Table of Content

20 June 2002, Volume 2 Issue 3

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3

Enzymatic Kinetics of Immobilized L-aminoacylase and Its Continuous Resolution of DL-methionine

WANG Shu-hao; LI Xiao-feng; WU Yan-ling; SONG Zheng-xiao; MA Zhong-hai; YUAN Ying-jin

. 2002, 2(3):  0-0. 

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In the first part of the article,a new algorithm for pruning network Dynamic Optimal Brain Damage(DOBD) is introduced. In this part, two cases and an industrial application are worked out to test the new algorithm. It is verified that the algorithm can obtain good generalization through deleting weight parameters with low sensitivities dynamically and get better result than the Marquardt algorithm or the cross-validation method. Although the initial construction of network may be different, the finial number of free weights pruned by the DOBD algorithm is similar and the number is just close to the optimal number of free weights.The algorithm is also helpful to design the optimal structure of network.

Removal of Arsenite and Arsenate from Solid Herb Samples by Supercritical CO2 Extraction with Ion-pairing

GUAN Yan-fen; WANG Tao

. 2002, 2(3):  0-0. 

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The removal of arsenite and arsenate from solid herb sample by ion-pairing supercritical CO2 extraction was explored. As a result of the insolubility of tetrabutylammonium bromide (Bu4NBr) in supercritical CO2, the extraction efficiency of supercritical extraction with non-in-situ retreatment of ion-pairing with Bu4NBr was much better than supercritical extraction with in situ ion-pairing. For the cases of non-in-situ ion-pairing, the extraction efficiency was strongly dependent on the total amount of Bu4NBr. The optimal amount of Bu4NBr was 130.0′10–6 mol/g solid sample under the experimental conditions.

Mechanism of Carbon Nanotube Growth in a Nano-agglomerate Fluidized Bed

LI Zhi-fei; LUO Guo-hua; WEI Fei; WANG Yao

. 2002, 2(3):  0-0. 

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Production of carbon nanotubes (CNTs) by catalytic chemical vapor deposition (CCVD) was studied using a nano-agglomerate fluidized bed with 44 mm inner diameter and 1000 mm height in the temperature range of 550~750oC. Morphology and quality of CNT products were determined by SEM, TEM and TGA. Compared with experimental results in a fixed bed under the same conditions, the present results by a nano-agglomerate fluidized bed showed a strong advantage on both productivity and quality of CNTs. Effect of reaction conditions on the growth of CNTs was also studied. Based on TEM photos of CNTs and on-line conversion data, the mechanism of carbon nanotube growth in the nano-agglomerate fluidized bed was also discussed.

Preparation and Characterization of Nd-Fe-B Alloy-densified Agarose Matrices for Expanded-bed Operation

TONG Xiao-dong; SUN Yan

. 2002, 2(3):  0-0. 

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Novel dense composite matrices have been prepared by coating 4% agarose gel onto Nd–Fe–B alloy particles by a water-in-oil emulsification method, and Nd–Fe–B alloy-densified agarose (NFBA) gels with different size distributions and densities, NFBA–S (50~165 mm, 1.88 g/ml) and NFBA–L (140~300 mm, 2.04 g/ml), were obtained. The expansion characteristics of the expanded bed with new matrices were found in accordance with the Richardson–Zaki equation. It allowed flow rate up to 154 cm/h for the NFBA–S and 660 cm/h for the NFBA–L to reach twofold bed expansion. Liquid-phase dispersion behavior in the expanded bed was examined by measurements of residence time distribution. It is shown that the axial dispersion level decreased with increasing flow rate or settled bed height. Moreover, the beds with the NFBA matrices have smaller axial dispersion level compared with that of Streamline SP. The results indicate that the NFBA gels exhibited promising properties for expanded bed operation.

Experimental Investigation of Pressure Drop Hysteresis in a Cocurrent Gas–Liquid Upflow Packed Bed

XU Hong-bin;MAO Zai-sha

. 2002, 2(3):  0-0. 

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Experiment on reaction of bentonite and calcined bentonite with sodium hydroxide was carried out, and the effects of reaction time and concentration of sodium hydroxide on the leached silicon and aluminium from bentonite were investigated. The dissoluble silicon and aluminium in the product from solid reaction of bentonite and sodium carbonate at different calcining temperatures and calcining time were determined. Chemical analysis and thermogravimetry show that the solid reaction of bentonite and sodium carbonate proceeds intensely at the temperatures close to the melting point of sodium carbonate, and 63.85%(w) of SiO2 and 96.78%(w) of Al2O3 in bentonite can be converted to water-soluble compounds.

The Foam Behavior Parameter in Foaming Process Caused by Reduction of Blast Furnace Dust and Sludge

WU Keng; YAO Ke-hu; CHU Shao-jun; NIU Qiang; DU Chun-rong

. 2002, 2(3):  0-0. 

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A gold leaching process by using in situ oxidation products of added elemental sulfur in Ca(OH)2 solution was investigated. A gold concentrate containing 45 g/t Au was tested and 85%~87% of gold were leached. The leached gold depends mainly on the initial molar ratio of elemental sulfur to the hydroxyl ion, the consumption of oxygen and the reaction temperature. Adding some surfactants, such as lignosulfonic calcium, at lower concentration increased the leached Au but at higher concentration decreased it. Both of thermodynamic analysis and experimental results show that thiosulfate is the major complexing agent for gold in the process.

Roles of Lignin Peroxidase, Manganese Peroxidase and Pellet of Phanerochaete chrysosporium in Decoloration of Dyes

ZHANG Yan-fang; LI Hua-zhong; HUA Zhao-zhe; CHEN Jian

. 2002, 2(3):  0-0. 

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4 cultures containing LiP and MnP, LiP only, MnP only , neither LiP nor MnP were obtained respectively in N-limited submerged culture of Phanerochaete chrysosporium and the roles of LiP, MnP and pellet in decoloration of dyes were investigated. All 4 cultures have considerable decoloration effect on 6 dyes: about 90% decoloration rate for methyl orange, orange I, methylene blue, 80% for congo red, direct blue and 60% for crystal violet. Biodegradation and absorption play main role in the process of decoloration with and without enzymes respectively. The pellet provided H2O2 and veratryl alcohol besides the absorption of dyes, which promoted the degradation of dyes.

Phase Equilibrium of the Quaternary K2SO4–(NH4)2SO4–CO(NH2)2–H2O System at 25oC

ZHANG Yong-jie; CAO Ji-lin; LI Lin; REN Bao-shan

. 2002, 2(3):  0-0. 

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The liquid–liquid equilibrium data for two ternary systems, ethanol–water–KF and ethanol– water–K2CO3, were determined at 25oC. Experiments show that by adding KF or K2CO3 into the ethanol–water system two phases are formed: an ethanol-rich phase with negligible salt and a water-rich phase with negligible ethanol, thus water can be separated out easily. A mathematical calculation of the liquid–liquid equilibrium data was carried out with the Pitzer theory on water activity in the aqueous phase, and with the Wilson or NRTL or UNIQUAC equations for that in the ethanol phase, which is in good agreement with experimental data.

Growth of Pseudomonas delafieldii R-8 and Biodegradation of Dibenzothiophene in Aqueous Solution

LUO Ming-fang; JIANG Cheng-ying; XING Jian-min; GOU Zhong-xuan; LI Shan; LIU Hui-zhou; CHEN Jia-yong

. 2002, 2(3):  0-0. 

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Pseudomonas delafieldii R-8 isolated from coal contaminated soils in our laboratory could metabolize DBT to 2-hydroxybiphenyl via the sulfur-specific pathway. Effects of initial pH, sources of carbon and nitrogen of the culture media were investigated by using DBT as the sole source of sulfur in aqueous phase. It was indicated that this strain grew well in the pH range of 6~9 and the optimal temperature for growth was 30oC. Glycerol was the optimal carbon source and the optimal concentration was 10 g/L. Organic nitrogen sources including yeast extract, bacto-typtone and beef typtone were conducive to the growth of this strain, but repressed the expression of the desulfurization activity of R-8 even in the presence of DBT. Ammonia acetate was the appropriate source of nitrogen at the concentration of 1.6 g/L. Although sodium sulfate, dimethyl sulfoxide, methionine, cysteine and DBT could be used as the sole sources of sulfur respectively, these sulfur-containing compounds except DBT could not induce the expression of the biodegradation activity of R-8.

Evaluation of Contribution of Drilling Additives to the COD of Drilling Wastewater and Their Coagulation Effects

YANG Min; WANG Yan-ming; WANG Dong-sheng; ZHOU Xiang-yu; GAO Ying-xin; JIA Wan-jin

. 2002, 2(3):  0-0. 

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The COD contribution of six drilling mud additives used in the Jidong Oil Field were determined and correlated. The COD contributions were found to be in the following order: sulfonated phenolic resin>NH4-HPAN>collapse preventing agent>silicon stabilization agent>PAC-141>acylonitrile-acrylamide-potassium. The correlations were used for estimation of COD values of 3 samples of wastewater corresponding to different additive formulations, the estimated values agree well with the measured ones when the dilution was considered. It is indicated that the COD was mainly contributed from additives. Results from coagulation experiments of mixture of drilling fluid additives and drilling wastewater indicate that the residual TOC value is larger than the prediction when the Zeta potential of the mixture system is over –50 mV; conversely, the residual TOC value is less than the prediction. The less the Zeta potential is, the less the removal of TOC is. SMP has the highest Zeta potential among the six drilling mud additives, so its TOC removal is the poorest.

Modeling of the Gas–Solid Turbulent Flow in a Riser Reactor

ZHENG Yu; WAN Xiao-tao; WEI Fei; JIN Yong

. 2002, 2(3):  0-0. 

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At the high current density of 7.5~20 A/dm2 for chromium electrowinning, the polarization curves of hydrogen evolution on a chromium electrode at the conditions of 30~55oC and pH=2.1~2.5 were obtained to explore the electrochemical process of hydrogen evolution at high current density. It was found that the potential of hydrogen evolution decreases with the increase of temperature and decrease of pH. The polarization curves are shifted toward more negative when adding (CH3)3NC16H33Br (CTMAB) in the sulfate solution. It is shown that the CTMAB can suppress hydrogen evolution moderately. When electrowinning chromium in the solution with 20 mg/L CTMAB, the current efficiency is increased by 8.1%. A series of data of over-potential on the chromium electrode at different temperatures with pH=2.1 was obtained. All the Tafle plots at different temperatures pass through a common point with the coordinate lgi equal to 1.72 and over-potential to 1.35 V.

Effect of Preparation Methods on the Properties of Zr0.9Ti0.1(Ni,Co,Mn,V)2+a Hydrogen Storage Alloys

ZHANG Guo-fan; WEN Ming-fen; ZHAI Yu-chun; MA Rong-jun; CHEN Lian; TONG Min

. 2002, 2(3):  0-0. 

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Based on the understanding that the cyanobacterial glycogen biosynthesis is a competitive pathway to cyanobacterial PHB biosynthesis, a genetically engineered cyanobacterium was constructed by partially replacing the agp gene encoding the ADP-glucose pyrophosphorylase involved in cyanobacterial glycogen synthesis by an erythromycin resistance cassette. The obtained mutant propagated faster and the final biomass was higher against its wild-type species, which indicated a much higher photosynthetic efficiency in the mutant. No glycogen was detected in the mutant. Under the photoautotrophic condition, the intracellular PHB content was improved to 15% of the dry weight as compared to 3.4% in the wild-type strain.

Preparation of Zeolite NaA Membrane on Rough Porous a-Al2O3 Tube

LIANG Yu-xiu; LU Jin-ming; LI Bang-min; WANG Jin-qu; YIN De-hong

. 2002, 2(3):  0-0. 

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The fermentation conditions of pectinase by Mucor mucedo and its enzymic properties were studied. The composition of fermentation medium was (g/L): wheat bran 50, sunflower calathide powders 30, (NH4)2SO4 30, KH2PO4 2.5, MgSO4×7H2O 0.5, NaNO3 0.2, FeSO4×7H2O 0.01. The pectinase activity can reach 275 U/ml after 3 d shaker culture under the conditions of 240 r/min, 30oC and initial pH 5.7. The optimum temperature and pH for the pectinase activity were 40oC and 5.0 respectively. The pectinase was stable in the pH range from 3.0 to 7.0.

Growth and Specific Desulfurization of a Newly Isolated Strain of Rhodococcus erythropolis

LI Shan; XING Jian-min; GOU Zhong-xuan; LUO Ming-fang; LIU Hui-zhou; CHEN Jia-yong

. 2002, 2(3):  0-0. 

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A newly isolated strain was identified as Rhodococcus erythropolis LSSE8-1, which can specifically remove sulfur from the model compound of dibenzothiophene (DBT) with 2-hydroxydiphenyl as the dead-end metabolic product. The optimal initial pH for growth varies from 6.5 to 7. Glycerol with the concentration of 8 g/L is the appropriate carbon source, and acetic ammonia at 2 g/L is suitable as nitrogen source for cell growth and desulfurization. It was found that R. erythropolis LSSE8-1 grew in the presence of sulfate or sulfur-containing amino acids but showed no desulfurization activity. Dimethylsulfoxide can enhance the cells yield and the activity of desulfurizing enzymes is not inhibited.

Process Engineering and Ecological Industry

JIN Yong; LIU Zheng; LI You-run

. 2002, 2(3):  0-0. 

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In baffled stirred vessels, the rotating impeller generates complex three-dimensional turbulent flow. In this article, the whole flow field in the baffled tank with a Rushton disk turbine was numerically simulated using the improved inner–outer iterative procedure and “snap-shot” method with the k–e turbulence model. As compared with published experimental data, the model prediction agrees well with the experimental data. The improved inner–outer iterative algorithm demands no empirical formula and experimental data, and the approach seems generally applicable for simulating stirred tanks under turbulent conditions.

Investigation of Leaching Arsenic-bearing Sulfide Copper Concentrate by Ferric Bacterium Solution

ZHOU E; LIU Zhong-hua; CHEN Wen; XIE Hai-yun; YUAN Zhang-fu;

. 2002, 2(3):  0-0. 

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Water removal from fermentation broth by applying DC electric field was investigated using yeast as a model system. The effects of the operation conditions including the starting concentration, pH, conductivity and magnitude of electric potential were examined, respectively. The measurement of z-potential of yeast cells indicated the dominating role of the surface charge of yeast cells on water removal efficiency. The present study showed the potential application of this new technique to dewatering the fermentation broth in recovery of extra-cellular product.

Kinetics of Chemically Plating Nickel on the Surface of Hexagonal Boron Nitride Micro-particles

LI Fan; ZHAO Xiao-feng; ZHANG Deng-jun; LI Bao-hou; LUO Shi-min

. 2002, 2(3):  0-0. 

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The fermentation process of Streptomyces coelicolor was studied in a 5 L batch system, and a kinetic model was proposed based on the Logistic and Luedeking-Piret equations for microorganism growth, product formation and substrate consumption. With the evaluated model parameters, the model appears to provide a reasonable description for the fermentation process under various conditions.

Effects of Precursors for Preparing Intermediate Layer on the Performance of Ti/SnO2+Sb2O3/PbO2 Anode

WANG Ya-qiong(王雅琼);TONG Hong-yang(童宏扬);XU Wen-lin(许文林)

. 2002, 2(3):  0-0. 

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principle of electrical power generation is applied to FeCl3 leaching of synthetic PbS in this study. The dual cell technique and Evans diagram were introduced to examine the factors that influenced the electrogenerative leaching, such as composition of PbS electrode, agitation, temperature, FeCl3 and NaCl concentrations. It is confirmed that certain quantity of electrical energy in addition to the leached products can simultaneously acquired in the electrogenerative leaching process. The internal resistance of the electrogenerative leaching system is the key factor to power output and temperature affects the output of electrogenerative leaching. The apparent activation energy is determined as 18.26 kJ/mol for FeCl3 leaching of synthetic PbS. Higher FeCl3 and NaCl concentrations affect the electrogenerative leaching process favorably.