Optimization of COD removal of raw landfill leachate using the magnetic graphene oxide/WO۳ nanocomposite: Isotherms, kinetics, and thermodynamics studies

Landfill leachate is the fluid percolating through the landfill and is one of the most important environmental challenges that lead to the contamination of water and soil resources. In this study, magnetic graphene oxide nanoparticles with WO۳ (GO-Fe۳O۴/WO۳) were synthesized through the hydrothermal method to eliminate chemical oxygen demand (COD) from leachate. The obtained products were characterized using X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Thermogravimetric analysis (TGA), and Vibrating sample magnetometer (VSM) analysis. The influence of various operating parameters, such as initial solution pH, adsorbent dosage, contact time, and temperature, on COD removal was studied. Additionally, kinetic, isotherm, and thermodynamic studies were conducted to evaluate the adsorption capacity of the adsorbent. The results revealed that the maximum adsorption capacity of GO-Fe۳O۴/WO۳ was ۲۵۰۰ mg/g adsorbent at pH ۴, a contact time of ۹۰ minutes, an adsorbent dosage of ۲۵ mg g-۱, and a temperature below ۲۹۸ K, respectively. According to the adsorption kinetic fitting results, the experimental adsorption data were well described by the pseudo-second order kinetic with an R۲ value of ۰.۹۷, and the Freundlich isotherm equation with an R۲ value of ۰.۹۹. The thermodynamic results indicated that the adsorption was spontaneous and exothermic for COD adsorption. In general, the adsorption process of the synthesized GO-Fe۳O۴/WO۳ nanocomposite revealed that it is highly effective for landfill leachate treatment and has great practical value in leachate treatment.