Surface modification of reverse osmosis membranes by grafting of polyamidoamine dendrimer containing graphene oxide nanosheets for desalination improvement

The use of grafting method by a dendrimer coupling with a nanomaterial in the modification of commercial polyamide reverse osmosis membranes is reported. This study provides the effect of grafting method with a hydrophilic polyamidoamine (PAMAM) dendrimer and graphene oxide (GO) nanosheet to reduce fouling. The response surface method with central composite design (CCD) was used to optimize the input variables of the grafting process, i.e. dendrimer concentration, grafting time and grafting temperature, and the responses of this method included flux, salt retention and antifouling. First, the grafting conditions were optimized and next, different amounts of GO were dispersed in optimum formulation. The modified membranes were tested using humic acid (HA) solution for fouling test and NaCl and NaNO₃ solutions for permeability and rejection tests by a cross-flow setup. The results from ATR-FTIR, SEM, AFM, contact angle and zeta potential analyses established successful grafting and modification. The modified PAMAM/GO and PAMAM membranes exhibited less fouling than the commercial reverse osmosis membranes. Among these, the modified membrane with 1.5 wt% PAMAM concentration at 30 °C of grafting temperature and 6 min grafting time with 1 wt% dispersed GO has the least amount of fouling and has the lowest contact angle, the best chlorine resistance; and improved desalination performance in real wastewater treatment.