title: Sorptive removal of HgIIby red mud (bauxite residue) in contaminated landfill leachate.
abstract: The ability of red mud (RM) (bauxite residue) to remove HgIIfrom landfill leachate (LL) was assessed. The studied aspects comprised the effects of time, pH, HgIIconcentration and the sorption isotherm, besides the influence of chloride and representative organic ligands. HgIIremoval by RM exhibited a complex kinetics where initial rapid sorption was followed by desorption at longer times. The sorption of HgIIon RM was strongly pH-dependent. Outstanding maximum sorption was observed at pH∼4-5 (≥99.6%), while it abruptly dropped at higher pH values down to a minimum ∼28% at pH∼10.5. Chloride decreased HgIIsorption at acid pH and shifted the pHmaxtowards higher pH∼9.4, which opposes to sorption in LL and suggests Cl-did not primarily control the process in LL. Amongst the organic ligands, acetate and salicylate slightly affected HgIIsorption. Conversely, glycine affected sorption in a pH-dependent manner resembling that in LL, which suggests the relevant role of the organic nitrogenated compounds of LL. EDTA suppressed HgIIsorption at any pH. HgIIspeciation modelling and dissolved organic matter (DOM) sorption support complexation of HgIIby DOM as the primary factor governing the removal of HgIIin LL. The sorption isotherm was better described by the Freundlich equation, which agrees with the heterogeneous composition of RM. The results indicate that HgIIsorption on RM is favorable, but reveal differences in sorption and reduced efficiency, in LL media. Notwithstanding, RM possesses a notable capacity to remove HgII, even under the unhelpful complexing and competing conditions of LL.
authors.affiliation: a Department of Soil Science and Agricultural Chemistry, Faculty of Pharmacy , University of Santiago de Compostela , Santiago de Compostela , Spain.
authors.forename: David A
authors.initials: DA
authors.lastname: Rubinos
authors.affiliation: a Department of Soil Science and Agricultural Chemistry, Faculty of Pharmacy , University of Santiago de Compostela , Santiago de Compostela , Spain.
authors.forename: María T
authors.initials: MT
authors.lastname: Barral
mesh_terms: D000327:Adsorption; D000537:Aluminum Oxide / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry; D004492:Edetic Acid / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008628:Mercury / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods
chemical_list: D002712:Chlorides; D009930:Organic Chemicals; D014874:Water Pollutants, Chemical; D004492:Edetic Acid; D008628:Mercury; D000537:Aluminum Oxide
keywords: bauxite waste; leachate; reuse; sorption; toxic metal; treatment