Organic matter removal and antifouling performance of sulfonated polyaniline nanofiltration (S-PANI NF) membranes

Abstract

Natural organic matter (NOM) removal from water prior to other treatment processes can improve treatment efficiency and final water quality. Here, NOM removal across five size fractions by newly developed sulfonated polyaniline nanofiltration (S-PANI NF) membranes was compared with a commercial membrane and conventional adsorption-coagulation-flocculation, optimized for NOM removal. Artificially prepared surface water and seawater containing 10 – 100 mg C L−1 NOM extract and a stabilized landfill leachate served as test solutions. S-PANI NF membranes showed best NOM separation performance for both surface and seawater followed by the commercial membrane and conventional treatment. For landfill leachate conventional treatment had the best performance followed by S-PANI NF membranes. S-PANI performed slightly better in removal of chemical oxygen demand (COD) (74%) compared to the commercial membrane (70%) and conventional treatment (70%). Both membranes performed consistent with increasing salinity and NOM concentration, while experiencing a modest carryover at higher salinity. During long-term fouling S-PANI exhibited slower growth in transmembrane pressure (TMP), less affinity towards organic matter and higher flux recovery compared to the commercial membrane, particularly at high NOM concentration. This is the first study to investigate S-PANI membranes for water treatment applications and under high-fouling conditions. Results indicate S-PANI NF membranes are promising for such applications. In addition, this study also provides an inter-process comparison for NOM removal over an extreme range of water matrix conditions.