title: Potential for use of industrial waste materials as filter media for removal of Al, Mo, As, V and Ga from alkaline drainage in constructed wetlands--adsorption studies.
abstract: The potential to remove Al, Mo, V, As and Ga from alkaline (pH 8.0-8.6) drainage originating from seawater neutralized bauxite processing residue storage areas using constructed wetland technology was studied in a laboratory study. Bauxite processing residue sand, bauxite, alum water treatment sludge and blast furnace slag were investigated as potential active filter materials. Al was shown to precipitate as Al(OH)3 in the pH range 7.0-8.0 in aqueous solution and 6.0-8.5 in the presence of silica sand particles that provided a surface for nucleation. For V As Mo and Ga, adsorption to the surfaces of the adsorbents decreased greatly at elevated pH values (>pH 6-9). Water treatment sludge and bauxite had a greater ability to adsorb V, As and Mo at high pH (As and V at pH 7-9 and Mo at pH 5-7) than processing sand and slag. Adsorption isotherm data for As and V onto all four adsorbent than processing sand and slag. Adsorption isotherm data for As and V onto all four adsorbent materials fitted equally well to the Langmuir and Freundlich equations but for Ga, and to a lesser extent Mo, the Freundlich equation gave higher R(2) values. For all four ions, the maximum adsorption capacity (Langmuir value qmax) was greatest for water treatment sludge. Bauxite adsorbed more Mo, Ga and V than residue sand or slag. The pseudo-second order equation gave a better fit to the experimental kinetic data than the pseudo-first order model suggesting that chemisorption rather than diffusion/exchange was the rate limiting step to adsorption. It was concluded that water treatment sludge and bauxite were the most effective adsorbents and that for effective removal of the target ions the pH of the drainage water needs to be decreased to 6.0-7.0.
authors.affiliation: School of Agriculture and Food Sciences/CRC CARE, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: T
authors.initials: T
authors.lastname: Hua
authors.affiliation: School of Agriculture and Food Sciences/CRC CARE, The University of Queensland, St Lucia, QLD 4072, Australia. Electronic address: r.haynes1@uq.edu.au.
authors.forename: R J
authors.initials: RJ
authors.lastname: Haynes
authors.affiliation: School of Agriculture and Food Sciences/CRC CARE, The University of Queensland, St Lucia, QLD 4072, Australia.
authors.forename: Y-F
authors.initials: YF
authors.lastname: Zhou
authors.affiliation: Legacy Management Europe, Rio Tinto, 725 rue Aristide Bergès, Voreppe BP 7, 38341 Cèdex, France.
authors.forename: A
authors.initials: A
authors.lastname: Boullemant
authors.affiliation: Rio Tinto Alcan, Queensland Research and Development Centre, 1 Technology Court, Pullenvale, Brisbane, QLD 4069, Australia.
authors.forename: I
authors.initials: I
authors.lastname: Chandrawana
mesh_terms: D000327:Adsorption; D000535:Aluminum / Q000737:chemistry; D000537:Aluminum Oxide / Q000737:chemistry; D001151:Arsenic / Q000737:chemistry; D005374:Filtration / Q000379:methods; D005708:Gallium / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste; D008670:Metals / Q000737:chemistry*; D008982:Molybdenum / Q000737:chemistry; D012722:Sewage / Q000737:chemistry; D014639:Vanadium / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*; D053833:Wetlands
chemical_list: D007220:Industrial Waste; D008670:Metals; D012722:Sewage; D014874:Water Pollutants, Chemical; D014639:Vanadium; D008982:Molybdenum; D005708:Gallium; D000535:Aluminum; D000537:Aluminum Oxide; D001151:Arsenic
keywords: Alkaline drainage; Bauxite; Bauxite residue mud; Wastewater; Water treatment sludge