Promoting the efficiency of tetracycline removal from tap water with commercial NF membranes via a facile post-treatment

How to simultaneously improve the water permeance and antibiotics/minerals selectivity is one of the key issues for promoting the efficiency of drinking water treatment with nanofiltration (NF) technology. In this study, the post-treatment with a ternary complex of ethanol-water-NaOH (denoted as EWN) was used on four commercial NF membranes (NF270, NF90, HS-200C, and DF100) to understand its modification mechanism and promote the tetracycline removal efficiency. It was confirmed that the polyamide layers of all four commercial NF membranes were thinner after EWN post-treatment along with a slight increase in the pore size and enhancement in hydrophilicity and electronegativity. As a result, the water permeation of NF270 was improved by 70% and that of the other three membranes was increased by 19–20% while keeping a high tetracycline rejection of over 99%. Simultaneously, mineral ions such as K+, Ca2+, Mg2+, and Cl- passed the post-treated commercial NF membranes more easily. This yields a facile strategy for the performance regulation of existing, or commercial NF membranes.