Design of hybrid g-C3N4/GO/MCE photocatalytic membranes with enhanced separation performance under visible-light irradiation

Photocatalytic membranes with concurrent catalytic oxidation and separating functions possess promising potentials for the degradation of organic pollutants in wastewater treatment. Herein, we designed a hybrid photocatalytic membrane (viz., g-C3N4/GO/MCE) by vacuum-filtration-assisted assembling method, consisting of graphitic carbon nitride (g-C3N4) nanosheets as a top layer, graphene oxide (GO) nanosheets as an interlayer, and commercial mixed cellulose ester (MCE) as a substrate layer. The microstructures, chemical compositions, and physicochemical properties of the designed g-C3N4/GO/MCE membranes were systematically characterized by a series of characterization techniques. Particularly, photocatalysis-filtration reactor cells were designed for the evaluation of the simultaneous separation and photocatalytic degradation performance in a single unit using both organic dyes and antibiotics as modeling pollutants in wastewater. Four parameters were adopted to represent the integrated photocatalysis-filtration performance of our designed photocatalytic membranes, including permeance (P), rejection (R’, filtration alone), removal (R, combined photocatalysis-filtration under light-irradiation), and degradation rate (D). The hybrid membranes showed superior permeance and solute removal under visible-light irradiation (300 W, λ > 420 nm), in which the permeance was 20% higher than that of no-irradiation conditions. In addition, 10 consecutive cycling tests and light-on/off cycles of the as-prepared g-C3N4/GO/MCE membrane toward RhB showed quite stable permeance in the range of 268.9 to 352.9 L h−1 m−2 bar−1, and the removal was maintained in the range of 88.4% to 95.4%, indicating excellent long-term stability. Remarkably, it also exhibited good removal performance of antibiotics (e.g., ofloxacin, norfloxacin, sulfamethoxazole, erythromycin, and roxithromycin). Accordingly, the designed hybrid g-C3N4/GO/MCE photocatalytic membranes with excellent photocatalytic activity and photocatalysis-filtration performance are promising for wastewater treatment and water purification applications.