Abstract
Abstract
A series of sulfur-containing activated carbons was prepared by impregnating a powdered activated carbon with elemental sulfur at different temperatures for the removal of Hg(II) from aqueous solutions. Batch adsorption tests were conducted to identify the optimal temperature for sulfur impregnation and to evaluate effects of water chemistry on Hg(II) removal. Results showed that impregnation at 400°C produced the best adsorbent (ACS-400), with the largest equilibrium uptake for Hg(II) of about 800 mg/g at pH = 5.5. The effect of pH on Hg(II) uptake depended on the initial mercury concentration (C0). At C0 = 43 mg/L, the removal ratios were consistently over 98% in the pH range of 2–11. Increasing C0 to 105 mg/L resulted in a decrease in Hg(II) removal at pH lower than 3.5. Ionic strength and the majority of water ionic constituents (e.g., sulfate, phosphate, calcium, and magnesium) had minor effects on Hg(II) uptake, but chloride and humic acid depressed Hg(II) uptake, with the effect of chloride more pronounced. It was suggested that the adsorption was caused by inner-sphere complexation, with sulfur atoms of elemental sulfur/thiophene and sulfoxide serving as the main binding sites. Findings of this study have significant implications for treatment of mercury (II) contaminated waters, both high concentration wastewater and micropolluted surface or drinking water.