Study On The Synthesis And Extraction Properties Of New Silver Extractant

Silver is an important noble metal element, solvent extraction is one of effective method for extracting high purity silver. The effective extractant for extracting silver is less, due to the specificity of extraction conditon of silver. It is one of research hot spot for noble metals hydro metallurgy to develop the extractant and establish the highly efficient extraction and separation system in the strong oxidizing environment for silver.Six kinds of new extractants,2-ethylhexylthiazoline sulfide(EHTLS), hepty thiazoline sulfide(HTLS),2-ethylhexyl-4-methylthiazole sulfide(EHMTS), heptyl-4-methylthiazole sulfide(HMTS) and2-ethylhexyl-4-methylthiazole sulfoxide (EHMTSO), hepty1-4-methylthiazole sulfoxide(HMTSO) were synthesized and their structures were characterized. Five new system of solvent extraction of silver were established. New way of solvent extraction and separation of silver in the medium of nitric acid were explored. The effect of various parameters such as concentration of extractant, concentration of nitric acid, phase ratio (O/A), contact time, concentration of metal ions, saturation capacity, stripping conditions and base metal ions, etc., had been investigated. In addition, the mechanism of extracting and stripping had been studied.The result showed that silver can be effectively extracted by sulfoxide and sulfide in the medium of nitric acid of6mol/L and0.5to4.0mol/L, respectively. Silver in sulfoxide extraction system could be stripped with acidic thiourea. Silver in sulfide extraction system could be stripped with thiourea or ammonia water. The separation coefficient of Ag+and Cu2+, Fe3+, Co2+, Ni2+and Zn2+reached103, respectively, indicating Ag+and Cu2+, Fe3+, Co2+,Ni2+and Zn2+were separated completely.The result showed that the single-stage extraction rate was over94%when concentration of nitric acid,6mol/L; concentration of EHMTSO,15%(v/v); phase ratio,1.0; contact time,5min and concentration of silver,1g/L. The saturation extraction capacity of silver more than15g/L. The stripping rate more than99percent when0.4(wt%) acidic thiourea solution was used. The separation coefficient of Ag+ and Cu2+, Fe3+, Co2+,Ni2+and Zn2+reached103, respectively.The result reveals that the single-stage extraction rate was reached97%when concentration of nitric acid,6mol/L; concentration of HMTSO,10%(v/v); phase ratio,1.0; contact time,5min and concentration of silver,0.1to9.0g/L. The saturation extraction capacity of silver more than15g/L. The stripping rate more than99percent when0.4(wt%) thiourea solution was used. The separation coefficient of Ag+and Cu2+, Fe3+, Co2+,Ni2+and Zn2+reached103, respectively.Experiments showed that the new systems of three thioethers extractant silver of isoamyl sulfide,2-ethylhexylthiazoline sulfide(EHTLS) and heptythiazoline sulfide (HTLS), the extraction time was less than10min, and the single-stage extraction rate was over98%, stripping rate was over95%, The separation coefficient (βAg/M) of Ag+and Cu2+, Fe3+, Co2+, Ni2+and Zn2+reached102, respectively. Saturated extraction capacity of isoamyl sulfide was the maximum.Ultraviolet Visable Spectrum, Infrared absorption Spectrum, and slope method showed that the extractants coordinated with Ag+via N or S atom. The molar ratio of Ag+to ligand was1:3. The X-ray crystal structures of the thiourea-Ag(Ⅰ), which was not reported previously, was obtained. The mechanism of stripping was explained at level of molecule structure.