A serendipity of nanofiltration membrane modification using a simple approach: Limited sulfonamidation, remarkable improvements

•Sulfuryl chloride (SC) was used for NF membrane surface modification and mechanism study.•SC behaved alike small and reactive diacyl chlorides in tuning pore size and surface charge.•SC was incorporated with a low percentage but endowed the membrane with substantial effects.•SC could elevate the crosslinking degree of the top segment of nascent membrane.•The effect of secondary amidation on membrane after heat curing would be restricted.