Selective extraction and separation of textile anionic dyes from aqueous solution by tetrabutyl ammonium bromide

Tetrabutyl ammonium bromide (TBAB) has been demonstrated to be a very effective reagent for selective extraction of anionic dyes from aqueous solution. The solution of TBAB in methylene chloride is able to extract 98% of 50 mg L−1 concentration of dye solution. The distribution ratio is reasonably high (D = 49.0) even in the presence of excess chloride and sulphate ions. Extracted dye in the organic phase can be back extracted with excess of salicylic acid and sodium carbonate solution. After salicylic acid-sodium carbonate stripping and water washing, the organic layer of TBAB becomes regenerated and it can be recycled for further extraction. The stripped solution on acidification precipitated salicylic acid and the dye is recovered.