Optimization of adsorption of metal ions from a ternary aqueous solution with activated carbon from Acacia senegal (L.) Willd pods using Central Composite Design

Abstract

Activated carbon was prepared from Acacia senegal using H3PO4, it was characterized using FTIR, SEM and BET. Optimization of adsorption of Cadmium, Chromium and Lead from ternary solution with the adsorbent was carried out using Design Expert software and the model validated. FTIR analyses showed the presence of some functional groups such as OH and CC which usually aid adsorption. SEM micrograph showed presence of pores of various sizes on the carbon surface, also responsible for adsorption of molecules of various sizes. BET analyses reported the carbon to have surface area of 427.5 m2/g, width of 5.839 nm signifying a mesopore responsible for various degrees of adsorption. The optimum factors which were responsible for 98.54%, 100.00% and 99.96% adsorption of Cd, Cr and Pb respectively predicted by the model were 145.06 mg/L, 144.15 mg/L, 63.83 mg/L, 8.0, 0.17 g and 8.46 min as initial concentrations of Cd, Cr, Pb, pH, dosage and contact time respectively. The optimum factors were further validated with coefficient of determination R2 ranging from 0.8267 to 0.9775. These models were also used to predict maximum adsorption of Cd, Cr and Pb from tannery water and ABU dam water, 73%, 82.54% and 87.23% were obtained as the experimental percentage removal of Cd, Cr and Pb respectively from ABU water, while removal from tannery wastewater stood at 62.75%, 85.2% and 77.83% for Cd, Cr and Pb respectively. Acacia senegal pod has been demonstrated to be an efficient precursor in activated carbon production for water treatment.