N-Phenyl acrylamide-incorporated porous silica-bound graphene oxide sheets with excellent removal capacity for Cr(iii) and Cr(vi) from wastewater

Abstract

The sophisticatedly altered Hummer's and sol–gel procedures were applied for the synthesis of graphene oxides and porous silica monolith particles respectively. The Fischer esterification protocol was used for coupling silica monoliths with graphene oxides. A N-phenyl acrylamide-incorporated porous polymer was synthesized at the surface of composites via reversible addition fragmentation chain transfer polymerization. The composition was confirmed by Fourier transform infra-red spectroscopy, FE-SEM, X-ray diffraction, zeta potential (zeta pH), Brunauer–Emmett–Teller (BET/BJH) analysis, and EDAX analysis. The resulting polymer-bound composite efficiently removed Cr(VI) and Cr(III) from waste water. Adsorption parameters such as contact time, pH effect, temperature, and adsorbent and adsorbate concentration were optimized for the optimal output of the composite. The kinetic and equilibrium models were applied to the adsorption of Cr(VI) and Cr(III) at the adsorbent surface. The maximum adsorption capacity (q_e) of Cr(VI) and Cr(III) was found to be 298.507 mg g⁻¹ and 401.874 mg g⁻¹, respectively, using the same initial concentration of Cr(VI) and Cr(III) [10–60 ppm]. The adsorption data of both states of the Cr-metal followed the pseudo 2nd-order kinetic model with regression values of 0.996 ∼ Cr(VI) and 0.999 ∼ Cr(III) at ambient temperature. Similarly, the adsorption data of Cr(VI) best fit into the Langmuir adsorption isotherm (R² = 0.972) while that of Cr(III) followed the Freundlich model (R² = 0.983).