Adsorptive removal of methylene blue dye using pine litter-derived activated charcoal

Azo dyes pose severe threats to aquatic ecosystems and human health due to their persistence and toxicity. Low-cost adsorbents are urgently needed for scalable wastewater treatment. Therefore, adsorption is considered the best method, and several types of low-cost adsorbents are in demand. ZnCl₂-activated pine charcoal was synthesized, characterized (SEM/FTIR/EDX/XRD), and tested under varied parameters (dose, pH, concentration). At optimum conditions, 99.90 ± 0.02 % removal of methylene blue with very high adsorption capacity was observed, i.e., 1440 mg/g. The pseudo-second-order reaction model provided the highest R² value of up to 0.9997. The recovery of 98.82 ± 0.14 % methylene blue in ethanol was observed. The study concluded that up to 3 cycles, 97.30 ± 0.27 % methylene blue dye can be removed. The study provides technical insights for synthesizing low-cost, highly efficient adsorbents in water purification in industrial and domestic setups.