Preparation of activated and non-activated carbon from Conocarpus pruning waste as low-cost adsorbent for removal of heavy metal ions from aqueous solution

Conocarpus pruning waste, an agricultural byproduct, was converted into low-cost activated and non-activated carbons and used for the remediation of Cd²⁺, Cu²⁺, and Pb²⁺ from aqueous solutions. The carbonization was carried out at 400 °C, while the activation was carried out in the presence of KOH and ZnCl₂. Batch single-solute and multi-solute equilibrium and kinetic experiments were carried out to determine the adsorption capacities of the prepared activated and non-activated carbons, and these were further compared with commercially available activated carbon. The results showed that KOH-activated carbon (CK) outperformed the other activated and non-activated carbons in terms of adsorption efficiency. CK removed >50% of the applied Cd²⁺ and Cu²⁺ and 100% of Pb²⁺ at the initial concentration of 40 mg L-1. Interestingly, the performance of Conocarpusderived non-activated carbon was better than that of the commercial activated carbon, as observed from the Langmuir maximum adsorption capacities of 65.61, 66.12, and 223.05 μmol g-1 for Cd²⁺, Cu²⁺, and Pb²⁺, respectively. The Pb²⁺ was the metal most easily removed from aqueous solution because of its large ionic radius. The kinetic dynamics were well described by the pseudo-second order and Elovich models.