Photodegradation and by-products identification of commercial extractant Cyanex 302

Abstract

The photodegradation of the organothiophosphorous extractant Cyanex 302 and purified bis(2,4,4-trimethylpentyl)monothiophosphinic acid dissolved in toluene was carried out in photoreactor using UV–Vis light irradiation. Possible degradation products were identified with the assistance of FT-IR, LC/MS/MS and GC/MS. The catalytic influence of zinc(II), copper(II) and cobalt(II) ions and the presence of trace values of water and aqueous solutions of sulphuric acids on the photodecomposition of Cyanex 302 were studied. The results demonstrated that the presence of trace amounts of water causes mainly the degradation of bis(2,4,4-trimethylpentyl)monothiophosphinic acid with the simultaneously fourfold increase in bis(2,4,4-trimethylpentyl)phosphinic acid concentration. The shaking with aqueous solution of sulphuric acids results in the decrease in the photodegradation probably by blocking of OH radical. Metal ions also affect the degradation causing the increase in bis(2,4,4-trimethylpentyl)phosphinic acid concentration. The photodegradation was also carried out in open atmosphere under sunlight and the obtained results were compared with those obtained in a Heraeus photoreactor.