title: Chromate and selenate hydrocalumite solid solutions and their applications in waste treatment.
abstract: Hydrocalumite, a calcium aluminate hydrate phase, consists of positively-charged structure units, and is therefore an ideal candidate for accommodating anionic contaminants. In this study, a series of batch experiments was carried out to examine the uptake of chromate and selenate by hydrocalumite. To determine the uptake capacity and long-term stability, hydrocalumite solid solutions between chromate/selenate and hydroxyl were synthesized over a reaction time of more than one year. At a ratio of water to initial solids added (CaAl2O4+CaO) of 75:1, the maximum uptake capacities were over 77 and 114 g/kg for Cr and Se, respectively. These values are very close to the theoretical uptake capacities of chromate and selenate hydrocalumite end-members (81 and 118 g/kg, respectively). The oxyanion removal efficiency from solution was above 95%. Due to the high uptake capacity and anion removal efficiency of hydrocalumites, their application in wastewater treatment is promising. Hydrocalumites are also important hydration products of cementitious materials and the long-term stability of these phases is of significance for application in solidification/stabilization technology.
authors.affiliation: Department of Earth Sciences, University of Waterloo, Waterloo, Ontario, Canada, N2L 3G1. mzhang@sciborg.uwaterloo.ca
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Reardon
mesh_terms: D017607:Aluminum Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D000838:Anions / Q000737:chemistry; D017610:Calcium Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D002840:Chromates / Q000737:chemistry*; D003460:Crystallization; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D010084:Oxidation-Reduction; D064586:Selenic Acid; D018036:Selenium Compounds / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D014865:Waste Disposal, Fluid / Q000379:methods*; D014877:Water Pollution, Chemical / Q000517:prevention & control; D014961:X-Ray Diffraction
chemical_list: D017607:Aluminum Compounds; D000838:Anions; D017610:Calcium Compounds; D002840:Chromates; D018036:Selenium Compounds; D012996:Solutions; C035219:calcium aluminate; D064586:Selenic Acid