination in FO processes. The thin-film composite (TFC) membranes exhibited a low critical flux for sodium alginate (SA) fouling with a value of 29.32 L/(m2?h), then followed nano-silica (SiO2) with a critical flux value of 32.17 L/(m2?h) and humic acid (HA) of 46.35 L/(m2?h). This indicated that the critical flux behavior in FO processes was dependent on the properties of both the membrane and foulants, including the membrane surface roughness, intermolecular adhesion of foulants, and the interaction between foulants and membrane. The atomic force microscopy (AFM) results revealed the deposition of foulants onto the ridge-and-valley structure of the membrane surface, leading to the deviation of water flux from the baseline with the increasing draw solution concentration. As the Ca2+ concentration increased from 0 mmol/L to 10 mmol/L, the critical flux for alginate fouling dramatically decreased from 29.22 L/(m2?h) to 9.48 L/(m2?h), which can be attributed to the interaction between alginate and membrane as well as the intermolecular aggregation of alginate and the interaction by Ca2+ binding. Moreover, the critical flux for SA?Ca2+ complexes fouling increased from 9.48 L/(m2?h) to 31.59 L/(m2?h) with the cross-flow velocity ranging from 5 cm/s to 15 cm/s, which indicated the improvement of the solution turbulence can enhance the critical flux, thereby expanding the operating ranges of flux. Related Articles | Metrics Select Study on phase equilibrium of NaCl–NaBr–CH 3OH ternary system at 273 K and 323 K and its application Yao WU Yun LI Hongfei GUO Xiuwu LIU Xueqing CHEN Jilin CAO Chin. J. Process Eng.    2021, 21 (3): 286-297.   DOI: 10.12034/j.issn.1009-606X.220084 Abstract （355）      PDF （903KB）（188）       Knowledge map    Save In order to separate sodium chloride and sodium bromide from the solid solution Na(Cl,Br) crystallized from bittern, the isothermal solubility data of NaCl–NaBr–CH3OH ternary system at 273 and 323 K was measured by isothermal solution equilibrium method, and the solid phase points were determined according to the measured liquid phase points and wet slag phase points, from which the phase diagrams at two temperatures were obtained. The results showed that the phase diagram characteristics of the ternary system were similar at 273 and 323 K. There was only one invariant point and two univariant curves, and there were three solid-phase crystallization regions: NaCl pure salt crystallization region, the co-crystallization zone of NaCl and Na(Cl,Br) solid solution and Na(Cl,Br) solid solution crystallization region. This was different from the phase diagram of NaCl–NaBr–H2O system, which only had the crystallization region of solid solution. The liquid composition of the invariant point at 273 K was 0.2904wt% NaCl, 14.66wt% NaBr and the liquid composition of the invariant point at 323 K was 0.2529wt% NaCl, 13.45wt% NaBr. The mass fraction of NaBr at the boundary of the solid solution crystallization region at 273 and 323 K was 28.93% and 34.28%, respectively. The solubility of NaBr in anhydrous methanol was much higher than that of NaCl, which indicated that NaBr had a strong salting-out effect on NaCl, and the solubility of these two solutes in methanol at 273 K was higher than that at 323 K, which was opposite to that in aqueous solution. According to the phase diagrams of NaCl–NaBr–CH3OH system at 273 and 323 K and NaCl–NaBr–H2O system at 298 K, the process for the separation of sodium chloride and sodium bromide was designed. Not only the pure salt of NaCl was obtained, but also solid solution with extremely high NaBr content was obtained. And the mass fraction of NaBr in the separated solid solution was 98.06% and 98.15%, respectively. Related Articles | Metrics Select Gas separation performance of [Emim][BF 4]-supported ionic liquid membranes prepared by supercritical fluid deposition Yuqing WANG Jutao LIU Qinqin XU Jianzhong YIN Chin. J. Process Eng.    2021, 21 (2): 134-143.   DOI: 10.12034/j.issn.1009-606X.220100 Abstract （359）      PDF （1072KB）（150）       Knowledge map    Save Supported ionic liquid membrane (SILM) technology is an attractive way for CO2 separation and capture, because of its combined advantages of both ionic liquid and membrane. The supercritical fluid deposition is a novel and promising preparation method to improve the CO2 permeation of the SILMs by confining ionic liquid only in the thin effective layer of support, leaving the large pores in the substrate open. To improve the preparation efficiency and the gas separation performance, the ionic liquid, [Emim][BF4], was confined into the asymmetry alumina supports to prepare SILMs by supercritical fluid deposition. The performance of SILMs was evaluated by analyzing the IL addition, the N2 and CO2 permeance and the ideal CO2/N2 selectivity. And the influences of deposition time, IL and ethanol addition were investigated. Comparing to those prepared with other ILs, [Emim][BF4]-SILMs can achieve better CO2 separation performance in a shorter time. The SILM prepared under the optimum condition, exhibited the IL addition of 2.6 mg/g, the CO2 and N2 permeance of 6.4 and 0.14 GPU, the CO2/N2 selectivity of 45.3. It was close to the upper limit of CO2/N2 selectivity of [Emim][BF4], and reached the Robeson upper bound as well, showing both high permeance and selectivity. It was found that higher surface tension of IL and higher IL concentration in supercritical CO2 improved the preparation efficiency significantly, while the IL concentration was mainly determined by IL type, ethanol and IL addition. Besides, using ILs with low viscosity, high CO2/N2 selectivity was conductive to obtaining SILMs with both high CO2 permeance and CO2/N2 selectivity. Related Articles | Metrics Select Extraction of Ag(I) and Tl(I) by thiacrown ether Xiankun CHENG Yanhang XIONG Xue HOU Huan TIAN Yongpan TIAN Liang XU Zhuo ZHAO Chin. J. Process Eng.    2021, 21 (2): 144-152.   DOI: 10.12034/j.issn.1009-606X.220076 Abstract （340）      PDF （1011KB）（137）       Knowledge map    Save Based on the coordination chemistry of crown ether and soft and hard acid-base theory (HSAB) of crown ether, five kinds of thiacrown ethers were designed and synthesized. And their complexation abilities to two soft acid ions-Ag(I) and Tl(I) were systematically investigated. Firstly, the five crown ethers and their complexes with Ag(I) and Tl(I) complexes were optimized by Gaussian 16 software. On this basis, the Gibbs free energy change (ΔG), enthalpy change (ΔH), internal energy change (ΔU) and other thermodynamic parameters of the complexation process of five sulfur crown ethers with Ag(I) and Tl(I) at 298.15 K were calculated. The simulation results showed that the five thiacrown ethers had changed after being complexed with Ag(I) and Tl(I), and the ΔG and ΔU of the five crown ethers after structural optimization were negative in the complexation process with Ag(I), showing a certain coordination ability. However, during the complexation with Tl(I), ΔG and ΔU were close to 0, and the coordination ability was relatively poor. On the basis of simulation calculation, the extraction ability of five crown ethers on Ag(I) and Tl(I) was investigated by solvent extraction. The experimental results showed that the complex constants of five thiacrown ethers for Ag(I) were 3.97, 6.58, 20.61, 9.76, 13.40, respectively in the single system. In the multi-system, thiacrown ethers 2, 3, 4, and 5 had higher extraction rate and selective recognition ability for Ag(I), while thiacrown ether 1 exhibited poor selective recognition ability for Ag(I), this may be due to the small cavity of thiacrown ether 1. However, the five thiacrown ethers had almost no selectivity for Tl(I), this may be related to the coordination properties of Tl(I). Finally, combined with the simulation results and extraction experiments, the extraction mechanism of five crown ethers on Ag(I) and Tl(I) was analyzed in detail. Related Articles | Metrics Select Comparison of the influence of Ca 2+ and Mg 2+ on floatability of molybdenite Shuai SHI Tingshu HE Hui LI Chin. J. Process Eng.    2021, 21 (2): 153-159.   DOI: 10.12034/j.issn.1009-606X.220028 Abstract （329）      PDF （671KB）（108）       Knowledge map    Save Ca2+ and Mg2+ are inevitably introduced into the production backwater when the mineral processing plants treat wastewater with precipitation agent, both of them would affect the flotation effect of molybdenite. The different influence of Ca2+ and Mg2+ on the flotation of the molybdenite was compared and investigated by flotation experiments of pure minerals, measurements of zeta-potential, X-ray photoelectron spectroscopy (XPS) and solution chemistry of Ca2+ and Mg2+. The results showed that both Ca2+ and Mg2+ could be adsorbed on the surface of the molybdenite, which changed the surface zeta-potential of the molybdenite and inhibited the floatability of the molybdenite. The inhibition was stronger with the increase of the pH value. Under the alkaline condition, the inhibition of Mg2+ on floatability of the molybdenite was stronger than that of Ca2+. And when the pH value was more than 9.0, the inhibition difference between the two ions was observed. When pH=11.0, the recovery of Mg2+ with a concentration of 800 mg/L decreased by about 34 percentage points compared with that of Ca2+ with a concentration of 800 mg/L. Both Ca2+ and Mg2+ could combine with MoO42– on the “edge” of molybdenite and form precipitation of molybdate salt, which existed on the surface of molybdenite in the form of chemical adsorption. When pH value was more than 9.15, calcium still existed in the form of Ca2+ and Ca(OH)+ and adsorbed on the surface of molybdenite, and the zeta-potential of the molybdenite in slurry containing Ca2+ showed an increasing tendency with the increase of the pH value. While magnesium deposit on the surface of molybdenite in the form of Mg(OH)2, and the zeta-potential of the molybdenite in pulp containing Mg2+ decreased rapidly with the increase of the pH value. This is the main reason for the difference between Ca2+ and Mg2+ in molybdenite?s floatability inhibition. Related Articles | Metrics Select Mass transfer dynamics and breakthrough characteristics of L-valine separation by ion exchange Jianjun CHEN Junwei ZHANG Qianning SONG Chin. J. Process Eng.    2021, 21 (1): 46-56.   DOI: 10.12034/j.issn.1009-606X.220013 Abstract （427）      PDF （876KB）（154）       Knowledge map    Save The separation effects of different types of resins, the mass transfer kinetics and the rate-controlling step, the breakthrough behavior in a fixed bed were studied respectively in order to investigate the kinetics and the dynamic breakthrough characteristics for the L-valine separated by ion exchange. The results showed that the adsorption capacity of strong acidic cation exchanger resin, with a better separation effect, were five to eight times that of other resins, meanwhile their selectivity was from 1.3 to 1.8. L-valine with amphoteric ionic sates in a neutral (or slightly acidic) solution, was beneficial to its exchange adsorption. Moreover, the pseudo-second order kinetic model was found to describe adsorption process of the L-valine well with 001×7 resin as a separation media, such a process was affected by the particle and the liquid film diffusions together at early stage and then by multiple factors at medium-latter stage. Thomas and Yoon-Nelson models could describe breakthrough behaviors of the L-valine and the L-leucine well. The equilibrium adsorption capacity qe, volume adsorption capacity N0 and operation time τ decreased gradually with enhancing flow rate of the L-valine feed, whereas the equilibrium adsorption capacity qe and volume adsorption capacity N0 increased but operation time τ decreased gradually with increasing feed concentration of the L-valine. The ratio of height to diameter should be less than 5 and had an opposite trend to the effect of feed concentration change of the L-valine. Related Articles | Metrics Select Experimental and model analysis of hydrochloric acid recovery by dynamic diffusion dialysis Shuai SUN Hongqian SUN Jing SONG Jingkui QU Yong WANG Tao QI Chin. J. Process Eng.    2021, 21 (1): 57-63.   DOI: 10.12034/j.issn.1009-606X.220052 Abstract （506）      PDF （757KB）（180）       Knowledge map    Save In recent years, membrane separation technology has become the focus of industrial waste acid treatment and recovery with many advantages. As a kind of environmentally friendly membrane separation technology, diffusion dialysis is widely used in the field of waste acid. The experiment was carried out with 0.55 mol/L hydrochloric acid as raw material. Besides, the effects of operating parameters such as the flow rate of feed acid (620 mL/min) and flow ratio of water and acid (0.61.4) were examined. The transport of hydrochloric acids through anion-exchange membrane DF-120 in a counter-current continuous dialyzer was investigated in detail. The important parameter, permeability coefficient of the membrane, was optimized by polynomial fitting. A simpler mathematical model of lumped parameters established, which could predict the hydrochloric acid recovery rate during the diffusion dialysis process. These obtained points were investigated to verify the mathematical model and it was proved excellent. The model was used for predictions under more detailed experimental operating conditions. It also provided reference methods and arguments for actual industrial production. Related Articles | Metrics Select Effect of different particle sizes of modified fly ash on phosphate adsorption performance Jianlin YANG Yuao ZHANG Shuhua MA Xiaohui WANG Chin. J. Process Eng.    2020, 20 (11): 1281-1288.   DOI: 10.12034/j.issn.1009-606X.219382 Abstract （365）      PDF （2547KB）（217）       Knowledge map    Save Excessive discharge of phosphorus in wastewater leads to increasingly serious water pollution. The fly ash was chemically modified into a hydrated calcium silicate adsorbent to explore its absorption effect on the phosphate. XRD, SEM, BET specific surface area and so on were used to characterize the adsorbents before and after particle size classification. Then the adsorption performance of the adsorbents with different particle sizes on phosphate was studied, and the adsorption mechanism was also investigated. The results showed that the chemical compositions of the adsorbents with different particle sizes showed significant segregation, and the pore structures were also significantly different. Specifically, compared to other adsorbent particles, the particles with the size of 50?75 μm had a higher content of calcium and silicon, lower content of aluminum, iron, and magnesium and thereof higher content of hydrated calcium silicate companied with aluminum-containing tobermullite crystals. The increase of calcium ions made it easy to combine with more phosphate to form a precipitate. At the same time, this particle had a higher specific surface area and more porosity and the loose and porous structure provided more active sites for calcium ions. When used as an adsorbent to adsorb phosphate, the saturated phosphorus adsorption capacity of the particles with the size of 50?75 μm can reach 17.1 mg/g, which was 19.58% higher than that of an unclassified adsorbent. Related Articles | Metrics Select Treatment performance of ammonia-nitrogen wastewater containing high salt by copper-loaded resin Ruoyu YIN Yunnen CHEN Caiqing HE Chen LIU Chin. J. Process Eng.    2020, 20 (11): 1289-1295.   DOI: 10.12034/j.issn.1009-606X.219368 Abstract （406）      PDF （947KB）（114）       Knowledge map    Save The ligand exchange adsorption method uses the ability of transition metal ions to form complexes. By supporting the transition metal on a certain adsorbent carrier, and then using the special complexation between the target pollutant and the transition metal, the target pollutant is adsorbed on the adsorbent. A ligand-loaded adsorbent was prepared by supporting Cu2+ with a resin as a carrier for the high-salt ammonia?nitrogen wastewater, and the ammonia nitrogen was selectively adsorbed onto the resin by the coordination of Cu2+ and ammonia nitrogen. Ammonia nitrogen is adsorbed to the resin in two ways: one is through the combination of NH4+ and OH? to generate NH3, which is coordinated with Cu2+on the resin; the other is that NH3 reacts directly with Cu2+ on the resin, so that ammonia nitrogen can be adsorbed. In this work, resins with different functional groups were selected as supports, modified with Cu2+, and their performance in treating high-salt ammonia nitrogen wastewater was studied. On the basis of selecting the best copper resin, the effects of pH, Na+ concentration, resin dosage and reaction time on the adsorption of ammonia nitrogen by copper resin were studied. In order to further explore the process of coordination adsorption, SEM, EDS and adsorption kinetics model were used to characterize the copper resin before and after ammonia nitrogen adsorption. The results showed that Cu2+ could combine with chelating resin D751 stably and exhibited salt tolerance and good adsorption effect of ammonia?nitrogen under wide pH value. Under the conditions of room temperature (25℃), pH=11, Na+ concentration of 4 g/L, resin dosage of 8 g/L, reaction time 60 min, the removal rate of ammonia?nitrogen by D751 copper-loaded resin was 34.8%. After adsorption of ammonia nitrogen by D751 copper resin, crystal structure substance appeared on its surface, which may be copper ammonia complex. In addition, the adsorption kinetics of D751 copper resin for ammonia nitrogen containing high saline was in good agreement with quasi-second-order kinetic model. Related Articles | Metrics Select Process and leaching kinetics of extracting copper and cobalt from high silicon low grade copper-cobalt ore by selective reduction ammonia leaching Ao GONG, Xuangao WU, Xiaoqiang YU, Dingchun WANG, Zhifeng XU, Lei TIAN Chin. J. Process Eng.    2020, 20 (10): 1156-1165.   DOI: 10.12034/j.issn.1009-606X.219351 Abstract （467）      PDF （3028KB）（187）       Knowledge map    Save The leaching process and kinetics of African high silicon low grade copper cobalt ore in ammonia leaching system were studied. Firstly, the controllable variable method was used to systematically study the effects of leaching agent concentration, additive dosage, reaction temperature, reaction time and liquid/solid ratio on the leaching rate of copper and cobalt through single factor experiments. Secondly, the phase and chemical composition of high silicon low grade copper?cobalt ore and leaching residue were analyzed by X-ray diffraction (XRD), inductively coupled plasma (ICP) and scanning electron microscope-energy spectrum (SEM-EDS). The results showed that the leaching rate of copper and cobalt can reach 97.29% and 95.18% respectively, under the technological conditions of ammonium sulfate as leaching agent with the concentration of 300 g/L, reducing agent of 0.7 g, leaching temperature of 353 K, reaction time of 240 min and liquid/solid ratio of 6:1. Finally, by analyzing the kinetic model of copper extraction by high silicon low grade copper?cobalt ore ammonia leaching, the activation energy, reaction order of ammonium sulfate concentration and particle size are 76.06 kJ/mol, 1.50 and 0.25, respectively, indicating that it should follow the interface chemical reaction control, and the corresponding kinetic equation was established. Related Articles | Metrics Select Preparation of magnetic coagulant aid from wastes for enhanced pollutant precipitation Xiaofei MENG Rong HOU He ZHAO Bin XU Linhao YANG Chin. J. Process Eng.    2020, 20 (10): 1166-1173.   DOI: 10.12034/j.issn.1009-606X.219353 Abstract （398）      PDF （2307KB）（141）       Knowledge map    Save In recent years, with the increasing of water treatment, the production of coagulated sludge has a sharp rise. So, the realization of coagulated sludge resource utilization is necessary. In this research, the coagulated sludge treated by carbonization at high temperature and polymerized ferrous sulfate (PFS) were added together to remove Fe(CN)63? pollutants. And the mechanism of coagulation was further studied. The structure of the coagulated sludge materials was characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and magnetic hysteresis curve. The pollutant of Fe(CN)63? coagulated by PFS and coagulated sludge was analyzed by the removal rate, particle size and shape. The results showed that the sludge materials contained a large amount of carbon and it had some functional groups like carboxyl on the surface. Iron and vanadium oxides which had complexation ability were formed on the surface carbonized sludge materials. The crystallinity and grain size of the coagulated sludge were more ordered and more uniform by carbonization at high temperature which could benefit to the growth of flocs in the process of coagulation. The removal of Fe(CN)63? increased by adding coagulated sludge. Especially, the removal of Fe(CN)63? increased to 99.45% by adding the sludge which was carbonized at 700℃ with PFS:RW700=1:1.43. By the analysis of particle size and shape, the coagulated sludge was beneficial to the enhancement of pollutants during coagulation process. By optimizing the ratio of sludge material to PFS, the removal of Fe(CN)63? pollutant was also close to 100% by reducing the dosage of PFS. Compared with the other coagulants, the cost of water treatment decreased. This study provided theoretical and technical basis for the resource recycling of coagulated sludge. This new type of sludge resource utilization had promising application in the field of cyanide removal. Related Articles | Metrics Select Recovery of manganese from the mother liquor after vanadium precipitation during vanadium extraction with calcified roasting and acid leaching process Juhua ZHANG Yue LIANG Wei ZHANG Zhengliang XUE Chin. J. Process Eng.    2020, 20 (10): 1174-1181.   DOI: 10.12034/j.issn.1009-606X.219354 Abstract （522）      PDF （1285KB）（209）       Knowledge map    Save Recovering manganese resource from the mother liquor on one hand can improve the economic benefit of the whole process, and on the other hand is beneficial to realizing closed cycle of mother liquor and then can increase the environmental interest of the whole process because it can avoid the enrichment of Mn in the solution during recycling mother liquor which will bring side effect to the quality of vanadium pentoxide. Using oxalic acid to effectively separate the Mn2+ from the mother liquor was proposed and the effects of the solution pH, adding amount coefficient of oxalic acid, reaction temperature and time on the recovery rate of Mn and phases composition of the precipitations were investigated, and the effect of the numbers of recycling mother liquor treated by oxalic acid to recover manganese on the leaching process was studied as well. The results showed that oxalic acid can effectively separate the manganese from the mother liquor and the recovery rate of manganese reached 94.33% under the conditions that the solution pH was 4.0, adding amount coefficient of oxalic acid was 1.5, reaction temperature was 50℃ and the reaction time lasted for 60 min. The obtained product was hydrated manganese oxalate with purity of 98%, present as tabular crystals and formed in flower cluster-like. After treated with oxalic acid to remove manganese, the mother liquor was recycled to leach the roasted slag, and it was found that the recycling numbers have little effect on the vanadium leaching rate and the concentration of manganese contained in the vanadium-bearing solution, indicating the proposed method was helpful for realization of closed-cycle of the waste water in the whole process of vanadium extraction with calcified roasting and acid leaching. Related Articles | Metrics Select Recovery of sulfuric acid regenerated from stainless steel pickling waste solution by solvent extraction Dong ZHANG Jian ZHANG Guanghao SHANG Hui SU Wensen LIU Yun ZHU Zhaowu ZHU Tao QI Chin. J. Process Eng.    2020, 20 (9): 1025-1034.   DOI: 10.12034/j.issn.1009-606X.219328 Abstract （477）      PDF （541KB）（182）       Knowledge map    Save As the output of the stainless steel is increasing year by year, the waste acid produced by pickling the stainless steel is also increasing year by year. The waste sulfuric acid solution discharged by pickling the stainless steel contains a large amount of free acid. According to the acid recycling process developed by our research group, the free acid concentration in the waste acid can increase to obtain the regenerated sulfuric acid while quite effectively recovering these valuable metal ions in the waste acid. In this work, the technology of recovering sulfuric acid from the stainless steel pickling waste solution by the solvent extraction was studied, aiming at the problems of high concentration of regenerated sulfuric acid in the stainless steel pickling waste solution, high consumption of neutralization treatment reagent, large amount of waste residue, and so on. It was found that the organic system of 40% (volume fraction, the same below) tris-2-ethylhexylamine (TEHA)+50% isomeric tridecyl alcohol+10% Exxsol D110 was the optimal composition. The extraction rate of sulfuric acid increased with the increased concentration of TEHA. With the temperature increasing of the extraction, the extraction rate of sulfuric acid decreased, indicating that the extraction reaction was exothermic reaction and the enthalpy (ΔH) of the extraction reaction was calculated as ?7.5708 kJ/mol. McCabe-Thiele diagrams were drawn according to the distribution curves of the extraction and the stripping. Under the condition of 30℃ and A/O=1:2, the extraction rate of sulfuric acid could reach 79.8% by 3 stages (theoretical). Using the deionized water as the stripping agent, the stripping rate of sulfuric acid could reach 85.5% after 3 (theoretical) stages at 30℃ and A/O=1:1. The kinetics of the extraction and stripping was very fast and the phase separation was rapid at the same time, which can perfectly meet the requirements of industrial continuous production. Related Articles | Metrics Select Removal optimization of methyl orange and Congo red adsorbed on MIEX resin using response surface methodology Yunhan JIA Lei DING Peiyue REN Ling LI Dandan WANG Chin. J. Process Eng.    2020, 20 (9): 1035-1044.   DOI: 10.12034/j.issn.1009-606X.219335 Abstract （465）      PDF （940KB）（144）       Knowledge map    Save Four factors including resin dosage, solution pH, methyl orange or Congo red concentration and adsorption time were selected to investigate the effects on the removal of methyl orange or Congo red adsorbed on MIEX resin using Box-Behnken response surface methods. According to the experimental results, the quadratic polynomial regression model was established to predict the removal of methyl orange or Congo red. Variance and significance were used to test the reliability of the regression equation. Based on the regression model, the operation parameters of the removal of methyl orange (Congo red) adsorbed on MIEX resin were optimized and the optimal conditions were obtained. Under the optimal conditions, the removal efficiency of methyl orange and Congo red on MIEX resin were 99.12% and 98.29%, respectively. The interaction between solution pH and resin dosage had a significant effect on the removal efficiency of methyl orange and Congo red. The saturated resin adsorbed methyl orange or Congo red were regenerated using NaCl solution, and the surface morphology of MIEX resin were characterized by field scanning electron microscopy. The results showed that the spent resin can be regenerated well with NaCl solution. Related Articles | Metrics Select Study of roasting–dissolving performance of high-sulfur and high-silicon bauxite Wenjie REN Huixin JIN Chaoyi CHEN Benjun XU Zhenshan XIE Chin. J. Process Eng.    2020, 20 (9): 1045-1052.   DOI: 10.12034/j.issn.1009-606X.219334 Abstract （357）            Knowledge map    Save The suspension roasting of bauxite can not only effectively desulfurize, but it can also improve the dissolution properties of low-grade bauxite. Furthermore, it provides a good solution for the industrial utilization of low-grade bauxite with high sulfur and high silicon. In this study, suspension roasting was used to treat high-sulfur and high-silicon bauxite, and the effects of different roasting temperatures on sulfur content were investigated. The effects of roasting on phase transition and microstructure of bauxite were analyzed via XRD and SEM. At the same time, the effect of different calcination temperatures on the solubility of alumina was also studied via dissolution tests. The results showed that suspension roasting desulfurization was feasible. Indeed, the sulfur in bauxite was removed at 550, 600 and 650℃, and the sulfur content in bauxite was reduced to less than 0.2wt% when the suspension roasting temperature was 600℃ or above. As shown by the XRD spectrum, the kaolinite phase in the bauxite was decomposed to form amorphous metakaolin via roasting, and when the roasting temperature reached 600℃ or above, the kaolinite phase was found to be completely decomposed. Furthermore, SEM images indicate that, when the roasting temperature was 600℃, the dense structure of the ore particles was seriously damaged, resulting in grain refinement. On the other hand, local sintering occurred when the temperature reached 650℃. In addition, the diaspore crystal was destroyed by roasting, and the diaspore was activated. In particular, the crystal destruction was found to be most extensive under 600℃ roasting conditions. Thus, the effect of alumina dissolution under the same dissolution conditions was more pronounced than that of row ores and roasting ores at other temperatures. The optimum dissolution conditions were found to be: dissolution temperature of 270℃, caustic concentration of 245 g/L, lime addition of 14wt%, and dissolution rate of 96% or above, which met the requirements of industrial utilization. Related Articles | Metrics Select Leaching copper from pyrite tailings in sulfuric acid medium Jinsong YE Tianhu CHEN Mengjuan TANG Yuhui LI Xinlai WEI Jie JIN Ke WU Chin. J. Process Eng.    2020, 20 (9): 1053-1062.   DOI: 10.12034/j.issn.1009-606X.220081 Abstract （514）      PDF （944KB）（122）       Knowledge map    Save In order to reutilize these industrial wastes of pyrite tailings, the effects of the six single factors of sulfuric acid concentration, leaching time, ore particle size, ore dosage, leaching temperature and agitation speed on leaching copper in the pyrite tailings and the subsequent L18(37) orthogonal optimization experiments had comprehensively been investigated. Furthermore, the mechanism inhibiting further acid leaching reaction had been revealed by the scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The research result showed that the optimal condition of leaching copper was sulfuric acid mass fraction of 30%, leaching time of 6 h, ore particle size of 150 ?m, ore dosage of 5 g, leaching temperature of 108℃, and agitation speed of 440 r/min. Under the condition, the Cu leaching rate can reach 50.68%. The priority of influencing factors of sulfuric acid mass fraction>leaching temperature>ore dosage>leaching time>ore particle size>agitation speed was obtained via the range analysis of the orthogonal test, and moreover the six factors were extremely significant via the variance test. Finally, the SEM and EDS had revealed that the surfaces of the leached residues had tightly been encapsulated by micron-sized particulate SiO2, so that it passivated the further leaching reaction progress and limited the constant increase of the leaching rate at the late stage of acid leaching. Therefore, it was very necessary to loosen the SiO2 coating layer and release its passivation at the later stage of leaching reaction for the sake of further improving the leaching copper in the silicon-rich pyrite tailings. Related Articles | Metrics Select Experimental study on separation of lead and zinc from tailings with high mud content in Yunnan Province Huichao JI Quanjun LIU Xu JIANG Jingshen DONG Chin. J. Process Eng.    2020, 20 (8): 912-920.   DOI: 10.12034/j.issn.1009-606X.219319 Abstract （409）      PDF （1064KB）（184）       Knowledge map    Save The separation of lead and zinc from tailings with high mud content in Yunnan was examined, which was characterized by a fine particle size, severe argillization, and relatively complex properties. A combination of flotation and gravity separation of mud and sand was adopted to effectively separate lead and zinc and realized the comprehensive recovery and utilization of the complex tailing resources. Results revealed that the lead content was 4.29wt% and that the zinc content was 4.99wt%. Lead mainly existed as cerussite and plumbojarosite. Lead and iron metasomatize to form different wrapping forms, making separation extremely difficult. Zinc mainly existed as zinc oxide, which exhibited a high degree of oxidation. Zinc oxidation rate reached up to 99%, and it was mainly difficult to separate hemimorphite. Ultimately, the lead concentrate with a lead grade of 33.87% and a recovery rate of 62.53% were obtained by the closed-circuit beneficiation process; the silver content in the lead concentrate and its recovery rate were 142.50 g/t and 30.92%, respectively; the zinc concentrate with a zinc grade of 15.21% and a recovery rate of 47.82% were obtained. Related Articles | Metrics Select Selective transformation and separation of rare earths from NdFeB magnet scraps based on sulfuric acid reduction Jinliang WANG Longjun WANG Fupeng LIU Chin. J. Process Eng.    2020, 20 (8): 921-928.   DOI: 10.12034/j.issn.1009-606X.219316 Abstract （571）      PDF （1340KB）（136）       Knowledge map    Save Considering the current status associated with the difficult extraction of rare earths in NdFeB magnet scraps in terms of economy and efficiency, rare earths were selectively separated from NdFeB magnet scraps by sulfating roasting. Fe2(SO4)3 was found to induce the sulfate transformation of rare-earth oxides, significantly reducing the amount of sulfuric acid. Almost 98% of rare earth oxides were transformed to soluble rare earth sulfate by the combined action of H2SO4 and Fe2(SO4)3 under conditions of a theoretical amount of sulfuric acid of 2.0 times, a roasting temperature of 750℃, and a roasting time of 1.5 h, while less than 0.1% of iron was leached, mainly existing in the form of a residue as a hematite (Fe2O3) phase; this hematite phase can be easily smelted in iron works. As a result, the reduction of sulfuric acid and the comprehensive utilization of NdFeB magnet scraps are achieved. Related Articles | Metrics Select Recovery of scandium and fluorine from molten salt electrolysis waste residues Yunfeng FU Weiwei WANG Chin. J. Process Eng.    2020, 20 (8): 929-937.   DOI: 10.12034/j.issn.1009-606X.219323 Abstract （511）      PDF （1131KB）（186）       Knowledge map    Save To realize the detoxification treatment of the fluorine-containing waste residue from the production of an Al–Sc master alloy by molten salt electrolysis and recover valuable elements, based on the characteristics of a high fluoride and low scandium content in mineralogical compositions, the two-stage hydrometallurgical leaching of electrolytic slag from the Al–Sc alloy prepared by molten salt electrolysis was conducted for the recovery of fluorine and scandium. X-Ray diffraction (XRD), X-ray fluorescence (XRF), ion chromatograph (IC), inductively coupled plasma atomic emission spectrometer (ICP-OES), scanning electron microscope (SEM) were employed to investigate the trend and distribution of fluorine, scandium, and aluminum in detail. Results revealed that during the alkali leaching process, the fluorine in the molten salt slag was converted into sodium fluoride with low solubility, and almost all of the fluorine can be dissolved into the solution by washing with water. The scandium in the molten salt slag remained in the alkali leaching slag; therefore, the separation of fluorine and scandium was realized. By utilizing the insolubility of α-Al2O3 in less concentrated sulfuric acid at a low temperature, the alkali leaching slag was then leached by sulfuric acid to separate and recover scandium from α-Al2O3. Effects of the leaching agent concentration, liquid to solid ratio, leaching temperature, time, and other process parameters on the leaching rates in the alkali leaching and acid leaching processes were investigated. The optimum reaction conditions were determined to be a sodium hydroxide concentration of 100 g/L, a liquid to solid ratio of 12:1, a leaching temperature of 90℃, and a leaching time of 1.5 h for the alkali leaching process, and the sulfuric acid concentration of 1.5 mol/L, a liquid to solid ratio of 6:1, a leaching temperature of 90℃, and a leaching time of 50 min for the acid leaching process. Under the optimized parameters, the leaching rates of soluble aluminum and fluorine in the molten salt residue after alkali leaching were 97.12% and 98.71%, respectively. The purity of the sodium fluoride product reached 98.70%. Furthermore, the leaching rate of scandium reached 92.01% during the subsequent acid leaching process. Related Articles | Metrics Select Experimental study on separation of zinc and silver flotation from a silver-rich zinc concentrate in Yunnan Jie LI Cuicui JI Xian XIE Bowen KANG Peiqiang FAN Chin. J. Process Eng.    2020, 20 (8): 938-946.   DOI: 10.12034/j.issn.1009-606X.219288 Abstract （506）      PDF （890KB）（124）       Knowledge map    Save Silver is a rare and precious metal with excellent performance and wide applicability, and is a dominant element in the national economy. Among the abundant silver mineral resources in China, associated silver reserves account for 88% of total silver reserves. Due to the pro-lead and pro-zinc nature of silver, associated silver is mainly hosted in deposits dominated by lead and zinc. For the comprehensive recovery of associated silver in lead-zinc ores, the traditional process mostly uses lead flotation and zinc suppression approaches to recover lead and zinc main metal minerals under high alkali, as well as enrichment of silver minerals in lead concentrates or zinc concentrates. However, the associated silver minerals in the high alkali process are easily inhibited and the losses are severe. Furthermore, the recovery rate of China's associated silver can only reach 60%~70%, while foreign countries generally reach 70%~80%. A silver-rich zinc concentrate in Yunnan mainly contains sphalerite, pyrite, galena, and cerussite; silver exists in cerussite in the form of isomorphism. According to the properties of ore samples, the technological process of lead flotation and zinc suppression was determined in a preliminary manner. Hydraulic analyses found that the highest silver content is present in particles with size –19+10 μm. On this basis, the effects of grinding fineness, inhibitors, activators, and collectors on flotation separation indexes were investigated. The results showed that the dosage of Na2SiO3, CuSO4, butyl xanthate, and terpenic oil were 2000, 200, 300, and 30 g/t, respectively. Furthermore, through a roughing, scavenging, cleaning, full-process closed-circuit experiment, it was possible to obtain a zinc concentrate with Zn grade of 61.08% and recovery rate of 95.89%, and a silver concentrate with Ag grade of 1548.32 g/t and recovery rate of 71.17%. In this way, flotation separation of zinc and silver was achieved, and the efficient enrichment of associated silver was obtained. Related Articles | Metrics Select Effect of pH on the chelating mechanism and stability constant of chitosan-Cu(II) chelate complex Ying FENG Qingjin ZHANG Juecheng WANG Jianwei ZHANG Chin. J. Process Eng.    2020, 20 (6): 646-654.   DOI: 10.12034/j.issn.1009-606X.219299 Abstract （980）      PDF （1116KB）（202）       Knowledge map    Save Heavy metal ions in water or soil are serious pollution, and human health is seriously endangered by pollution. The removal of heavy metal ions quickly and efficiently has become an important research field. Chitosan is a natural high molecular polymer with excellent flocculation and metal chelation. The effect of pH values on the stability constant and chelation properties of chitosan chelated Cu2+ was studied by ultraviolet spectrophotometry in this work. The chelation performances of chitosan to copper ions were investigated with the pH value increasing from 1 to 9. The experimental results showed that the chelating ability of active groups on chitosan carbon chain with copper ion was enhanced with the increase of the pH value. When the pH values of the solution system ranged from 5 to 6, the stability constant of the chelate was the maximum value of 1.1×108, when the pH was close to 7, some chelate products precipitated and the stability constant decreased. The change of pH value had no obvious effect on the coordination ratio (n) of the chelate under acidic conditions and the ratio (n) was 2. The chitosan-Cu(II) chelate could be separated out by adjusting the pH value of the solution. With the increase of pH value, some floccules precipitated from the solution and the concentration of Cu2+ decreased. When the pH value was about 9, the Cu2+ concentration reached a minimum value of 1.5 mg/L. The precipitate of chitosan reacted with copper ions was analyzed by microscopic image, X-ray diffraction pattern and Fourier transform infrared spectroscopy (FT-IR), the results showed that the main component of the precipitate was chitosan-Cu(II) formed by chelation of –NH2 with Cu2+. This study could provide a theoretical basis for the removal of metal ions by chitosan. Related Articles | Metrics Select Performance and modelling of bromide dynamic adsorption onto D301 anion exchange resin Chunyi YUAN Yuzhu SUN Ying YANG Xingfu SONG Jianguo YU Chin. J. Process Eng.    2020, 20 (6): 655-666.   DOI: 10.12034/j.issn.1009-606X.219342 Abstract （641）      PDF （494KB）（151）       Knowledge map    Save The adsorption of bromide ions from the mother liquor produced during the process of mining potassium from rock-salt mines onto D301 anion exchange resin in a Perspex column was investigated. Relevant breakthrough curves were obtained, which would provide valuable information for the process design at a real scale. Experiments were carried out to study the effects of the initial adsorbate concentration, bed length, and flow rate. The bed capacities were found to increase with increasing initial adsorbate concentration and decreasing flow rate. When the initial Br? concentration increased from 1000 mg/L to 4000 mg/L, the adsorption capacity increased from 1.8 mg/mL to 6.4 mg/mL. The breakthrough time and the exhaust time increased with increasing bed length and decreasing flow rate, whereas they remained almost the same when changing the initial adsorbate concentration. Five adsorption models, including Bed Depth Service Time (BDST), Thomas, Yoon-Nelson, Wolborska and Modified dose response (MDR) were applied to predict the breakthrough curves and to determine the characteristic parameters of fixed-bed column. The MDR model was found to be the best fit to the experimental data. This study indicates that the D301 anion exchange resin can be used to extract bromide ions from mother liquors effectively in the competition with high concentrations of chloride ions. Related Articles | Metrics Select Occurrence state and separation method of heavy metal element arsenic in coal fly ash Fuli LIU Shuhua MA Kun REN Xiaohui WANG Chin. J. Process Eng.    2020, 20 (5): 540-547.   DOI: 10.12034/j.issn.1009-606X.219275 Abstract （595）      PDF （933KB）（186）       Knowledge map    Save The migration, transformation and accumulation in the environment of heavy metal elements in coal fly ash are the barriers to the comprehensive utilization of coal fly ash. To clarify the occurrence state of heavy metal elements in coal fly ash and to explore an efficient removal method, it is the key to solve the large-scale utilization of coal fly ash. The improved BCR continuous extraction method found that the water soluble and acid exchangeable states of heavy metal element arsenic in fly ash accounted for a high proportion, which proved that heavy metal arsenic easily migrated in the environment and affected the surrounding environment. Based on the occurrence characteristics of heavy metal arsenic in coal fly ash, a new method for removing heavy metal element arsenic by sulfuric acid was established. The effects of sulfuric acid concentration, reaction temperature and reaction time on the removal rate of heavy metal arsenic were investigated. The results showed that the removal rate of arsenic increased with the increase of the concentration of sulfuric acid solution, decreased with the increase of reaction temperature, and increased with the increase of reaction time. Considering the removal rate of heavy metal arsenic, the loss rate of constant elements in coal fly ash and the degree of damage of spherical particles, the optimum conditions for removing heavy metal arsenic from coal fly ash by one-step method of sulfuric acid determination were as follows: the sulfuric acid concentration of 2.0 mol/L, the reaction temperature of 20℃, and the reaction time of 60 min. At this time, the removal rate of heavy metal arsenic reached 75.21%. Related Articles | Metrics Select Effect of surface wettability on separation performance of trapezoidal demister Jiarong WANG Zhongli JI Weiwei MA Jinjie LU Bo YANG Chin. J. Process Eng.    2020, 20 (4): 410-417.   DOI: 10.12034/j.issn.1009-606X.219236 Abstract （625）      PDF （649KB）（137）       Knowledge map    Save The trapezoidal demisters are commonly used to remove droplets over 10 ?m in the field of natural gas purification. In order to solve the problem that the separation efficiency of the demisters obviously reduced at high gas velocity in the actual industry, the biomimetic microstructure was constructed on the surface by the wire electrical discharge machining (WEDM) technology to obtain a hydrophobic surface. Furthermore, the effects of surface wettability on the separation efficiency and pressure drop for the demisters were evaluated experimentally using atomized droplets. The results showed that the surface with biomimetic microstructure had good hydrophobic function and resistance reduction effect, which accelerated the drainage rate of liquid film. When the gas velocity exceeded 5 m/s, the liquid film thickness was relatively thin, which effectively suppressed the re-entrainment phenomenon of the droplets and improved the separation efficiency. In addition, the flow field distribution in the hydrophobic trapezoidal demisters was relatively flat, and the flow resistance was very small. The total pressure drop was only half of the demisters with hook. Therefore, the composite separation performance of the hydrophobic trapezoidal demisters with high efficiency and low resistance was optimal. Related Articles | Metrics Select DFT study on the extraction and separation of copper and nickel with Metral54-100 Xingguo LUO Hui HUANG Chang WEI Xingbin LI Zhigan DENG Minting LI Chin. J. Process Eng.    2020, 20 (3): 308-317.   DOI: 10.12034/j.issn.1009-606X.219231 Abstract （516）      PDF （1338KB）（199）       Knowledge map    Save In order to discuss the extraction and separation mechanism of copper and nickel by 1-phennyl-1,3-sebacic-diketone (Mextral54-100) from ammonia solution, the binding energy, global activity indices, local activity indices and infrared spectrum (FT-IR) of copper complexes and nickel complexes were calculated by density functional theory DFT/B3LYP/6-31G+(d, p), based on quantum chemistry. The results showed that the extracting power of copper was beyond nickel with Mextral54-100. Global reactivity indexes pointed out that the order of the activity of the copper complexes was a>b>c, the order of the activity of the nickel complexes was d>e>f. The molecule frontal orbital analysis of the complexes indicated that the |Δe| (Δe=eHOMO?eLUMO) of a was |Δe|a=0.158, the |Δe| of d was |Δe|d=0.138, thus, the reaction activity of a was higher than that of d, and the copper complexes were easier than nickel complexes in the stripping process by the theoretical calculation results. Local activity indices showed out that the carbonyl exhibited the highest reactivity and was the active center. The more substitution number of ammonia molecules in the complexes, the stronger electron-donating ability of copper(II) and nickel(II), and the structure of the complex was similar to the stable octahedral structure. The ammonia molecules were replaced one by one by the carbonyl group in extractants, avoiding the co-extraction of ammonia effectively. The experimental results of extraction and stripping of copper and nickel from ammonia solution by Mextral54-100 were in good agreement with the theoretical calculation results by DFT, and which could be verified the accuracy of theoretical calculation results by FT-IR. What was more, DFT was expected a novel method to study the extraction and separation mechanism copper and nickel from ammonia solution in the future. Related Articles | Metrics Select Phase equilibrium and separation of AlCl 3–FeCl 3–HCl–H 2O system Lixiang WU Jing ZHAO Fangbin XUE Huaigang CHENG Fangqin CHENG Chin. J. Process Eng.    2020, 20 (3): 318-323.   DOI: 10.12034/j.issn.1009-606X.219223 Abstract （558）      PDF （4156KB）（122）       Knowledge map    Save In order to extract high purity AlCl3?6H2O from acid leaching solution of aluminum/iron-containing fly ash, it is necessary to determine the phase equilibrium data of AlCl3–FeCl3–HCl–H2O quaternary system under acidic condition. The phase equilibrium data of the AlCl3–FeCl3–HCl–H2O system with H+ concentration of 1.3 mol/L at 20 and 30℃ were determined using the isothermal dissolution equilibrium method. The phase diagrams and density?composition charts of the system were drawn. The results showed that the salt?water system was simply co-saturated at 20 and 30℃, and there was not any double salt and solid solution. The density of saturated solution increased gradually with the increase of FeCl3 concentration, and finally tended to be stable. After reaching the co-saturation, the density of solution at 30℃ was obviously higher than that of solution at 20℃. With the increase of temperature, the solubility of FeCl3 increased from 43.59% to 49.34%, the solubility of AlCl3 was about 30.70%, which was almost unchanged. It was also found that the crystallization zone of FeCl3?6H2O decreased and the crystallization zone of AlCl3?6H2O increased. According to the AlCl3–FeCl3–HCl–H2O phase diagram, the isothermal evaporation route analysis of the acid leaching liquor was carried out. The simulated acid leaching solution of aluminum and iron was used to evaporate and crystallize. The purity of AlCl3?6H2O directly separated from acid leaching solution reached 96.61%, and the recovery rate was 75.88%. Then the acid leaching liquor with different iron content was added to evaporate and crystallize, and the products were compared and analyzed. It was found that the purity of the product increased gradually with the decrease of iron content in the feed acid leaching liquor. When the contents of AlCl3 and FeCl3 in solution were 14.83% and 0.33%, the purity of AlCl3?6H2O crystals reached 99.61%, with the decrease of iron content in acid leaching solution, the purity of crystalline products was higher. Related Articles | Metrics Select Dissolution of neutralized slag acid leaching substances of coal gangue Guangya ZHENG Zhengjie CHEN Jupei XIA Weijie WANG Fang GU Yibo SHI Haolin LI Wanlin LI Chenglong LIU Chin. J. Process Eng.    2020, 20 (2): 174-181.   DOI: 10.12034/j.issn.1009-606X.219178 Abstract （534）      PDF （948KB）（121）       Knowledge map    Save Coal gangue is a kind of coal-bearing kaolinite associated with coal and a kind of solid waste discharged during coal mining and coal washing. The output of coal resources in our country is huge, so there is a large amount of solid waste emission of coal gangue. The high value-added comprehensive utilization is of great significance to the economy, the environment and the society. The neutralized slag acid leaching substances of coal gangue was used to extract the valuable elements from the acid solution. The effects of dissolution temperature, dissolution time and mass ratio of liquid to solid on the dissolution process of acid solution were researched in this work. Based on the single factor experiment, the dissolution conditions were optimized by these orthogonal experiments. The phase and micro morphology of the neutralized slag acid leaching substances of coal gangue, the acidified product and the acid slag were analyzed by XRD and SEM. The results indicated that the dissolution rates of valuable element oxides were TiO2 82.63%, Fe2O3 96.48%, Al2O3 98.33%, CaO 87.72%, MgO 95.31%, respectively, when dissolution temperature was 80℃, dissolution time was 40 min, mass ratio of liquid to solid was 3:1. Only SiO2 and a small amount of TiO2 were found in acid slag after neutralization residue dissolved. The existence of CaSO4 indicated that the valuable elements in coal gangue and residue acid were fully dissolved through this process. This method had the advantages of short dissolution time, less water consumption and higher dissolution rate of valuable elements in acid leaching system. With this research, it is expected to provide a new approach for the efficient utilization of coal gangue resources. Reference | Related Articles | Metrics Select Catalytic effect of sodium carbonate on the carbothermic reduction of nickel slag Xiaoming LI Zhenyu WEN Yi LI Weian WANG Xiangdong XING Chin. J. Process Eng.    2020, 20 (2): 182-188.   DOI: 10.12034/j.issn.1009-606X.219187 Abstract （660）      PDF （1382KB）（132）       Knowledge map    Save Nickel slag, a byproduct come from the nickel flash smelting process, contains a high content of iron and different quantities of valuable metals, such as nickel, copper, cobalt, etc. It is a potential metal resource for the iron and steel industry. The reasonable development and utilization of nickel slag meets the requirements of comprehensive utilization of secondary resources, with environmental, economic, and social benefits. However, nickel slag is difficult to reduce because of its complex mineral composition and containing a lot of fayalite, so catalyzing the reduction of nickel slag to extract valuable metal has become an urgent issue. This work took the nickel slag with total iron content of 39.40wt% and SiO2 content of 32.50wt% as raw materials, the thermodynamic calculation and experimental were carried out with different proportions of sodium carbonate added. The results showed that with the increase of the proportion of sodium carbonate from 0 to 6wt%, the degree of metallization and iron recovery rate of the reduced products increased. The content of sodium carbonate increased to 8wt%, the degree of metallization and recovery rate of iron in the reduced products remained the same or even slightly decreased. The results of SEM showed that the particle size of iron in the reduction product without sodium carbonate added was only 6 μm, and EDS analysis showed that fayalite was abundant. However, the particle size of iron in the reduction product for nickel slag added with 6wt% sodium carbonate was 17 μm, and the content of fayalite was significantly decreased. The diffraction intensity of metallic iron was significantly increased in the XRD pattern. These results indicated that sodium carbonate can promote the reduction of nickel slag and the obtained large size of iron was helpful for subsequent magnetic separation. Reference | Related Articles | Metrics Select Effect of blending component on etherification of phenolic-oil over KH 2PO 4/Al 2O 3 Bo YUAN Ze WANG Wenli SONG Songgeng LI Chin. J. Process Eng.    2019, 19 (6): 1101-1110.   DOI: 10.12034/j.issn.1009-606X.219155 Abstract （504）      PDF （626KB）（98）       Knowledge map    Save The polarity of phenolic-oil can decrease with improved miscibility in gasoline or diesel, if the phenolic mixture can be converted to aryl ethers. As the following work of early-stage studies, in this work, based on the prior well-estimated catalyst of KH2PO4/Al2O3, a novel process with addition of blending component was put forward and the effects of blending components on the vapor-phase etherification of phenols with methanol were investigated systematically, using phenolic-oil as research object. Five blending components (acetic acid, formic acid, acetone, furan and ethyl acetate) were screened and the effect of acetone was found to be the best in promoting the conversion of alkylphenols to aryl ethers. The effect of acetone dosage was examined at a constant temperature of 500℃. It was found that the liquid recovery deceased with increasing dosage of acetone before 70wt%, and then turned to a stable trend at even higher dosages. Guaiacol or any other alkoxyphenol was not detected in all cases. Alkylphenols decreased remarkably at higher acetone dosages compared with that without blending component. Aryl ethers were most generated at the acetone dosage of 50wt%. With even higher dosage of acetone, aromatics and other compounds were more generated, leading to a remarkable decrease of aryl ethers. Furthermore, with the optimized acetone percentage of 50wt%, the influence of temperature on the alkylation reaction was investigated. It was found that the liquid recovery deceased with increasing of the temperature, and decreased even faster in the range from 500 to 550℃. The content of aryl ethers reached to a maximum value (29.06area%) at 500℃ and aromatics were most generated (26.01area%) at 450℃ Considering the both factors of liquid recovery and polarity of liquid product, the optimized conditions were determined as 450℃ with 50wt% of acetone dosage, with summary content of aromatics and aryl ethers (52.90area%). It was speculated that the carbonyl group of acetone interacted with the hydroxyl group of phenols, leading to the release of CO2, and meanwhile aromatics and arylethers were generated from alkylphenols and alkoxyphenols respectively. Reference | Related Articles | Metrics Select Reduction?magnetic separation of stainless steel pickling sludge by biomass Yi ZHANG Qiang SONG Xinqian SHU Chin. J. Process Eng.    2019, 19 (6): 1111-1119.   DOI: 10.12034/j.issn.1009-606X.219134 Abstract （474）      PDF （620KB）（221）       Knowledge map    Save Pickling sludge can be produced from metal surface treatment process. Researches showed that the pickling sludge contained a large amount of Fe, which was a potential recyclable resource. However, the existing high-temperature reduction roasting processes mostly used coke or coal as reductant, which resulted in the disadvantage of high reaction temperature, energy consumption large and easy to produce greenhouse gases. Using biomass as reductant, the factors affecting the reduction-magnetic separation process of acid-washed sludge at low and medium temperature were conducted by employing a pyrolysis-magnetic separation process in this work. The chemical composition and phase analysis of pickling sludge and product were analyzed by XRF and XRD. According to the thermodynamic analysis, the possible reduction reaction in the process of biomass reduction of magnetic separation and pickling sludge was proposed. The effects of pyrolysis temperature, varieties and quantity of straws, magnetic field strength and magnetic particle size on product grade and recovery were investigated. The results showed that without reducing agent, the recovery rate of iron was low, which was 63.79% at 700℃. The reduction magnetization of pickling sludge promoted by adding biomass, and the recovery rate of the product reached the maximum value of 92.65% when the dosage of cotton stalks was 5wt%. The addition of biomass had little effect on the Fe content of products. The increase of magnetic field intensity improved the recovery of Fe, but the grade of product decreased. The magnetic particle size had little influence on the recovery rate. The optimum technological conditions of experiment were pyrolysis temperature of 700℃, addition of 5wt% cotton stalks, magnetic particle size less than 0.074 mm particles accounted for 70% of the total quality, magnetic field intensity of 200 mT. Under the conditions of the process, the iron grade of product recovered from pickling sludge was 67.72wt%, and the recovery rate was 91.83%. Reference | Related Articles | Metrics Select Analysis of chemical looping reaction characteristics and mechanism of bituminous coal Xiaoqing SUN Peng CHEN Yongzhuo LIU Qingjie GUO Chin. J. Process Eng.    2019, 19 (6): 1120-1128.   DOI: 10.12034/j.issn.1009-606X.219135 Abstract （551）      PDF （739KB）（122）       Knowledge map    Save Coal chemical looping combustion technology is one of the important technologies for the clean utilization of coal, which has received a lot of attention recently. A large number of studies have shown that the conversion properties of coal are closely related to its functional group structure. However, there are few studies on the relationship between the evolution of functional group and the characteristics of chemical looping reaction, especially the comparative studies on different types of oxygen carriers have not been reported so far. In order to explore the relationship between the functional group structure in coal and the characteristics of chemical looping combustion, the chemical looping combustion experiments of bituminous coal were carried out by means of the small fixed-bed reactor and Fourier infrared analyzer. The results showed that after adding iron-based oxygen carrier (Fe4Al6) or copper-based oxygen carrier (Cu4Al6), the CO2 concentration of Juye (JY) coal increased by 52.25% and 59.16%, respectively. The maximum carbon conversion rate increased by 8.93% and 30.36%, respectively. The reaction effect of Cu4Al6 was better. When Cu4Al6 was used as bed material, the evolution of surface functional groups in JY coal was accelerated, the reaction rates of aliphatic hydrocarbon structure, aromatic carbon skeleton and aromatic CH were significantly improved. Aliphatic ?CH3 and ?CH2 in coal were active, and reaction rate was quite fast, which were the main sources of gas phase products in the initial stage of chemical looping combustion. Aromatic carbon skeleton and aromatic CH were stable and inactive, and reaction rate was relatively slow, which were the main sources of gas phase products in the middle and late stages of chemical looping combustion. Reference | Related Articles | Metrics Select Separation of methane from low concentration coal bed methane by hydrate-based process Qiunan Lü Xiaosen LI Gang LI Zhaoyang CHEN Chin. J. Process Eng.    2019, 19 (6): 1129-1134.   DOI: 10.12034/j.issn.1009-606X.219126 Abstract （550）      PDF （488KB）（104）       Knowledge map    Save A method of separating and concentrating CH4 from coal bed methane (CBM) by hydrate formation was proposed. The separation experiments of CBM simulation gas (13.11vol% CH4+86.89vol% N2) were carried out by adding promoter solution of 5.8mol% Tetrahydrofuran (THF)?0.03mol% Sodium dodecyl sulfate (SDS). The effect of pressure, temperature and reaction time on gas consumption, reaction rate, methane concentration in the hydrate, methane recovery and separation factor were investigated. The concentrations of methane in the residual gas phase and the decomposed gas phase were determined by chromatographic analysis. The results indicated that the higher pressure, lower temperature, longer reaction time facilitated gas consumption, methane recovery and separation factor. With the increase of pressure, the recovery of CH4 and the separation factor of CH4 increased. It illustrated that higher pressure resulted in better separation efficiency for CBM. As the temperature decreased, nitrogen competed with methane to enter hydrate crystals, which led to the reduction of methane concentration in the hydrate phase. The temperature was the key factor affecting the methane separation factor, and the increase of temperature was propitious to improve the selectivity of methane hydrate. The maximum methane recovery rate was up to 98.65%, and the maximum separation factor was 14.83. With the increase of reaction time, the concentration of CH4 in decomposition gas increased. This indicated that CH4 and N2 molecules entered the hydrate lattice with the reaction proceeding, but the amount of CH4 entering the hydrate was more than that of N2 in the later stage of the reaction. This technology can effectively separate methane from low concentration coal bed methane and was valuable to storage and transportation of CBM and to disposal of mine methane. Reference | Related Articles | Metrics Select The process of salt recovery from lysine ion-exchange waste water by diffusion dialysis-electrodialysis Yun WEI Qian WANG Wei CONG Chin. J. Process Eng.    2019, 19 (5): 975-981.   DOI: 10.12034/j.issn.1009-606X.218182 Abstract （630）      PDF （545KB）（292）       Knowledge map    Save During the current fermentation process of producing lysine, large amount of organic waste water containing high-concentration salt were generated with the addition of inorganic acid-base regulators. When directly using conventional electrodialysis method to recover (NH4)2SO4 from lysine ion- exchange waste water, the ion-exchange membranes of electrodialysis were easily contaminated by pollutants in the waste liquid like high-valent ions, proteins, sugars and so on. In the diffusion dialysis method using membrane, there were many advantages such as low energy consumption, easy for operation, no pollution of the environment and so on. To reduce the membrane fouling during electrodialysis process and improve its performance, diffusion dialysis with anion-exchange membrane was adopted to clean lysine ion-exchange waste water, then carried out electrodialysis. The results showed that when the flow rate of diffusion dialysis was 5.6 L/h, among inorganic ions and organics investigated, 90.1% of Mg2+, 94.5% of total organic nitrogen, 80.3% of the protein, 86.0% of the total sugar and 79.3% of chemical oxygen demand (COD) were rejected reasonably and nearly 30% of (NH4)2SO4 were recovered by diffusion dialysis with the dialysis coefficient of 2.24×10?7 cm2/s. Moreover, compared with the process performance of (NH4)2SO4 recovery from lysine ion-exchange waste water by electrodialysis directly, the experiment that cleaned the feed solution by diffusion dialysis firstly and then carried out electrodialysis could increase the membrane flux of SO42? and the average current efficiency by 55.7% and 18.3% respectively, and decrease the operation time and the energy consumption of unite flux by 26.1% and 42.3% respectively. It was proved that cleaning lysine ion-exchange waste water by diffusion dialysis was a feasible method to mitigate ion-exchange membrane fouling and improve the process performance of electrodialysis. Reference | Related Articles | Metrics Select Effect of vortex finder structure on the separation performance of hydrocyclone for natural gas hydrate Dangfei WANG Guorong WANG Shunzuo QIU Lin ZHONG Shouwei ZHOU Qingyou LIU Chin. J. Process Eng.    2019, 19 (5): 982-988.   DOI: 10.12034/j.issn.1009-606X.219105 Abstract （649）      PDF （2148KB）（242）       Knowledge map    Save In the view of the problems of pipeline jam，tools erosion and high energy consumption in pipeline transportation caused by the slurry with high content of sand in the process of the solid fluidized mining for the non-diagenetic natural gas hydrate in the shallow seabed, the downhole hydrocyclone has been designed for in-situ desanding and purification of hydrate slurry. The vortex finder is an important structure of hydrocyclone, which greatly affects the separation performance of the hydrocyclone. The hydrocyclone model with nominal diameter of 100 mm and computational fluid dynamics (CFD) numerical method were used to study the influence of vortex finder structure on separation performance of hydrocyclone. The results showed that under the condition of 9 m/s inlet flow rate, the separation efficiency of gas hydrate increased with inner diameter, on the contrary, the separation efficiency of sand decreased. The pressure drop of hydrocyclone decreased gradually with the increase of inner diameter. The separation efficiencies of gas hydrate and sand increased slightly with wall thickness, while the pressure drop of hydrocyclone increased firstly and then decreased with the increase of wall thickness. It was concluded that the separation efficiency of gas hydrate decreased firstly and then increased, while the separation efficiency of sand increased firstly and then decreased, and the pressure drop of hydrocyclone had been less affected. The inner diameter had the greatest influence on the separation performance of hydrocyclone for gas hydrate, followed by the insertion depth of vortex finder, and the wall thickness of overflow tube had the least influence on the separation performance of hydrocyclone. The research work had certain guiding significance for the field application of hydrocyclone in gas hydrate exploitation. Reference | Related Articles | Metrics page Page 1 of 3 Total 97 records First page Prev page Next page Last page