Effects of Temperature on the Solvent Extraction of Zinc and Cadmium Complexes with 8-Quinolinol and 2-Methyl-8-quinolinol into 1,1,2,2-Tetrachloroethane, 1-Octanol, and p-Xylene

Abstract

Abstract The effects of temperature on the extraction of zinc(II) and cadmium(II) complexes with 8-quinolinol (HQ) and 2-methyl-8-quinolinol (HR) into three different types of organic solvents whose boiling points are relatively high were studied. 1) In the case of 1,1,2,2-tetrachloroethane (TCE), the extraction equilibrium can be written as follows (except for that of zinc with 2-methyl-8-quinolinol): 2M2++6HQ(o)+X−\ightleftarrowsM2Q3(HQ)3+(o)+X−(o)+3H+, where X− refers to various inorganic anions. An ion-pair of the binuclear complex (complex ion pair) dissociates into a complex cation and an inorganic anion in the organic phase. The distribution ratios decrease remarkably with an increase in temperature. 2) In the 1-octanol (S) extraction system, zinc and cadmium are extracted as solvent-adducts, such as MQ2·S2. The distribution ratios are almost constant with a change in temperature. 3) In the p-xylene extraction system, a hydrated metal complex, MQ2·2H22H2O, may precipitate and be deposited at the interface of both phases, except for the extraction of zinc with 2-methyl-8-quinolinol. 4) The zinc complexes of 2-methyl-8-quinolinol are extracted into TCE and p-xylene as anhydrous complexes, such as MR2. The distribution ratios increase with an increase in temperature. Moreover, zinc can be separated from cadmium at high temperatures using 2-methyl-8-quinolinol and TCE.