Arsenic Removal From Refractory Gold Ores By Bio-oxidation And Ag+、Cu2+ Strengthen The Bio-oxidation Process

Arsenic not only does great harm to animals and plants,but also affects the recycling of metals in the exploitation of metal resources.The development of refractory gold resources is due to the harmful elements such as arsenic and sulfur,which leads to low gold recovery.China has been the world’s largest gold production for 14 consecutive years,and the efficient utilization of refractory gold resources is imminent.Therefore,the pretreatment of this kind of resources to eliminate the factors affecting gold recovery is becoming more and more important.Bio-pretreatment has been widely paid attention because of its advantages such as low pollution,low energy consumption and simple operation.But there are also problems such as low processing efficiency and long cycle.This paper focuses on the biological removal of arsenic from refractory gold ores.Based on the optimization of various influencing factors,the optimal process of arsenic removal is obtained.（1）Taking temperature,initial p H and bacterial load as the influencing factors,and arsenic leaching rate as the response value,the refractory gold ore with arsenic content of 3%and 13%was optimized,respectively.For refractory gold ore with3%arsenic content,The significance of the three influencing factors were:bacterial load（C）>bacterial load（B）>Temperature（A）;For refractory gold ore with 13%arsenic content,the significance of the three influencing factors are as follows:initial p H（B）>bacterial load（C）>Temperature（A）.Within the range of selected factors,the response surface model established has a good guiding effect.After optimization,the arsenic leaching rate of refractory gold mine with 13%arsenic content reached 37.85%by using the optimal condition temperature of 31℃,initial p H of 2.27,bacterial load of 11%and the optimal condition temperature of31℃.（2）Metal ions such as Ag⁺and Cu²⁺can promote bio-oxidation of arsenic.bioleaching with20mg/L Ag⁺after seven days,the leaching rate of arsenic reached 53.38%,which was increased by 15.53%compared with that without metal ions.bioleaching with 16mg/L Cu²⁺After seven days,the leaching rate of arsenic reached 50.46%,which was 12.61%higher than that without adding metal ions.（3）The different conditions of biological oxidation leaching change The existing form of arsenic.（1）bioreaching without adding metal ions after Three days,arsenic mainly existed in the form of arsenopyrite,and a small part was converted to As³⁺.After seven days of bioreaching,arsenopyrite still existed,and most of it existed in the form of As³⁺and As⁵⁺.（2）Three days after bioleaching with Ag⁺,arsenic mainly exists in the form of As⁵⁺and As₂O₃,and a small amount of arsenopyrite also exists.Seven days after bioleaching,a small amount of arsenopyrite still exists in the mineral,mainly in the form of As₂O₃.（3）Three days after biological leaching with Cu²⁺,arsenic mainly exists in the form of As³⁺and a small amount in the form of As₂O₃ and As⁵⁺.Seven days after biological leaching,arsenic mainly exists in the form of As₂O₃ and As⁵⁺,and there is still a small amount of arsenopyrite in the mineral.（4）After three days of bioleaching without adding metal ions,the existing forms of sulfur are As₂S₃,SO₃^2-,SO₄^2-,and the main existing forms are SO₄^2-.After seven days of bioleaching,the change of sulfur form is not much different from that of three days of bioleaching.After three days of bioleaching with the addition of Ag⁺,a small amount of sulfur exists in the form of S₂^2-,and most of sulfur exists in the form of SO₃^2-and SO₄^2-.After seven days of bioleaching,most of sulfur exists in the form of S-O intermediate and SO₃^2-.After three days of bioleaching with the addition of Cu²⁺,the sulfur mainly exists in the form of SO₄^2-and S₂^2-,and there is almost no sulfur in the form.After seven days of bioleaching,the sulfur is basically converted to SO₄^2-.