Fabrication of Polysulfone-based (ZnOGO-NiO) Mixed Matrix Membrane for the Adsorptive Removal of Lead (Pb+2) and Cadmium (Cd+2) Heavy Metal Ions from wastewater

Abstract

The presence of heavy metal ions, such as chromium, lead and cadmium, in industrial wastewater discharge streams are major contaminants that poses a risk to human health. These HMs should be separated from the wastewater to ensure the reuse of the discharged water again in the process and also to mitigate their environmental impacts. The distinctive mechanical properties of 2D graphene oxide (GO), antifouling characteristics of zinc oxide (ZnO), and metal oxide (NiO) nanoparticles can be combined to produce composites supporting special features for various applications in wastewater treatment. In this study, solution casting and phase inversion methods were employed to synthesize polysulfone-based GO, ZnO-GO and ZnO-GO-NiO mixed matrix membranes with different compositions and the effects of variation in composition on the removal of lead (Pb2+) and cadmium (Cd2+) ions were examined. Several characterization techniques including X-ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) were applied to investigate the crystallinity, functional groups, morphology, and elemental analysis of the synthesized nanoparticles and composite membranes, respectively. The composite membranes were also analyzed in terms of their porosity, pore size, permeability, contact angle, surface zeta potential, surface roughness, thermal stability, mechanical strength, and flux regeneration at the different transmembrane pressure of 2-3 kgcm-2 . The effect of variation in feed concentrations on the total adsorption capacity was investigated by varying the feed concentrations from 50 to 200 mg L-1 and fixed pH value of 5.5. Highest adsorption capacity was measured to be 308.16 mg g-1 and 354.80 mg g-1for Pb (II) and Cd (II) respectively, for membrane (M4_A) having 0.3 wt.% of ZnO-GONiO nanocomposite, at 200 mg L-1 of feed concentration and 1.60 mL min-1 of permeate flux. Yet, the lower feed concentration and flow rate allowed the membrane to operate for a longer period of time while maintaining a better efficiency without regeneration. The Pb (II) and Cd (II) adsorption breakthrough curves were created, and the experimental data was compared with the Thomas model that shows ± 4.7% error and 0.99 correlation coefficient (R2 ).