title: Mechanisms of mercury removal by biochars produced from different feedstocks determined using X-ray absorption spectroscopy.
abstract: Thirty-six biochars produced from distinct feedstocks at different temperatures were evaluated for their potential to remove mercury (Hg) from aqueous solution at environmentally relevant concentrations. Concentrations of total Hg (THg) decreased by >90% in batch systems containing biochars produced at 600 and 700 °C and by 40-90% for biochars produced at 300 °C. Elevated concentrations of SO4(2-) (up to 1000 mg L(-1)) were observed in solutions mixed with manure-based biochars. Sulfur X-ray absorption near edge structure (XANES) analyses indicate the presence of both reduced and oxidized S species in both unwashed and washed biochars. Sulfur XANES spectra obtained from biochars with adsorbed Hg were similar to those of washed biochars. Micro-X-ray fluorescence mapping results indicate that Hg was heterogeneously distributed across biochar particles. Extended X-ray absorption fine structure modeling indicates Hg was bound to S in biochars with high S content and to O and Cl in biochars with low S content. The predominant mechanisms of Hg removal are likely the formation of chemical bonds between Hg and various functional groups on the biochar. This investigation provides information on the effectiveness and mechanisms of Hg removal that is critical for evaluating biochar applications for stabilization of Hg in surface water, groundwater, soils, and sediments.
authors: Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave. W., Waterloo, ON N2L 3G1, Canada.
authors: Peng
authors: P
authors: Liu
authors: Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave. W., Waterloo, ON N2L 3G1, Canada. Electronic address: ptacek@uwaterloo.ca.
authors: Carol J
authors: CJ
authors: Ptacek
authors: Department of Earth and Environmental Sciences, University of Waterloo, 200 University Ave. W., Waterloo, ON N2L 3G1, Canada.
authors: David W
authors: DW
authors: Blowes
authors: E I. du Pont de Nemours and Company, 974 Centre Road, Wilmington, DE 19805, United States.
authors: Richard C
authors: RC
authors: Landis
mesh_terms: D000327:Adsorption; D000383:Agriculture; D002606:Charcoal / Q000737:chemistry*; D008372:Manure; D008628:Mercury / Q000737:chemistry*; D013455:Sulfur / Q000032:analysis; D014866:Waste Products; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D014934:Wood; D056928:X-Ray Absorption Spectroscopy
chemical_list: D008372:Manure; D014866:Waste Products; D014874:Water Pollutants, Chemical; C540010:biochar; D002606:Charcoal; D013455:Sulfur; D008628:Mercury
keywords: Biochar; Black carbon; Mercury; Sulfur; X-ray absorption spectroscopy