title: Sorption of Co2+ and Sr2+ by waste-derived 11 A tobermorite.
abstract: Newsprint recycling gives rise to significant volumes of waste sludge which can be de-watered and combusted for energy-recovery. The residual combustion ash, whose primary crystalline constituents are; gehlenite (Ca2Al2SiO7), åkermanite (Ca2MgSi2O7), beta-dicalcium silicate (Ca2SiO4) and anorthite (CaAl2Si2O8), is currently consigned to landfill disposal. It is demonstrated herein that a mixed product of Al-substituted 11 tobermorite (Ca5Si6O18H2 * 4H2O) and katoite (Ca3Al2SiO12H8) can be synthesised from newsprint recycling combustion ash via a hydrothermal route. Batch sorption studies confirm that this mixed product is an effective sorbent for the exclusion of Co2+ and Sr2+ from acidic aqueous media. Kinetic sorption data are analysed in accordance with the pseudo-first- and pseudo-second-order models, and steady-state data is fitted to the Langmuir and Freundlich isotherms. The Langmuir and pseudo-second-order models are found to provide the most appropriate descriptions of the sorption processes. The maximum uptake capacities for Co2+ and Sr2+ at 20 degrees C are 10.47 and 1.52 mg g(-1), respectively, and the respective apparent pseudo-second-order rate constants are estimated to be 5.08 x 10(-3) and 6.96 x 10(-3) g mg(-1) min(-1).
authors.affiliation: Department of Engineering Materials, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK. n.j.coleman@sheffield.ac.uk
authors.forename: Nichola J
authors.initials: NJ
authors.lastname: Coleman
authors.forename: David S
authors.initials: DS
authors.lastname: Brassington
authors.forename: Atiya
authors.initials: A
authors.lastname: Raza
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Mendham
mesh_terms: D000327:Adsorption; D000535:Aluminum / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry*; D003247:Conservation of Natural Resources; D007474:Ion Exchange; D007700:Kinetics; D008854:Microscopy, Electron; D008956:Models, Chemical; D009524:Newspapers as Topic; D017640:Silicates / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D013324:Strontium / Q000737:chemistry*; D018505:Waste Management / Q000379:methods; D014961:X-Ray Diffraction
chemical_list: D017640:Silicates; D003035:Cobalt; D000535:Aluminum; D013324:Strontium