Regenerable magnetic iron oxide incorporated chitosan beads for sulfate (SO42−) removal from wastewater: Isotherms, kinetics and mechanism

Abstract

Sulfate contamination removal from mine waste and industrial water is a primary environmental concern, with high concentrations leading to disease. This research focuses on the preparation of iron oxide-incorporated chitosan beads (IOICBs) for the effective adsorption removal of sulfate. The IOICBs were synthesized by a chemical co-precipitation approach and characterized by Scanning Electron Microscopy, x-ray Diffraction, Brunauer–Emmett–Teller analysis, Fourier Transform Infrared Spectroscopy, and energy-dispersive x-ray mapping for structural, chemical, and morphological properties. The sulfate adsorption on IOICBs was investigated in batch mode studies using UV–Vis spectroscopy. The effect of several parameters, such as adsorbent dosage, pH, initial concentration, and contact time, on the sorption capacity of the IOICBs was studied. The IOICBs have a high efficacy for sulfate removal from contaminated water at pH 2 with a maximum sorption capacity of 147.7 mg/g at room temperature. The mechanism suggested that the presence of acidic NH4+ functional groups on the surface of chitosan facilitates the chemisorption of the sulfate ions. The adsorption equilibrium is in good agreement with the Langmuir Isotherm (R2 = 0.997), and the kinetics analysis suggests the adsorption is a pseudo-second-order process (R2 = 0.992), confirming the chemisorption of sulfate species on IOICBs. After sulfate adsorption, the IOICBs were regenerated in 0.1 M NaOH solution, reused for multiple sorption/desorption cycles, and the reusability remained at over 83% after four consecutive cycles. Thus, IOICBs are potential absorbents for removing industrial pollutants such as sulfate ions from wastewater.