Hong Ying Yang

Biotransformation of Arsenopyrite by Phanerochaete chrysosporium

Abstract. In this study, the arsenopyrite was used as representative of gold-bearing sulfides in Carlin-Type gold ores to test the ability of oxidation on them by P. chrysosporium. After shaking incubation for 20 days, the conversion rates of iron, sulfur and arsenic in arsenopyrite were 6.28%, 35% and 21.76%, which were 44.86, 2.98 and 48.36 times compared with the asepsis system, respectively. It indicated that the P. chrysosporium could improve obviously the biotransformation rate of arsenopyrite by its own metabolic activity. The electrochemical oxidation behavior of arsenopyrite in the leaching system without and with P. chrysosporium were detected with electrochemical technology. The results showed that the P. chrysosporium did not change the oxidation mechanism of arsenopyrite, but strong oxidizing environment, which was structured by its products-oxidative enzymes and hydrogen peroxide, could promote the transformation from Fe2+ to Fe3+. P. chrysosporium could significantly decrease pitting potential and improve polarization current of arsenopyrite electrode and then accelerate its corrosion process. These indicated that P. chrysosporium was an available microorganism for degrading and transforming sulfides. P. chrysosporium could break gold inclusion and improve gold leaching rate, and finally realized economical and efficient application of Carlin-type gold ores.

Bioleaching Experiments on a Low-Grade Complex Zinc Ore from Inner Mongolia

When dealing with a low-grade complex Zinc ore from Inner Mongolia, problems of low leaching rate, high energy consumption, low economic benefits and pollution were encountered. To treat this low-grade zinc ore economically and effectively, bioleaching was used. This approach produces reliable data for an environmentally friendly and efficient processing of the zinc ore. The results indicate that Zinc occurs in the ore mainly as sphalerite, the latter also containing Indium. The experimental results demonstrated an excellent leaching performance: A leaching rate of nearly 100% is achieved at a temperature of 45°C, a pulp concentration of 10%, an initial pH of 1.8, and an aeration rate of 0.8m3/h. In the initial stage the leaching rate is higher than at the end. It starts with 85% of zinc leaching rate in three days. The Indium in the sphalerite is leached almost completely. This makes a further comprehensive use of such resources possible.

Screening of Important Variables of Organic Acids Degradation by Phanerochaete chrysosporium Using Plackett-Burman Design in Refractory Arsenic-Bearing and Carbonaceous Gold Ores

In this study, the important variables of organic acids degradation with Phanerochaete chrysosporium were selected in refractory arsenic-bearing and carbonaceous gold ores. The eight variables of fungal degradation of carbonaceous matter were confirmed by the previous single factor experiments, which were guaiacol concentration, dextrin concentration, tween-80 concentration, oxalic acid concentration, hydrogen peroxide concentration, pulp density, fungal concentration and action time. The most important factors influencing organic acids degradation (p < 0.05), as identified by a two-level Plackett-Burman design with above-mentioned eight variables, were pulp density, oxalic acid concentration and action time. The pulp density could influence the effective contact area between organic acids and fungi, the shear stress and the mass transfer efficiency of degradation system. Oxalic acid could affect the fungal growth and the enzymes activity by adjusting pH value of degradation system. Organic acids could not be fully degraded when the fungal action time was the very short or excessively long. A long action time could lead to the lack of nutrients and the accumulation of toxic and harmful substances.

The Mechanism of In and Ge Occurrence in Sphalerite Crystal and the Influence on Properties: A DFT (Density Function Theory) Simulation

In and Ge can be found in Sphalerite crystal which can influence bio-leaching properties of Sphalerite significantly. Occurrence states of In and Ge in Sphalerite crystal and their influence on Sphalerite was calculated by Castep package. The most stable occurrence states are In and Ge substitute for Zn atom in Sphalerite crystal. When In and Ge existed in Sphalerite crystal, the Density of states (DOS) of Sphalerite crystal moved to left, meaning a more reducibility structure. It can explain why In and Ge bearing Sphalerite is easier to bio-leach than the pure sphalerite.

Research on Bio-Leaching of Nickel-Bearing Tailings in Jilin, China

Gradually bio-metallurgy technology is becoming an irreplaceable new technology. The nickel-bearing tailings in Jilin, China contains Ni 0.13 %, Cu 0.03%, Co 0.01%, S 15.20%, Fe 6.30%. A comparative study of the HQ0211 bacteria, indigenous bacteria (after the domestication named ZXJE511 bacteria) and acid pool leaching revealed that the local species ore leaching was preferably the best way. At pH 2.0, room temperature (about 23°C), pulp density 20%,the Ni, Co and Cu leaching rates were 70.08%, 40% and 57.67 % , respectively ,after 38 days of bioleaching, proving the superiority of the bacterial leaching of Ni, Co, Cu from tailings. Biological leaching tailings solved the problem of the conventional methods which could not be addressed by acid leaching. This technology is environmentally friendly and can make maximum use of the resources, thereby avoiding the waste of the resources.

The Mechanism of Skutterudite Acid Leaching: A DFT Study of H+ Effect on CoO (010) Surface

A DFT study of H+ effect on CoO(0 1 0) surface was carried out. What could be seen from the inter atomic distance and the density of states (DOS) was: Co-O bonds were broken strongly and H-O bonds formed strongly when one H+ was adsorbed on the O atom, and Co-O bonds were not broken and H-O bond not formed strongly when two H+ were adsorbed on the O atom, so the Skutterudite acid leaching process cannot be described as two H+ were adsorbed on the O atom and formed the H2O molecules to enter the solution. But that can be described as one H+ was adsorbed on the O atom and formed the OH- to enter the solution, the OH- was combined with the H+ in the solution to form the H2O molecule.

The Efficient Recovery of Cobalt from Low Grade Refractory Carrollite with Bioleaching Technology

Cobalt, having many diverse and critical uses, is an essential metal in todays society. However, the recovery of cobalt is difficult due to its associated mineral characteristics. A biohydrometallurgical process has been developed for cobalt recovery from low grade refractory carrollite. After direct oxidation for 6 days, 96.51 % Co and 26.32 % Cu were extracted from the ore using a pulp density of 10 %. The bioleaching solution contained 22.62 gL-1 ferric iron while the concentration of cobalt was only 0.83 gL-1. Therefore, a goethite deironization process was then conducted. Different conditions, such as pH value, temperature, standing time and oxidant concentration were studied in detail. The results showed that when the pH value was 4.0, oxidation temperature was 70 °C, standing time was 1 h, and oxidant concentration was 8%, then the iron removal and the loss of cobalt were 99.9 % and 0.5 %, respectively. The goethite precipitate had good filterability. The sum recovery of cobalt in the whole extraction process attained more than 95 %. The biohydrometallurgy process for the recovery of cobalt has economic and environmental advantages over the other methods.