Development and Characterization of Biomass-Derived Carbons for the Removal of Cu2+ and Pb2+ from Aqueous Solutions

This research explores the synthesis and application of carbon-based adsorbents derived from olive stones and almond shells as low-cost biomass precursors through carbonization at 600 °C combined with chemical activation using KOH, H3PO4, and ZnCl2 with carbon/activating agent (C/A) ratios of 1:2 and 1:4 (w/w) at 850 °C for the removal of Cu2+ and Pb2+ ions from aqueous solutions. The carbons produced were characterized using different techniques including SEM-EDX, FTIR, XRD, BET analysis, CHNS elemental analysis, and point of zero charge determination. Batch-mode adsorption experiments were carried out at adsorbent doses of 2 and 5 g L−1, initial metal concentrations of 100 and 500 mg L−1, and natural pH (around 5) with agitation at 350 rpm and 25 °C for 24 h. KOH-activated carbons, especially at a 1:4 (w/w) ratio, exhibited superior adsorption performance mainly due to their favorable surface characteristics and functionalities. Pb2+ was entirely removed (100%) at the highest initial concentration of 500 mg L−1 and an adsorbent dosage of 5 g L−1, while for Cu2+, the maximum adsorption efficiency was 86.29% at an initial concentration of 100 mg L−1 and a dosage of 2 g L−1. The results of this study will help advance knowledge in the design and optimization of adsorption processes for heavy metal removal, benefiting industries seeking green technologies to mitigate environmental pollution.