A facile synthesis of Fe3O4–charcoal composite for the sorption of a hazardous dye from aquatic environment

•Fe3O4–charcoal composite was fabricated for removal of methylene blue from solution.•TEM showed non-agglomerated spherical particles of ∼13.8 nm diameter.•The composite was mesoporous in nature with BET surface area of 387.28 m2 g−1.•Batch and fixed-bed dye sorption capacity was found to be 97.49 and 90.85 mg g−1.•Dye-laden composites were regenerated by microwave-chemical desorption and reused.

Herein, we synthesized Fe3O4–charcoal composite using chemical precipitation technique and utilized it for the sorption of methylene blue from aqueous solution. The synthesized composite was characterized by Infra-red spectroscopy, N2 adsorption-desorption isotherm, X-ray diffraction, selected area electron diffraction, transmission electron microscopy, and vibrating sample magnetometer. The composite depicts absorption bands conforming to Fe–O, –OH, CO, and C–O vibrations. The composite was mesoporous in nature with a surface area of 387.30 m2 g−1. The observed diffraction planes correspond to face-centered cubic Fe3O4 and disordered graphitic carbon. The spherical Fe3O4 particles (average diameter ∼13.8 nm) were uniformly distributed in the carbon matrix of the charcoal. The saturation and remanent magnetizations demonstrate its potential for magnetic separation and reuse. The composite showed dye sorption capacities of 97.49 mg g−1 and 90.85 mg g−1 in batch and fixed-bed system. Pseudo-second order kinetics and Temkin isotherm best represented the sorption data. The sorption process was endothermic, spontaneous, and administered by electrostatic, π-π dispersive interactions, film, and intraparticle diffusion. Microwave irradiations followed by methanol elution regenerated the dye-loaded composite with nearly no loss in sorption capacity. The recovery of energy and potential utilization of bottom ash enhances the prospective of Fe3O4–charcoal composite for industrial applications.

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