Recovery of diluted draw solution (phosphate) by Micellar enhanced membrane filtration in forward osmosis process

• Main Authors: Shu-Ying Wu, 吳舒穎
• Other Authors: Shiao-Shing Chen
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/login?o=dnclcdr&s=id=%22103TIT05087103%22.&searchmode=basic

碩士 === 國立臺北科技大學 === 環境工程與管理研究所 === 103 === Forward osmosis (FO) is an emerging membrane separation process. Recently, FO process has been applied in many applications. However, its application is still hindered due to lack of economic diluted draw solution recovery. In this study, anionic (sodium dodecyl sulfate, SDS), cationic (cetyltrimethylammonium bromide, CTAB) and nonionic (Polyethylene glycol tert-octylphenyl ether, Triton X-100) surfactants were used to couple with Na3PO4 for enlarging draw solution particle size that could improve the solute retention. Three kinds of nanofiltration (NF) membranes (HL, DL, and TS80 with MWCO of 100 to 500) and three kinds of ultrafiltration (UF) membranes (GE, GH and GK with MWCO of 1000 to 3000) were used to evaluate the draw solution recovery. The influence of operating parameters and the physicochemical properties of phosphate on the draw solution recovery were also investigated. The results demonstrate that coupling surfactant with highly charged phosphate is promising as draw solutes for application of FO, especially of Triton X-100. Strong hydrophobic interactions between tail groups of Triton X-100 and membrane are believed to be the main mechanism for minimizing salt leakage. In addition, the flux increased but solute rejection decreased as MWCO increased for different UF membranes. For NF membrane, TS80 membrane has the highest retention because of low MWCO, and although the HL and DL membranes have similar MWCO, the HL membrane presented the higher flux, attributed to the more hrdrophilic properties of the membranes. Moreover, the result of MEUF process demonstrated that coupling Triton X-100 with Na3PO4 can be regenerated with recoveries 76.8% of phosphate. Surfactant retention efficiency can reach 99% when surfactant concentration was increased, but the retention efficiency of phosphate was not improved. It is due to the high concentration of the feed solution and the physicochemical properties of phosphate ions. When using NF process, the retention efficiency of phosphate can achieve 95%.