A novel gold nanocomposite membrane with enhanced permeation, rejection and self-cleaning ability

The trade-off relationship between permeability, selectivity, and antifouling capability of nanocomposite membranes is the focal point of effective membrane technology. This study introduces a new gold nanocomposite membrane with enhanced antifouling behavior and permeability, as well as improved rejection capability for water treatment. Different (0.5, 1 and 2 wt%) concentrations of citrate-stabilized (coating) gold nanoparticles (CT-GNPs) having a core size of 50 nm were embedded into the polysulfone (PSF) membranes by the phase inversion method, resulting in alterations on PSF membrane performance. The intrinsic physicochemical properties and operational ability of all gold nanocomposite membranes were evaluated with regard to the self-cleaning, flux and selectivity criteria for water purification process. The PSF/0.5% GNPs demonstrated the optimal pore structure, morphology, and electrochemical surface properties among the gold nanocomposite and pure PSF membranes. The negative surface charge and the super hydrophilic functional group of CT-GNPs enhanced the permeation (at least three times in comparison with pure PSF membranes) and rejection ability of nanocomposite membranes. In addition, CT-GNPs showed digestive behavior towards humic acid (HA), a natural foulant, that significantly enhanced the antifouling ability (FRR = 95%) of the gold nanocomposite membranes by degrading the HA formed cake layer on the membrane surface and fragmenting the large HA aggregates that blocked the pores. The degradation of HA compounds by the embedded CT-GNPs occurred during the filtration process at room temperature and under the regular visible light. The stability of embedded GNPs into the polymeric matrix of membranes was evaluated at static and dynamic conditions for several days, and no release of CT-GNPs was observed.