Determination of thermodynamic parameters for surfactant mediated cloud point extraction of Brilliant cresyl blue dye in aqueous solutions

Abstract

A surfactant-mediated cloud point extraction (CPE) method utilizing Triton X–114 (TX–114) and sodium dodecyl sulphate (SDS) has been established for the determination of brilliant cresyl blue (BCB) dye in aqueous solutions at a pH of 3.4 (Citrate buffer). The effect of pH, surfactants, temperature, time and salt has been optimized for maximum recovery of BCB dye. The linear range and detection limit of BCB were found to be 0.0–19.29 μg mL–1 and 9.42 ng mL–1 respectively. The CPE method has achieved a recovery of 94.1-100.8 % in aqueous solutions. The negative values of Gibbs free energy change (ΔG0) show that CPE of BCB is feasible and spontaneous. The positive values of enthalpy change (ΔH0) show that the solubilizaton of BCB extraction is endothermic in nature. The positive values of entropy change (ΔS0) show that the dye molecules are arranged in the most orderly pattern in the micellar phase. These results indicate that thermodynamic parameters are the direct evidence of the good recoveries achieved by this CPE method.