Synthesis of magnetite nanoparticles deposited on heat-treated graphitic carbon nitride for the removal of methylene blue dye molecules by adsorption

This study focuses on synthesis of magnetite (Fe₃O₄) nanoparticles (NPs) dispersed in heat-treated graphitic carbon nitride substrate (Fe₃O₄/g-C₃N₄) for the removal of aqueous methylene blue (MB) molecules by adsorption. Characterization data reveal that Fe₃O₄ NPs are successfully incorporated onto g-C₃N₄. The material is tested for its efficacy toward the adsorptive removal of MB dye molecules from DI water. The study reveals that the adsorption of MB onto Fe₃O₄/g-C₃N₄ is dependent on pH of the test solution, with MB adsorption capacity increases with rising solution pH. The maximum amount of MB adsorbed is 660.38 ± 20.00 mg g⁻¹ over the concentration range 5–200 mg L⁻¹ and a pH of 11, based on the Langmuir model. Regeneration studies confirm that the material can be reused for five test runs without major loss of adsorption efficiency. The same process has been successfully implemented for the MB-spiked river water samples. The drop in the maximum MB adsorption capacity in MB-spiked river water sample may be attributed to (1) the blockage of pore mouths and the external surface of the adsorbent by dissolved and suspended solid particles in the river water sample, and (2) competition between dissolved organic matter (DOM) and MB molecules for available adsorption sites. This study has opened up a new horizon for the extensive applications of Fe₃O₄/g-C₃N₄, particularly in environmental remediation.