title: Visible-spectroscopy study of the adsorption of alizarinate by Al-montmorillonite in aqueous suspensions and in solid state.
abstract: The adsorption of the monovalent anionic dye alizarinate onto Na- and Al-montmorillonite was carried out by adding the dye into aqueous clay suspensions. Electronic spectra of aqueous suspensions and of air-dried dye-clay complexes were studied. Na-montmorillonite adsorbed only part of the added dye. With total amount of alizarinate up to 5 mmol dye per 100 g clay the adsorption of the dye takes place on the broken bonds, leading to peptization of the clay. Al-montmorillonite adsorbed alizarinate completely up to 10 mmol per 100 g clay. Above this loading there was a partition of the dye between the clay and the supernatant. The maximum adsorption for Na- and Al-clay was 4 and 25 mmol dye per 100 g clay, respectively. Absorption bands in the spectrum of Al-montmorillonite suspensions (488-504 nm) appear at longer wavelengths than in the spectrum of air-dried Al-montmorillonite (415-455 nm). Thermo-X-ray study of these clay-alizarinate complexes suggests that the organic compound was located in the interlayer space in Al-montmorillonite but was not located there in Na-montmorillonite. In Al-montmorillonite alizarinate formed a coordination complex with exchangeable Al(3+). In Na-montmorillonite it formed bonds with Al exposed on the broken-bonds sites.
authors.affiliation: Tel-Hai Technological College, Upper Galilee 12210, Israel.
authors.forename: M
authors.initials: M
authors.lastname: Epstein
authors.forename: S
authors.initials: S
authors.lastname: Yariv
mesh_terms: D000327:Adsorption; D000535:Aluminum / Q000737:chemistry*; D000880:Anthraquinones / Q000737:chemistry*; D001546:Bentonite / Q000737:chemistry; D055592:Biophysical Phenomena; D001703:Biophysics; D004396:Coloring Agents / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000737:chemistry; D008956:Models, Chemical; D015233:Models, Statistical; D012822:Silicon Dioxide / Q000737:chemistry; D012964:Sodium / Q000737:chemistry; D013052:Spectrometry, X-Ray Emission; D013053:Spectrophotometry / Q000379:methods*; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D000880:Anthraquinones; D004396:Coloring Agents; D014867:Water; D001546:Bentonite; C010078:alizarin; D012822:Silicon Dioxide; D012964:Sodium; D000535:Aluminum; D008274:Magnesium