Removal of acid dye from wastewater by cloud point extraction and regeneration of surfactant by pH regulation

Abstract This work concerns the coacervate extraction of industrial dye, namely Acid Green 9 (AG-9) from aqueous solution by nonionic surfactant Lutensol AO7 and TX-114 (readily biodegradable). Binary water/surfactant and pseudo-binary phase diagrams were plotted. The extraction results as a function of wt% of the surfactant and temperature are expressed by: percentage of solute extracted, E%, residual concentrations of solute and surfactant in the dilute phase (X s,w and X t,w respectively) and volume fraction of coacervate at equilibrium (Фc). For each parameter, whose values are determined by a design of experiments, these results are subjected to empirical smoothing in three dimensionsusing response surface methodology (RSM). The aim of this study is to find out the best compromise between E % and Фc. Under optimal conditions, the extraction extent of AG-9 reaches 98 % and 96 % using TX-114 and Lutensol AO7, respectively. The effect of Na2SO4 and CTAB addition is also studied. Finally, the possibility of recycling the surfactant is proved.