Reusable magnetic graphene oxide based anion exchanger for the separation and removal of anionic dyes

Abstract

This work evaluates the synthesis and characterization of the graphene oxide based magnetic anion exchanger, as well as its removal performance of Congo red (CR) in aqueous solutions. The structure and morphology of nanoadsorbents derived from graphene are characterized by XRD, Raman, XPS, FTIR, FESEM, HRTEM, and TGA. The study examined the adsorbent dosages, contact time, pH effect, adsorption capacity, isotherm, and kinetics of adsorption of CR dye on quaternary ammonium functionalized magnetic graphene oxide (NMGO). The adsorption capacity of NMGO was compared with graphene oxide (GO), magnetic graphene oxide (MGO), and quaternary ammonium derived graphene oxide (NGO) at both pH 7.0 (neutral) and pH 3.0 (acidic). Kinetic studies indicate that the adsorption behaviour follows the pseudo-second order model as well as the Langmuir isotherm model where the NMGO adsorption capacity for CR is 780.43 and 888.78 mg g⁻¹ at pH 7.0 and 3.0, respectively. According to multiple studies on regeneration and reuse, the highly selective and superparamagnetic NMGO's performance remained above 90% after seven cycles of removing anionic contaminants from aqueous solutions. The fact that it can be regenerated and reused for multiple cycles makes it an appealing choice for cost-effective wastewater treatment.