MEMBRANE EXTRACTION OF MERCURY (II) AND SILVER (I) BY BIS(DI(2-ETHYLHEXYLOXY)THIOPHOSPHORYL)DISULFIDE

A supported liquid membrane containing bis(di(2-ethylhexyloxy)thiophosphoryl)disulfide (BTPD) as a novel membrane carrier was prepared and tested. Metal ion transfer was shown to be accelerated by the presence of thiourea or thiosulfate in the receiver stripping solutions. Under varying conditions, mercury and silver transfer rates of up to 7 and 3 mumol/m2s, were measured. Mercury transport mechanism was demonstrated to be dependent on the nature of the anion. Mercury nitrate transport appears to be mainly due to a coupled Hg2+-H+ facilitated diffusion mechanism, according to the ion-exchange stoichiometry. Mercury halides were transported mainly as neutral complexed species due to carrier-facilitated diffusion. Selectivity of the membrane for mercury and silver over zinc, nickel, cadmium and copper has been found to be of the order of 10(3).