Solvent extraction of methyl violet with salicylic acid from aqueous acidic solutions

The solvent extraction of methyl violet from aqueous acidic solutions by salicylic acid in xylene was studied. Inorganic acids such as hydrochloric acid (HCl), sulphuric acid (H2SO4) and nitric acid (HNO3) were used to adjust the pH of aqueous feed phase. HCl was shown to give higher efficiency of extraction and higher distribution coefficient at pH=6.0+/-0.1 than H2SO4 and HNO3. The distribution coefficient increased from 4 to 24 when salicylic acid concentration was increased from 1.4x10(-2) to 3.6x10(-2) mol L-1. The presence of salt such as sodium sulphate (Na2SO4) in the feed phase decreased the extraction efficiency. The extracted dye was stripped into 9 mol L-1 of aqueous acetic acid solution. The loading capacity was found to be 5.1 mg of dye per 3.6 x 10(-2) mol L-1 of salicylic acid (25 mL of xylene contain 0.0125 g of salicylic acid). (C) 2010 Elsevier B.V. All rights reserved.