Iron oxide nanoparticles as efficient adsorbents for malachite green dye removal: Isotherms, kinetics, and thermodynamics analysis

The presence of dye contamination in waterbodies has emerged as a widespread environmental issue and poses a significant threat to the well-being of humans and the aquatic ecosystem. Nanotechnology has emerged as a promising field in tackling dye pollution. Nanomaterials such as iron oxide nanoparticles have gained considerable interest for potential applications in treating dye-contaminated wastewater. Hence, the current work focuses on the synthesis of iron oxide nanoparticles (FMNP) using the chemical co-precipitation method and its adsorptive performance for removing malachite green (MG) dye from wastewater. The synthesized FMNP was characterized using SEM–EDS, XRD, FTIR, BET, TGA, and Raman analysis. As obtained from SEM and XRD analysis, the FMNP has cubic crystals with an average crystal size of 8.0 nm and a crystallinity of 78.643%. The average pore size, specific surface area, and micropore volume were 4.217 nm, 172.548 m².g⁻¹, and 0.342 cm³.g⁻¹, respectively. Batch adsorption studies revealed that MG dye adsorption was sensitive to solution pH, initial MG dye concentration, contact time, dosage, and temperature. Under optimum conditions of pH 12, MG dye concentration 50 mg.L⁻¹, contact time 90 min, dosage of 0.2 g.L⁻¹, and at 328.15 K, a maximum removal of 98.814% was attained with a maximum adsorption capacity of 606.06 mg.g⁻¹. MG dye adsorption best fits the Langmuir isotherm and pseudo-second-order kinetics. The economically feasible reusability of the synthesized FMNP is demonstrated by its consistent performance across several cycles. The results demonstrate the significance of using this mesoporous FMNP as an adsorbent for effectively treating dye wastewater.