The Chinese Journal of Process Engineering

Simulation of the Dynamic Process of Heat Transfer between High-temperature Emulsion Phase and Immersed Surface

WANG Li;WU Ping

. 2006, 6(3): 339-346.

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A theoretical model of heat transfer between high-temperature emulsion phase and an immersed surface proposed by the authors was used to simulate the dynamic heat transfer between emulsion phase and an immersed surface for 9 kinds of Geldar B type particles. The simulation results show that the nonuniformity in the emulsion phase and the temperature distribution near an immersed surface is significant as the distance to the surface is less than one particle diameter. With the extension of the residence time of emulsion phase on the surface, the efficiency of heat transfer decreases. For the particles used at 950℃ bed temperature, the relative contributions of conductive, radiative and convective heat transfer to the total heat transfer are 85%~45%, 15%~45% and about 10%, respectively. When the particle diameter is less than 0.6 mm, the contribution of convective heat transfer to total heat transfer is small.

Simulation of Liquid Holdups in the Lower Coke Zone of Blast Furnace with a Packed Bed

XIONG Wei;BI Xue-gong;ZHOU Guo-fan

. 2006, 6(3): 347-351.

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Holdup characteristics of liquid in a packed bed were experimentally examined for clarifying the holdup of molten materials in the lower coke zone of a blast furnace. The viscosity, density and surface tension of the liquid, size and shape of particles and liquid velocity were varied in the experiments. The results show that: increasing viscosity, surface tension and reducing density of liquid cause static liquid holdup hs to increase. These factors in order of degree of influence are density, surface tension and viscosity of liquid, and reducing size, shape factor and porosity of packing causes hs to increase. The bigger the static liquid holdup hs, the bigger the total liquid holdup ht when ul increases in all the combinations of liquids and packings, so those factors affecting hs are also the main factors affecting dynamic liquid holdup hd. Correlations for hs, hd without gas flow and for ht in countercurrent gas-liquid two-phase flow were obtained. hs is the determinant of the holdup of molten materials in the absence of gas flow, and the most important factor affecting hs is the size of coke in a blast furnace.

Exit Structure of the Mist Swirl Separators in Acrylonitrile Production Units

WEI Wei-sheng;YANG Yan-wen;XU Jian;FAN Yu;BAO Xiao-jun

. 2006, 6(3): 352-356.

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The mist separator is a key apparatus in the acrylonitrile producing process, which is used to remove sulfuric acid mist from the gas product. High separation efficiency is necessitated to avoid the blockage and corrosion of the downstream facilities. The structure of the exit of the separator is one of the most important factors for increasing the separation efficiency. In the present investigation, 3-D gas flow field of the mist swirl separator was simulated using general CFD code PHOENICS. It was found that the separation efficiency of the mist separator could be improved by increasing the opportunity for liquid droplets to move towards the wall, as well as by decreasing the re-entrainment. The exit structure of mist swirl separator was then optimized experimentally according to the above CFD simulation findings. A new type of exit, double-deck sleeve, was developed and its structure was optimized. The experimental results showed that this structure had higher separation efficiency than other structures. High separation efficiency could be obtained at both low and high gas velocities, indicating better operating flexibility. The industrial application showed that the mist swirl separator with the optimized exit structure had higher separation efficiency than that of the original design.

Removal of Anionic Metal Ions from Wastewater by Hydroxide-type Adsorbents

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. 2006, 6(3): 357-362.

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Generally speaking, anionic metal concentrations in wastewater from industries and mineral processing plants are well above the allowed limits for effluent set by the Ministry of Environment of Japan. Nowadays, the removal of anionic ions has been considered difficult and development of new process is desperately needed. In this paper, we report the development of three hydroxide-type adsorbents, illustrating their adsorption efficiency in removing As, Se, Mo and Sb ions from aqueous solutions. The main finding of this work was that the adsorption behavior was influenced very much by both the pH and the adsorbent concentration. Nevertheless, the newly developed hydroxide-type adsorbents were very effective in reducing the concentration of those anionic ions.

Partition Behavior of Penicillin in Three-liquid-phase Extraction System

TAN Xian-dong;JI Rong-qing;CHANG Zhi-dong

. 2006, 6(3): 363-368.

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Partition behavior of penicillins G and V was studied in a novel three-liquid-phase extraction system, which is composed of butyl acetate (BA), polyethylene glycol (PEG), ammonia sulfate [(NH4)2SO4] and water (H2O). The main components in the top, middle and bottom phases are butyl acetate, polyethylene glycol aqueous solution and ammonia sulfate aqueous solution, respectively. Some parameters such as partition coefficients Di/j and mass fractions Ei of penicillins G and V were determined at the room temperature, respectively. Experimental efforts have been made to investigate the partition behavior of penicillin in the three-liquid-phase extraction system, including initial concentrations of phase-forming components [PEG and (NH4)2SO4], PEG molecular weight, pH, initial concentration of penicillin. The results indicated that penicillins G and V have the similar partition behavior. They preferentially distribute into the middle phase with the increase of initial concentration of phase-forming components and into the top phase with the decrease of pH, while partition coefficient Dm/b is hardly affected by pH value. The variation of PEG molecular weight has little effect on mass fractions of penicillin. The increase of initial concentration of penicillins G and V could lead to the increase of Dt/b, Dm/b and the decrease of Dt/m, while their mass fractions in all phases were almost independent on their initial concentrations.

Microscopic Study on Stability of Emulsion Liquid Membrane and Extraction Efficiency of Cr(VI) from Wastewater

WEN Li-Xiong;ZHAO Min;CHENG Jing;GAO Rui-fa;CHEN Jian-feng

. 2006, 6(3): 369-374.

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Using a capillary video microscopy technique, the stability of TBP-Span80-kerosene emulsion liquid membrane (ELM) system was investigated by preparing a single W1/O/W2 double emulsion globule. The efficiency of ELM for removing Cr(VI) was also studied. Combining these two experiments, the effects of pH, Span80, TBP and NaOH on both the stability and Cr(VI) extraction efficiency were analyzed. It was found that the oil-soluble surfactant was the key factor for the ELM stability and the system stability was enhanced with increasing surfactant concentration. In order to remove Cr(VI) effectively with ELM, the surfactant concentration must be above the minimum concentration required for the stability of ELM. Acidity reduces the stability, but it is required for the removing process, and it is favorable to the oil-water separation after the reaction. Tributyl phosphate (TBP) has no remarkable impact on the stability, however, NaOH in the internal water phase has great effect on both stability and Cr(VI) extraction efficiency. There are optimal values for all these factors to achieve the best Cr(VI) removing performance, and the extraction efficiency of Cr(VI) can exceed 99.3% after a single treatment step.

Synthesis of Novel Chelating Adsorbents for Boron Uptake from Aqueous Solutions

WANG Li-na;QI Tao;ZHANG Yi

. 2006, 6(3): 375-379.

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Two kinds of novel chelating adsorbents have been synthesized to separate boron from aqueous solutions. One is the boron-specific chelating resin, synthesized by the functionalization of macroporous poly (glycidyl methacrylate-co- trimethylolpropane trimethacrylate), with N-methylglucamine. The other is the organic-inorganic hybrid mesoporous SBA-15 with polyol functional groups, prepared by a two-step post-grafting method. The resin can adsorb boron in almost all pH range, and its maximum uptake capacity reaches 1.15 mmol/g. The present study of the polyol-functionalized SBA-15 shows that the post-grafting is successful and the resulting adsorbent has the uptake capacity of 0.63 mmol/g.

Technology and Mechanism for Extracting Berberine from Rhizoma coptidis by Two Steps of Releasing and Inner Ebullitio

WEI Teng-you;ZHAO Zhong-xing;TONG Zhang-fa

. 2006, 6(3): 380-383.

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A two-step method of releasing and inner ebullition was used to intensify the process of extracting berberine in the plant of Rhizoma coptidis. In this method, a little lower boiling point release-solvent was first used to saturate the plant so that the activated component inside the plant could be released adequately, and then the solvent in which temperature was higher than the lower boiling point was added rapidly, as a result, the release-solvent inside the plant was heated to boiling and the mass transfer was intensified. The experimental results of extracting berberine from Rhizoma coptidis showed that the two steps of extraction only needed 6 min, the concentration of berberine in the extract was 53.5% and the granule sizes between 160 and 400 mm did not take effect on the extraction. Compared with the traditional extraction methods, the two-step extraction of Rhizoma coptidis is not only more advantageous, but also more easily performed. It is expected to have a promising future in application.

A Surfactant-enhanced Oxidation-Extraction Process for Desulfurization of Oils

HUANG Dan;WANG Yu-jun;LUO Guang-sheng

. 2006, 6(3): 384-387.

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The desulfurization of oils using oxidation-extraction process does not need expensive equipment and the process is short. To solve the problems that the oxidation reaction rate is low and the quantity of oxidant is large, a new method is proposed to improve the reaction and mass transfer performance by adding a surfactant at a little amount into the reaction systems. A model system of dibenzothiophene DBT/octane, and oil products from a petrochemical company were taken as the working system respectively, with hydrogen peroxide as oxidant, phosphotungstic acid as oxidation catalyst, and acetonitrile/water azeotropic mixture as extractant. For the model system, the reaction time decreased from 24 h to 7 h at 50℃ by adding the surfactant of hexadecyltrimethyl ammonium bromide (CTAB) into the reaction systems, and the sulfur content was detected to be below 10′10-6 after only oxidation process. For light oils and diesel oils, the H2O2:oil volume ratio in the oxidation reaction could decrease from 1:1 to 1:25. The quantity of oxidant H2O2 decreased significantly, and the desulfurization rate after single-stage oxidation-extraction was above 50%, which was much higher than that of multi-stage extractions without oxidation.

Theoretical Study on Sulfur Dioxide Absorption with Citrate Solution

XUE Juan-qin;HONG Tao;WANG Zhao-qi;LI Lin-bo

. 2006, 6(3): 388-391.

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The citrate absorption of SO2 is currently one of the most successful and economic methods to harness sulfur dioxide pollution. In order to theoretically elucidate the mechanism of SO2 absorption by citrate solution and provide theoretical instruction for experiments and industrial process, the theory of multi-buffer solution, combined with computer numerical calculation methods, was applied to study the distribution parameters of the components of the citrate solution in the process of SO2 absorption and the following results were obtained: (1) HCi2- and H2Ci- in the citrate solution played the dominant role in the absorption and desorption processes; (2) Through the calculation for the buffer capacity of citrate solution, it was found that the pH of the absorption and desorption solution should be in the range of 2~8, while at pH=4.5 the buffer capacity reached its maximum. Some valuable parameters were obtained, which are instructive to the ensuing experiments and industrial design.

Simulation and Extraction Experiment Study of DEM Condensation and Ethanol Recovery with Composite Extraction Tower

GU Zheng-gui;LIN Jun;SU Fu;WANG Qiong

. 2006, 6(3): 392-395.

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In this work the technological process of extractive separation with composite extraction tower was designed for the DEM-ethanol-water system. Ethylene glycol and water were selected as solvents of extraction separation, the separation results of extraction were simulated by triangle matrix, and at the same time tested. The results show that the purity of DEM at the top of extraction tower reaches 99.61%, the conversion rate of DEM reaches 99%, when the tower plate number is 35, and the ratio of water, ethanol and DEM in the solution is 1:1:1, the aqueous solution containing solvent and ethanol is treated by regenerative tower, 95% ethanol is obtained at the tower bottom, other materials can be used by cycling. The results can be provided as basis for further pilot test.

Experimental Study of Plasma Under-liquid Electrolysis in Hydrogen Generation

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. 2006, 6(3): 396-401.

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The application and characteristics of relatively big volume plasma produced with cathodic glow discharges taking place across a gaseous envelope over the cathode which was dipped into electrolyte in hydrogen generation were studied. A critical investigation of the influence of methanol concentration and voltage across the circuit on the composition and power consumption per cubic meter of cathode liberating gas was carried out. The course of plasma under-liquid electrolysis has the typical characteristics of glow discharge electrolysis. The cathode liberating gas was in substantial excess of the Faraday law value. When the voltage across the circuit was equal to 550 V, the volume of cathodic gas with sodium carbonate solution was equal to 16.97 times the Faraday law value. The study showed that methanol molecules are more active than water molecules. The methanol molecules were decomposed at the plasma-catholyte interface by the radicals coming out the plasma mantle. Energy consumption per cubic meter of cathodic gases (WV) decreased while methanol concentration of the electrolytes increased. When methanol concentration equaled 5% (j), WV was 10.381′103 kJ/m3, less than the corresponding theoretic value of conventional water electrolysis method. The cathodic liberating gas was a mixture of hydrogen, carbon dioxide and carbon monoxide with over 95% hydrogen, if methanol concentration was more than 15% (j). The present research work revealed an innovative application of glow discharge and a new highly efficient hydrogen generation method, which depleted less resource and energy than normal electrolysis and is environmentally friendly.

Function of Surfactants in Preparation of White Carbon Black Powder with Carbonization Method

HE Kai;CHEN Hong-gang

. 2006, 6(3): 402-407.

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White carbon black was prepared from limekiln gas and water glass by carbonization method with addition of the surfactants as modifiers such as polyethylene glycol (PEG6000), neopelex (SDBS) and carboxymethylcellulose which were used to modify the prepared product by organic wet method. Silicon-alcohol groups as surfactant of white carbon black are taken by organic groups to advance the affinity to polymer colloidal particles and the reactivity. The priority order of product characteristics (yield of white carbon black, specific surface area, sorption rate of DBP) in single matching of the modifiers is polyethylene glycol (PEG6000) > carboxymethylcellulose > neopelex (SDBS). The priority order of product characteristics in multi-matching of the modifiers is polyethylene glycol (PEG6000) > multi-modifiers > neopelex (SDBS). The product grain size distribution was examined with scanning electron microscope, and infra-red spectrogram in the single matching and multi-matching of the surface modifiers. The experimental results can provide basic data and technical guidance for preparing the white carbon black of surface with excellent features.

Construction and Preliminary Studies on the Direct Microbial Fuel Cell

LIAN Jing;FENG Ya-li;LI Hao-ran;LIU Zhi-dan;ZHONG liang

. 2006, 6(3): 408-412.

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The mediators added in indirect microbial fuel cells are often toxic, unstable and costly. Direct microbial fuel cells do not need mediators during oxidation of carbohydrate or organic acids, overcoming the above problems, so it can be used in bioremediation and treatment of waste water. In the present work, Geobacter metallireducens, a dissimilatory ferric reducing microorganism that can use Fe(OH)3 as the electron acceptor, was used to construct the direct microbial fuel cell. Geobacter metallireducens was inoculated into chambers in which a graphite electrode served as the sole electron acceptor and acetate was the electron donor. Electricity production and mechanism were preliminarily studied. The direct microbial fuel cell was successfully constructed. It was proved that microbial electricity production was mainly due to the cells attached to the electrode. Electrode-attached cells completely oxidized acetate to the levels below detection limit (<10 mmol/L). The electron recovery was 80%, and current density was up to 704.4 mA/m2.

A Two-step Sulfuric Acid Leaching Process of Ti-bearing Blast Furnace Slag

YAN Fang;LI Chun;LIANG Bin

. 2006, 6(3): 413-417.

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The leaching behavior of water-quenched Ti-bearing blast furnace slag in sulfuric acid was investigated. The leaching process proceeded fast in the initial period, as shown by the dissolution results of aluminum and magnesium compounds, and part of amorphous titanium compounds. The leaching reaction was slowed down in the last period due to the formation of insoluble layer over the un-reacted calcium titanate particles. A two-step leaching process was designed, in which the slag was pre-leached with a 20% sulfuric acid solution. The pre-leaching could dissolute most of aluminum, about 64% of magnesium and 46% of titanium. The residue of pre-leaching was further leached with the help of mechanical milling. The two-step leaching operation resulted in a total Ti leaching rate over 94%.

Copper Extraction from the Sacchrin-containing Acid Wastewater and Comprehensive Treatment of Esterification Wastewater

CUI Yu-min;ZHANG Ying;SU Ling-hao

. 2006, 6(3): 418-422.

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Copper and polymerized ferric sulphate were prepared by using scrap iron coils to react with acid wastewater containing copper ion. Esterification wastewater was treated by using polymerized ferric sulphate as flocculant. The results showed that 8.5 kg of copper powder and 230 kg of polymerized ferric sulphate containing Fe3+ 158~160 g/L were obtained from 1 t of acid wastewater containing copper ion, and the removal rates of H2SO4 and Cu2+ in the acid wastewater could gain 83.5% and 85.0%, respectively. Under optimum conditions, the rem

Partial Oxidation of tert-Butanol to Methacrolein on Mo-Bi-Co-Fe-based Complex Catalyst

Pang Hai-jian;LI Zeng-xi;WANG lei;WANG Zheng-ping;CHENG Wei-guo;ZHANG Suo-jiang

. 2006, 6(3): 423-426.

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The catalyst performance for the partial oxidation of tert-butanol to methacrolein was systematically investigated in a fix-bed reactor. The results indicated that the reaction conditions, such as reaction temperature, reactant ratio and space velocity, affected the performance of the catalyst obviously. The most appropriate reaction conditions are temperature 380℃, O2:IB=3 (molar ratio) and space velocity 1800 h-1. During 1500 h continuous operation test the catalyst showed good stability under the above conditions, the conversion rate of tert-butanol maintained in 83%~87% and the selectivity of methacrolein was about 73%.

Effect of Mechanical Activation on the Transparency of Cassava Starch Paste

HUANG Zu-qiang;HU Hua-yu;TONG Zhang-fa;QIN Xue-jiang;LI Xuan-hai

. 2006, 6(3): 427-430.

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Cassava starch was mechanically activated by a stirring-type ball mill, the effect of mechanical activation on the transparency of cassava starch paste and the variation of the transparency with different mechanical activation times and paste concentrations in the process of storage were investigated respectively. Moreover, the variation of cassava starch crystalline structure in the process with mechanical activation was studied by employing an X-ray diffractometer. The results indicated that the transparency increased with increasing of mechanical activation time. The increased transparency is due to that the crystalline structure of cassava starch could be destroyed by mechanical activation and the crystallinity decreased from polycrystalline to amorphous state. The main factor of transparency change was the retrogradation of starch paste during storage (storage temperature 4℃), it was proved to be in favor of the retrogradation of starch paste, and the transparency decreased abruptly when mechanical activation time was 2 h, however, once above 3 h, cassava starch would be overly degraded and the transparency decreased slowly. It was also found that the extent of transparency change was related to paste concentration during storage of mechanical activated starch paste, when starch paste concentration was about 10 g/L, retrogradation would be difficult, but the retrogradation was enhanced and the transparency decreased abruptly at the paste concentration up to 50 g/L.

Behavior of SiO2 during Leaching Process of Alumina Sinter

LI Xiao-bin;XU Hua-jun;LIU Gu-hua;PENG Zhi-hong;ZHOU Qiu-sheng;LIU Yun-feng

. 2006, 6(3): 431-434.

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Some important secondary reactions during alumina sinter leaching have been analyzed thermodynamically, and the behavior of SiO2 in the process also investigated. The results show that 2CaO×SiO2 can exist much more stably in caustic solution than in soda solution and sodium aluminate solution. Only the reaction of 2CaO×SiO2 with Na2CO3 can cause the concentration of SiO2 to rise with increasing leaching temperature. NaAl(OH)4 and Na2CO3 play a much more important role than NaOH in the secondary reactions. With the increasing of free Na2Ok concentration, the concentration of SiO2 decreases gradually. Moreover, the effect of Na2CO3 on dissolution of hydrogarnet in sodium aluminate solution is less than that in soda solution.

Analysis on Availability of the Carbon Element in Alcohol Production

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. 2006, 6(3): 435-438.

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According to the concept of circular economy, the mass integration of alcohol production was investigated though the analysis of the carbon element contained in raw material cassava. Through the mass integration, the distillage wastewater turned into carbon resource and produced a great deal of by-product biogas while its chemical oxygen demand (COD) was reduced from 50000 mg/L to not more than 300 mg/L, the local secondary effluent standards, and other by-products such as CO2 (liquidized) and fusel oil were recovered. In the way, the consumption of raw material was only 2.2 tons cassava to produce 1 ton alcohol (96%, j) in the case study, much lower than the average level 2.92 t/t in China. The carbon element balance for production of alcohol was made through testing the concentrations of the carbon element of all mass flows. The results showed that the mass integration helped the availability of the carbon element increased from 44.74% to 64.75%.

Nutritional Storage Ability of Four Harmful Algae from the East China Sea

LU Song-hui;LI Ying

. 2006, 6(3): 439-444.

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Four species of representative harmful algae from the East China Sea, Skeletonema costatum, Pseudo-nitzschia pungens, Prorocentrum donghaiense and Alexandrium catenella, were choosen as the target species. The nutritional storage ability of algal cells for nitrogen and phosphorus and the growth potential of four species were studied and contrasted. The results showed that the luxury coefficients of nitrogen RN (41.5 and 42.4) and phosphorus RP (4.3 and 10.7) of P. donghaiense and A. catenella were higher than those of RN (2.6 and 6.0) and RP (2.5 and 1.2) of S. costatum and P. pungens. The differences in the ecological strategy among the four species resulted in the successional spring blooming of dinoflagellates and diatoms in the East China Sea. The growth potentials of storage nitrogen tN (5.32 and 6.81 d) and storage phosphorus tP (2.08 and 4.31 d) of P. donghaiense and A. catenella were higher than those of tN (0.56 and 1.24 d) and tP (0.53 and 0.13 d) of S. costatum and P. pungens. The higher growth potential and k-strategistis of P. donghaiense and A. catenella are very important in co-occurring and long-lasting spring blooming in the East China Sea.

Optimization of Fermentation Conditions on Sisomicin Biosynthesis

CHEN Jian-feng;CHEN Hao;ZHANG Yuan-xing;GUO Yang-hao;MENG Chun;SHI Xian-ai

. 2006, 6(3): 445-449.

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The effects of cobaltous chloride, methionine, phosphate and fermentable sugar on sisomicin biosynthesis in a batch fermentation process were investigated. Fermentation conditions of sisomicin biosynthesis in a batch fermentation process were optimized. It was found that the supplementation with some components in medium was significant to sisomicin production. Methylation of precursor gentamicin A in sisomicin biosynthesis was stimulated by 6~10 mg/L cobaltous chloride or 1.0~2.0 g/L methionine. The best time of methionine supplementation was in the pre-middle stage of sisomicin biosynthesis. High phosphate concentration would result in high pyruvic acid concentration and amylase activity, and low alkaline phosphatase activity and sisomicin concentration. It is beneficial to sisomicin biosynthesis that the phosphate concentration is controlled under 3.14 mmol/L in cell growth phase and below 0.10 mmol/L in sisomicin biosynthesis phase. Compared with that in the batch fermentation, while fermentable sugar was controlled in 8.5~11.5 g/L, either at constant or varying maltose feeding rate or at constant starch hydrolysate feeding rate, the ferment level of sisomicin in the fed-batch fermentations was distinctly increased.

Control of Browning in Cell Subculture of Cistanche deserticola

LI Juan;LI Chun;QIU Zhu-yu;SHEN Hui-hui;LIU Hui-yin

. 2006, 6(3): 450-453.

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Browning forms easily during cell culture of Cistanche deserticola. By comparing the content of phenol, browning degree and activity of polyphenol oxidase (PPO) between browning and unbrowning cells, enzymatic action of PPO was considered as the main factor of browning. The optimum pH of PPO is from 5.8 to 6.0 by determining the activity of PPO with pH from 2.0 to 8.0. The effects of inhibitors, including vitamin C (Vc), citric acid and sodium sulfite, on the activity of PPO of Cistanche deserticola were investigated at the optimum pH. These inhibitors all can restrain the activity of PPO, Vc can restrain prominently the activity of PPO, increasing its concentration. When the concentration of Vc reached 0.6 mg/L, the activity of PPO decreased to 5.1% of the optimum activity of PPO. Then the medium containing activated carbon and VC for cell subculture was obtained. The optimal B5 medium including 1.0 g/L activated carbon, 3.0 mg/L Vc, 1.0 mg/L IAA and 4.0 mg/L KT can effectively restrain browning of cells. The browning degree of the cells in the optimal B5 medium decreased to 21%. The cells of Cistanche deserticola grew better in the optimal medium and the maximum relative increment of cell growth (dry weight) was 25.4%.

Separation of 1,3-Propanediol from Fermentative Broth by Combination of Ultrafiltration and Alcohol Precipitation

ZHANG Dai-jia;GAO Su-jun;SUN Ya-qin;XIU Zhi-long

. 2006, 6(3): 454-457.

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The separation of 1,3-propanediol from fermentative broth by a combination of ultrafiltration and alcohol precipitation was well investigated. The broth was firstly filtered by ultrafiltration, and 99% of cell, 89.4% of protein, and 69% of nucleic acid could be removed. The obtained broth was further condensed by vacuum distillation and alcohol was added. Then, the macromolecular impurities, such as nucleic acids, polysaccharides and proteins, as well as small molecules (inorganic and organic salts) precipitated. The optimal volume ratio of alcohol added to condensed fermentation broth was determined to be 2:1. As a result, protein, nucleic acid and conductivity decreased by 97.4%, 89.7%, and 95.8% respectively. The influences of pH and water content in condensed broth on alcohol precipitation were also investigated. It can be found that the lower the water content, the more the impurity removed. 90% of impurities were removed when water content was 1%. The pH value of broth had great effect on precipitation, most impurity precipitated under strong acid or alkaline condition.

Regulation of Stereochemical Composition of Poly-g-glutamic Acid in Bacillus subtilis NX-2

WU Qun;XU Hong;XU Lin

. 2006, 6(3): 458-461.

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The stereochemical composition of poly-g-glutamic acid (g-PGA) and glutamate racemase activity in Bacillus subtilis NX-2 were modulated by variation of Mn2+ concentration in the culture medium. As the concentration of Mn2+ varied from 0 to 0.09 g/L, the proportion of D-glutamic acid increased gradually from 18% to 77%, which was different from other g-PGA producers in species of B. subtilis ever reported, and the glutamate racemase activity increased from 0.200 to 0.441 U/mg, while the D-amino acid aminotransferase changed a little, suggesting that glutamate racemase was involved in D-glutamic acid supply and different Mn2+ concentrations could change stereochemical composition of g-PGA by regulating glutamate racemase activity. When Mn2+ concentration was 0.03 g/L, the proportion of D-glutamic acid remained constant throughout cultivation, approximately 75%, this was different from B. subtilis F-2-01, the stereochemical composition of g-PGA produced by the microorganism changed during cultivation. Key words: poly-g-glutamic acid; stereochemical composition; glutamate racemase; Mn2+

Biodegradation of Leather Waste by Enzymatic Treatment

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. 2006, 6(3): 462-465.

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The treatment of shavings, trimmings and splits of leather waste from tanneries has a potential to generate value-added products. In this study enzymatic treatment of leather waste was performed. This method utilizes alkaline protease produced by Bacillus subtilis in our laboratory by submerged fermentation. Optimum conditions of pH, time duration, temperature and concentration of enzyme were determined for maximum degradation of leather waste. The amount of degradation was measured by the release of amino acid hydroxyproline. Amino acid composition in the hydrolysate obtained by the enzyme hydrolysis was determined. This relative simple biotreatment of leather waste may provide a practical and economical solution.

Pyrolysis Process from Precursor to Prepare a BCN Compound

YANG Jian;QIU Tai;SHEN Chun-ying

. 2006, 6(3): 466-471.

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C3N6H6(H3BO3)2 was synthesized with C3N6H6 and H3BO3 as raw materials in aqueous solution, which was then used as the precursor for preparation of a BCN compound by pyrolysis in flowing N2 atmosphere. The pyrolysis process was investigated by means of TG-DSC-MS coupling technique, FT-IR, XRD and SEM. The results indicate that the precursor C3N6H6(H3BO3)2 is a 3D supramolecular compound which is constructed by different hydrogen-bonding interactions between C3N6H6 and H3BO3 molecules. With the increase of pyrolysis temperature, C3N6H6 and H3BO3 unit in the precursor is gradually decomposed, accompanied by the release of H2O, NH3, CO2, and NO2 gases. After 1000℃, the pyrolysis process has completed and B-N, B-C, and C-N chemical bonds established in the products, which means the formation of turbostratic-structure BCN compounds with atomic-level hybrid of B, C, and N elements. A novel nitrogen-rich BCN compound with an approximate composition of B3CN3 was obtained from the pyrolysis at 1900℃. The B3CN3 compound shows bar-like or fibrous morphology similar to the precursor, but there is an obvious reduction in its crystal size compared with the precursor.

Synthesis of Nitrogen-doped Titania by Solvothermal Reactions in Alcohols

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. 2006, 6(3): 472-476.

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Nitrogen-doped titania nanoparticles were obtained by the homogeneous precipitation in hexamethylenetetramine- titanium trichloride-alcohol aqueous solutions at 90℃ followed by heating at 190℃. Anatase, rutile and brookite were obtained, where the crystallite size, specific surface area and color greatly changed as 5~50 nm, 20~200 m2/g and light gray to yellow, depending on the solvent and pH. The products after calcination were yellow, indicating doping with nitrogen ion. All colored titania showed photocatalytic activity under visible light irradiation for the oxidative decomposition of nitrogen monoxide in air. Especially, the nanoparticles of anatase type nitrogen-doped titania obtained using methanol aqueous solution showed excellent photocatalytic activity.

Mechanochemical Synthesis of Visible-light Induced Photocatalyst with Nitrogen and Carbon Doping

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. 2006, 6(3): 477-481.

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Nitrogen and/or carbon doped titania photocatalysts were prepared by a novel mechanochemical method. The prepared powders possessed two absorption edges around 400 and 540 nm wavelengths and showed excellent photocatalytic ability for nitrogen monoxide oxidation under visible light irradiation. Under the irradiation of visible light of wavelength >510 nm, 37% of nitrogen monoxide could be continuously removed by the carbon and nitrogen co-doped titania prepared by planetary ball milling of P-25 titania-10% hexamethylenetetramine mixture followed by calcination in air at 400?C.

Preparation and Characterization of Three-dimensional Photocatalyst-TiO2 Particulate Film Immobilized on Activated Carbon Fibers

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. 2006, 6(3): 482-487.

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A novel three-dimensional photocatalyst, TiO2 particulate film immobilized on activated carbon fibers (TiO2/ACFs), was prepared by liquid phase deposition. The photocatalyst was characterized by SEM, XRD, BET surface area and photodegradation of methylene blue solution. TiO2 particulate film, with a thickness of nearly 200 nm and grain sizes of 30~50 nm, was deposited on almost each carbon fiber. The inner space between adjacent fibers remained as unmodified ACFs, therefore, both UV illumination and polluted solutions were allowed to pass through the felt-form photocatalyst to form a three-dimensional environment for photocatalytic reactions. With BET surface areas of 400~600 m2/g, the TiO2/ACFs exhibited an enhanced adsorption of pollutants for photocatalysis. Comparative degradations indicated that photocatalytic activity of the TiO2/ACFs was slightly higher than that of Degussa P-25 TiO2. Two special properties, the three-dimensional structure and combined effects of ACFs' adsorption and titania's photodegradation, made contribution to high photocatalytic activity. Additionally, the TiO2/ACFs exhibited high stability and potentially application for practical usage.

Preparation of Isolated Single-walled Carbon Nanotubes with High Hydrogen Storage Capacity

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. 2006, 6(3): 487-490.

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Isolated single-walled carbon nanotubes with high proportion of opening tips were synthesized by using alcohol as carbon source. The mechanism of cutting action of oxygen was proposed to explain its growth. Compared with carbon nanotubes synthesized with benzene as carbon source, their specific surface area was heightened by approximately 2.2 times (from 200.5 to 648 m2/g) and the hydrogen storage capacity was increased by approximately 6.5 times (from 0.95 to 7.17%, w) which had exceeded DOE energy standard of vehicular hydrogen storage.

Microstructure and Mechanical Properties of Mg-Li-Mn Alloy

LI Hong-bin;JI Hai-bin;YAO Guang-chun;LIU Yi-han;GUO Zhi-qiang;LIU Zhen-gang

. 2006, 6(3): 491-494.

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Mg-Li-Mn alloy is produced and rolled to thin sheet at room temperature in the present work. Adding Mn from 0.5% to 2% to the alloy can refine the crystalline grains. The resulting microstructure of alloy consists of α-Mg, β-Li and new Mn-rich phase. Uniaxial tension tests are carried out at room temperature. The prepared sheets have good tensile strengthen and yield strength. They can be raised by 16% and 17%, respectively, with Mn content increasing from 1% to 2%. It is observed that the existence of Mn on the grain boundary makes the grains refined, and hard particles of MgMn2O4 and Li0.5MnO2 forming in the alloy improves its mechanical properties.

Effect of MnO2 Doping on Properties of Nickel Ferrite as Inert Anode

XI Jin-hui;YAO Guang-chun;LIU Yi-han;ZHANG Xiao-ming

. 2006, 6(3): 495-498.

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In order to improve the properties of nickel ferrite ceramic as inert anode in aluminium electrolysis, MnO2 as additive was doped in NiFe2O4 spinel. The nickel ferrite ceramic with MnO2 was made by solid-phase reaction at 1200℃ for 6 h. XRD analysis showed that when MnO2 was added, no new phase existed, and MnO2 and NiFe2O4 formed solid solution; Mn4+ replaced part of Fe3+ and the resulting sample still had the structure of NiFe2O4 spinel. The effect of MnO2 addition on the density, conductivity, thermal shock resistance and bending strength of the samples was also studied. The results showed that Mn4+ replacing part of Fe3+ caused the crystal lattice of NiFe2O4 spinel to become aberrated, which could promote sintering and improved the density. Because Mn4+ replaced part of Fe3+ and produced conduction electrons, the conductivity of the sample was improved; thermal shock resistance and bending strength were also promoted.

Effect of Crystallization Temperature on Structure and Morphology of Mesoporous SBA-15

ZHOU Li-hui;ZHANG Li-zhong;LIU Hong-lai

. 2006, 6(3): 499-502.

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Highly ordered hexagonal mesoporous SBA-15 with different pore sizes and BET surface areas was prepared under different crystallization temperatures, using nonionic triblock P123 as template. By means of XRD, SEM, N2 adsorption-desorption and TEM, the effects of crystallization temperature on morphology, surface area and pore size of SBA-15 were investigated. The results indicate that the best crystallization temperature is about 120℃. With increasing of crystallization temperature, the pore size of SBA-15 is increased and BET surface area decreased. When the crystallization temperature is 140℃ or higher, SEM images reveal that the morphology of SBA-15 is changed from "wheat-like" agglomerate particles to "banana-like" short rods. These results are discussed further in terms of the synthesis mechanism of SBA-15 and structure characteristics of P123 surfactant.

Swelling and Mechanical Behavior of Poly(vinyl alcohol)/Bentonite Hybrid Hydrogels

TONG Xin;ZHANG Zhen-fang;LU Yan-cheng;ZHENG Jing-jing

. 2006, 6(3): 503-506.

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Bentonite was added into PVA hydrogels to modify the mechanical properties. A series of PVA/bentonite hybrid hydrogels were prepared by freezing/thawing method. For comparison, the PVA hydrogels by different numbers of cycles and with different loadings of bentonite were prepared. X-ray diffraction results show that the exfoliated structure exists in the hybrid hydrogels. For the PVA/bentonite (2.0%, w) hybrid hydrogel by 5 cycles, compared with the pure PVA hydrogels by 5 cycles (PVA5), the tensile modulus, tensile strength and strain at break are increased by 44.0%, 74.2% and 25.2%. Its swelling behavior is similar to that of PVA5. The tensile strength and strain at break of PVA/bentonite (0.5%, w) hydrogel by 5 cycles are higher than those of PVA5. Its final swelling ratio at 400 min is the biggest in all specimens.

Clean Processing and Utilization of Coal Energy

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. 2006, 6(3): 507-511.

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The dominant status of coal on the energy production and consumption structure of China will not be changed in the middle period of this century. To realize highly efficient utilization of coal, low pollution and low cost are great and impendent tasks. These difficult problems can be almost resolved through establishing large-scale pithead power stations using two-stage highly efficient dry coal-cleaning system before coal burning, which is a highly efficient, clean and economical strategy considering the current energy and environmental status of China. All these will be discussed in detail in this paper.

Microrganism Metabolic Engineering in Lactic Acid Production

WANG Hai-yan;LIU Ming;WANG Hua-jun;CAO Zhu-an

. 2006, 6(3): 512-516.

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Metabolic engineering can regulate the metabolic networks of the microbial cells. It plays an important role in selecting microorganisms and optimizing the process to enhance metabolites production. The progress of the metabolic engineering research in lactic acid production was reviewed. Metabolic pathways in homo-fermentation and hetero-fermentation for lactic acid production were compared. The metabolic model of lactic acid bacteria, the application of lactate dehydrogenase and the production of lactic acid with Rhizopus oryzae fermentation were summarized. The gene regulatory knockout of ethanol metabolic pathway for improving the lactic acid production was introduced. The influences of bioinformatics and stress response on the metabolism of lactic acid were discussed. And the trends in microbial production of lactic acid were also predicted.

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