title: The capacity of biochar made from common reeds to neutralise pH and remove dissolved metals in acid drainage.
abstract: We tested the capacity of biochar (made at 450 °C from a common reed species) to neutralise pH and remove metals in two acid drainage waters (pH 2.6 and 4.6) using column leaching and batch mixing experiments. In the column experiments, the acid drainage water was neutralised upon passage through the biochar with substantial increases (4-5 pH units) in the leachate pH. In the batch experiments, the leachate pH remained above 6.5 when the drainage:biochar ratio was less than approximately 700:1 (L acid drainage:kg biochar) and 20:1 for the pH 4.6 and pH 2.6 drainage waters, respectively. Dissolved metal concentrations were reduced by 89-98 % (Fe ≈ Al > Ni ≈ Zn > Mn) in the leachate from the biochar. A key mechanism of pH neutralisation appears to be solid carbonate dissolution as calcite (CaCO3) was identified (via X-ray diffraction) in the biochar prior to contact with acid drainage, and dissolved alkalinity and Ca was observed in the leachate. Proton and metal removal by cation exchange, direct binding to oxygen-containing functional groups, and metal oxide precipitation also appears important. Further evaluation of the treatment capacity of other biochars and field trials are warranted.
authors.affiliation: Water Quality Science, PO Box 310, Belair, SA, 5052, Australia. luke.mosley@adelaide.edu.au.|Acid Sulfate Soils Centre, University of Adelaide, Adelaide, SA, 5005, Australia. luke.mosley@adelaide.edu.au.
authors.forename: Luke M
authors.initials: LM
authors.lastname: Mosley
authors.affiliation: Environment Protection Authority (South Australia), GPO Box 2607, Adelaide, SA, 5001, Australia.
authors.forename: Philip
authors.initials: P
authors.lastname: Willson
authors.affiliation: Environment Protection Authority (South Australia), GPO Box 2607, Adelaide, SA, 5001, Australia.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Hamilton
authors.affiliation: South Australian No Till Farmers Association, PO Box 923, Clare, SA, 5453, Australia.
authors.forename: Greg
authors.initials: G
authors.lastname: Butler
authors.affiliation: Department of Environment, Water and Natural Resources, GPO Box 1047, Adelaide, SA, 5001, Australia.
authors.forename: Russell
authors.initials: R
authors.lastname: Seaman
mesh_terms: D002606:Charcoal / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D019216:Metals, Heavy / Q000302:isolation & purification*; D008906:Mining; D013431:Sulfates / Q000737:chemistry*; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*; D014961:X-Ray Diffraction
chemical_list: D002606:Charcoal; D019216:Metals, Heavy; D013431:Sulfates; D062065:Wastewater; D014874:Water Pollutants, Chemical; C540010:biochar
keywords: Acid neutralisation; Acid sulphate soils; Black carbon; Mine drainage; Organic matter; Phragmites australis