Utilizing biosorbents for sustainable mercury removal from aqueous solutions: Efficiency and practical applications

Mercury contamination in water bodies presents serious health risks and ecological challenges because of its hazardous nature and long-lasting presence. Traditional remediation methods frequently lead to secondary pollution or lack sustainability. This research explores the feasibility of activated carbon produced from Christ's Thorn tree leaves as an innovative and affordable biosorbent for removing mercury ions (Hg(II)). Optimal adsorption parameters were identified as a pH of 7.5, a contact duration of 90 minutes, an initial mercury level of 0.25 mg/L, and a biosorbent amount of 0.2 g. Under these conditions, the maximum adsorption capacity (q max ) was determined to be 0.83 mg/g, achieving a removal rate of 87 %. The adsorption mechanism was most accurately explained by the Freundlich isotherm (R 2 = 0.96, AARD = 5.2 %), indicating multilayer uptake on an uneven surface. Kinetic analysis showed that the pseudo-second-order (PSO) model gave the most accurate prediction (R 2 = 0.98, AARD = 4.5 %), implying that chemical bonding was the primary mechanism. Moreover, the Elovich model effectively described the initial sorption speed, further confirming the strong interaction between Hg(II) ions and the biosorbent. The material's reusability across seven cycles with minimal performance degradation underscores its potential for practical mercury remediation applications. This work highlights the efficiency, eco-friendliness, and cost-effectiveness of Christ's Thorn tree leaves as a biosorbent, offering a promising approach for mercury extraction from potable water and industrial effluents. Future investigations should focus on upscaling for industrial deployment and evaluating its performance for other toxic metals. • Utilizing activated carbon derived from Christ's Thorn tree leaves as a novel and cost-effective biosorbent. • Effective removal of mercury ions (Hg(II)) from aquatic environments with a removal efficiency of 87 %. • Optimization of adsorption conditions, including pH = 7.5, contact time of 90 minutes, and a biosorbent dosage of 0.2 g. • Freundlich isotherm identified as the best model, indicating multilayer adsorption on a heterogeneous surface. • Pseudo-second-order (PSO) model highlighting chemisorption as the dominant mechanism. • Reusability of the biosorbent for 7 cycles with minimal efficiency loss.