Enhanced phenol removal from wastewater via sulfuric acid activated eggshell derived carbon

This research explores the development of an innovative activated carbon adsorbent (ACES) derived from waste eggshells through sulfuric acid activation to effectively remove phenol from simulated wastewater. Optimization of adsorption parameters was conducted using Design-Expert 13 software and response surface methodology (RSM). Under optimal conditions (initial phenol concentration of 25.015 mg/L, adsorbent dosage of 4.913 g/L, pH of 4.693, and temperature of 25.013 °C), ACES achieved an outstanding phenol removal efficiency of 99.87%. Characterization studies revealed a high BET surface area of 1034.775 m²/g and enhanced porosity, significantly contributing to adsorption performance. Mechanistic insights showed that electrostatic attraction, π-π interactions, and hydrogen bonding drove adsorption. The Langmuir model provided the best fit for phenol adsorption on ACES (R² = 0.9845), indicating monolayer adsorption on uniform sites. Kinetic analysis revealed that the adsorption followed pseudo-second-order kinetics, with a rate constant (k) of 0.0078 g·min⁻¹·mg⁻¹ and a high correlation coefficient (R² = 0.9886), pointing to chemisorption rather than physical adsorption. Thermodynamic analysis further confirmed that the process is spontaneous and exothermic, accompanied by increased randomness at the adsorbent-adsorbate interface. ACES exhibited good reusability, retaining 80% efficiency after four regeneration cycles. The findings of this research highlight a sustainable approach to utilizing waste eggshells for phenol removal, offering potential applications in wastewater treatment.