Adsorption of Aqueous Mercury(II)Species by Commercial Activated Carbon Fibres with and without Surface Modification

Abstract

The adsorption of HgCl2, [HgCl4]2– and Hg2+ onto a series of activated carbon fibres was studied. These included the as-received commercial activated carbon fibre (K), that obtained after modification via by sulphuric acid oxidation (KAC) and that obtained after modification by reaction with pentaethylenehexamine (KBAS). The effects of concentration (10–1500 mg/l), solution pH (1–10) and temperature (25°C, 35°C and 45°C) were studied. The mercury(II) adsorption isotherms followed the Langmuir model with maximum adsorption capacities of 361.0, 142.2 and 300.3 mg/g for HgCl2, [HgCl4]2– and Hg2+, respectively. Fibre K proved to have the highest adsorption capacity towards HgCl2 but the best results for the adsorption of [HgCl4]2– and Hg2+ were obtained with the fibre KAC. The performance of fibre KBAS was always worse than those of the other two fibres tested. The negative values obtained for ΔH0 and ΔG0 indicate that the adsorption was an exothermic and spontaneous process and also demonstrated that the adsorption of Hg(II) is a feasible process.