Effective removal of organic pollutants by adsorption onto chitosan supported graphene oxide-hydroxyapatite composite: A novel reusable adsorbent

Abstract

A hetero-structured adsorbent with outstanding adsorption performance has acquired an increased attention due to their excellent behaviour in environmental applications. Tailoring of graphene oxide and hydroxyapatite with suitable biopolymeric adsorbents would enhance the porosity, stability, specific surface area and shows high sorption performance. Herein, chitosan reinforced graphene oxide-hydroxyapatite (CS@GO-Hap) matrix was fabricated efficiently in the atmosphere of nitrogen by co-precipitation technique. Here, chitosan acted as a host in the preparation and provided the surface for a composite generation. The batch mode method was applied to investigate the adsorption performance of CS@GO-Hap composite, showed an adsorption efficiency of 43.06, 41.32 and 40.03 mg/g for the removal of the toxic Congo Red (CR), Acid Red 1 (AR1) and Reactive Red 2 (RR2) dyes from water, respectively. The composite showed enhanced adsorption at the pH of 2 and the removal efficiency of CS@GO-Hap composite decreased with increase in pH. The adsorption kinetic and isotherm fitted well with pseudo-second-order and the Freundlich model, respectively. The thermodynamic study of the adsorption of dyes showed that the process was spontaneous. The regeneration experiments emphasized that the desorption was ideal, and exhibited more than 65% regeneration ability with 0.1 M NaOH solution. The mechanism of dyes adsorption on CS@GO-Hap composite involved the electrostatic force interaction, surface complexation, hydrogen bondings and π−π stacking interactions. The findings of the study revealed the exceptional behaviour of CS@GO-Hap composite in removing the azo dyes from aqueous solutions and the great significance of the composite in the future application in water/wastewater treatment process.