title: Photochemically induced formation of the "Al13" tridecameric polycation in the presence of Fe(III) and organic acids.
abstract: We found that light-induced Fe(III) reduction associated with the oxidation of a simple hydroxy-carboxylic acid (lactate) caused the formation of the AlO4Al12(OH)24(H2O)12 polycation ("Al13"). Initial conditions were a lactate:Al:Fe ratio of 1:0.76:0.11 in a partially neutralized solution. Base was added rapidly and no Al13 was detected in samples kept in the dark. With exposure to light, Fe(III) reduction was rapid and Fe(II) reached a maximum within 1 day. After the maximum, steady-state Fe(II) declined from 54% to 43% over eight days. During this same time period, the lactate concentration fell to 2% of the original, pH rose from 4.05 to 4.46, and the Al13 detectable by 27Al NMR increased to 2.3 mmol l(-1) (51% of the total solution Al). The formation of Al13 is attributed to the pH rise resulting from the removal of the organic acid buffer. Similar photo-induced chemical changes occur in natural waters and may promote the formation of Al13, conditions permitting.
authors.affiliation: Department of Plant and Soil Science, University of Vermont, Burlington 05405, USA. dross@zoo.uvm.edu
authors.forename: D S
authors.initials: DS
authors.lastname: Ross
authors.forename: R J
authors.initials: RJ
authors.lastname: Bartlett
authors.forename: H
authors.initials: H
authors.lastname: Zhang
mesh_terms: D000535:Aluminum / Q000737:chemistry*; D004785:Environmental Pollutants; D005290:Ferric Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009930:Organic Chemicals; D010084:Oxidation-Reduction; D010777:Photochemistry; D011073:Polyamines / Q000737:chemistry*; D000071228:Polyelectrolytes
chemical_list: D000535:Aluminum; D004785:Environmental Pollutants; D005290:Ferric Compounds; D009930:Organic Chemicals; D011073:Polyamines; D000071228:Polyelectrolytes