Effect of electrolyte on BTEX romoval using aqueous surfactant two-phase systems technique formed by cationic and anionic surfactant mixtures

Abstract

Contamination of benzene, toluene, ethylbenzene, and xylene (BTEX) are commonly found in industrial wastewater causing several concerns including environmental problems and health effects to human. A new separation technique to remove BTEX from wastewater by using mixtures of cationic and anionic surfactants is called aqueous surfactant two-phase system (ASTP). A phase separation occurs at certain surfactant composition and concentration forming two immiscible phases. One is surfactant-rich and the other is surfactant-diluted. Most of contaminants concentrate in the surfactant-rich phase leaving the surfactant-depleted phase containing only small amount of contaminants as treated water, In this research, the effect of added electrolytes on the critical aggregation concentration (CAC) and the extraction efficiency of ASTP formed by mixtures of cationic (dodecyltrimethylammonium bromide; DTAB) and anionic (alkyl diphenyl oxide disulfonate; DOWFAX 8390)surfactants were investigated. The results show that the CAC value decreases with the addition of electrolyte in the following order; NaF > KCl ~ NaCl > LiCl > and MgCl[subscript 2]. But the addition of Nal shows the opposite result in which the CAC value is enhanced upon added electrolyte. In addition, the extraction of BTEX from wastewater at total surfactant concentration of 50 mM with 2:1 molar ratio of DTAB:DOWFAX in the presence of electrolyte (LiCl, NaCl, KCl, and MaCl[subscript 2]) is enhanced as compared with the absence of electrolyte. At 1.0 M NaCl, about 95% of xylene, 92% of ethylbenzene, 90% of ethylbenzene, 90% of toluene and 79% of benzene are extracted into the surfactant-rich phase, respectively. Nevertheless, different cation of inorganic electrolyte equally enhances the efficiency on VOC extraction. the higher degree of hydrophobicity shows the greater potential of contaminant to be extracted in the surfactant-rich phase in the following order: xylene > ethlbenzene > toluene > benzene.