The Chinese Journal of Process Engineering

Effect of magnetic Fe₃O₄@SiO₂ nanoparticles structure on its adsorption to DNA

Huifang XING Liangrong YANG Jiemiao YU Huizhou LIU Hao YU Wanbo LI Shuidong CUI

Chin. J. Process Eng.. 2018, 18(6): 1119-1125. DOI: 10.12034/j.issn.1009-606X.218234

Asbtract ( )

PDF (3302KB) ( )

References | Related Articles | Metrics

DNA purification is considered to be a critical step in biomedical applications such as genetic therapy and clinical diagnosis. These years, the magnetic silica beads are widely used in DNA purification due to the advantages of averting the use of some toxic organic solvents and being easy to auto-magnetic separation. Among them, magnetic Fe3O4@SiO2 nanoparticles (NPs) were widely used because of their stability, monodispersity, selectivity, and high separation efficiency in magnetic field. However, the shape and structure of particles may affect the DNA isolation efficiency, such as the DNA adsorption capacity and recovery rate. It has not yet been fully explored. In this work, a series of Fe3O4 NPs with different core diameters were synthesized firstly by co-precipitation and hydrothermal methods, and then further coated by silica through St?ber method. The resultant Fe3O4@SiO2 NPs were characterized by SEM, TEM, IR and BET, respectively. The DNA adsorption capacity of Fe3O4@SiO2 NPs were studied by UV?Vis, and the magnetic separation properties were also determined by magnetic response time. The results showed that in the range of 20?750 nm of particle size, the larger size particles could provide more unit planar binding sites when combining with DNA, which increased the combination stability and binding probability. Thus, the DNA binding capacity of the particles increased with the increase of particles size. In addition, the magnetic response time of Fe3O4@SiO2 NPs with different core?shell structures were also different. When the size of the core was similar, the thicker SiO2 shell around would weaken the dipole?dipole interactions between particles and reduce particles aggregation, thus the magnetic response time of NPs increased, leading to a low recovery rate within a limited operating time. Comparing the DNA adsorption capacity and recovery efficiency of particles. The Fe3O4@SiO2 NPs around 200 nm was the optimal choice for blood DNA purification, which had high recovery rate (95.2%) in a short magnetic response time (10 s).

Frontiers of molecular dynamics simulations of protein systems-reexamine from the mesoscience perspective

Ying REN Ji XU

Chin. J. Process Eng.. 2018, 18(6): 1126-1137. DOI: 10.12034/j.issn.1009-606X.218238

Asbtract ( )

PDF (1006KB) ( )

References | Related Articles | Metrics

Proteins are the essential parts of living organisms and they participate in virtually every process within cells. An in-depth understanding of the spatiotemporal multi-scale structure and the dominating mechanisms of protein structures would be the basis for scientific exploration of the origin of life, the mechanisms of diseases and the development of new drugs. Due to the limitations of the spatial and temporal resolutions of current experimental methods, computer simulations, especially molecular dynamics simulations, have become one of the most important methods to study the structure and function of protein systems. This article reviewed the progress of molecular simulations and their application in the research of protein systems during the past half century, especially for molecular dynamics simulations and enhanced sampling methods. The time and space involved in protein simulations covers a wide range of scales, which makes it a great challenge to simulate the spatial-temporal multi-scale structures quickly and accurately, or to investigate the physiological process and the underlying dominating mechanisms. Therefore, this article summarized the recent development of the theoretical models and computing algorithms, and their applications in the investigations of the molecular mechanisms of the native structures and structural changes of the structured proteins, the dynamic structure ensemble of intrinsic disordered proteins and the coupled folding and binding with target protein or other biological molecules, protein complex such as molecular chaperonin, virus particle, etc. Furthermore, the evolution of the popular softwares for molecular dynamics simulations driven by the rapid development of high-performance super computers, and their acceleration of the spatial-temporal scales in molecular dynamics simulations of protein systems, were further discussed. At the end of the article, based on the rapid development of mesoscience theory and its successful applications in a variety of complex systems, the future simulation methods and theoretical research of protein systems were prospected.

Progress on preparation of special powders using HF thermal plasma

Fangli YUAN Huacheng JIN Guolin HOU Liuyang BAI Fei DING Baoqiang LI Yunfa CHEN

Chin. J. Process Eng.. 2018, 18(6): 1138-1144. DOI: 10.12034/j.issn.1009-606X.218240

Asbtract ( )

PDF (8171KB) ( )

References | Related Articles | Metrics

High frequency (HF) thermal plasma with high processing temperature (up to 10000 K) in the flame zone and fast quenching rate (105?106 K/s) at the flame tail is one of the most important methods to prepare special powders. In addition, thermal plasma is a powerful tool for synthesizing well-dispersed powders in a continuous and scalable process. In this manuscript, progress on preparation of special powders using HF thermal plasma in our team was introduced. Powders with large size were fed into plasma flame and vaporized to make them vaporation, and ultrafine powders were produced after fast quenching by physical vapor deposition (PVD). Spherical nanopowders of Si, Fe, Co, Ni could be prepared by PVD. Synthesized Si nanopowders display perfect spherical shape with smooth surface and good dispersity, which exhibit super electrochemical performance as anode for Li-ion batteries. Powders with irregular shape fed into plasma flame were melted to form spherical liquid drops and fast quenched to form spherical powders. W, Mo, Nb, Cr, Ni, Ti, V spherical powders could be prepared using HF thermal plasma. Hydrogen plasma with reactive radicals could help to enhance the hydrogen reductive reaction, which could make precursors to be reduced transiently to get metal nanopowders by chemical vapor deposition (CVD). W, Ni and Cu spherical nanopowders could be prepared using CVD. Synthesized W nanopowders with well defined spherical particles exhibit high sintering activity and strengthen the mechanical properties of obtained compacts. Oxygen plasma with reactive radicals can help to tune the growth of oxides in the plasma, and oxides with various morphologies can be produced using oxygen plasma. Al2O3 spherical nanopowders can be prepared and their sintering behavior shows that the aggregates are avoided and the grains are always uniform during sintering, owing to the employment of well dispersed spheres.

The technical state and development trend of the direct reduction of titanomagnetite by fluidized bed

Haoyan SUN Qingshan ZHU Hongzhong LI

Chin. J. Process Eng.. 2018, 18(6): 1145-1159. DOI: 10.12034/j.issn.1009-606X.218275

Asbtract ( )

PDF (773KB) ( )

References | Related Articles | Metrics

Vanadium and titanium are the important production and living materials. More than 90% vanadium and titanium resources deposit in titanomagnetite. China is rich in titanomagnetite ore. But due to the limitation of blast furnace operating condition in the modern blast furnace?converter industrial process, titanium element in titanomagnetite has not been extracted and utilized. The direct reduction?electric furnace smelting process, which is the new generation environmental technology of titanomagnetite resource comprehensive extraction and utilization, has received extensive attention. By dividing the reactions in blast furnace into reduction and smelting two steps, the direct reduction?electric furnace smelting process is very beneficial to the reaction condition control. With the same smelting reactor, the process can be classified as rotary kiln, rotary hearth furnace, shaft furnace and fluidized bed direct reduction according to the different reduction reactors. Taking the advantages of high heat and mass transfer efficiency and directly using ore powder, the fluidized bed exhibits the significant advantage in the industrial application of the direct reduction of titanomagnetite. In this work, the fluidized direct reduction process of titanomagnetite was expound and compared. By analyzing the difficult reduction characteristics of titanomagnetite ore, the reduction reinforcing method by pre-oxidation was emphatically introduced. The titania?ferrous oxides in titanomagnetite ore need much higher reduction potential than normal iron oxides, resulting in the low metallization degree and the high cost. The pre-oxidation can dissociate the titania?ferrous oxides to easily reducible free Fe2O3, improving the reaction efficiency and balance metallization degree. Concluding the main influence factors of defluidization, containing operating temperature, metallization degree, particle size, reducing atmosphere, particle shape and gangue content in the fluidized direct reduction process, five restrain methods for defluidization including inert additive, carbon coating, field force addition, granulation and bed structure improvement were summarized. Further, research and development directions were proposed for MgO inert additive, carbon coated and the bed structure improving methods.

Preparation process of high-quality LiPF₆ crystals

Yongfeng ZHAO Haitao ZHANG

Chin. J. Process Eng.. 2018, 18(6): 1160-1166. DOI: 10.12034/j.issn.1009-606X.217428

Asbtract ( )

PDF (815KB) ( )

References | Related Articles | Metrics

Much more attentions are being devoted to high performance energy storage and conversion devices to conquer global warming issue and energy crisis. Lithium-ion battery, the most promsing device, is composed of anode, cathode, separator and electrolyte. Note should be highlighted that the performance of battery is determinded by electrolyte, espcially the safety issue. The demand of lithium-ion batteries and their electrolytes is growing rapidly with the rapid development of new energy vehicles recently. Lithium hexafluorophosphate (LiPF6) crystal is a white crystal with trigonal crystallographic structure. It is the key electrolyte material for Li-ion batteries. LiPF6 is combustible, corrosive and of poor thermal stability. Therefore, some toxic and corrosive precursors are employed, and their synthesis is required to be conducted within an anhydrous and anaerobic environment. Furthermore, many high temperature and low temperature treatments are involved in the synthetic procedure. Therefore, it is a huge challenge to produce high-purity LiPF6 crystals with an electronic grade in an industrial-scale. Fortunately, some industrial processes have been developed successfully by domestic enterprises even there is still some room for improving them. Here, the synthetic methods of LiPF6 and the domestic large-scale production processes are reviewed with the hope of providing some knowledge for future upgrade of the industrialized LiPF6 processes and a guideline for developing new synthetic routes. This review will concentrate on the development and intrinsic correlation among market demand of lithium-ion battery, role of electrolyte in lithium-ion battery, LiPF6 industrialized production procedures, and planned incremental capacity. In addition, the perspectives of potential electrolyte are summarized on basis of the progress of high-capacity and high-voltage electrode materials. There is no doubt that the future emphasis should be paid to the optimization of process, true demand of market, novel lithium salt, fluoridized solvents, and green techniques.

Advances on high-voltage electrolyte of lithium ion batteries

Juntian FAN Tao DONG Lan ZHANG Shimou CHEN

Chin. J. Process Eng.. 2018, 18(6): 1167-1177. DOI: 10.12034/j.issn.1009-606X.218133

Asbtract ( )

PDF (482KB) ( )

References | Related Articles | Metrics

To satisfy the increasing discharge capacity demand of next generation electric devices, various high working voltage cathodes have been explored. However, traditional carbonate solvents, such as ethylene carbonate and ethyl methyl carbonate-based electrolytes are prone to oxidative decomposition at high voltage (>4.3 V, vs. Li/Li+), which results in the increase of irreversible capacity and the inferior cycling performance of lithium ion batteries. To solve the problem, it is necessary to design high-voltage tolerant electrolyte based on theories and experiments. Specifically, new high-voltage solvents such as sulfone and ionic liquid are determining factors to improve the stability of electrolyte as they could improve the interfacial stability between the high voltage cathode and the electrolyte intrinsically. Another method to solve the problem is the addition of high-voltage additives because a small amount of additives could form an effective solid electrolyte interface layer and decrease the interfacial reaction dynamically. Moreover, additives can solve the problem economically and effectively. In addition, optimizing the physical and chemical properties of conventional electrolyte is a new strategy to exhibit new properties. For example, a novel formula such as superconcentrated electrolyte has wide electrochemical window and superior cycling performance. However, it is well known that high voltage solvents are often characterized by high viscosity, low reductive stability and reductive decomposition products cannot form an effective interfacial layer on the anodes. The addition of additives may have negative impact on other properties of lithium ion batteries such as the initial coulombic efficiency. And the superconcentrated electrolyte is very expensive and high viscosity. Although they have some defects, it is also very significant to study them because they can give a guide to investigate electrolyte with superior performance. Thus, this review summarized the advances and perspectives on the development of high-voltage solvents, additives and superconcentrated electrolyte of lithium ion batteries.

Numerical simulation of interface evolution of single bubble rising through sudden expansion channel

Yunzhou BAO Chenhan WU Ying ZHANG

Chin. J. Process Eng.. 2018, 18(6): 1178-1186. DOI: 10.12034/j.issn.1009-606X.217435

Asbtract ( )

PDF (1283KB) ( )

References | Related Articles | Metrics

A single bubble driven by buoyance rising through a sudden expansive channel was simulated by Front Tracking Method (FTM). Firstly, the influence of the width ratio of the narrow channel and the wide channel on shape and rising velocity of bubble was investigated. It was found that the morphology of bubble interface presented different characteristics in the three parts, i.e., the narrow channel, the expansion part and the wide channel, respectively. When the bubble left the expansion, the surrounding fluid flowed from both sides of the bubble into the bottom area, causing both sides of the bubble to be squeezed, the bubble reached the highest aspect ratio. With the increase of the channel width ratio, the flow field of the bubble was less inhibited by both sides of the wall, and the maximum aspect ratio of the bubble decreased. When Wn/We reached over 4/6, the influence of expansion segment can be ignored. Then the influence of Eotvos number Eo and Mo number were analyzed. At low Eo, when the Mo number reduced, the bubble was more likely to deform, the aspect ratio of the bubble decreased and the bubble?s rising speed increased. When the Eo number increased, the deformation became more serious when the bubble rised. Changing the position of the bubble relative to the narrow channel at the initial moment also affected the shape of the bubble. When the initial position of the bubble was close to the single side wall, due to the low flow velocity of the surrounding fluid near the wall, the bubbles would be stretched horizontally while moving, and the bubble deformed badly in the horizontal direction. Asymmetrical pressure distributions occurred on the left and right sides of the bubble level. The pressure on the side of the bubble near the wall surface was lower, making the movement path of the bubble in the narrow channel appear to swing left and right. After leaving the expansion part, the movement of bubbles gradually stabilized due to the absence of wall constraint on the bubbles. When the bubble was far away from the expansion part, the influence of the wall surface decreased. After 2.3 times from the expansion part, it can be considered that the bubble enters a stable rising state.

Improvement of EMMS/DP drag model based on MP-PIC method

Xiaozan WANG Yong JIANG Fei LI Wei WANG

Chin. J. Process Eng.. 2018, 18(6): 1187-1197. DOI: 10.12034/j.issn.1009-606X.218115

Asbtract ( )

PDF (3316KB) ( )

References | Related Articles | Metrics

The energy minimization multi-scale drag model for discrete particle method (EMMS/DP) is a heterogeneous drag model applicable for discrete particle simulations. Particles distribute heterogeneously in circulating fluidized bed (CFB) flows due to clustering effect. Discrete particle method can provide detailded particle distributon information including particle position and particle velocity, but need assume evenly gas distribution inside computational cells. The inconsistence between particle field resolution and gas flow field resolution can lead to deviation between simulation result and actual measurement for heterogeneous gas?solid flows. To solve this problem, EMMS theory is applied to resolve the flow field around particles by accounting for the existence of particle clusters. Subsequently the heterogeneous drag force as well as the heterogeneous index (HD) are calculated based on the decomposed flow field to close the the interphase interaction terms in gas and particle momentum equations. Since the online calculation of EMMS/DP drag is very time consuming in real simulations, a predifined gas?solid flow field is applied to generate the HD database. The generated HD database can be used directly in discrete particle simulations thereafter, but will not increase computation load significantly. The current work improves the generating method of predifiend gas?solid flow field by taking consideration of the inhomogensou particles distributtion. In this work, HD was correlated with solid concentration and slip velocity based on the generated HD database to account for the dynamic effects of meso-scale structures. A comparison between HD at particle sacle and HD at computational cell scale was illustrated. The improved EMMS/DP drag model coupling with the multi-phase particles in cell (MP-PIC) method was used to simulate the gas?solid two phase flows in two CFB risers to verify the model. The simulation results were in good agreement with the experimental data. The grid-independence and effect of the coarse grained model parameter for MP-PIC on simulation results were also studied.

Design of two-stage swirling gas?liquid separator and simulation of flow field characteristics

Zhaoming YANG Jianlei CHEN Yunrui HAN Limin HE Xiaoming LUO

Chin. J. Process Eng.. 2018, 18(6): 1198-1209. DOI: 10.12034/j.issn.1009-606X.218124

Asbtract ( )

PDF (1559KB) ( )

References | Related Articles | Metrics

The undersea separation was widely used in the petroleum industry to improve the efficiency and keep the well pressure. High gas?liquid ratio condition exists in offshore gas field frequently and for this condition, a novel two-stage gas and liquid cylindrical cyclone was designed. In order to increase the separation efficiency, some parts had been added in the separator. The size parameters of the separator were designed by using effective volume transformation methods, and a method for diameter determination was also proposed based on the characteristics of liquid drop breaking in swirl field. This determination described the liquid drop’s changing shape and breaking in the gas cyclone field and the critical relative velocity of the gas phase and liquid phase when the liquid drops started to break had also been calculated. The model based on the pressure field by the solution of Navier?Stocks equation and had also been verified by the experiments which had measured the liquid drops diameters by using Malvern laser particle size analyzer and the data from model and experiments kept high consistency. Different turbulence models, different meshing schemes and different discrete formats had been compared in order to choose the best numerical simulation plan and this plan also had been validated by existing experimental data. The characteristics of asymmetry were analyzed by CFD about the internal flow field of the simplified model and the influence of structural parameters and operational parameters were also obtained. The results of the models showed that it was very diffcult for oil drops in different diameters to break in the gas cyclone fields. The results of the numerical simulation showed that the length of the separator had little effect on the asymmetry characteristics of the internal flow field and the inlet velocity and the ratio of the length and width of inlet would not make the internal flow field become unstable.

Adsorptive properties of methylene blue using biomass material based on rice husks by microwave-assisted activation

Qianqian ZHONG Yaqin ZHAO Aibing WU Lei WANG Li SHEN Peng WANG

Chin. J. Process Eng.. 2018, 18(6): 1210-1218. DOI: 10.12034/j.issn.1009-606X.218125

Asbtract ( )

PDF (527KB) ( )

References | Related Articles | Metrics

Microwave assisted KOH activation has been utilized for preparation of biomass adsorption material based on agricultural waste rice husks (RH). Batch experiments were conducted to evaluate the sorption performance of cationic dye methylene blue (MB) by modified rice husks (MRH) from aqueous solutions. The effects of solution initial pH, dosage of the adsorbents, salt concentration, the dyeing and finishing auxiliary concentration, contact time and temperature on MB adsorption were investigated. The results showed that MRH had a wide appropriate pH range of 5?11 for MB adsorption, which showed the potential applicability in the actual water body. With NaCl concentration increasing from 0 to 0.2 mol/L, the removal efficiency of MB decreased from 58.24% to 1.86%; while, MB removal increasesd with increasing SDBS concentration. The sorption process for MB onto MRH was an endothermic reaction and the adsorption process reached equilibrium within 30?45 min. The obtained product MRH had a maximum MB adsorption capacity of 109.9 mg/g. The experimental kinetic data were well described by the pseudo-second order model and the best ?tting for MB experimental equilibrium data was achieved with the Langmuir isotherm, which was a rapid and monolayer adsorption process. Film diffusion was the rate-limiting step which was primarily responsible for the adsorption of MB on MRH. Physical adsorption inside the pores of biomass materials and O?H functional groups adsorption both contributed to the adsorption mechanism.

The regeneration of sodium ferrite from iron-based desulfurization residue and its circulation desulfurization

Yifei LI Zhihong PENG Yilin WANG Guihua LIU Qiusheng ZHOU Tiangui QI Xiaobin LI

Chin. J. Process Eng.. 2018, 18(6): 1219-1225. DOI: 10.12034/j.issn.1009-606X.217429

Asbtract ( )

PDF (667KB) ( )

References | Related Articles | Metrics

Along with the increasing scarcity of high quality bauxite and the gradual growth of alumina capacity, resource is crucial for restricting alumina industry development in China. As for there are large amount of refractory diasporic bauxite with high sulfur content in many regions of China, it is significant to investigate the efficiently utilization method of high sulfur bauxite. There are some related research showed that sodium ferrite was used to remove the sulfur in sulfur bearing sodium aluminate solution and the desulfurization effect was verified, which was prepared by Fe2O3 and Na2CO3. For the purpose of sodium ferrite regeneration, this dissertation presented a roasting-leaching process of sulfur removal from desulfurization residue. The process entailed roasting of desulfurization residue in oxidizing atmosphere and the roasted product was leached with water subsequently. Iron-based desulfurization residue (NaFeS2?2H2O) was a solid phase product from the sodium ferrite after removed the S2? in sodium aluminate solution. The regeneration and cyclic desulfurization of iron-based desulfurization residue (NaFeS2?2H2O) by oxidizing roasting and water leaching were investigated by DTG and XRD. The results indicated that oxidizing atmosphere was beneficial to the decomposition of NaFeS2?2H2O and the separation of sulfur and iron in the roasting process. The desulfurization rate was 70% by roasting the iron-based desulfurization residue under oxidizing atmosphere at 950℃ for 1 h. The sulfur content in roasted residue can be further reduced to less than 0.2% after leaching by water and the total sulfur removal rate could reach 99%. The sodium ferrite was prepared by the leaching residue and the cyclic desulfurization rate was up to 67.65%, which was very close to the initial desulfurization rate (69.09%). This conclusion indicated that the iron-based desulfurization residue can be regenerated and cyclic desulfurized. The sulfur in the desulfurization residue was discharged in the form of SO2 during the roasting process, while the rest sulfur was removed in form of Na2SO4 by water leaching. These results will contribute to the purification of the sulfur containing sodium aluminate solution and the utilization of the high-sulfur bauxite.

Influence of copper morphology on copper and gold leaching rates in calcine and acid leaching residue

Wei YANG Huan CAO Kai ZHANG Gang WANG

Chin. J. Process Eng.. 2018, 18(6): 1226-1231. DOI: 10.12034/j.issn.1009-606X.218112

Asbtract ( )

PDF (919KB) ( )

References | Related Articles | Metrics

Taking gold?copper concentrate of a certain gold smelting plant as the research object determined changing situation of distribution of copper oxide, secondary sulfide copper and primary sulfide copper in calcine and acid leaching residue at different roasting temperature, roasting time and initial acid concentration of acid leaching; researched influence of copper morphology on copper and gold leaching rates in calcine and acid leaching residue with way of leaching. And ascertained the measures to improve the copper leaching rate of the gold?copper concentrate. The results showed that the morphology of copper had a significant influence on copper and gold leaching rate when gold?copper concentrate was treated by roasting?acid leaching?cyanidation process. When the content of cyanide soluble copper (copper oxide and secondary sulfide copper) in acid leaching residue was beyond 0.10%, the gold leaching rate was reduced. The gold?copper concentrate bearing mainly primary sulfide copper mine obtained a good indicator in the roasting temperature 690℃, roasting time 1.5 h, initial acid concentration of acid leaching 35 g/L, quality of leaching liquid-solid ratio 3:1, leaching time 1 h, leaching temperature 85℃, initial concentration of NaCN 1.0?1.2 g/L, leaching time 24 h, pH of system 10?11, mass ratio of leaching liquid to solid 2:1. The copper leaching rate reached 95.40%, and gold leaching rate was up to 97.33%. The measures to improve the copper leaching rate of the gold?copper concentrate are increasing roasting temperature from 650℃ to 690℃, extending the roasting time from 1.0 h to 1.5 h and increasing initial acid concentration of acid leaching from 30 g/L to 35 g/L. Gold-copper concentrate bearing mainly primary sulfide copper mine can effectively reduce cyanide soluble copper content in the acid leaching residue by increasing roasting temperature, extending the roasting time and increasing initial acid concentration of acid leaching. These measures improved the leaching rate of copper meanwhile reduced the impact on gold leaching rate.

Recovery of cephalexin with complexation

Xin WANG Zhengsheng MA Qingfen LIU

Chin. J. Process Eng.. 2018, 18(6): 1232-1238. DOI: 10.12034/j.issn.1009-606X.218132

Asbtract ( )

PDF (371KB) ( )

References | Related Articles | Metrics

Cephalexin (CEX) was a widely used antibiotic in clinic. The proportion of CEX in crystalline mother liquor was about 10%, which must be recovered in order to decrease economic losses, environmental pollution and prevent the rise of drug-resistant bacteria. The preparation of CEX by enzymatic-catalyzed is a green pharmaceutical technology, but recovery of CEX from the crystalline mother liquor had not been studied systematically. In this work, the recovery of CEX in the crystalline mother liquor by enzymatic-catalyzed preparation was investigated with benzene and naphthalene compounds as complexing agents. The effect factors including complexing agent type, complexing agent dosage, pH, temperature, concentration of residual raw materials and by-product on CEX complexation process were systematically studied, and an optimization scheme was proposed. The results showed that CEX complexation rate was higher using naphthalene compounds as complexing agents than that of benzene compounds. The type of complexing agent and its dosage, pH were key factors on CEX complexation rate, while the temperature, concentration of residual raw materials and main by-product, such as 7-amino-3-desacetoxicephalosporanic acid (7-ADCA), phenylglycine methyl ester hydrochloride (PGME) and phenylglycine (PG) had no significant effect on CEX complexation rate. The optimum parameters were as follows: 1-naphthol dosage of 4.4 g/L, pH of 4.72 and temperature of 293 K. Under the optimal conditions, the CEX complexation rate was more than 97.0%, which increased by 5.0% compared to that in the conventional industrial process. Using dichloromethane as a decomplexing agent, the total recovery rate of CEX was more than 92%. Furthermore, the CEX products were analyzed by HPLC, the content of CEX, 1-naphthol were 98.5% and 0.009%, respectively. While the impurities in the CEX products, such as 7-ADCA, PGME and PG were not detected. The quality of CEX products conformed to Chinese pharmacopeia standard. This work suggested an effective approach for CEX recovery and pollutions decrease.

Design and optimization of liquid holdup on reactive distillation tray considering hydraulic feasibility

Zixin LIN Ran AN Weizhong AN Lianxi HUANG Haiyan BIE Jianmin ZHU

Chin. J. Process Eng.. 2018, 18(6): 1239-1244. DOI: 10.12034/j.issn.1009-606X.217414

Asbtract ( )

PDF (539KB) ( )

References | Related Articles | Metrics

The liquid holdup is limited by the physical space of the column and should not be appointed at random. To obtain the design and optimization of liquid holdup on reactive distillation trays, an optimization of tray configuration framework considering hydrodynamic feasibility was proposed. The effect of the liquid holdup on the reaction was studied, and the most optimal liquid holdup was obtained, through simultaneous design of three aspects of the liquid holdup, tray configuration and the hydrodynamic feasibility. Using the synthesis of diphenyl carbonate (DPC) by the transesterification of dimethyl carbonate (DMC) with phenol (PhOH) as an example, the implemented process of this method was described in detail. In the process of implementation, sieve tray was employed as illustrated configuration according to the traditional design method of distillation tray, with the maximum reactants conversion as objective function, weir height and column diameter of tray as decision variable and hydrodynamic feasibility of tray as constraints, a step-by-step simulation and design method was developed to achieve the optimization of liquid holdup on reactive distillation trays. Aspen Plus and Cup-Tower software were used to conduct the process simulation with chemical reaction kinetics and hydraulic computation respectively. The results showed that, the weeping was the main limiting factor to increase the liquid holdup. In the column with a diameter of 0.7 m and 0.06 m weir height, the maximum liquid holdup of 18.5 L was obtained, compared to the basic design an increase of holdup of tray by 1.39 times and PhOH conversion by 33.6% under the condition of satisfying hydraulic feasibility could be obtained. The temperature of the reboiler did not exceed 195℃ with optimizing the liquid holdup. In addition, the reaction rate of PhOH was higher than that of the initial design, which showed the validity of the proposed method for the DPC reactive distillation process.

Effect of pulverized coal particles on emission characteristics of aggregate drying pulverized coal burner

Jing WANG Haiying CHENG Zhiyong HU Zhenliang WANG

Chin. J. Process Eng.. 2018, 18(6): 1245-1252. DOI: 10.12034/j.issn.1009-606X.217425

Asbtract ( )

PDF (978KB) ( )

References | Related Articles | Metrics

Pulverized coal used as fuel of burner in the process of aggregate drying had the significant economic and comprehensive benefits. However, pulverized coal combustion generated a variety of noxious gases which polluted the atmosphere. Effective reduction of pollutant emission was significant for pulverized coal burner’s industrialization and became an important issue in coal combustion. Pulverized coal particle size affected the turbulence, diffusion and coupled motion of internal flow field in pulverized coal burner, thus affected its emission characteristics. Based on the technology of aggregate drying and followed the essential mechanism of coal combustion, a three-dimensional physical model was established by the modeling software CREO. Computer aided engineering software Gambit was used to make unstructured mesh generation for the pulverized coal burner. Control model of pulverized coal combustion behavior was constructed to simulate the internal fields of aggregate drying pulverized coal burner in Fluent software. The standard k?? model was used to describe the turbulent motion of turbulent flow in the process of pulverized coal combustion, and the P1 radiation model was used to describe the phenomenon of thermal radiation and heat transfer between solid phase and air phase. The stochastic particle trajectory model was used to describe the dispersion of discrete phase and the eddy dissipation model was used to describe the motion and combustion of turbulent eddy. The kinetics/diffusion-limited model was chosen as the combustion model in process of pulverized coal combustion. The influence of pulverized coal particle size on emission characteristics during pulverized coal combustion process in aggregate drying was analysed with the pollutant mass fraction as the evaluation standard. The results showed that with the increase of particle size, because of incomplete combustion of pulverized coal, the CO emission increased and the CO2 emission declined. With the increase of particle size, the emission of SO2 grew, the optimal emission of NO was when pulverized coal particle size was 100 μm.

Adsorption of vanadium ion in solution on nano zero-valent irons

Changduo ZHAO Xiaobo YANG Meiling FAN Wenbin HU Qibin XIA

Chin. J. Process Eng.. 2018, 18(6): 1253-1260. DOI: 10.12034/j.issn.1009-606X.217434

Asbtract ( )

PDF (997KB) ( )

References | Related Articles | Metrics

Nano zero-valent iron (nZVI) was synthesized by the liquid-phase reduction method, and characterized by powder X-ray diffraction (PXRD), scanning electron microscope (SEM), transmission electron microscope (TEM), the Brunauer-Emmett-Teller (BET) and X-ray photoelectron spectroscopy (XPS) method. The adsorption performance of vanadium (V) on nZVI was investigated by rationally adjusting the parameters, such as additive amount of nZVI, initial concentration of vanadium(V) and initial pH value. Additionally, the adsorption isotherms and kinetic curves of vanadium(V) on nZVI were measured. The results showed that nZVI exhibited a regular core?shell structure with an average particle size of 10~30 nm and the BET surface area of 53 m2/g. Furthermore, the adsorption capacity of vanadium(V) decreased with the increase in initial pH value and nZVI amount added, respectively. The maximum vanadium(V) adsorption capacity reached 227.8 mg/g at 25℃. The adsorption isotherms of vanadium(V) on nZVI fitted well with Langmuir model, and the adsorption kinetics of vanadium(V) on nZVI could be well described by a pseudo-second-order kinetic model. The nZVI synthesized in this work will provide an useful insights into the comprehensive utilization of waste SCR denitration catalyst.

Preparation and infrared radiation characterization of Ni doped lanthanum aluminate coatings

Pengfei LIU Weihua LU Zhao HAN Yixiang CHEN Jiangtao LI

Chin. J. Process Eng.. 2018, 18(6): 1261-1266. DOI: 10.12034/j.issn.1009-606X.217439

Asbtract ( )

PDF (792KB) ( )

References | Related Articles | Metrics

Ni ion doped LaAlO3-based infrared radiation materials were synthesized with lanthanum nitrate, aluminum nitrate, and nickel nitrate as starting materials via sol?gel method. Infrared radiation coatings were then prepared on the surface of alumina ceramic substrate by spraying process with inorganic binders of aluminium dihydrogen phosphate, aluminum sol, silica sol and sodium silicate, respectively. The thermal stability of the powder was analyzed by thermogravimetri-differential thermal analyzer. The XRD, ultraviolet-visible-near-infrared spectrophotometer and dual-band IR-2 emissivity tester were used to study the crystalline phase, reflectance and the 3?5 ?m infrared emissivity of powder and coatings, respectively. The thermal shock resistance of the coatings were tested by air cooling. In addition, the effects of the binders on the phase composition，thermal stability and infrared emissivity of the coatings were also investigated. The results showed that Ni ion doping improved the performance of infrared absorption of LaAlO3 coatings, the infrared emissivity as high as 0.94 in the spectral region of 3?5 ?m, which was 161% higher than that of LaAlO3. The coatings had the least impurity phase in case of aluminum sol as binder and at the same time the coatings had the highest infrared emissivity and the best thermal shock resistance. The infrared emissivity of the coatings was as high as 0.95 and 0.93 in the band of 0.76?2.5 and 3?5 ?m respectively. Furthermore, the coatings also had good thermal shock resistance, it’s did not appear significantly peeling failure phenomenon after 50 thermal shocks. The coatings had a significant effect on enhanced radiation heat transfer, and the experimental energy saving rate reached 31.7%. This new type of high emissivity infrared radiation coatings had promising application in the field of thermal energy saving.

Characteristics of dynamic pressure in circulating fluidized bed with internals

Wenqing XU Xuejing HUANG Jun XIE Tingyu ZHU?

Chin. J. Process Eng.. 2018, 18(6): 1267-1275. DOI: 10.12034/j.issn.1009-606X.218116

Asbtract ( )

PDF (1619KB) ( )

References | Related Articles | Metrics

The circulating fluidized reactor is applied widely in desulfurization and denitriding due to high gas?solid contact efficiency. And in order to enhance the effect of mass transfer in solid?gas phase, an internal was installed in the cold circulating fluidized bed (CFB) platform, and the pressure character under different conditions was studied. To investigate the characteristics of pressure fluctuations in circulating fluidized bed, the dynamic pressure of gas solid two-phase flow in circulating fluidized bed riser were systematically measured with quartz sand in it by the dynamic pressure sensors. The results showed that when a complex internal was installed in the CFB, the line of system pressure distribution matches the theory of the pressure balance and presents a shape of "8". The main bed drop includes the inlet pressure drop, the venturi pressure drop, the riser pressure drop and the outlet pressure drop. The venturi pressure drops occupied the major part with a percentage of exceeding 60%. The superficial gas velocity and the particle circulating flow rate affected the main bed pressure drop simultaneously. The inlet pressure drop increased with the increase of the superficial gas velocity, while hardly being affected by the particle circulating flow rate. The venturi pressure drop changed similarly with the main bed pressure drop. The outlet pressure drop increasesd slightly with the increase of the superficial gas velocity, while hardly being affected by the particle circulating flow rate. The power spectrum analysis of the transient pressure of the circulating fluidized bed showed that the pressure fluctuation had a corresponding dominant frequency which had the corresponding size of vibrational energy. The smaller the superficial gas velocity was, the larger the particle circulating flow rate was, and the pressure fluctuation would be bigger. The system pressure drop increased with the increase of the height of the particle in the pipe. And the component could increase the pressure in the circulating fluidized bed and also reduced the non-uniform degree of the pressure while optimizing the flowing field.

Effect of Fe₂O₃ addition on the carbothermic reduction of titanium-bearing blast furnace slag

Kaifei WANG Guohua ZHANG Lu WANG Guozhi ZHOU

Chin. J. Process Eng.. 2018, 18(6): 1276-1282. DOI: 10.12034/j.issn.1009-606X.218120

Asbtract ( )

PDF (7788KB) ( )

References | Related Articles | Metrics

Titanium is a very kind of important and useful metal, which is widely used in the aerospace and chemical industries. By the beneficiation process of Panzhihua Iron and Steel Co., titanomagnetite concentrates and ilmenite concentrates are produced. The titanomagnetite concentrates are widely used as the raw materials for the blast furnace process now, by which most of the iron and vanadium can be reduced into the hot metal. However, almost all of the titanium remain in the slag to form the high titanium bearing slag, which contains about 21wt%?25wt% of TiO2. In the present study, the carbothermic reduction experiments of titanium-bearing blast furnace slag were carried out in argon atmosphere at high temperature. The main subject was to separate the reduction product TiC from the remaining slag considering the small grain size of the produced TiC during the carbothermic reduction process. The influences of adding Fe2O3 on the reaction process were studied by XRD and SEM?EDS. The results showed that during the carbothermic reduction process, it can be known that the changes of standard Gibbs free energy was negative at 1773 K. Adding a small amount of Fe2O3 into the raw material was beneficial for the dispersion of Fe phase in the liquid slag as well as the growth of TiC particle size. When the content of Fe2O3 was increased to 5wt%, TiC which grows attached to the Fe phase will settle down and concentrate at the bottom of the reduction product to achieve the preliminary enrichment of TiC. This finding may contribute to the seperation and extraction of titanium from titanium bearing blast furnace slag in the form of TiC phase.

Preparation and preliminary immunoassay of group C and group W135 meningococcal polysaccharide conjugate vaccines

Miaomiao JIANG Jing ZHANG Xulin LU

Chin. J. Process Eng.. 2018, 18(6): 1283-1292. DOI: 10.12034/j.issn.1009-606X.218122

Asbtract ( )

PDF (639KB) ( )

References | Related Articles | Metrics

Bacterial meningitis is an acute infection of the fluid surrounding the brain and spinal cord that can rapidly lead to death. Capsular polysaccharides are a major virulence factor and form the basis for serogroup designation and protective vaccines. Polysaccharide vaccines have been replaced by glycoconjugate vaccines in order to improve the immunogenicity in infants and young children and inducing memory responses. The conjugates also induced high antibody avidity and prolong the IgG persistence. Moreover, compared with the polysaccharide vaccine, the conjugate vaccine can induce a long-lasting, protective memory T-cell response and elicit a comprehensive humoral and cellular immune response. In this study a new synthetic strategy was used to prepare two kinds of monovalent effective meningococcal vaccines. Group C and group W135 meningococcal capsular polysaccharide (GCMP and GWMP) were aldylated with sodium periodate, followed by the conjugation with tetanus toxoid (TT) via the heterotelechelic crosslinker N-β-maleimidopropionic acid hydrazide, separately. The BALB/c mice were immunized with the two conjugates. The polysaccharide (PS) specific antibody and the TT specific antibody in sera by indirect ELISA, and the avidity of PS specific antibody by thiocyanate elution were determined. The results showed that the mass ratios of PS to protein were 0.4 (GCMP-TT) and 1.0 (GWMP-TT). The PS specific antibody in GCMP-TT group were 3.2, 1.4 and 1.2 times, higher than those in GCMP group in primaty, 1st boost and 2nd boost, which were 2.5, 2.2 and 2.8 in GWMP-TT group, indicating the immune enhancement of both conjugate vaccines. The ratios of IgG2a to IgG1 were much higher in PS-TT groups than that in PS groups, demonstrated the conversion of TI antigen to TD type. The doubled avidity index of PS specific antibody in PS-TT groups showed the effective immune memory induced by the conjugation of carrier proteins to polysaccharides. This study confirmed that this synthetic route can effectively synthesize vaccines with better immunogenicity and improve the immune effect of the meningitis vaccine, and has a good application prospect.

Selective oxidation of n-butane to maleic anhydride catalyzed by Ti/Zr modified VPO

Yajing LI Linlin NAN Bin HE Ruixia LIU Dankui LIAO

Chin. J. Process Eng.. 2018, 18(6): 1293-1301. DOI: 10.12034/j.issn.1009-606X.218135

Asbtract ( )

PDF (1554KB) ( )

References | Related Articles | Metrics

Maleic anhydride (MA) is a kind of important organic chemical raw materials and fine chemical products, has a wide application and strong market demand, while vanadium phosphorus oxide (VPO) catalyst is the most effective catalyst for n-butane selective oxidation to maleic anhydride. However, the catalysts suffer from the shorts of low activity, selectivity. Many efforts had been devoted to improve their catalytic performance. Among them, modification with metal promoters was considered as an effective method. In the present work, Ti/Zr promoter was selected as additive to modify VPO during its preparation with organic medium method. Their catalytic performance for selective oxidation of n-butane to produce maleic anhydride were tested in fixed-bed reactor at 420℃ with gas hourly space velocity of 2000 h?1. The effects of metal element, precursor and additive amount of promoters on the catalytic performance were investigated in details. The change of phase structure, the morphology as well as electronic properties of catalysts were characterized by X-ray diffraction, Raman, SEM, XPS. Compared with VPO catalyst without promoter, the VPO catalysts modified with Ti/Zr promoter effectively improved the catalytic performance for n-butane conversion rate and maleic anhydride selectivity. Especially, for the VPO catalyst promoted by Zr(NO3)4 doping with molar ratio of Zr to V of 1.5%, the conversion rate of n-butane can reached 99.1% and the yield to maleic anhydride was 54.4%. The promoters did not change the phase structure of the catalyst, but promoted the formation of the active phase (VO)2P2O7 and change the morphology of the catalyst, forming smaller size of VPO sheet and correspondingly exposing more active sites, furthermore, the interaction between the promoters and V has great effects on the concentration of P and the valence of V on the surface of VPO catalyst. In addition, the chemical compound formation of promoter elements had an important influence on the performance of VPO catalyst. When Zr(NO3)4 was used as the promoter, the conversion of n-butane was much higher than that with the promoter of ZrO2. Further, the promoter elements also had important influence on the performance of VPO catalyst. Compared with ZrO2, the catalysts modified by TiO2 showed better catalytic performance because Ti can better enter the lattice of catalyst instead of V.

UV-Vis characterization of valence state of vanadium in sodium vanadium fluorophoshpate

Zizheng TONG Junmei ZHAO Xing SHEN Huizhou LIU

Chin. J. Process Eng.. 2018, 18(6): 1302-1306. DOI: 10.12034/j.issn.1009-606X.218137

Asbtract ( )

PDF (496KB) ( )

References | Related Articles | Metrics

Sodium vanadium fluorophosphates, Na3(VO1?xPO4)2F1+2x (0≤x≤1), have obtained widespread attention as cathode materials for sodium ion batteries, because of its electrochemical stability, high working voltage and specific capacity. In Na3(VO1?xPO4)2F1+2x (0≤x≤1), the valence state of vanadium is flexible, it could be +3, +4 or mixed valence of +3 and +4. When x=1, the valence state of vanadium is +3, the formula could be written as Na3(VPO4)2F3. When x=0, the valence state of vanadium is +4, the formula could be written as Na3(VOPO4)2F. When 0<x<1, the valence state of vanadium would be mixed valence between +3 and +4, the compound is solid solution of Na3(VPO4)2F3 and Na3(VOPO4)2F. Valence state of vanadium is directly related to the crystal structure and electrochemical properties of Na3(VO1?xPO4)2F1+2x (0≤x≤1), so characterize valence of vanadium in Na3(VO1?xPO4)2F1+2x (0≤x≤1) precisely is of great significant. Various methods have been used to characterize the valence state of vanadium in Na3(VO1?xPO4)2F1+2x (0≤x≤1), such as X-ray photoelectron spectroscopy, Fourier transform infrared spectrometer, Rietveld X-ray diffraction, 31P nuclear magnetic resonance, 23Na nuclear magnetic resonance, 19F nuclear magnetic resonance and X-ray adsorption near edge structure. However, all those methods need expensive equipment and complicate data processing. To characterize valence state of vanadium in an easier way, a new method to use UV?Vis absorption to characterize the valence of vanadium in Na3(VO1?xPO4)2F1+2x (0≤x≤1) was developed in this work. Crystal parameters obtained from Rietveld XRD had been used to confirm the results obtained by UV?Vis absorption spectra. The results showed that the valence states of Na3(VOPO4)2F, Na3(VO0.5PO4)2F2 and Na3(VPO4)2F3 were +3.993, +3.097 and +3.603, it was credible for UV?Vis absorption spectra to be used to characterize apparent valence of vanadium.

Process simulation and system exergy analysis for dimethyl carbonate production with transesterification

Songsong CHEN Li DONG Junping ZHANG Weiguo CHENG Wei HUA

Chin. J. Process Eng.. 2018, 18(6): 1307-1314. DOI: 10.12034/j.issn.1009-606X.218138

Asbtract ( )

PDF (1259KB) ( )

References | Related Articles | Metrics

As a kind of green solvent and chemical intermediate, dimethyl carbonate (DMC) is an important derivation of the downstream production chains of coal chemical industry, methanol (MeOH) chemical industry and CO2 chemical industry. However, the disadvantages of high energy consumption and complicated operation in the current MeOH-DMC azeotrope separation process have greatly restricted the industrial economic benefits. Concentrating on the problems of MeOH?DMC azeotropic system separation in transesterification, the process simulation and energy integration of three azeotrope separation methods had been completed, including pressure-swing distillation method, ethylene carbonate (EC) extractive distillation method and ethylene glycol (EG) extractive distillation method. And the energy consumption of three methods was compared under the same separation target, which was in the following order: EG extractive distillation method>EC extractive distillation method>pressure-swing distillation method. The operation parameters of three kinds of azeotrope separation process were determined by using sensitivity analysis method. And exergy analysis method was adopted to investigate the exergy loss in the pressure-swing azeotrope separating process which had the lowest energy consumption. The results showed that the internal circulation exergy was 1.55 times of the input total exergy in the DMC production process, and the exergy loss was about 7.9%.

Analysis on thermal stability of molten nitrates at high temperatures

Chongjing HU Ze SUN Long HUANG Haijun ZHANG Xingfu SONG Jianguo YU

Chin. J. Process Eng.. 2018, 18(6): 1315-1322. DOI: 10.12034/j.issn.1009-606X.218143

Asbtract ( )

PDF (698KB) ( )

References | Related Articles | Metrics

As heat transfer fluids and heat storage mediums, the molten nitrates have been widely used in the solar thermal power generation system in latest years, among which Solar salt system (60% NaNO3?40% KNO3, mass ratio) is the most optimized one. However, there still exists lots of problems in large-scale industrial application, for example, the high temperature stability of Solar salt system is not clear enough. Thus this work aims to investigate the thermal stability of Solar salt system under the conditions of thermal storage and constant high temperatures. The thermal decomposition temperature of Solar salt system was detected by thermo-gravimetric (TG). Meanwhile, constant high temperature experiment of NaNO3, KNO3 and Solar salt were studied in an open system at different temperatures. The constant thermal stability values of Solar salt system and the roles of NaNO3 and KNO3 played in its high-temperature instability were obtained. The high temperature instability of Solar salt system was manifested as mass loss, which was mainly caused by thermal decomposition and volatilization of components. The TG result showed that the thermal decomposition temperature of Solar salt system was 590.6℃ in nitrogen atmosphere. The constant high-temperature experiment showed that Solar salt system was unstable above 500℃ in air, and the higher temperature was, the more unstable of it. The degree of instability was NaNO3>Solar salt system>KNO3 under the same temperature. The content of the decomposed product NO2? eventually reached an equilibrium at some time, and the equilibrium content of NO2? increased while equilibrium time of the reaction decreased as the rising of temperature. However, another decomposed product metal oxides was low. Besides, the mass loss of Solar salt caused by thermal decomposition and volatilization was close to 1:1. In the Solar salt system, NaNO3 was the main cause of thermal decomposition, and KNO3 played the role of anti-volatilization.

Simulation of extractive separation process of methyl methacrylate-methanol-H₂O azeotropic system

Junping ZHANG Songsong CHEN Guiyang SHENG Lei WANG Yuanli JIANG Xiaohua GU, Xiangping ZHANG

Chin. J. Process Eng.. 2018, 18(6): 1323-1331. DOI: 10.12034/j.issn.1009-606X.218148

Asbtract ( )

PDF (592KB) ( )

References | Related Articles | Metrics

As one of the important oxygen-containing chemicals, methyl methacrylate (MMA) is widely used in producing organic glass (PMMA), coatings, ACR/MBS and so on. The triple azeotropic systems of MMA?methanol?water are formed in the production process, which resulting in difficulty in product purification. In order to solve the problem on separation of MAA?methanol?water azeotropic system, the separation processes of using a single solvent (water or n-hexane) and bi-solvent (a combination of water and n-hexane) as the extractants were established in this study. The models of extraction processes for single solvent and bi-solvent system were simulated. The ratio of solvent and operating temperature were analyzed and systematically optimized using sensitivity analysis method. It demonstrated that the extraction process using bi-solvent had relatively lower energy consumption compared to those of the single ones, and the energy consumption was reduced by 15.0% (vs. n-hexane) and 34.9% (vs. water), respectively. Meanwhile, the influence of three extraction processes on the environmental impact assessment was quantitatively analyzed using green degree analysis method. The results suggested that bi-solvent process was much more environmental friendly. The green degree of separation process using water, n-hexane and bi-solvent as extractant was ?7.25, ?21.3 and ?6.75 gd, respectively.

Effects of humic acids with different molecular weights on the adsorption behavior of bromide on MIEX resin

Lei DING Yang GAO Yunhan JIA Meiying ZHONG

Chin. J. Process Eng.. 2018, 18(6): 1332-1339. DOI: 10.12034/j.issn.1009-606X.218160

Asbtract ( )

PDF (571KB) ( )

References | Related Articles | Metrics

The effects of humic acid (HA) with different molecular weights on the adsorption behavior of bromide on magnetic ion exchange (MIEX) resin were investigated by static adsorption test. The results showed that four fractions of humic acid with different molecular weights (<1000, 1000?5000, 5000?10000, >10000) decreased the removal efficiency of bromide by magnetic ion exchange resin from 80.05% to 75.39%, 26.32%, 42.67% and 49.03% at pH 7.0, respectively. However, each fraction of humic acid with different molecular weights mentioned above improved the removal rate of bromide by magnetic ion exchange resin at acidic (pH<5.0) or alkaline (pH>9.0) condition and the increase of removal efficiency was the most obvious when the pH was 11.0. The humic acid with molecular weight >10000 shortened the time needed to attain the equilibrium of bromide adsorbed on magnetic ion exchange resin from 60 min to 20 min, and those with molecular weights 1000?5000, and 5000?10000 reduced the adsorption equilibrium time of bromide to 40 min. The process of bromide adsorbed on magnetic ion exchange resin followed the pseudo-second-order kinetic equation, regardless of whether humic acid existed or not. The adsorption equilibrium capacity of bromide on magnetic ion exchange resin was significantly reduced by various molecular weight humic acid components, which shortened sharply of the humic acid with molecular weight >10000. But the adsorption equilibrium model type of bromine on magnetic ion exchange resin was not changed. Both Langmuir isotherm model and Freundlich isotherm models described the equilibrium of bromide adsorbed on magnetic ion exchange resin well. The effects of humic acids with different molecular weights on the removal of bromide by magnetic ion exchange resin is closely related to pH of solution, and various humic acid components accelerated the adsorption process of bromide on magnetic ion exchange resin, but not change the type of adsorption equilibrium and kinetic models.

Preparation of glass fiber reinforced polyamide 6/yttrium hypophosphite composites and their flame retardant properties

Gang TANG Haohao JIANG Lijuan CHEN Hao ZHANG Chunlin LIU Zijian ZHOU

Chin. J. Process Eng.. 2018, 18(6): 1340-1346. DOI: 10.12034/j.issn.1009-606X.218104

Asbtract ( )

PDF (3814KB) ( )

References | Related Articles | Metrics

A novel rare earth hypophosphite—yttrium hypophosphite (YHP) was synthesized by co-precipitation method using yttrium(III) chloride hexahydrate (YCl3?6H2O) and sodium hypophosphite (NaH2PO2) as raw materials, and it was characterized by XRD, FT-IR, SEM and TGA. Furthermore, YHP was used as flame retardant to prepare a series of glass fiber reinforced polyamide 6/yttrium hypophosphite composites (GFPA/YHP) by melting bending method. TG, limiting oxygen index (LOI) test, underwriters laboratories (UL) 94 (UL-94) testing and microscale combustion calorimetry (MCC) were used to investigate the effects of YHP loading on thermal stability, flame retardany and combustion properties of GFPA/YHP composites. The results showed that YHP was prepared, it presented rod-like structures with a size of 20?100 ?m in length and 5?20 ?m in width, and presented high thermal stability with degradation temperature (T5%) of 410℃, maximal mass loss rate temperature (Tmax) of 410℃ and char residue at 750℃ of 90.8wt%. The addition of YHP decreased T5% but increased char residue and thermal stability in high temperature of GFPA/YHP composites. When 20wt% YHP was loaded, GFPA/YHP20 presented T5% of 373℃ with Tmax of 414℃ and char residue at 700℃ of 50.42wt%. YHP could significantly enhance flame retardancy of the composites, GFPA/YHP20 (with 20wt% YHP) reached UL-94 V-1 rating with limiting oxygen index (LOI) of 27.5vol%. YHP could significantly decrease heat release rate (PHRR) and total heat release (THR) of GFPA/YHP composites in combustion process. PHRR and THR values of GFPA/YHP20 were decrease to 327 W/g and 15.8 kJ/g, which were reduced 14.1% and 25.1% compared with GFPA, indicating YHP could effectively reduce fire hazard of GFPA/YHP composites in combustion process.

Table of Content