Liquid-Liquid Extraction of Bivalent Zinc and Cadmium from Aqueous Solutions by Long-Chain Alkyl Quaternary Ammonium Carboxylates

摘要

The extraction of zinc and cadmium from aqueous solutions by long-chain alkyl quaternary ammonium carboxylates, prepared by combination of trioctylmethylammonium chloride (R_3R'NCl) and carboxylic (octanoic, decanoic and lauric) acids (R"COOH), in benzene has been investigated in the vicinity of neutral pH. The organic phases were examined by infrared spectral measurements. As a result, it is found that the extraction efficiency is in the order Zn Cd with R_3R'NR"COO concentrations which are higher or lower than 0.05 mol dm~(-3), respectively. In addition, the extraction processes for Zn(II) and Cd (II) may be expressed as Zn~(2+)(aq) + 2Cl~- (aq) + 3R_3R'NR"COO(org)<=> (R_3R'N) [Zn (R"COO)_3] (org) + 2R_3R'NCl(org) and CdCl~+ (aq) + Cl~+ (aq) + 2R_3R'NR"COO (org) <=> (R_3R'N)_2[Cd(R"COO)_2Cl_2] (org), respectively.