Sameer Boopathy
Independent Researcher
India
Abstract
Removal of heavy metals from industrial wastewater is a critical environmental challenge. Activated carbon, with its high surface area and porous structure, has been extensively used as an adsorbent for metal ions such as Pb²⁺, Cd²⁺, Cr³⁺, Cu²⁺, and Ni²⁺. This study reviews adsorption mechanisms, kinetics, and equilibrium isotherms reported up to 2015. A batch-mode experimental investigation was conducted to assess removal efficiency of Pb²⁺ and Cd²⁺ under varying initial concentrations (10–100 mg/L), contact times (0–120 min), and pH (4–8). Statistical analysis (ANOVA) was performed to evaluate significance of operating parameters. Data fitted to Langmuir and Freundlich isotherms and pseudo-first/second-order kinetics models. Maximum monolayer adsorption capacities of 142 mg/g for Pb²⁺ and 98 mg/g for Cd²⁺ were obtained. Removal efficiencies above 90 % were achieved under optimum conditions (pH 6, contact time 90 min). Kinetic analysis indicated that the pseudo-second-order model provided the best fit (R² > 0.99). Equilibrium data conformed more closely to the Langmuir model (R² = 0.995) than Freundlich (R² = 0.937). ANOVA results showed that pH and initial concentration significantly influenced adsorption (p < 0.05). Identified research gaps include scale-up challenges, regeneration of spent carbon, and real wastewater matrix effects. This work consolidates pre-2015 findings and presents original batch adsorption data to advance activated carbon applications for heavy-metal remediation.
Keywords
activated carbon, heavy metals, adsorption kinetics, isotherms, wastewater treatment
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