title: Calcium silicate sorbent from secondary waste ash: heavy metals-removal from acidic solutions.
abstract: The layer lattice, ion-exchange material, Al-substituted 11 A tobermorite, has been synthesised via an alkaline hydrothermal route from a secondary waste ash arising from newsprint recycling. The hydrogarnet, katoite (Ca3Al2SiO12H8), was also formed. Batch sorption analyses have confirmed that the Al-substituted 11 A tobermorite-bearing product is an effective sorbent for Co2+, Cd2+ and Zn2+ ions from acidified aqueous media. Kinetic sorption data were analysed in accordance with the pseudo-first- and pseudo-second-order models and steady state data were fitted to the Langmuir and Freundlich isotherms. The Langmuir and pseudo-second-order models provided the most appropriate descriptions of the sorption processes. The maximum uptake capacities for Co2+, Cd2+ and Zn2+ at 20 degrees C were found to be 10.47, 2.92 and 3.09 mg g(-1), respectively, and the respective apparent pseudo-second-order rate constants were estimated to be 5.08 x 10(-3), 1.10 x 10(-3) and 1.13 x 10(-3) g mg(-1) min(-1).
authors.affiliation: Medway School of Science, University of Greenwich, Chatham Maritime, Kent, ME4 4TB, UK.
authors.forename: N J
authors.initials: NJ
authors.lastname: Coleman
authors.forename: D S
authors.initials: DS
authors.lastname: Brassington
authors.forename: A
authors.initials: A
authors.lastname: Raza
authors.forename: W E
authors.initials: WE
authors.lastname: Lee
mesh_terms: D000327:Adsorption; D002104:Cadmium / Q000737:chemistry; D002118:Calcium / Q000737:chemistry; D017610:Calcium Compounds / Q000737:chemistry*; D003300:Copper / Q000737:chemistry; D007700:Kinetics; D019216:Metals, Heavy / Q000737:chemistry*; D008956:Models, Chemical; D009524:Newspapers as Topic; D017640:Silicates / Q000737:chemistry*; D018505:Waste Management / Q000379:methods*; D015032:Zinc / Q000737:chemistry
chemical_list: D017610:Calcium Compounds; D019216:Metals, Heavy; D017640:Silicates; D002104:Cadmium; C512534:tobermorite; D003300:Copper; D015032:Zinc; D002118:Calcium