Chemical surface characteristics and adsorptive efficiency of olive stone–based activated carbon in Cu(II) and Zn(II) removal: comparative evaluation with commercial carbons
摘要
This research is dedicated to the preparation of activated carbon using olive stones (OSAC) and evaluates its performance in removing Cu2⁺ and Zn2⁺ ions from water, compared to two commercial carbons: powdered activated carbon (PAC) and granular activated carbon (GAC). OSAC exhibited the largest BET surface area (1299 m2 g−1), significant micropore volume (0.432 cm3 g−1), and an abundance of oxygen-bonded functional groups. Adsorption kinetics were best represented by the pseudo-second-order model. The stirring speed, the pH of the solution, and the dose of adsorbent had a significant influence on the adsorption efficiency of Cu2⁺ and Zn2⁺ ions. Equilibrium isotherms fitted the Langmuir model, showing high maximum adsorption capacities for OSAC, as 50.29 mg g−1 for Cu2⁺ and 43.72 mg g−1 for Zn2⁺ at 20 °C, exceeding those obtained for PAC (39.48 mg g−1 and 37.16 mg g−1) and GAC (33.88 mg g−1 and 28.13 mg g−1) for Cu2⁺ and Zn2⁺. Thermodynamic data revealed that the adsorption mechanism is spontaneous and endothermic (ΔG° < 0, ΔH° > 0) governed by chemisorption in addition to physisorption. Collectively, these results establish OSAC, with enhanced surface properties, as a highly effective adsorbent. This provides an eco-friendly approach for the removal of heavy metals from wastewater, surpassing commercial activated carbons use.