Tailoring the adsorption behavior of bone char for heavy metal removal from aqueous solution

Abstract

This paper evaluates the pyrolysis conditions applied during the synthesis of bovine bone char and the effect of these parameters in its adsorption properties for heavy metal removal from aqueous solution at batch reactors. The synthesis route has been analyzed in detail and the surface interactions involved in the adsorption process has been studied and discussed using different characterization techniques, given a special emphasis on X-ray photoelectron spectroscopy (XPS) analysis. A proper selection of the pyrolysis conditions improved the metal uptake of bone chars by 143% where the adsorption capacities ranged from 68.3 up to 119.4 mg/g. The removal performance followed the trend Cd2+ > Zn2+ > Ni2+. However, the multicomponent removal of Zn2+, Cd2+, and Ni2+ ions in both binary and ternary mixtures was a strong antagonistic adsorption process. XPS analysis confirmed that the ion exchange between the calcium, from the hydroxyapatite structure of bone char, and the heavy metals in solution played an important role in the adsorption process. These findings are useful to enhance the efficacy of heavy metal removal from aqueous solution using bone char.