Fractionation and Concentration of High-Salinity Textile Wastewater using an Ultra-Permeable Sulfonated Thin-film Composite

Abstract

A sulfonated thin-film composite (TFC) nanofiltration membrane was fabricated using 2,2'-benzidinedisulfonic acid (BDSA) and trimesoyl chloride (TMC) on a polyether sulfone substrate by conventional interfacial polymerization. Due to a nascent barrier layer with a loose architecture, the obtained TFC-BDSA-0.2 membrane showed an ultrahigh pure water permeability of 48.1 ± 2.1 L^-1 m^-2 h^-1 bar^-1, and a considerably low NaCl retention ability of <1.8% over a concentration range of 10-100 g L^-1. The membrane, which possesses a negatively charged surface, displayed an excellent rejection of over 99% toward Congo red (CR) and allowed the fast fractionation of high-salinity textile wastewater. The prepared membrane required only 3-fold water addition to accomplish the separation of multiple components, whereas the commercial NF270 (Dow) membrane required 4-fold water addition and almost double the length of time. Furthermore, the TFC-BDSA-0.2 membrane was subsequently tested for the dye concentration process. It maintained a high flux of 8.2 L^-1 m^-2 h^-1 bar^-1 and a negligible dye loss, even when the concentration factor reached ∼10. Finally, by using a 20% alcohol solution as a back-washing medium, a flux recovery ratio (FRR) of 95.6% was achieved with TFC-BDSA-0.2, and the CR rejection ability remained the same. These results prove the outstanding antifouling and solvent-resistant properties of the membrane.