Study On A New Solvent Extraction System Of Pt(?) In Alkaline Cyanide Solution

For the platinum group metals leaching solution obtained by the pressure cyanidation process,zinc-dust cementation process is mainly used to refine and purify platinum.This method first destroys cyanide in solution,and then replaces platinum with zinc powder.The operation is complicated and the metal zinc is difficult to recycle.In order to solve the problems of total wet process,a new solvent extraction method for separating Pt(CN)42-froM alkaline cyanide solution was proposed in this paper.This new method is not only simple in operation,high in separation efficiency,large extraction capacity,and low cost.In this paper,a new extraction system of Pt(CN)42-in alkaline cyanide solution medium was established using quaternary ammonium salt and quaternary phosphonium salt as extractants.The main extraction parameters were studied:the type of diluent,the concentration of metal ions,the concentration of extractant,cosolvent,pH,oscillation time,phase ratio,maximum extraction capacity,reusability,stripping conditions,etc.With Methyltrioctylammonium chloride,tricaprylmethylammonium maltolate Trihexyl(tetradecyl)phosphonium bromide,and Trihexyl(tetradecyl)phosphonium bis-2,4,4-trimethylpentylphosphinate as extractants,four new systems for the extraction of Pt(CN)42-in alkaline cyanide medium were established.The single factor extraction experiments showed that the four extraction systems had better extraction performance for Pt(CN)42-and the extraction rate was more than 99.0%under the conditions of contact time of 5 min and phase ratio(O/A)of 1.0.Potassium iodide was used as stripping agent to strip four extraction systems of Pt(II).The stripping rates were more than 96.0%.Extraction saturation capacity:Cyphos IL104>Aliquat-336-Mal>Cyhpos IL102>Aliquat-336.Mixed ion separation studies show that Pt(CN)42-,Fe(CN)63-and Co(CN)63-can be co-extracted by four extraction systems and can be efficiently separated from mixed solution containing Pt(CN)42-,Fe(CN)63-and Co(CN)63-through two-step stripping process.First,Fe(CN)63-and Co(CN)63-in mixed organic phase were stripped potassium chloride solution.Second,Pt(CN)42-in the loaded organic phase could be stripped using potassium iodide solution.The regeneration of extraction system can be realized by halide solution.The four extraction systems all had good reusability.After four extraction-stripping processes,recovery ratios for Pt(CN)42-was more than 91.0%.The extraction of Pt(CN)42-by quaternary ammonium salt and quaternary phosphonium salt in alkaline cyanide solution is ion exchange mechanism.The results were studied by IR,UV-Vis,1H-NMR,isomolar continuous transformation and Karl Fischer titration.(1)For Aliquat-336 and Aliquat-336-Mal systems,four n-octanol molecules form supramolecular anions through hydrogen bonds with one Pt(CN)42-anion,and then form ion associations with quaternary ammonium salt extractant cations.(2)For Cyphos IL 102 and Cyphos IL 104 system,Pt(CN)42-anion forms ion association complex with quaternary phosphonium salt extractant cations.