Synthesis and characterization of activated carbon from acrylic acid-modified black liquor of sugarcane bagasse for enhanced cadmium removal

This study explores the valorization of black liquor (BL), a byproduct of sugarcane bagasse pulping, into activated carbon (AC) for enhanced cadmium (Cd) removal from aqueous solutions. Through acrylic acid (AA) modification in the hydrothermal process and chemical activation with potassium hydroxide (KOH), the synthesized AA-modified activated carbon (AACBL) exhibited exceptional textural properties, including a surface area of 1541.3 m2/g and a total pore volume of 0.84 cm³/g, representing a threefold increase compared to unmodified AC (500.16 m2/g, 0.26 cm2/g). Comprehensive characterization revealed that the raw BL contained 40% lignin, 30% ash, and 25% holocellulose, with an elemental composition of 56.85% oxygen and 38% carbon, providing an optimal precursor for AC production. The AA modification facilitated enhanced graphitization and pore development, as confirmed by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM). Adsorption studies demonstrated that AACBL achieved a maximum Cd adsorption capacity of 434 mg/g, significantly outperforming conventional adsorbents. Kinetic analysis revealed that adsorption followed a pseudo-second-order model (R2 > 0.99), indicating chemisorption as the rate-limiting step. This research highlights the potential of BL-derived AC as a sustainable, high-performance adsorbent for heavy metal remediation, offering a dual solution for industrial waste management and environmental protection. The findings underscore the importance of chemical modification in optimizing adsorbent properties, paving the way for scalable applications in wastewater treatment and resource recovery.