Crystal Violet Removal Using Biomass-Derived Activated Carbons: Influence of Precursor Characteristics, Adsorption Behaviour and Comparison with Commercial Activated Carbon

Abstract

Activated carbons derived from yam, crofton weed, and squash biomass were prepared under identical phosphoric acid activation conditions to isolate the influence of precursor identity on crystal violet adsorption. Although all three carbons were synthesized using the same protocol, they developed distinct pore structures, surface chemistries, and charge properties, which produced clearly different adsorption behaviors. Among the prepared adsorbents, YPAC showed the most consistent and practically useful performance, achieving 98.65% crystal violet removal, the highest adsorption affinity, and the best regeneration stability over five adsorption-desorption cycles. In contrast, SPAC exhibited a higher Langmuir monolayer capacity but weaker affinity and poorer operational stability, demonstrating that theoretical capacity alone does not fully represent adsorption performance. FTIR, XPS, pH, isotherm, kinetic, and thermodynamic analyses collectively indicated that dye uptake was governed by a combination of pore accessibility, oxygen-containing surface groups, electrostatic attraction, and π-π interactions. The prepared carbons also remained effective in natural groundwater samples and outperformed commercial activated carbon under identical treatment conditions. Overall, the study shows that precursor-controlled structure development, even under identical activation conditions, can strongly determine adsorption efficiency and durability.