The laboratory tests of biooxidation and cyanidation were carried out by using samples of the complex refractory gold ore from China. The elemental composition was 16.8 % iron, 18.6 % sulfur, 4.88 % arsenic,2.30 % carbon and 3.49 % antimony. Gold is assayed at 46 g/t. The arsenic oxidation of 88.11 %,carbon removal rate of 32.34 % and antimony oxidation of 23.92 % over 16d was achieved in shake flasks in the presence of the mixed culture (HQ0211: Thiobacillus ferrooxidans Leptospirillum ferrooxidans and Thiobacillus thiooxidans). The continuous bioreactor tests resulted in greater dissolution rates for arsenic, carbon and antimony, which led to a greater extent of sulphide oxidation within a shorter period of time. The maximum oxidation of arsenic and antimony was 90.72 % and 40.09 % respectively and the removal rate of carbon is 63.48% after 8d in the continuous bioreactor tests. After bioleaching, the gold recovery of the oxidation residue was 98.02 % with the cyanidation method, which was showed the biological pretreatment was applicable to the complex refractory gold ore.
Abstract. In this study, the effect ofPhanerochaete chrysosporiumon graphite was investigated, and graphite was used as a substitute of elemental carbon in carbonaceous gold ores. Under the condition of optimum process, the fungal degradation rate of graphite reached to 13.49%, and the carbon content of graphite was decreased by 5.13%. XRD analysis indicated thatPhanerochaete chrysosporiumcould destroy the crystal structure of graphite. FTIR analysis indicated thatPhanerochaete chrysosporiumcould increase the number of aliphatic structures and oxygen-containing groups. The cyanide leaching gold tests showed thatPhanerochaete chrysosporiumcan decrease the preg-robbing capacity of graphite, about 9.52%. It indicated thatPhanerochaete chrysosporiumis an available microorganism, which was employed to pre-treat carbonaceous matter in carbonaceous gold ores to reduce the interference of gold cyanidation leaching.
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.
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.
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