Hexavalent chromium recovery by liquid-liquid extraction with 2-octylaminopyridine from acidic chloride media and its sequential separation from other heavy toxic metal ions

A systematic study of extraction of chromium(VI) with 2-octylaminopyridine (2-OAP) in xylene at room temperature has been conducted. Quantitative extraction of chromium(VI) was observed in the 0.4-0.8 M concentration range of hydrochloric acid. From the extracted complex species in the organic phase, chromium(VI) was back extracted with 7 N ammonia (3 × 10 mL), and was determined by spectrophotometric method. Various parameters such as 2-OAP concentration, equilibrium period, effect of various diluents, aqueous: organic volume ratio, acidity and diverse ions were studied. The extraction reaction proceeds with ion-pair formation and the stoichiometry of extracted species was found to be [(2OAPH+) CrO3Cl−](org). The separation and determination of chromium(VI) from associated and toxic metals in binary, ternary and multicomponent mixture were carried out. The method permits the sequential separation of chromium(VI) from other toxic metals and has been used to separate and determine chromium(VI) from alloys, and effluent water samples from tannery industries.