Using Pinus armandii-derived activated carbon for remediation of methylene blue contaminated wastewater

The present work evaluates the performance of activated carbon, obtained from the shoots of a Chinese Pine species, the Pinus armandii , activated with zinc chloride (ZnCl 2 ), for its efficacy in removing the Methylene Blue (MB) dye. The characterization of the adsorbent was performed using different analytical techniques (such as SEM, XRD, and the BET method). The BET analysis revealed a high (425.82 m²/g) surface area and a mesoporous morphology (having an average pore diameter of 2.7 nm) in the resulting biomass-based activated carbon. Optimal conditions for MB removal were determined through comprehensive batch adsorption experiments. The influence of major operational parameters (pH 7, adsorbent dosage 27 mg, contact time 180 min, and MB concentration 100 ppm) on the adsorption behavior was systematically studied. Under the optimized conditions, the adsorbent exhibited a Q max value of 73 mg/g. Over a wide pH range between 2 and 12, the removal efficiency of MB by CP-A remained high at 95-100%, with a U-shaped trend consistent with a pHpzc below 4. Results showed that the adsorption fitted the Langmuir model, with MB molecules forming monolayers on the adsorbent surface, and followed pseudo-second-order with a rate constant k 2 of 0.001 min -1 and a high correlation coefficient R 2 of 0.99, confirming chemisorption as the main removal pathway. The activated carbon derived from Pinus armandii shoots is a highly effective and eco-friendly adsorbent for wastewater dye removal. Schematic diagram showing the preparation of mesoporous carbon starting from the powder of Pinus armandii stem bark, following the activation by zinc chloride, along with some representative results exhibiting the efficient adsorptive removal of Methylene Blue (MB) • Activated carbon was prepared from a Chinese pine species, the Pinus armandii , through zinc chloride activation. • Adsorption dynamics of the activated carbon were evaluated using various isotherms and kinetic models. • The extent of adsorbed methylene blue in the form of a monolayer on the activated carbon was determined to be 73 mg/g. • The findings highlight the potential of Pinus armandii -derived activated carbon as a sustainable adsorbent for wastewater treatment.