Circular economy approach for thermal regeneration of graphene-encapsulated magnetic nanoparticles as an efficient adsorbent for sustainable 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.