Optimization Of Biological Oxidation Of High Arsenic Gold Concentrate By Ceramic Ultrafiltration Membrane And Mechanism

Refractory gold ores usually need oxidation pretreatment to better recover gold.Biological oxidation is a green and environmental protection pretreatment technology,which has broad application prospects.In actual production,due to the limited tolerance of microorganisms to heavy metal ions,there have always been the problems of low pulp concentration and poor treatment efficiency in the oxidation process.Aiming at the prominent problems existing in the industrial biological oxidation of high arsenic gold concentrate,this paper adopts a new ceramic ultrafiltration membrane technology to separate and remove the harmful components such as arsenic ion and sulfate ion produced in the oxidation process,synchronously improve the pulp concentration and microbial density,and then improve the efficiency of biological oxidation pretreatment.The main results achieved are as follows:The characteristics of biological oxidation of high arsenic gold concentrate pulp are found out.Some arsenic ions and sulfate ions are successfully removed by ceramic ultrafiltration membrane,which can increase the pulp concentration and microbial density by more than twice,significantly improve the secondary oxidation efficiency,save more than50%of the installed capacity of the subsequent secondary oxidation process,and significantly reduce the production cost.Through the comparison of membrane flux,ion permeability,mineral particle and bacterial interception rate,the ceramic membrane with 200 nm pore size was selected as the highest separation efficiency.The high-speed rotating membrane module operation mode with centrifugal force can not only realize continuous separation operation,but also effectively reduce membrane pollution;The membrane flux recovery rate can reach more than 98%by using high-pressure air flow backwashing for the polluted membrane modules.The pulp with increased concentration can be further biooxidized.Compared with the conventional concentration（<10%）pulp,arsenic ions and sulfate ions in the liquid phase of concentrated pulp（20%）accumulated to about twice in the later stage of oxidation,but did not affect the activity of microorganisms;The study on the dissolution behavior of arsenic and sulfur in gold concentrate shows that their oxidation reaction conforms to the law of reaction kinetics;XPS analysis shows that arsenic mainly exists in As³⁺and most sulfur exists in SO₄^2-.The process conditions of concentrated pulp are consistent with the existing production conditions,and the industrial transformation is simple;And the oxidation effect is better.The total arsenic removal rate of oxidized slag of gold concentrate of concentrated pulp can reach96.58%and the total sulfur removal rate can reach 78.82%,which is better than the oxidation effect of conventional concentration pulp under the same conditions,and the gold leaching rate of cyanide leaching can be further improved.The study on the mechanism of oxidative arsenic removal of high arsenic gold concentrate under acidic conditions shows that increasing the pulp concentration is conducive to the oxidation of arsenopyrite.The pulp concentration increased from 10%to 20%,and the apparent activation energy of arsenopyrite oxidation decreased from 93.26 k J/mol to 67.01k J/mol,which were all controlled by chemical reaction;Thermodynamic studies show that when arsenopyrite reaches reaction equilibrium in oxidized pulp under experimental conditions,iron in solution mainly exists in the form of Fe²⁺and Fe³⁺;The oxidized sulfur combines with arsenic to form a compound,which will also exist in the form of HAsO₃^-.