Mechanism And Application Research On Cadmium-Methylene Blue Containing Wastewater Treatment With SDS By Micellar-enhanced Ultrafiltration

Micellar-enhanced ultrafiltration (MEUF) is a surfactant-based combined with ultrafiltration new method for the treatment of wastewater containing heavy metals and/or organic pollutant. Performance, mechanism and application of retention of Cd2+and methylene blue (MB) by using MEUF were studied in this paper. Sodium dodecyl sulfate (SDS) was selected as the surfactant and hollow fibre was adopted as the ultrafiltration membrane. Effects of operation parameters on removal of Cd2+and MB were systemically investigated. The way of improving of separation process by using MEUF was studied to decrease permeate concentrations of Cd2+, MB and SDS. The micelle size and Zeta potential of SDS micelles were determined by dynamic light scattering measurements (DLS). Two methods, acidification followed by ultrafiltration and chelation followed by ultrafiltration, were tested for separation of Cd2+/MB from SDS micelles in retentate solution of MEUF and the reuse of SDS.Firstly, the present situation and harm of heavy metal and organic pollution were summarized, the application prospect and existence question of the technique of MEUF in the industrial wastewater treatment technology were introduced, and the purpose and content of the research were also proposed. Next, MEUF was applied to treat cadmium-containing wastewater and methylene blue-containing wastewater. The best removal efficiency of Cd2+and MB was more than99.2%and99.5%, respectively. Micelles and the contaminants reacted completely under the normal temperature. The operation pressure of system was only0.03Mpa. And then the Cd2+-MB complex wastewater was treated by MEUF, which result showed that Cd2+and MB could be removed simultaneously efficiently and quickly with MEUF. The removal efficiency of Cd2+and MB could reach to98%and99%, respectively, which indicated there were no significant interrelations between Cd2+and methylene blue with regard to their separation effects compared with single removal of Cd2+/MB. The concentration of surfactants and contaimnants, temperature, the pH value, operation pressure, standing time, operation mode and concentrated coefficient had the obvious influence on retention efficiency. MEUF with the mixture of nonionic surfactant (brij35、TritonX-100) and SDS was studied. Dosage of SDS reduces obviously and residue of SDS and total concentration of surfactants in permeat decreased. Effects of concentration of Cd2+/MB and surfactant on the self-assemblv of SDS micelle are investigated from the point size and Zeta potential of micelle and the characteristic and variety rule of micelle were revealed. Recovery and reuse of SDS in the retentate stream of MEUF were conducted by two methods of acidification followed by ultrafiltration and chelation followed by ultrafiltration. Separations of Cd2+/MB from SDS micelles in retentate solution of MEUF were conducted by two methods of acidification followed by ultrafiltration and chelation followed by ultrafiltration. It was obtained good efficiency that reuse SDS in MEUF. It was shown that the method of chelation followed by ultrafiltration was more suited for recovery SDS from Cd2+-MB complex wastewater.The study showed that both single cadmium-containing wastewater/methylene blue-containing wastewater and Cd2+-MB complex wastewater were efficiently and quickly purified with MEUF. Advanced removal of SDS from wastewater was achieved with MEUF by the mixture of nonionic surfactant (brij35、TritonX-100) and SDS. The interaction between micelle and Cd2+/MB was detected by microcosmic detection to analyze the effect factors of Cd2+/MB removal on microcosmic level.In this paper, keys including parameters of control, process optimization, process and reactive mechanism between SDS and Cd2+and MB were studied and discussed. This study provided foundation for application and popularization of printing and dyeing wastewater treatment by MEUF. It was also theoretically helpful for simultaneous removal of Cd2+and MB in sewage plant.