Eco-Friendly Alginate-Coated Nano Iron Oxide-Graphene Oxide Nanocomposite for High-Performance Adsorption and Photocatalytic Detoxification of Harmful Dyes in Wastewater Treatment

Abstract

This research presents the development of an innovative and eco-friendly composite material, Alginate-Coated Nano Iron Oxide-Graphene Oxide (Alg-Fe₃O₄@GO), designed to enhance the adsorption and photocatalytic degradation of cationic dyes in wastewater treatment. The composite combines the biocompatibility of alginate with the high surface area and photocatalytic properties of graphene oxide and nano iron oxide. A comprehensive evaluation of the Alg-Fe₃O₄@GO composite was conducted to assess its efficiency in removing Methylene Blue (MB) and Malachite Green (MG) from aqueous solutions. Characterization techniques, including X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET) surface area analysis, and Thermogravimetric Analysis (TGA), confirmed its structural and functional properties. BET analysis indicated a significant surface area of 317.8 m²/g, suggesting substantial adsorption capacity. Adsorption experiments revealed a maximum capacity of 163.8 mg/g for MB, achieving a removal efficiency of 98.5%, and 107.5 mg/g for MG, with a removal efficiency of 90.8% after 240 min of contact time at an initial dye concentration of 100 mg/L for both dyes. Kinetic studies indicated that the adsorption followed the Pseudo-Second Order model (R² > 0.99 for both dyes), while equilibrium data fitted well with the Langmuir Isotherm Model, indicating monolayer adsorption. Thermodynamic analysis indicated that the adsorption process was endothermic, with enthalpy changes of ΔH° = +25.33 kJ/mol for MB and ΔH° = +20.83 kJ/mol for MG, alongside a spontaneous nature (ΔG° < 0). Photocatalytic tests under visible light showed dye degradation efficiencies of 85.0% for MB and 78.0% for MG within 120 min. The composite retained over 85% of its initial adsorption capacity after six regeneration cycles, underscoring its potential as a sustainable, high-performance material for wastewater treatment.