Zero-Waste Conversion of Juglans regia and Allium sativum Biomass into Porous Carbons for Dye Removal and Recovery from Water.

Biomass-derived porous carbons are promising sustainable adsorbents for wastewater treatment. However, most reported materials require chemical activation, while the relationships between biomass precursor, pore structure, adsorption mechanism, and regeneration remain insufficiently understood. In this work, non-activated carbon materials were prepared from Juglans regia (JR) and Allium sativum (AS) biomass by pyrolysis at 400 and 900 °C and evaluated for the removal of methylene blue (MB), rhodamine B (RB), crystal violet (CV), and malachite green (MG). Carbonization at 900 °C markedly enhanced porosity, yielding a surface area of 790 m2 g-1 for JR900 and 177 m2 g-1 for AS900, together with predominantly microporous structures and negatively charged surfaces at neutral pH. The pseudo-second-order model best described adsorption kinetics, while intraparticle diffusion analysis indicated a multistep adsorption process. Equilibrium data were well fitted by both Langmuir and Freundlich isotherm models. JR900 exhibited the highest adsorption capacities for MB (321 mg g-1) and RB (304 mg g-1), whereas AS900 showed superior performance toward MG (278 mg g-1). Stable dynamic filtration, efficient regeneration, and nearly complete dye recovery demonstrate the potential of these non-activated biomass-derived carbons for sustainable dye removal and recovery from water.