l-Tartaric acid tailored polyamide thin-film composite membrane with enhanced performance for salt and molecular removal

High performance polyamide (PA) thin-film composite (TFC) membranes are in great demand. However, it is still a challenge to further enable PA TFC membranes to overcome the perm-selectivity tradeoff. Here, l-tartaric acid (LTA) and piperazine were first used as the aqueous phase monomers to fabricate LTA integrated PA (LTA/PA) TFC membranes via interfacial polymerization (IP) with trimesoyl chloride. The physicochemical property and separation performance of the PA TFC membranes were regulated via LTA concentrations. The introduction of LTA made the PA layer of the membrane thinner and smoother with enlarged pore size. The LTA/PA TFC membrane prepared with a higher LTA content had a maximal water flux (207.6 LMH/bar, 20 times higher than that of the control membrane), with superior rejections for the dyes (>98.0 %) and low removal rates for the salts (<4.5 %). Of note, the water flux of the membrane prepared with a low LTA content was enhanced to 18.9 LMH/bar without sacrificing the rejection of Na2SO4 (RNa2SO4 > 98.0 %). The membranes with optimal LTA content break the tradeoff towards some dyes or salts, and presented superior performance compared with most other reported polymeric membranes. This work highlights the great potential of constructing natural acid-modulated PA composite membranes in water purification.