title: Absorption of the selenite anion from aqueous solutions by thermally activated layered double hydroxide.
abstract: The presence of selenite or selenate in potable water is a health hazard especially when consumed over a long period of time. Its removal from potable water is of importance. This paper reports technology for the removal of selenite from water through the use of thermally activated layered double hydroxides. Mg/Al hydrotalcites with selenite in the interlayer were prepared at different times from 0.5 to 20 h through ion exchange. X-ray diffraction of the MgAlSeO3 hydrotalcites indicates that the selenite anion entered the interlayer spacing of Mg/Al hydrotalcite and MgAlSeO3 hydrotalcite was formed. Raman spectra proved the presence of selenite anion in the hydrotalcite interlayer as the counter anion. The band intensity and width of MgAlSeO3 hydrotalcite in the region of 3800-3000 cm(-1) increase with the adsorption of selenite by the Mg/Al hydrotalcite. The characteristic bands of free selenite anions in the MgAlSeO3 hydrotalcites are located between the region between 850 and 800 cm(-1). The Raman spectra of the lower wave number region of 550-500 cm(-1) show a shift toward higher wave numbers with adsorption of the selenite. An estimation of the amount of selenite anion removed by the thermally activated layered double hydroxide was obtained through the measurement of the intensity of the selenite Raman bands at 814 and 835 cm(-1) resulting from the amount of selenite anion remaining in solution. Thermally activated LDHs provide a mechanism for removing selenite anions from aqueous solutions.
authors.affiliation: Inorganic Materials Research Program, School of Physical and Chemical Sciences, Queensland University of Technology, 2 George Street, GPO Box 2434, Brisbane, Queensland 4001, Australia.
authors.forename: Rui
authors.initials: R
authors.lastname: Liu
authors.forename: Ray L
authors.initials: RL
authors.lastname: Frost
authors.forename: Wayde N
authors.initials: WN
authors.lastname: Martens
mesh_terms: D000042:Absorption; D000535:Aluminum / Q000737:chemistry; D000536:Aluminum Hydroxide / Q000737:chemistry; D000838:Anions / Q000302:isolation & purification*; D006878:Hydroxides / Q000737:chemistry*; D008274:Magnesium / Q000737:chemistry; D008276:Magnesium Hydroxide / Q000737:chemistry; D018038:Sodium Selenite / Q000302:isolation & purification*; D012996:Solutions; D013059:Spectrum Analysis, Raman; D013696:Temperature; D013997:Time Factors; D014961:X-Ray Diffraction
chemical_list: D000838:Anions; D006878:Hydroxides; D012996:Solutions; C010467:hydrotalcite; D000536:Aluminum Hydroxide; C031356:hydroxide ion; D000535:Aluminum; D018038:Sodium Selenite; D008274:Magnesium; D008276:Magnesium Hydroxide