GB787296A - Improvements in or relating to removing impurities from platinum - Google Patents

Abstract

Aqueous solutions containing platinum as part of a complex anion and also containing a cation impurity are purified by contacting the solution with a solid cation exchange material which absorbs the cationic impurity. The cation impurity may be copper, nickel, iron, manganese, magnesium, sodium or potassium. The platinum metal anion may be one containing F, Cl, Br, I, CN, NH2, NO or OH, for example chloroplatinic bromoplatinic, iodoplatinic fluoroplatinic, bromoplatinous, iodoplatinous, bromo-chloroplatinic, bromo-chloroplatinous, cyanoplatinic, aminoplatinic, nitrosoplatinic, hydroxyplatinic, the corresponding platinous acids or cyanochloropoplatinic, or hydroxy-chloroplatinic acid. The preferred cation exchangers are strongly acidic, such as sulfonated coal or carbonaceous zeolites orsynthetic resins of the phenolic or non-phenolic type, in particular a sulfonated copolymer of styrene and divinylbenzene. These materials may be employed as powders or chips or spheroids. The cation exchange material may be regenerated with an acid solution, and if a small amount of platinum is retained on the cation exchanger it may be removed with water washing and the solution so obtained may be contacted with an anion exchanger which picks up the platinum anion. The anion exchange material may then be burned to leave an ash of the platinum which may be taken up in water and re-purified. According to examples: (1) platinum containing minor percentages of iron and copper impurity were dissolved in aqua regia the solution evaporated to dryness and the resulting salt dissolved in distilled water. The solution was then again evaporated to dryness and the salt again dissolved in water and the resulting chloroplatinic acid solution containing the copper and iron impurities was passed through a bed of commercial "Amberlite" (Registered Trade Mark) cation exchange resin whereby the iron and copper impurities were retained. (2) Platinum containing iron and copper was dissolve in aqua regia as in Example (1) and the solution of chloroplatinic acid resulting was passed through a phenolic type cation exchange resin which freed the chloroplatinic acid from iron and copper impurities. The resin was then washed with distilled water to remove traces of platinum therefrom and the resulting solution contacted with an anion exchange resin of low ash content which picked up the platinum from the solution. The anion exchange material was then burned and the resulting platinum containing ash was dissolved in aqua regia and purified as before.