A selective, sensitive and efficient liquid-liquid extraction (LLE) of industrial waste water containing dyes namely Methylene Blue (MB) and Eriochrome Black T (EBT) has been studied using Bis(2,4,4-trimethyl pentyl)dithiophosphinic acid(Cyanex 301) in dichloromethane, as an extractant. Dye free aqueous phase was obtained and the dye mixture was extracted into organic phase. With the lowering of pH there was an increase in efficiency of extraction. The dyes could be separated from each other by treating the organic layer, with sodium hydroxide solution. Methylene blue remained in the organic phase and Eriochrome black T got stripped into the aqueous phase. MB & EBT were later determined spectrophotometrically at 654nm& 530 nm respectively. The method was optimized by varying experimental parameters such as feed source pH, effect of diluent, cyanex concentration, extraction time, aqueous to organic ratio, effect of salt concentration, and effect of concentration of stripping agent. The dyes were totally extracted, separated and determined at the optimum conditions.
