Effective Adsorptive Removal of Methylene Blue and Alizarin Red S from Aqueous Solutions Through Biodegradable Polyvinyl Alcohol Based Hydrogel

Abstract

Industries use dyes as coloring agents and dyes-contaminated water can cause serious threats to aquatic life and humans. Thus, remediation strategies focused on wastewater treatment are in high demand. For this purpose, a biodegradable polyvinyl alcohol-based hydrogel (PVAH) was synthesized by using epichlorohydrin as a cross-linker for the adsorptive removal of dyes. The synthesized PVAH was characterized using SEM and FTIR. In addition, the point of zero charge and swelling ratio were calculated to be at pH 7 and 560%, respectively. The prepared hydrogel was used for the adsorptive removal of Alizarin Red S (ARS) and methylene blue (MB) from water contaminated with the mentioned dyes. Different experimental parameters, such as concentration of dye, pH, dosage of adsorbent, sample volume, time of contact, and temperature, were optimized. The maximum amount of dyes removed by the synthesized hydrogel under the optimized conditions is 9.98 mg g⁻¹ and 19.97 mg g⁻¹ for MB and ARS, respectively. Langmuir–Freundlich isotherm models were used, and the results showed that the adsorption mechanism followed the Freundlich isotherm model. The kinetic data results suggested that it perfectly fit the pseudo-second-order kinetic model. PVA hydrogel crosslinked with epichlorohydrin showed good removal efficiency for MB and ARS.