Microwave-Driven Upcycling of Biomass and Soft Slaughterhouse Waste into Activated Carbon for Efficient Cr(VI) Removal

This study demonstrates the rapid microwave-assisted upcycling of diverse bio-wastes—including aloe vera industrial leaf waste (av), corn cob agricultural residues (cc), and soft slaughterhouse (sh) by-products (pork liver, lung, and heart) into high-surface-area activated carbons for efficient hexavalent chromium removal via ZnCl₂-activated microwave pyrolysis. To process the challenging high-moisture animal organs, a hybrid approach combining microwave-assisted hydrothermal pre-treatment with subsequent ZnCl₂-activated microwave pyrolysis was developed to promote chemical dehydration and aromatic network development. Structural characterization by N₂ porosimetry, FT-IR, Raman, and XRD confirmed the formation of stable, amorphous porous networks, with surface development strongly dependent on both precursor type and pyrolysis temperature. The materials exhibited high specific surface areas (BET) of 1442, 1120, and 775 m²/g for cc, av, and sh, respectively, and they also demonstrated high water dispersibility. Cr(VI) adsorption data were best described by the Langmuir isotherm model, while thermodynamic analysis confirmed the spontaneous and endothermic adsorption process. The maximum adsorption capacities (qmax) at pH 3 were 157, 112, and 71 mg/g for the activated carbons derived from cc, av, and sh, respectively. Agricultural-derived carbons exhibited superior adsorption performance, whereas all materials remained competitive, demonstrating a potential sustainable circular-economy strategy for waste valorization.