Nontoxic polyvinylpyrrolidone-propylmethacrylate-silica nanocomposite for efficient adsorption of lead, copper, and nickel cations from contaminated wastewater

Abstract

Water pollution with heavy metals poses many global challenges, especially concerning environmental sustainability, which raises more attention to the field of increasing the performance of the adsorbent materials for toxic heavy metals. This study presents the synthesis of silica nanocomposite from rice straw residues with a high surface area and activating its surface with (3-aminopropyl)triethoxysilane and 3-(trimethoxysilyl)propyl methacrylate (VNH2–SiO2), and the exploitation of acrylates group to link vinylpyrrolidone monomer to produce nontoxic polyvinylpyrrolidone-propylmethacrylate-silica nanocomposite (PVP-SiO2). FTIR and low/high angle-XRD, surface-area profiles are used to identify the properties of these materials. The BET-surface area of silica and activated silica, VNH2–SiO2, and PVP-SiO2 materials were of 985, 603, and 388 m2 g−1, with a pore diameter of 4.1, 2.8 and 2.1, respectively. The obtained PVP-SiO2 showed fast adsorption rates and good adsorption capacity of 142.8, 111, 46.08 mg/g, toward lead, copper, and nickel cations, respectively, compared to VNH2–SiO2. Strengthening the structure of silica pores with the groups of carbonyl, amine, and pyrrolidone rings has helped to enhance the adsorption of metal cations on the PVP-SiO2 nanocomposite. By applying the polymer to a sample that mimics a contaminated industrial wastewater sample, the adsorption efficiency was estimated at 99% and decreased to 96% after reuse for four times. Adsorption kinetics are well-matched with the model of pseudo-first-order, whereas the adsorption equilibrium coincided well with the Langmuir model. The calculated thermodynamic parameters (Δ G°, Δ H°, and Δ S°) indicate that the adsorption of lead, copper, and nickel ions on PVP-SiO2 was endothermic and spontaneous. The study of the possibility of material reuses demonstrated that the proposed PVP-SiO2 can be used multiple cycles without a significant reduction in the original adsorption performance.