Adsorptive Removal of Methylene Blue Using HCl-Activated Cactus Biomass: Box–Behnken Design Optimization

This work examines the generation and optimization of activated carbon from cactus biomass via chemical activation with hydrochloric acid (HCl) to assess its efficacy and sustainability as an adsorbent for removing methylene blue from aqueous solutions. The preparation procedure involved two primary steps: carbonization of the cactus biomass at a regulated temperature, followed by chemical activation with HCl to augment the material's porosity, surface area, and active functional groups. The resulting adsorbent was characterized and used in methylene blue adsorption experiments

A Box–Behnken experimental design was employed to optimize the process and assess the effects of critical operating factors. The effects of solution pH, initial dye concentration, and adsorbent dose, as well as their interactions, were systematically examined. Statistical analysis revealed that all parameters significantly influenced the adsorption capacity. The experimental data conformed well to a quadratic model, yielding a high coefficient of determination (R² = 0.97), thereby affirming the model's robustness and predictive accuracy. Under optimal conditions, the cactus-derived activated carbon exhibited exceptional methylene blue removal efficiency, indicating robust adsorption capacity.

To evaluate the environmental and economic advantages of the proposed adsorbent, the study conducted comparative analyses of precursor availability, energy requirements during carbonization, chemical consumption during activation, and estimated production cost per unit mass of activated carbon. Life-cycle considerations, including the renewability of cactus biomass and its reduced environmental footprint relative to conventional activated carbon derived from non-renewable sources, were also assessed. These methodological approaches helped quantify reductions in waste generation, energy input, and overall treatment cost.

These findings underscore the efficacy of cactus biomass as an economical, renewable precursor for the manufacture of activated carbon. The study emphasizes its environmental and economic advantages, suggesting its promising application in wastewater treatment processes for the removal of synthetic dyes and other persistent organic contaminants