Waste plastic derived Co3Fe7/CoFe2O4@carbon magnetic nanostructures for efficient dye adsorption

Highlights: • Core-shell magnetic carbon nanostructure with excellent dye adsorption performance. • Clean production of Co₃Fe₇/CoFe₂O₄ magnetic nanoparticles embedded in carbon. • Efficient removal of methyl orange and methylene blue dyes from their aqueous solutions. • Excellent monolayer adsorption capacity of 278 and 238 mg/g for MB and MO, respectively. • The thermal regeneration of the exhausted adsorbent with excellent regeneration efficiency. -- Abstract: A mesoporous carbon nanostructure (MCN) with embedded Co₃Fe₇/CoFe₂O₄ magnetic nanoparticles is synthesized by a clean and low-cost ball-milling/molten salt processing approach, employing metal oxides and waste plastic materials, without the involvement of environmentally-problematic raw materials or products. The structure, morphology and magnetic properties of MCN are analyzed by a variety of techniques. A systematic investigation is conducted to evaluate the performance of this nanostructured material as regenerable adsorbent for the efficient removal of methyl orange (MO) and methylene blue (MB) dyes from their aqueous solutions at various conditions, in terms of the dye concentration, the adsorbent dosage and the pH level of the solution. The dye adsorption of MCN is in accordance with the pseudo-second-order kinetic model and the Langmuir isothermal model with an excellent monolayer adsorption capacity of 278 and 238 mg/g for MB and MO, respectively. Moreover, the material is characterized to be ferromagnetic with the Ms value of 17.9 emu/g, ensuring the facile separation of the exhausted adsorbent from the treated water. The adsorption performance of MCN can be regenerated, with an adsorption capacity of greater than 95% of the original performance, after five successive regeneration cycles.