| With the continuous exploitation of gold resources,the gold grade has gradually declined,and low-grade refractory gold has gradually become an important source of gold production.Because it is difficult to recover the refractory gold ore efficiently by traditional dressing and smelting method,and the traditional cyanidation method is faced with environmental protection,acid-base conversion and other problems,based on this,this paper takes a low-grade arsenic bearing refractory gold ore in Xinjiang as the research object,carries out the mechanism and process research of biological pre-oxidation thiourea leaching gold,and provides theoretical guidance for practical industrial application.In this paper,we domesticated and cultured the strains preserved in the laboratory,and got a high-efficient strain suitable for the treatment of the ore.The best culture conditions were:culture temperature 30 0C,pH 1.5?1.8,culture period 15 days.The oxidation rate of as and s can reach 80.32%and 41.04%respectively.The effects of temperature,thiourea concentration,pH value,liquid-solid ratio and stirring speed on the leaching rate of gold were investigated for the pre-oxidized residue.The optimal conditions were obtained:temperature 25?,thiourea concentration 25 kg/t,pH 1.5,liquid-solid ratio 5:1,stirring speed 350 r/min.At this time,the leaching rate of gold reached 97.84%.Based on the shrinking core model,the activation energy of thiourea leaching process and the management relationship of each factor were obtained,and the semi empirical kinetic equation was established.Several main factors influencing the decomposition of thiourea in practical production are discussed.Fe3+ is one of the most important factors influencing the decomposition of thiourea,and the mechanism of decomposition is explained.According to the unreacted nuclear model,the semi empirical kinetic equation of thiourea decomposition in acid condition was established.In order to provide guidance for the next engineering application,the column leaching experiment was carried out by simulating the industrial system.The pH value of pre-oxidation is 1.5?1.8,and the period is 60 days.Thiourea is used to leach the pre-oxidation residue,the leaching pH value is 1.5,the leaching time is 30 days,the leaching rate is 88.39%,and the amount of thiourea is 5.26 kg/t.In order to further reduce the consumption of thiourea,the leaching solution containing thiourea was recycled.The leaching rate of gold is 79.74%,which shows that thiourea can be recycled to some extent.Based on the experimental results,the mechanism of gold leaching by thiourea was studied,and it was found that the concentration of thiourea was the main factor affecting the gold leaching under acid conditions.The activation energy of this process is 12.116 kJ/mol,which indicates that the effect of increasing gold leaching rate by heating up is limited,and the correlation index of thiourea concentration is higher,which has the greatest influence on the leaching process.The decomposition mechanism of thiourea was discussed.It was found that Fe3+ was the main factor affecting the decomposition of thiourea under different conditions,and the kinetic model was established.The correlation index of Fe3+ concentration was higher than that of bacterial inoculation amount and water quality,which had the greatest influence on the decomposition process of thiourea.Based on the environmental pollution and damage caused by the traditional cyanidation process and the problems affecting the gold leaching rate in the industrial application,such as the formation of a secondary package after the acid-base conversion process,the remaining alkali of the previous batch of ore consumes a large amount of acid in the acid balance of the next batch of ore,etc.,the above problems can be effectively solved by adopting the biological pre-oxidation thiourea gold leaching combined process.It is an environmental friendly and efficient gold leaching process.The results of this paper provide a solid theoretical basis for the next large-scale industrial application. |
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