Papers by Author: Jian Kang Wen

Abstract: An integrated sulfate reducing process was used to treat Acid Mine Drainage with high concentrations of Cu2+, Fe and SO42-. The water treatment system integrated a sulfidogenic UASB bioreactor with a precipitation reactor which was used to recover copper. Sodium lactate was used as energy source. The effective volume of the UASB reactor was 2 L and the hydraulic retention time was 12.57h. In the sulphate removal reactor, sulphate was removed from 21160 to 195 mg/L with a rate of 4427.8 mg/L/d. Cu2+ and Fe was removed by biologically generated S2- and OH- from 360 and 6520 to 0.049 mg/L and less than 10 mg/L respectively. The average COD, copper and iron removal rate was 2523.2, 15.21 and 274.98 mg/L/d separately. The effluent pH reached 6.0-7.0. The results showed potential usage of this bioreactor in treating Acid Mine Drainage.

Abstract: Based on the bioleaching mechanism and electrochemical studies of metal sulfides, the dissolution rate of secondary copper sulfides and pyrite are controlled by redox potentials. Experiment on the bioleaching of the secondary copper sulfides under constant potential by sparging with nitrogen gas demonstrated, by analyzing Cu and Fe content of the bioleaching solution and residues, the pyrite and secondary cooper sulfides dissolution rates have large difference in various redox potential. The pyrite and secondary cooper sulfides have good selection when the redox potential controlled between 700mV and 760mV, we can realize the secondary copper sulfides bioleaching process be controlled, then supply theoretical guide for the iron-acid balance during copper bioleaching process.

Abstract: The distribution and diversity of acidophilic microbe at the ore surface of Zijinshan commercial low-grade copper bioleaching heap operated at pH 0.8 were investigated. Samples taken from -1m, -2 m, -3m from the top of heap surface were investigated by 16S rRNA gene clone library. Phylogenetic analyses of 16S rRNA fragments revealed that the retrieved bacterial sequences mainly related to genus Acidithiobacillus (64.6%), genus Leptospirillum (27.3%), genus Sulfobacillus (3.1%) and genus Ferrimicrobium(1.6%). For archaea, only Ferroplasma acidiphilum was detected. Bacterial diversity in the heap was increased from surface layer to underground. The proportion of genus Leptospirillum was sharply reduced (from 48.5% to 5%) from higher depth to lower depth and reverse correlation of increased A.ferrooxidans (from 0.9% to 15%) and S. thermotolerans (from undetectable to 7%) were found in the heap. Sulfur oxidizers including A.albertensis, A.caldus and A.thiooxidans also vertically increased from higher depth to lower depth (from 50.5% to 80%). These results indicated that genus Acidithiobacillus especially sulfur oxidizers A.albertensis, A.caldus and A.thiooxidans may play very important roles in the commercial low-grade copper bioleaching heap.

Abstract: During Zijinshan copper heap bioleaching, pyrite was leached in plenty resulting in high ferric concentration in solution. This affected bioleaching and extraction processing greatly. The paper studied the factors influencing in the course of leaching of pyrite and a mixture of chalcocite and pyrite respectively. It focuses on the effect of the redox potential for copper bioleaching so as to find key factors affecting the dissolution difference between chalcocite and pyrite. The experiment results showed that redox potential is an important influencing factor in bioleaching. Copper and pyrite extents of the leaching process were 95% and 11% respectively and there is great dissolution difference between them at redox potential 700 mV (SHE). It is indicated that copper can be selectively bioleached by controlling redox potential of bioleaching. The conclusion will provide theoretic foundation on balance of acid and iron during bioleaching for copper of higher S/Cu ratio. A simple sulfide, pyrite and chalcocite, were selected as test minerals. The samples were obtained from rich mineral in Zijin Mine. The concentrated samples were milled to obtain the size fraction of 320 mesh percent of 90. Bacterium culture: 9K culture medium contained the following composition in kg/m3 distilled water: (NH4)2SO4, 3.0; K2HPO4·3H2O, 0.5; KCl, 0.1; MgSO4·7H2O, 0.5; Ca(NO3)2·2H2O, 0.01. The initial ferrous concentration was 9.0g/L, the initial pH was adjusted to 1.6, and the temperature set at 30°C. The rotation speed of shaking bed was 150r/min. A three-day-old inoculum previously grown in medium was used in bioleaching process. A 5% inoculum was added to give an initial bacteria concentration in the medium was (3-6)×107 cells/m3. The experiments investigated factors influencing bioleaching including ferrous concentration and redox potential during bioleaching. The extent Cu leached was over 90%. Cu leached velocity increased as redox potential turned higher. Cu leached velocity rapid increased at redox potential 700mV. During chalcocite and pyrite bioleaching, redox potential is important factor to influence of bioleaching rate and the results showed that pyrite and chalcocite bioleaching rate was correlated with redox potential. It is indicated that copper can be selectively bioleached during copper bioleaching by controlling redox potential of bioleaching. It can be concluded that: (1) Pyrite and chalcocite bioleaching rate was correlated with redox potential. Redox potential was shown to be the key factor affecting the dissolution difference between chalcocite and pyrite. (2) Chalcocite and pyrite leaching efficiency were 95% and 11% respectively and there is great dissolution difference between them at redox potential 700 mV (SHE). (3) It is indicated that copper can be selectively bioleached during copper bioleaching by controlling redox potential of bioleaching.

Abstract: Based on the bioleaching mechanism and electrochemical studies of covellite, the dissolution rate of covellite mineral is accelerated through increasing the redox potential (Eh) of the leach. In the present work, some methods were adopted to enhance the bioleaching of covellite concentrate (collected from Zijinshan copper mine, Fujian province, China) by adding different oxidants such as pure pyrite, ferric ions and H2O2. The goal of this study was to provide appropriate operating parameters for the industry application and increase the efficiency of the bioleaching of copper mine. The results showed that the optimal way to increase the redox potential (Eh) level was the addition of pure pyrite. This method could effectively raise the Eh of bioleaching process while the effect of environmental change was negligible. It could quicken the leaching process and enhance the final copper recovery through the addition of pyrite by 1:1 or 1:2 ratio of covellite concentrate to pyrite.

Abstract: In this study, the viscosities and conductivities of bioleaching solution were determined by Ubbelohde viscometer and conductivity meter, respectively. The mean ionic activity coefficients, relative partial molar free energies of copper bioleaching solution at above experimental temperatures ranging from 298 K to 313 K have been calculated. Simultaneously, these characters of copper bioleaching solution were compared with and without mesophilic bacteria. The experimental data showed that the viscosities and thermodynamic properties for bioleaching solution would be crucial to minimize the third phase formation so as to increase extraction efficiency.