Abstract
Purification of commercial phosphoric acid produced by the wet process from toxic heavy metals such as zinc and manganese is considered to be a very important environmental and economical process. The commercial bis(2,4,4-trimethylpentyl)- phosphinic acid (Cyanex-272) is proposed as an extractant for the efficient removal of Zn(II) and Mn(II) from crude phosphoric acid samples of concentrations of 25% and 45%. Various parameters affecting the extraction rate of Zn(II) and Mn(II) were investigated. The results were assessed to obtain the optimum conditions for the fast and efficient removal of both cations from crude phosphoric acid using Cyanex-272 as an extractant in various diluents. The selectivity sequence of different diluents for Zn(II) and Mn(II) extraction were: kerosene > n-hexane > cyclohexane > toluene > benzene > chloroform. The stripping of the investigated metal ions is efficiently performed with ammonium thiocyanate which has been selected as a suitable stripping agent.