High-performance PVC/polyacrylate-graphene oxide membranes for Pb (II) and Hg (II) ion removal from polluted water: synthesis, characterization, and adsorption studies.

Abstract

Heavy metals cause significant harm to both flora and fauna. Hence, it is mandatory to efficaciously eliminate them from drinking water preceding their release into the ecosystem. Herein, we first prepared Na-polyacrylate (PA) powder from sim-sim balls and graphene oxide (GO) using sugar cane bagasse as an adsorptive material. The prepared adsorbents were mixed with poly(vinyl chloride) (PVC) to fabricate novel adsorptive composite polymer membranes, pure PVC, PVC/GO, and PVC/PA-GO shortly named as PPGO-CPMs using the solution casting method. The as-synthesized membranes were used for the removal of Hg (II) and Pb (II) from contaminated water through the adsorption technique. Among the prepared PPGO membranes, PVC/PA-GO showed a maximum adsorption capacity of 18.04 ± 0.3 mg/g and 17.73 ± 0.4 mg/g for Pb (II) and Hg (II) respectively. PVC/PA-GO also showed greater removal efficiency for Pb²⁺ (72.87 ± 0.4%) and Hg²⁺ (71.62 ± 0.5%) among the other CPMs. Additionally, the effects of changes in initial metal concentration, interaction time, solution pH, and temperature on the removal performance were investigated. Maximum removal efficiencies for all the membranes were observed at 40 ppm initial metal concentration, a reaction time of 300 min, a pH value of 6, and 338 K temperature. The adsorption mechanism was studied through the linear form of Langmuir and Freundlich adsorption models. By comparing R², it was found that the Freundlich model best explained the adsorption process. For understanding reaction kinetics, pseudo-first-order and second-order kinetics were studied. The adsorption data was best aligned with pseudo-first-order kinetics. Adsorption on the surface of PVC was exothermic while it was endothermic on the surface of PVC/GO and PVC/PA-GO membranes. Functional groups present in PPGO-CPMs were confirmed by Fourier transform infrared spectroscopy (FTIR). Thermo gravimetric analysis/differential scanning calorimeter (TGA/DSC) tool reported high thermal stability, and the X-ray diffraction technique described the amorphous nature of the prepared composites. Porosity, water uptake, and ion adsorption capacity of the composite membranes were also studied to understand the hydrophilic nature of the CPMs. These resulting composites can help to treat water as a pH-stable composite membrane at pH 6.