Production of activated carbon from bamboo chopsticks and its application in methylene blue adsorption

Abstract

Activated carbon from bamboo chopsticks (BCAC) was prepared via hydrothermal pretreatment with 3.5% H₂SO₄ followed by KOH activation. Pretreatment reduced lignin, ash, and moisture while enriching cellulose, hemicellulose, and total carbohydrates. The optimal activation condition was 800 °C for 120 min, yielding a BET surface area of 397.6 m²/g and micropores with an average size of 1.2 nm. XRD, SEM, and FT–IR confirmed the structural transformation from cellulose-rich biomass to amorphous carbon, characterized by the emergence of graphitic domains and oxygenated functional groups. MB adsorption performance was strongly pH-dependent, enhanced above the pHpzc (3.4). Kinetic analysis revealed that the pseudo-second-order model provided the best description of the process, indicating chemisorption with multi-step diffusion. The Langmuir isotherm provided the best fit, with a maximum adsorption capacity of 54.95 mg/g. FT–IR after adsorption revealed multiple interaction mechanisms, including electrostatic attraction, π–π stacking, hydrogen bonding, and van der Waals forces. Desorption studies indicated ethanol was more efficient than HCl in regenerating BCAC, and reusability tests showed stable performance over two cycles before declining. These findings highlight BCAC as a promising, low-cost adsorbent for dye removal, demonstrating potential for wastewater treatment applications.