Adsorption of Transition Metals from Aqueous Solutions by Modified Activated Carbons

Samples of a wood-based activated carbon, Ceca BGP, have been modified by acid and air oxidation. The physical and chemical characterizations of these samples in the form of scanning electron micrographs (SEM), Brunauer-Emmett-Teller (BET) and Lang-muir surface area measurements, Fourier transform infra red spectroscopy (FTIR) analysis, sodium capacity determination, pH titration and zeta potential measurements have been conducted to determine their performance as sorbents for trace transition metal removal. Density functional theory (DFT) has been used to analyse the pore size distribution data. The adsorption of transition metal ions (Cu, Zn, Ni and Cd) from aqueous solution onto these sorbents has been studied in batch equilibrium experiments. The influence of pH on metal sorption capacity has been examined. The kinetic performance of acid oxidized samples has been assessed and the results have been analysed by a particle diffusion model. The breakthrough experiments have been conducted in mini-columns to study the selectivity towards the desired metal ion. Results indicated that sorption capacity has been markedly enhanced by modification due to addition of weakly acidic functional groups to the surface of the carbons. The BGP OxII sample showed about 100 times higher copper capacity than conventional Ceca BGP. The metal sorbed carbons have been regenerated using 0.1M hydrochloric acid solution. Both modified samples demonstrated good regeneration efficiencies with 100% of the copper recovered with 0.1M HC1 solution during elution cycles compared to the amount of metal removed during the sorption experiments.