Pretreatment Of High Impurity Copper Anode Slimes And New Recovery Technologies For Rare Precious Metals

Copper anode slime is one of the important raw materials for extracting rare metals,which contains a large amount of valuable elements: Cu,Ag,Au,Se,Pb,Sb and platinum group metals etc.The complete procedure of processing of the anode slime mainly includes the following steps: first,using the pretreatment to remove the base metal;then,selecting pyro-treatment or hydro-treatment technology to enrich and produce precious metal alloy or powder;finally,taking advantage of refining to obtain precious metal products.These processes linked together,constitute a complete anode slime treatment process.Moreover,the pretreatment process is the most important link,which can determine the quality of copper anode slime treatment process.By comparison,the traditional copper anode slime pretreatment process exists a lots of defects,such as the lower removal rate of copper and selenium,the difficult recovery of Te,the dispersion and the secondary pollution of As.In order to implement the strategy of sustainable development and realize efficent,full and comprehensive utilization of resources,this paper is devoted to achieve the high efficient removal and recovery of Cu,Se,Te and As,and to enrich the rare metal.According to the research experience of home and abroad,this paper presents the integrated process of pretreatment,including the leaching of alkaline high-pressure oxidation and the acid leaching at atmosphere pressure.Beyond that,this process recovered valuable metal from leaching liquor,which is obtained by reducing and extracting sodium sulfite.The main research contents and conclusions of this paper are as follows:?1?The E-pH diagram of As-H₂O?Se-H₂O?Cu-H₂ O and Pb-H₂ O systems have be calculated and drew to demonstrate the possibility of alkaline oxidative leaching As and Se from the viewpoint of thermodynamics.And the behaviors of others metals in copper slime were studied as well.It shows that As and Se exist in the alkaline solution in the form of Na₃AsO₄ and Na₂SeO₄,while Cu?Pb?Bi?Te?Ag?Au exist in the alkaline leaching residue in the form of oxide,oxysalt or elementary substance.In addition,the influence factors of alkaline leaching of copper anode slime were analyzed by dynamic principle,and thus the increase of reaction temperature,the appropriate concentration of NaOH and the stirring speed could be determined,which could promote the leaching process.?2?The effects of various parameters in alkaline leaehing of copper anode slime were investigated in detail and the optimum conditions were determined.It was found that 98.20% As,93.63% Se,0.89% Te,0.03% Cu and 5.17% Sb were extracted from leaching solution under the optimum conditions.The optimum conditions were: oxgen partial pressure was 0.6Mpa,leaching temperature was 200?,NaOH concentration was 2mol/L,the liquid-solid ratio was 6:1,leaching time was 3h,and stitring speed was 650r/min.?3?The effects of various parameters in sulfuric acid leaching of residue by alkali leaching copper anode slime were studied.It was found that 93.88% Cu,84.06% Te and 0.18% Ag were extracted from leaching solution under the optimum conditions.The conditions were: H₂SO₄ concentration was 3mol/L,NaCl concentration was 6%,the liquid-solid ratio was 5:1,leaching temperature was 60? and leaching time was 1.5h.?4?The effects of various parameters in acidified with HCl and Na₂SO₃ reduction of alkali leaching liquor were studied.It was found that 96.66% Se was reduced under the optimum conditions.It includes: HCl concentration was 10%,reducted temperature was 90?,Na₂SO₃ concentration was 80g/L,reducted time was 125 min.For the extraction of copper,this was in the acidic leaching solution,using AD-100.The optimum conditions were: initial pH was 2.5,A:O was 2:1,AD-100 concentration was 25%,and when reaction time was 10 min,the extraction rate of copper reached 92.62%.What's more,each Cu2+ with two solvent molecules could form AD2 Cu.Also,the effects of various parameters in Na₂SO₃ reduction of extraction raffinate were studied.It was found that 99.48% Te was reduced under the optimum conditions.It includes: Na₂SO₃ concentration was 20g/L,reducted temperature was 90?,reducted time was 125 min and stitring speed was 650r/min.All the results show that the high pressure alkaline oxidation-normal pressure acid leaching proeess of copper anode slime is feasible.This method is not only remove the As,Se,Cu,Te efficiently,but also realizes the further enrichment of precious metals.In addition,Na₂SO₃ can recover the Se in alkali leaching liquor and the Te in extraction raffinate directly and effectively.The pretreatment and recovery method is clean and green;there is extended significance to popularize.