Synergistic adsorption of methylene blue from aqueous medium using MgO-Y2O3@gC3N4 (MYCN) nanocomposite: Performance evaluation and kinetic study

Abstract

Synthetic dyes pose a formidable challenge in wastewater treatment, resisting conventional oxidation and reduction reactions and posing risks to human health and the environment. This study introduces the innovative nanocomposite MgO-Y₂O₃@gC₃N₄ (MYCN) as a highly effective adsorbent for eliminating methylene blue (MB) dye. The MYCN nanocomposite was synthesized by dispersing Magnesium oxide and Y₂O₃ nanoparticles in isopropanol using an ultrasonic bath for 0.40 hours at 500 rpm, followed by the addition of g-C₃N₄ nanosheets. The resulting mixture underwent heating, grinding, and annealing processes for 1.5 hours at 145 °C. Through structural analysis using XRD, characteristic peaks corresponding to individual components were confirmed, while TEM, EDX, and BET techniques revealed the successful integration of MgO and Y₂O₃ with g-C₃N₄ nanosheets. The adsorption efficiency of the MYCN nanocomposite was extensively evaluated under varying experimental conditions, including contact time, initial MB concentration, and solution pH. With its impressive surface area of 90.2 m².g⁻¹, the nanocomposite exhibited remarkable adsorption capacity, leading to significant removal of MB dye from aqueous solutions. Although pH had a minimal influence on dye removal, the highest adsorption rate (94.34 %) was achieved at pH 7. Optimal adsorption conditions were determined as a contact time of 120 minutes, an initial MB concentration of 5 mg/L, and a pH of 7. To characterize the adsorption behavior and determine equilibrium concentrations, Freundlich and Langmuir's isotherm models were employed. The Langmuir model displayed an excellent fit to the experimental data, supported by a high regression coefficient (R² > 0.95), indicating a monolayer adsorption process.