Self-cleaning properties of L-Histidine doped TiO2-CdS/PES nanocomposite membrane: Fabrication, characterization and performance

Abstract

The polyethersulfone (PES) membrane incorporated with L-Histidine doped TiO2-CdS photocatalytic nanocomposite is fabricated to improve the membrane performance and its antifouling properties. The L-Histidine doped TiO2-CdS/PES nanofiltration membrane was characterized by scanning electron microscopy (SEM), contact angle and atomic force analysis (AFM) analyses. SEM images and contact angle results are demonstrated that membrane porosity and its hydrophilic properties increase with adding of L-Histidine doped TiO2-CdS photocatalytic nanocomposite. Moreover, AFM images of the modified membranes indicate favorable changes in surface roughness resulting in the improvement of antifouling properties. The pure water flux, flux recovery ratio (FRR) during filtration of milk powder and activated sludge suspension were also measured in a dead end cell. Increasing membrane permeability and FRR value approved its effective role of the added nanoparticles into the PES matrix. The M3 (0.5 wt% of NPs) membrane is selected as an optimal nanocomposite membrane which exhibits a much higher pure water flux (42.1 kg/m2 h) and FRR value (90 and 97% during filtration of milk powder and activated sludge suspension, respectively). The photocatalytic capability and antifouling properties of the M3 membrane as an optimum membrane were also investigated in a cross flow cell under continuous visible light irradiation. As a result, the high permeation flux (34.7 kg/m2 h), COD removal (100%) and FRR value (99%) was achieved during filtration of biologically treated palm oil mill effluent (POME) with COD concentration of 1000 mg/L at feed flow rate of 150 L/h and pressure of 5 bar. Effect of feed flow rate (50 and 150 L/h) and COD concentration (1000, 3000 and 5000 mg/L) on the membrane performance and its fouling resistance was also evaluated. Increasing feed concentration shows a negative effect on the membrane performance while feed flow rate increases separation performance and self-cleaning properties of the M3 membrane.