Comprehensive Study of Nickel Adsorption from Tannery Effluent Using Rumex Abyssinicus-Based Activated Carbon: Optimization, Isotherm, Kinetic, and Economic Perspectives for Egypt

The widespread discharge of nickel-contaminated wastewater into aquatic environments Presents a major threat to both human well-being and the environment. To address this issue, a sustainable and efficient adsorbent, Rumex abyssinicus-based activated carbon (RAAC), was developed for nickel removal. RAAC was synthesized by chemically activating Rumex abyssinicus with phosphoric acid and pyrolyzing it at 500°C. Characterization revealed that RAAC possesses a highly porous structure, making it highly effective for adsorption. Using factorial analysis methods, the adsorption process was optimized by investigating key parameters: pH, interaction duration, starting nickel levels, and the amount of adsorbent used. Nickel removal efficiency reached 99.2% under optimal conditions: a pH of 9, a 40-min interaction period, an initial nickel level of 40 mg/L, and an adsorbent amount of 0.2 g/100 mL. The Langmuir isotherm provided the best fit for the experimental data, suggesting monolayer adsorption with a maximum adsorption capacity of 101.33 mg/g. The Dubinin-Radushkevich (D-R) isotherm further confirmed the adsorption behavior, yielding a maximum capacity of 76.07 mg/g and an adsorption energy of 107.40 kJ/mol, indicating a chemisorption mechanism. Kinetic analysis demonstrated that the adsorption process adhered to the pseudo-second-order model, further supporting the dominance of the chemisorption mechanism. The production cost of RAAC was calculated to be $3.55/kg. This study demonstrates that RAAC is a highly efficient and sustainable material for nickel removal.