title: The removal of sulphate from mine water by precipitation as ettringite and the utilisation of the precipitate as a sorbent for arsenate removal.
abstract: The aim of this research was to investigate sulphate removal from mine water by precipitation as ettringite (Ca6Al2(SO4)3(OH)12·26H2O) and the utilisation of the precipitate as a sorbent for arsenate removal. The mine water sulphate concentration was reduced by 85-90% from the initial 1400 mg/L during ettringite precipitation depending on the treatment method. The precipitation conditions were also simulated with MINEQL + software, and the computational results were compared with the experimental results. The precipitated solids were characterised with X-ray diffraction and a scanning electron microscope. The precipitated solids were tested as sorbents for arsenate removal from the model solution. The arsenic(V) model solution concentration reduced 86-96% from the initial 1.5 mg/L with a 1 g/L sorbent dosage. The effect of initial arsenate concentration on the sorption of arsenate on the precipitate was studied and Langmuir, Freundlich, and Langmuir-Freundlich sorption isotherm models were fitted to the experimental data. The maximum arsenate sorption capacity (qm = 11.2 ± 4.7 mg/g) of the precipitate was obtained from the Langmuir-Freundlich isotherm. The results indicate that the precipitate produced during sulphate removal from mine water by precipitation as ettringite could be further used as a sorbent for arsenate removal.
authors.affiliation: University of Oulu, Research Unit of Sustainable Chemistry, P.O.Box 3000, FI-90014, University of Oulu, Finland; Kajaani University of Applied Sciences, P.O. Box 52, FI-87101, Kajaani, Finland. Electronic address: emma-tuulia.tolonen@oulu.fi.
authors.forename: Emma-Tuulia
authors.initials: ET
authors.lastname: Tolonen
authors.affiliation: University of Oulu, Research Unit of Sustainable Chemistry, P.O.Box 3000, FI-90014, University of Oulu, Finland.
authors.forename: Tao
authors.initials: T
authors.lastname: Hu
authors.affiliation: University of Oulu, Research Unit of Sustainable Chemistry, P.O.Box 3000, FI-90014, University of Oulu, Finland.
authors.forename: Jaakko
authors.initials: J
authors.lastname: Rämö
authors.affiliation: University of Oulu, Research Unit of Sustainable Chemistry, P.O.Box 3000, FI-90014, University of Oulu, Finland; University of Jyvaskyla, Kokkola University Consortium Chydenius, Unit of Applied Chemistry, P.O. Box 567, FI-67701, Kokkola, Finland.
authors.forename: Ulla
authors.initials: U
authors.lastname: Lassi
mesh_terms: D000327:Adsorption; D001149:Arsenates / Q000737:chemistry / Q000302:isolation & purification*; D011232:Chemical Precipitation; D004577:Electron Probe Microanalysis; D006863:Hydrogen-Ion Concentration; D008903:Minerals / Q000737:chemistry*; D008906:Mining; D013052:Spectrometry, X-Ray Emission; D013431:Sulfates / Q000737:chemistry / Q000302:isolation & purification*; D014874:Water Pollutants, Chemical / Q000737:chemistry / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*; D014961:X-Ray Diffraction
chemical_list: D001149:Arsenates; D008903:Minerals; D013431:Sulfates; D014874:Water Pollutants, Chemical; C501337:ettringite
keywords: Arsenate sorption; Ettringite precipitation; Industrial wastewater treatment; Mine water; Sulphate removal; Waste utilization