Removal of BTEX, MTBE and TAME from aqueous solutions by adsorption onto raw and thermally treated lignite

Abstract

The removal of BTEX (benzene, toluene, ethyl-benzene and m-,p-,o-xylenes), MTBE (methyl tertiary butyl ether) and TAME (tertiary amyl methyl ether) from aqueous solutions by raw (Lraw) and thermally treated lignite at 250°C, 550°C and 750°C (L250, L550 and L750, respectively) was studied, through batch experiments. Selected physical characteristics of both raw and treated lignite such as surface area and pore volume distribution were determined. Competitive adsorption effects were also explored. It was proved that the examined lignite samples were quite effective in removing BTEX, MTBE and TAME from aqueous solutions, with sample treated at 750°C being the most effective. Among the contaminants, BTEX appeared to have the strongest affinity, based on mass uptake by lignite samples. BTEX presence was found to significantly prevent MTBE and TAME adsorption on lignite (up to ∼55%). In all cases, equilibrium was achieved within 3h. The kinetics data proved a closer fit to the pseudo second order model, while the isotherm experimental data were a better fit to the Freundlich model, producing in some cases values of the isotherm constant 1/n less than one, indicating favorable adsorption. Respective batch experiments using commercial activated carbon (AC) were also conducted for comparison.