Enhanced removal of toxic Disperse Blue 35 dye through cloud point extraction: influence of parameters and solvent regeneration

The release of the dye Disperse Blue 35 (DB35) into water has serious environmental and health consequences, due to its toxicity and resistance to degradation. This paper investigates the effectiveness of cloud point extraction (CPE) to remove this industrial dye from aqueous solution by Lutensol AO7 and Triton X-114, two environmentally friendly nonionic surfactants. First, the partial phase diagrams of the water–surfactant binary systems are constructed. Then, the effects of pollutants, sodium sulfate and cetyltrimethylammonium bromide on the cloud point temperature (T c) are determined. The experimental results are expressed by four responses: Extraction efficiency (E), residual concentrations of solute and surfactant in the dilute phase (X s,w and X t,w, respectively) and the volume fraction of coacervate (Ф c). An empirical smoothing method was applied. For each parameter, the results obtained were modeled using the response surface methodology (RSM) and represented on three-dimensional diagrams. The results show that the efficiency of dye extraction with Lutensol AO7 and Triton X-114 at a concentration of 6 wt% is about 95 % and 82 %, respectively. The influence of salt and ionic surfactant on the effectiveness of CPE for the removal of DB 35 dye was determined. The regeneration of surfactant was only achieved by pH adjustment.