Advanced thin-film composite polyamide membrane for precise trace short-chain PFAS sieving: Solution, environment and fouling effects

Abstract

Membrane separation technology has been favorably applied to acquire non-polluting permeate in conditions of contaminative aqueous environment. However, some emerging contaminants with critical impacts on human health and environmental safety such as poly- and perfluoroalkyl (PFAS) compounds composed of various molecular chains are frequently found in water treatment process steps. Especially, short-chain PFASs remain poorly understood in nanofiltration membrane. A thin-film composite membrane with a hyaluronic acid interlayer (TFCi) had been finely tailored to simultaneously gain ameliorative permeate and rejection. Experiments were performed on a small-scale installation to investigate the correlation between operating parameters and short-chain PFASs removal performances. Results showed effectual trace short-chain PFASs rejection during various pressure, temperature, pH, concentration and fouling conditions. Alginate fouling micelles increased PFAS retention and generated a rapid flux decline; nevertheless, the pollutant could be largely removed by washing. Furthermore, molecular dynamics simulations were utilized to reveal the mechanism of the trace short-chain PFASs rejection competence. The hyaluronic acid interlayer was able to suppress the diffusion rate toward the reaction boundary, facilitating the formation of fast water transport pores with good rejection performance for PFAS in polyamides. These results provide important insights into the mechanism of trace hydrophobic contaminants removal system and the interlayer design approach for efficient short-chain PFAS removal using nanofiltration membranes.