Fundamental Study on the Removal of Methylmercuric Chloride from Aqueous Solution by Mercapto Collectors

Abstract

The reaction between methylmercuric chloride and mercapto collector, such as alkylxanthates (KRX) and dialkyldithiophosphates (KRP), has been studied by means of polarography and potentiometric titration in relation to the removal of methylmercuric ion in aqueous solution.
Although methylmercuric chloride gave sparingly soluble, precipitate with xanthates, the composition of which was 1: 1, water soluble complex was also formed. The solubility products of the precipitates decreased, while the stability constants of the complexes increased, with increasing the number of carbon atoms in alkyl radical (Table 2). Similar behavior was noted in the case of dialkyldithiophosphates, though larger solubility products were given as compared to the xanthate system. The test to remove methylmercuric chloride by precipitation with amylxanthate showed the limited success; the residual concentration of mercury (several mg) was inevitable (Table 3). This residual concentration of mercury was in fairly good agreement with that of the complex formed, indicating that it is difficult to remove methylmercuric chloride by mercapto collectors to the level of " not detectable", differing from the case of inorganic mercuric ion where the formation of soluble complex can virtually be ignored.