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

Abstract

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.