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Dissolution of Basaltic Glass: Effects of pH and Organic Ligands
Published online by Cambridge University Press: 15 February 2011
Abstract
Dissolution of powdered glass from Kilauea volcano, Hawaii (ca 51% SiO2) was studied in a fluidized-bed, flow-through reactor at room temperature in both dilute HCI and organic ligand-bearing solutions (citrate and oxalate) to determine the effects of pH and organic acids on the dissolution rate. Dissolution was non-stoichiometric in both HCI and organic solutions; however, the relative release rates of various ions and the composition of leached layers or secondary phases are fimctions of pH and organic ligand concentration and type. In HCl solutions, the minimum glass dissolution rate, as assessed from the Na leaching rate, was 7.4 × 10−12 gm cm−2 sec−1, comparable with previous results, and was virtually independent of pH. Addition of citrate and oxalate increased the non-stoichiometry of dissolution. At pH 7, the overall rate of glass dissolution decreased (by as much as 5 times) at low ligand concentrations (< 1 mM), but increased by as much as five times at higher concentration (3 mM). High ligand concentrations do increase the release rate of some elements, especially multivalent cations, such as Fe3+ which form strong organic complexes, by as much as 100 times.
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- Copyright © Materials Research Society 1996
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