Rates of feldspar dissolution at pH 3-7 with 0-8 m M oxalic acid

Lisa L. Stillings, James I. Drever, Susan L. Brantley, Yanting Sun, Rachael Oxburgh

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Feldspar dissolution rates were measured in flow-through reactors, over a pH range of 3-7, oxalic acid concentration of 0-8 m M, and feldspar compositional range of An0-An76. Dissolution rates in O and l m M concentrations of oxalic acid increased linearly with increasing mole percent anorthite in the solid. Dissolution was nonstoichiometric in oxalic acid, due to a preferential release of Al at steady state, 1 m M concentrations of oxalic acid increased dissolution rates by a factor of 2-5 at pH 3 and 2-15 at pH 5-6. At pH 5-6 the rate enhancement due to oxalic acid may increase with increasing anorthite content of the feldspar. The ligand-promoted rate, RL, defined as the observed total rate in oxalic acid minus the proton-promoted rate, Rt - RH, was estimated as 10-12.8(aHOx-+ aOx2)0.75, suggesting that both HC2O-4 (bioxalate) and C2O2-4 (oxalate) play a role in the dissolution mechanism.

Original languageEnglish (US)
Pages (from-to)79-89
Number of pages11
JournalChemical Geology
Issue number1-4 SPEC. ISS.
StatePublished - Oct 30 1996

All Science Journal Classification (ASJC) codes

  • Geology
  • Geochemistry and Petrology


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