Circular economy approach for thermal regeneration of graphene-encapsulated magnetic nanoparticles as an efficient adsorbent forsustainable wastewater management

High-performing nanostructured magnetic adsorbents, featuring enhanced dye adsorption from wastewater at various conditions of pH, and separability through the application of magnetic fields, offer significant technical advantages for streamlined water purification processes. Moreover, the efficient regeneration of exhausted magnetic adsorbents provides additional benefits in terms of the sustainability of adsorption process and promoting circular economy principles. Here, we explore the performance of the graphene encapsulated magnetic adsorbent Ni0.4Fe2.6O4/(Fe,Ni)@graphene (GMA) for decolorization of wastewater containing crystal violet (CV), and its reusability properties through thermal regeneration of the exhausted adsorbent at temperatures ranging from 200 to 600 ◦C. The graphene layer around GMA provides an enhanced adsorption capacity and stability for the agent. Meanwhile, the application of a straightforward and potentially low-cost thermal treatment offers a rapid regeneration strategy, facilitating efficient recycling of the adsorbent. While maintaining structural and morphological stability up to 400 ◦C, samples regenerated at this temperature exhibit a BET surface area and pore volume of 207.46 m2/g and 0.44 cm3/g, respectively, closely resembling those of the original adsorbent. The regenerated sample recovers over 92 % of the original adsorption capacity. At the same time, approximately 86 % of the saturation magnetization (Ms) of the sample can also be restored through the thermal regeneration, with magnetic remanence and coercivity remaining nearly unchanged compared to the original adsorbent, ensuring the functionality of the regenerated adsorbent.