This study reports the synthesis of waste-derived magnetic activated carbon from annatto seed husk biomass using post-consumer toner waste as an iron source for efficient crystal violet (CV) adsorption. Comprehensive characterization demonstrates the formation of a highly porous magnetic carbon framework. Toner promotes the decomposition of polymeric binders, generating additional cavities, increasing surface area, and imparting sufficient magnetization for rapid separation from aqueous media. Its incorporation systematically modulates material properties with loading. At intermediate content (0.25 g), toner facilitates the formation of a highly porous structure, increasing the surface area up to 1143.99 m² g⁻¹ and pore volume to 0.7045 cm³ g⁻¹, whereas higher loading (0.50 g) leads to partial pore blockage due to iron-rich agglomerates. Increasing Fe content enhances the magnetic response (1.57–8.09 emu·g⁻¹), reaching ~85.6 emu·g⁻¹, close to bulk Fe 3 O 4 , thus enabling rapid magnetic separation. As a result, the material exhibits a predominantly mesoporous structure and high adsorption capacities, reaching 579 mg g⁻¹ at 25 °C and exceeding 1000 mg g⁻¹ at 55 ºC. Adsorption proceeds through a combined physisorption–chemisorption mechanism, with π–π interactions and Fe–O functionalities acting as active sites. Classical thermodynamic evaluation indicates a spontaneous (ΔG°0) adsorption process, consistent with favorable macroscopic energetics. Complementary statistical analysis, supported by high ln W values (~10¹⁹) and the Boltzmann relation ( S = k B ln W ) , reveals a large molecular configurational space. This work is the first to chemically integrate toner waste with biomass to produce magnetic, high−performance activated carbon for dye removal.
Fertonani et al. (2026) studied this question.