Effect Of An Divalent Electrolyte On The Coagulation Of Anionic Surfactants With Al³⁺

Surfactant is a carrier of insoluble environmental hazardous substances to water body, it is becoming an ubiquitous question in aquatic environment owing to its popular usage. To enhance removal efficiency of residual surfactents in water system, the coagulation characteristics of anionic surfactants Sodium Dodecylbenzenesulfonate (SDBS) and Sodium dodecyl sulfate (SDS) of concentrations above and below the critical micelle concentration (CMC) using different dosage of AICl3 salt and the effect of an divalent electrolyte Ca2+ on the coagulation of anionic surfactants SDBS and SDS with Al3+ were investigated at 298.15K. The water used in this paper was 0.0014 mol/L CaCl2 solution, and its concentration was determined on the referencess of tap water. The coagulation characteristics of Zeta potential, surface tension, z-average size, electrical conductivity and pH were determined at 298.15K.Results showed that,(1) The optimum coagulation molar ratios of anionic surfactants SDBS and SDS of concentrations above and below the CMC with Al3+ were obviously different, this may be on account of the presence of micelles.(2) At optimization coagulation areas, pH values of SDBS/Al3+ and SDS/A13+ coagulation systems were around 3.5 and below 4.0 respectively whether the surfactant concentrations above or below the CMC.(3) The aggregates completely disappeared were observed only in two systems of SDS (0.01 mol/L)/Al3+ and Ca2+/SDS(0.01 mol/L)/Al3+, but not observed in the systems of SDS (0.001 mol/L)/Al3+, SDBS/Al3+ and Ca2+/SDBS/Al3+.(4) The effect of Ca2+ on the optimum coagulation molar ratios, conductivity and pH of coagulation of anionic surfactants with Al3+ were ignored.(5) Comparing SDBS/A13+ and Ca2+/SDBS/Al3+ systems, the z-average size value of coagulation of SDBS(0.01 mol/L)/Al3+ was larger than that of Ca2+/SDBS(0.01mol/L)/Al3+ system owing to the formation of the precipitate of Ca(DBS)2 possiblely.(6) Comparing SDS/Al3+ and Ca2+/SDS/Al3+ systems, Zeta potential absolute value and surface tension value of SDS(0.01mol/L)/Al3+ system were smaller than Ca2+/SDS(0.01mol/L) /Al3+ system, but the Zeta potential absolute value and surface tension value of SDS(0.001mol/L)/Al3+ system were larger than Ca2+/SDS(0.001mol/L)/Al3+ system.