Abstract: The extraction of zinc by di(2ethylhexyl)dithiophosphoric acid(D2EHDTPA)trioctylamine(TOA) was investigated.Conductance titration and interfacial pressure measurement showed that when D2EHDTPA and TOA were mixed they reacted and formed an electrolyte of ionic pairs.The extraction of zinc by the electrolyte was of antisynergistic nature,and the reaction was Zn2＋＋2BHA(O) → ZnA2(O)＋2B(O)＋2H＋ (subscript (o) stand for “oil phase”).The zinc extraction was an endothermic reaction ,the heat of reaction was 130.1 kJ•mol－1.Some phenomena of interface concerned were also discussed.

Key words: Zinc, Solvent extraction, Antisynergism, Thio-substituted organophosphoric acid, Trioctylamine, Interface properties