The Technology And Mechanism Of Bacteria Leaching High-arsenic Copper Sulfide Concentrate And Comprehensive Utilization Of Arsenic

It is difficult to separate copper and arsenic in mineral processing and to remove arsenic from the procedure in production of the non-ferrous metal, also difficult to make the arsenic innocent and recycle. The usage of high-arsenic materials were limited because the arsenic in the high-arsenic copper sulfide concentrate harms the qualities of copper and acid and pollutes the environment in the existing copper process which used in many large-middle scale high-arsenic copper mines in Yunnan province. It is of far reaching importance for exploration of high-arsenic copper sulfide concentrate and comprehensive utilization of arsenic if the problems as above questions can be resolved.In order to provide a new treatments for the development and utilization of high-arsenic copper sulfide concentrate, an innovative process for high-arsenic copper sulfide concentrate with bio-oxidation respectively Thiobacillus ferrooxidans(T.f) and moderate thermophile S.P has been studied out. The technology and mechanism of bacteria leaching the concentrate are researched, and the optimal technological conditions of extracting Fe³⁺ from bacteria leaching solution have been confirmed and the thermodynamics and technological process of comprehensive utilization arsenic by form of copper arsenate has been discussed.The innovations of this paper are as follows. Firstly the dynamic mathematical model of the moderate thermophile oxidation Fe²⁺ has been established. Secondly the technology process and mechanism of leaching high-arsenic copper sulfide concentrate by moderate thermophile has been studied, and the leaching rate of Cu is 97.06% and As is 94.13% under the optimum conditions. Thirdly the Eh-pH diagrams for Cu-As-H₂O system are drawn and the thermodynamic analysis of copper arsenate preparation has been carried out. Finally an innovative process of comprehensive utilization of Cu and As has been proposed and obtained six kind compound of Copper arsenate.Some results have been worked out and introduced as follows:(1) Growth of T.f in high concentration ferrous ion culture mediumThe environmental conditions such as temperature, pH, Fe²⁺ concentration, Fe³⁺ concentration and etc effect on the growth of T.f and the oxidation of Fe²⁺. The best conditions for the growth of T.f has been studied. When the initial concentration of Fe²⁺ changed, the growth of T.f and the oxidation rate of Fe²⁺ are influenced. With the increment of initial concentration of Fe²⁺,the ratio of [Fe³⁺]/[Fe²⁺] and the oxidation rate of Fe²⁺ decreased obviously. The growth of T.f would be inhibited when the initial Fe²⁺ concentration is more than 70g/l.(2) The technology process and mechanism of T.f leaching high-arsenic copper sulfide concentrateThe experiments of T.f leaching high-arsenic copper sulfide concentrate show that under the suitable leaching conditions the concentrate is leached 47% of Cu and 50% of As after 25 days. When the initial concentration of Fe²⁺ is within the range of 0.178～0.893mol/L, the leaching rates of metals are decreased. These results indicate the leaching effect is unobvious using the bacterial strain which endure high concentration of Fe²⁺. If the initial concentration of Fe³⁺ is 0.388mol/L, the leaching rate of Cu is 51.20%, but it continue in high concentration of Fe³⁺ in system the leaching process are inhibited. The results of leaching by T.f indicate that the residue contain 29.33% of CuFeS₂, 12.22% of Cu₃AsS₄, 1.04%of FeAsS, 25.89% of FeS₂, and 24.53% of Fe_1-xS. The leaching rate of minerals are 45.24% of CuFeS₂, 48.19% of Cu₃AsS₄, 52.46% Fe_1-xS, 54.62% of FeAsS, 4.68% of FeS₂.(3) The kinetics of moderate thermophile S.P oxidization Fe²⁺The environmental conditions such as sulfur, temperature,pH value, Fe²⁺ concentration, Fe³⁺ concentration and etc effect on the growth of moderate thermophile S.P. The optimum conditions for growth of moderate thermophile S.P are obtained. The dynamic model of the moderate thermophile S.P oxidation Fe²⁺ has been established by analyzing and calculating test data with the Matlab software. It indicates the existence of the optimum conditions including temperature and pH value and initial concentrations of Fe²⁺ and Fe³⁺ for the bio-oxidation Fe²⁺.To increase the initial concentration of Fe³⁺ can enhance the oxidation rate of Fe²⁺.(4) The technology process and mechanism of moderate thermophile S.P leaching high-arsenic copper sulfide concentrate The experiments of moderate thermophile S.P leaching high-arsenic copper sulfide concentrate show that high concentration Fe³⁺ has speeded leaching process up in the presence of bacteria, after 25 days the concentrate are leached 82.39% of Cu and 78.21% of As, and after 35 days the leaching rate of Cu and As is both above 90%. If the initial concentration of Fe³⁺ is in the range of 0.08～0.32mol/L, the leaching rate of Cu is 86.34～97.06%, As 89.22～94.13%. It shows that the concentration of Fe³⁺ became higher, the leaching rates of metals have been increased and the leaching process has been accelerated. The results of leaching by moderate thermophile S.P indicate that the residue contains 1.15% of CuFeS₂, less than 0.5% of Cu₃AsS₄, 59.71% of FeS₂, almost all of Fe_1-xS, FeAsS and Cu₃AsS₄ are leached out, and the leaching rates of minerals separately are 96.15% of CuFeS₂, 8.33% of FeS₂. Furthermore, there is 38.60% of element sulfur in the residue.(5) Removal of Fe³⁺ by solvent extraction with P204 from bacterial leaching solution of copper concentrate oreThe separation of Fe and Cu in P204-kerosene system has been studied. The factors of influencing on the balance of Fe³⁺ extraction are analyzed, and the process of removal of Fe³⁺ by solvent extraction with P204 from bacterial leaching solution has been researched on.P204 can be used to extract Fe³⁺ from sulphate solution selectively. Under the conditions of extraction temperature at 25℃, phase ratio at 1:1, aqueous pH at 1, concentration of P204 in kerosene being 30%(φ), and 3-step extraction, Fe³⁺ is extracted up to 77%～93% at the first step, Cu and As are hardly extracted, and the content of Fe³⁺ in raffinate is in the range of 0.007～0.164 g/L at the second step, finally it is under 9 mg/L. On the conditions of H2SO4 concentration at 4mol/L, and 5-step stripping, the stripping rate of Fe³⁺is 72.93～89.20% for the 0.77～15.32 g/L of Fe³⁺ in P204.(6) Copper arsenate preparation process from leaching liquor after removal Fe³⁺The Eh-pH diagrams for Cu-As-H₊2O system are calculated and drawn and the thermodynamic analysis of copper arsenate preparation from leaching liquor after removal Fe³⁺ has been carried out. The molecular formula of copper arsenate is influenced by the Cu,As quality ratios and pH values. The results of X-ray analysis show that the forming process of copper arsenate is complicated, and the formed molecular formulas are in different types under the condition of pH at 4.0～8.0, and they are CuAs₂O₄, C₄H₆As₆Cu₄O₁₆,Cu₅As₂O₁₀·5H₂O,Cu₅As₄O₁₅·9H₂O, Cu₂AsO₄OH·3H₂O and Cu₂AsO₄0H. The comprehensive utilizations of most of arsenic are in the form of copper arsenate, and the content of arsenic is 9.11～35.82mg/L in solution after its precipitated.No waste residue and waste gas have been discharged in the whole process, and the entire processing is clean completely.