Solvent Extraction Method For Separation And Recovery Of Indium From Wet Zinc-smelting Indium Solution

Indium is a very important rare metal which is extensively applied in the modern electronics industry because of its specific physical and chemical performance.But,indium has no independent deposits and it is recovered almost exclusively as a by-product from the indium-containing materials.The traditional methods of recovering indium include neutralization,precipitation,secondary leaching,extraction,replacement and so on.The process have disadvantages,for example,long flows and low rate of indium,and the stripping process was only achieved by using high concentration hydrochloric acid,resulting in a large amount of high concentration of chlorine wastewater.In this paper,based on shortcomings of the traditional indium synthesis recovery process,the extraction of indium by ion exchange and neutral extractant,and direct extraction of indium from wet zinc leaching solution were studied.Besides,by using water as stripping agent,the amount of hydrochloric acid and discharge of chlorine-containing wastewater was reduced.The main research work is as follows:(1)The behavior and mechanism of extraction of indium by different acid phosphorus(phosphine)extractants from low acid were studied.It was found that the extraction extraction of indium by several extractants belongs to the cation exchange mechanism and the extracted species was existed as InA3·3HA.The results show:when D2EHPA was used for recovery of indium from leaching solution of zinc oxide containing 3.2 g/L indium,the separation of zinc,iron and cadmium and other metal ions was achieved.Quantitative indium was extracted by 10%D2EHPA at O/A ratio of 1/2.Indium in the D2EHPA loaded organic was effectively stripped by 6 mol/L HCl.(2)The behavior and mechanism of extraction of indium with different neutral extractants from solution containing high concentration HCI were studied.It was found that the extraction of indium by three kinds of neutral extractants belonged to complexing mechanism.The extraction persentages of indium and other metal ions from the stripping solution of loaded D2EHPA with 20%TBP+15%P350 were studied.The results show:99%of indium in the D2EHPA loaded organic stripping solution which contains 6.8 g/L indium was selective extracted by TBP/P350 with two countercurrent extraction stages at O/A ratio of 2/3.Then indium in the TBP/P350 loaded organic was stripped by water.(3)A pilot test and continuous countercurrent extraction test were developed to study the extraction and stripping acticities and distribution of indium and other metal ions from the leaching solution of zinc oxide were also studied.The extraction efficiency of indium with 10%D2EHPA was more than 99%with three stages countercurrent extraction,while the separation factors ?In/Zn and ?In/Fe were 73807,54130,respectively.Indium in the strip solution can be used for extraction with 20%TBP+15%P350.And the TBP/P350 loaded organic phase was efficiently stripped by water with two stages countercurrent to obtain the indium-rich solution.The whole recovery efficiency was 80%.Comparing to traditional processes,more than 61%of chloride ion was reduced.The recovery efficiency of indium was icreased by 15-20%.