Research status of carbonaceous matter in carbonaceous gold ores and bio-oxidation pretreatment

Carbonaceous gold mines are important refractory gold ores. The previous results demonstrate that the carbonaceous matter is mainly composed of elemental carbon, organic acid and hydrocarbons. The dissolved aurocyanide complex is robbed by adsorption of carbonaceous matter, which is similar to activated carbon in cyanide leaching of gold. The pretreatment methods of carbonaceous gold ores were introduced, including high temperature roasting, bio-oxidation, chemical oxidation, competitive adsorption, barrier inhibition and microwave roasting. Recently, bio-oxidation was developed rapidly due to its advantages such as mild conditions, simple processes, low energy consumption and friendly environment. The known microorganisms related with bio-oxidation pretreatment mainly are chemolithotroph bacteria such as Thiobacillus ferrooxidans, Thiobacillus thiooxidans and Leptospirillum ferrooxidans. The researches on decomposing and passivating carbonaceous matter were commenced by Phanerochaete chrysosporium, Pseudomonadaceae and Streptomyces setonii. Finally, the main problems were analyzed and the application prospect of this technique was looked forward.

Simultaneous extraction of gold and zinc from refractory carbonaceous gold ore by chlorination roasting process

A novel process based on chlorination roasting was proposed to simultaneously recover gold and zinc from refractory carbonaceous gold ore by using NaCl as chlorination agent.The effects of roasting temperature,roasting time and NaCl content on the volatilization rates of gold and zinc were investigated.The reaction mechanism and the phase transition process were also analyzed by means of SEM,EDS and XRD.The results demonstrated that under the optimal conditions of NaCl content of 10%,roasting temperature of 800℃,roasting time of 4 h and gas flow rate of 1 L/min,the rates of gold and zinc were 92%and 92.56%,respectively.During low-temperature chlorination roasting stage,a certain content of sulfur was beneficial to the chlorination reactions of gold and zinc;and during high-temperature chlorination roasting stage,the crystal structure of vanadium-bearing mica was destroyed,and the vanadium-containing oxides were beneficial to the chlorinating volatilization of gold and zinc.Eventually,the chlorinated volatiles of gold and zinc could be recovered by alkaline solution.

Influence of Phanerochaete chrysosporium on degradation and preg-robbing capacity of activated carbon

The effect of Phanerochaete chrysosporium on degradation and preg-robbing capacity of activated carbon,which was used as a substitute of carbonaceous matter in carbonaceous gold ores,was studied.After 14 d treatment with Phanerochaete chrysosporium,the degradation rate of activated carbon reached 27.59%.The XRD and FTIR analyses indicate that Phanerochaete chrysosporium can distort the micro-crystalline structure of activated carbon,increase the number of oxygen-containing groups and aliphatics and make the aromatic structures be oxidized and exfoliated.The gold-adsorption tests show that Phanerochaete chrysosporium can reduce the preg-robbing capacity of activated carbon by 12.88%.This indicates that Phanerochaete chrysosporium is an available microorganism,and it can be employed to reduce the preg-robbing capacity of carbonaceous matter and improve the gold leaching rate.The combined effect of passivation,alkalization and oxidation of biological enzymes-free radicals of Phanerochaete chrysosporium on carbonaceous matter was also discussed.