Polyvinylpyrrolidone-Aminopropyl-SBA-15 schiff Base hybrid for efficient removal of divalent heavy metal cations from wastewater.

The mesoporous silica-polymer hybrid was prepared as an adsorbent for divalent heavy metals (Pb(II), Ni(II), and Cu (II)) from rice husk and polyvinylpyrrolidone (PVP) through three successive steps. The first is the preparation of the mesoporous silica (SBA-15), the second is grafting 3-aminopropyltrimethoxysilane on SBA-15, and the following step is the formation of Schiff base (PVP-SBA-15) between amine end-capped silica and PVP moieties. The materials were characterized by different techniques, including FTIR, low and wide-angle XRD, N2-adsorption, and HR-TEM. The NH2-SBA-15 displayed a moderate affinity toward heavy element ions under study. Grafting of PVP moieties introduces a high affinity toward heavy metal ions, and the adsorption is a well-fitted Langmuir adsorption model. A series of experiment adsorption equilibrium reported with SBA-15, NH2-SBA-15, and PVP-SBA-15, which showed an adsorption capacity of 128 mg/g (Cu (II)), 175 mg/g (Pb (II)) and 72 mg/g for Ni(II). Kinetic studies have shown that the best way to describe the adsorption process of heavy metals is pseudo-first-order. The value of ΔG°, ΔH°, and ΔS° demonstrated that the adsorption of heavy metals on the PVP-SBA-15 was endothermic in nature and spontaneous. These results exhibited that PVP-SBA-15 material has considerable competence in eliminating heavy metals from wastewater.