Poly(allyl alcohol-co-vinyl acetate)-grafted concrete waste for adsorptive removal of As(III)

Abstract

This study focused on the synthesis of concrete waste grafted with a polymer of allyl alcohol and vinyl acetate as a novel nano adsorbent and the investigation of its ability in the adsorptive removal of Arsenic (As(III)) from aqueous solutions. The prepared nano adsorbent was characterized using X-ray diffraction, thermogravimetric analysis, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier-transform infrared spectroscopy. Various parameters were optimized by response surface methodology and central composite design model to achieve the highest As(III) removal efficiency, including the solution's temperature, contact time, and pH. The model predicted a maximum removal efficiency of 92 % under the optimal conditions (temperature = 25 °C, contact time = 24 min, and pH = 7), resulting in a sorption capacity of 6.81 mg g−1. The zero point of charge for the nano adsorbent was obtained at about 6.5. The experimental data for As(III) sorption onto the nano adsorbent was well-fitted by the Freundlich isotherm and pseudo-1st-order kinetic models. This suggests that the adsorption process involves the formation of a multilayer of As(III) on the adsorbent surface, and it occurs through physical interactions rather than chemical reactions. The reusability of the nano adsorbent was evaluated, demonstrating a removal efficiency exceeding 72 % even after seven recycling cycles. The presence of interfering cations influenced the removal efficiency in the following order: Pb2+>Mn2+>Cu2+>Zn2+>Ni2+. The prepared nano adsorbent showed significant efficiency in removing As(III) from well water and river water samples, with a repeatability range of 1.09–2.51 %.