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I.

INTRODUCTION

IN the conventional process of zinc refining, a series of process steps is needed to remove the impurities in the solution before electrowinning the zinc. In the future, successful solvent extraction processes may extract zinc selectively from solution, eliminating many solutionpurification steps. Di-n-butyl butylphosphonate (DBBP) has a high selectivity and loading capacity for zinc from a solution resulting from ferric chloride leaching of a complex sulfide ore. I~,21Phase disengagement was also relatively rapid with DBBP diluted in Escaid 1 10. The aim of this work was to study the extraction reaction of zinc with DBBP in chloride solutions and to identify the stoichiometry factors of each reactant and product species. For a solvating extractant, such as DBBP, extraction occurs as the extractants replace water molecules in the primary hydration sheath of the extracted species. Therefore, the number of water molecules involved was also of interest. II.

EXPERIMENTAL

were conducted at room temperature, A / O = 1 : 1, and the organic phase was 50 pct by volume DBBP in Escaid 110 unless otherwise noted.

C. Analysis Direct analysis of zinc concentration in both aqueous and organic phases was adopted in this study to obtain more reliable data on the distribution of zinc in these two phases. Zinc concentrations in aqueous and organic phases were determined using a PERKIN-ELMER* 603 atomic ab*PERKIN-ELMER is a trademark of Perkin-Elmer Physical Electronics, Eden Prairie, MN.

sorption spectrophotometer. For zinc analysis in the organic phase, standard solutions were made by diluting a standard zinc solution of 5000 parts per million (ppm) in oil with a blending oil. The blending oil consisted of 16 pct base oil, 0.6 pct stabilizer, and 83.4 pct kerosene (volume-to-volume ratio). The standard zinc solution of 5000 p p m in oil, base oil, and stabilizer was supplied by the Conostan Division, Conoco Inc., Ponca City, OK.

A. Reagen~ All reagents used in this study were The DBBP was obtained from Albright Richmond, VA, and the Escaid 110, luent, was from Exxon Co., Houston,

of reagent grade. and Wilson, Inc., serving as a diTX.

B. Procedure In the extraction tests, organic solvent was mixed with the aqueous feed in a 500-ml beaker with the desired aqueous to organic volume ratio (A/O). Mechanical agitation was applied for 15 minutes. Agitation of 30 minutes provided identical results, indicating that extraction equilibrium was reached within 15 minutes. The mixture was then poured into a separatory funnel and allowed to settle in the funnel for 30 minutes. Both the organic and aqueous phases were sampled for chemical analysis. Aqueous samples were filtered before analysis. All tests H.K. LIN, Associate Professor, is with the Mineral Industry Research Laboratory, University of Alaska Fairbanks, Fairbanks, AK 997751180. Manuscript submitted June 23, 1992. METALLURGICAL TRANSACTIONS B

III.

RESULTS AND DISCUSSION

In each test, the zinc mass balance was calculated by analyzing the zinc concentration in b