title: The effect of magnesium on partial sulphate removal from mine water as gypsum.
abstract: The aim of this research was to investigate the effect of magnesium on the removal efficiency of sulphate as gypsum from mine water. The precipitation conditions were simulated with MINEQL + software and the simulation results were compared with the results from laboratory jar test experiments. Both the simulation and the laboratory results showed that magnesium in the mine water was maintaining sulphate in a soluble form as magnesium sulphate (MgSO4) at pH 9.6. Thus magnesium was preventing the removal of sulphate as gypsum (CaSO4·2H2O). However, change in the lime precipitation pH from 9.6 to 12.5 resulted in magnesium hydroxide (Mg(OH)2) precipitation and improved sulphate removal. Additionally, magnesium hydroxide could act as seed crystals for gypsum precipitation or co-precipitate sulphate further enhancing the removal of sulphate from mine water.
authors.affiliation: University of Oulu, Research Unit of Sustainable Chemistry, University of Oulu, P.O. Box 3000, FIN-90014, Finland.
authors.forename: Emma-Tuulia
authors.initials: ET
authors.lastname: Tolonen
authors.affiliation: University of Oulu, Thule Institute, University of Oulu, P.O. Box 7300, FIN-90014, Finland.
authors.forename: Jaakko
authors.initials: J
authors.lastname: Rämö
authors.affiliation: University of Oulu, Research Unit of Sustainable Chemistry, University of Oulu, P.O. Box 3000, FIN-90014, Finland; Kokkola University Consortium Chydenius, P.O. Box 567, FIN-67101, Kokkola, Finland. Electronic address: ulla.lassi@oulu.fi.
authors.forename: Ulla
authors.initials: U
authors.lastname: Lassi
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry; D002133:Calcium Sulfate / Q000032:analysis / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry; D013431:Sulfates / Q000032:analysis / Q000737:chemistry*; D014867:Water / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry; D018508:Water Purification / Q000379:methods*
chemical_list: D017610:Calcium Compounds; D010087:Oxides; D013431:Sulfates; D014874:Water Pollutants, Chemical; D014867:Water; C016538:lime; D008274:Magnesium; D002133:Calcium Sulfate
keywords: Lime precipitation; Magnesium ion; Mine water; Sulphate removal; Wastewater treatment