Separation and recovery of Cr(VI) from simulated plating waste using microcapsules containing quaternary ammonium salt extractant and phosphoric acid extractant

The separation and recovery of Cr(VI) from a simulated plating waste aqueous solution, containing Cr(VI), Ni(II), Cu(II), and Zn(II), have been investigated, using microcapsules consisting of styrene-divinylbenzene copolymer and containing, as the extractant, tri-n-octylmethylammonium chloride (TOMAC) or bis(2-ethylhexyl)phosphoric acid (D2EHPA). The extractants were encapsulated successfully into the microcapsules by the addition of the extractants to the dispersed phase, during the polymerization process, and possess an extractability for the metals identical with that for the conventional liquid-liquid extraction system. Chromatographic operation, using a column packed with microcapsules, showed that perfect separation and recovery of toxic Cr(VI) was achieved with the TOMAC microcapsules, with further separation of the three other metals then being carried out with D2EHPA microcapsules.