2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM
Paper No. 141-7
Presentation Time: 8:00 AM-4:45 PM

The Effects of Solution Chemistry on the Solubility of Synthetic Jarosite at 50C: Implications for Terrestrial and Martian Environments

RIDLEY, Moira K., Department of Geosciences, Texas Tech University, Lubbock, TX 79409-1053, Moira.Ridley@ttu.edu, FROST, Gwendolynne R., ConocoPhillips, San Juan Business Unit, 3401 E. 30th Street, Farmington, NM 87401, and ZHOU, Jian, Department of Geosciences, Texas Tech University, Box 41053, Lubbock, TX 79409-1053

Jarosite, a hydrous sulfate mineral (KFe3(SO4)2(OH)6), is widespread on Earth. The mineral forms mainly in acid-sulfate rich environments; particularly associated with acid mine drainage (AMD) systems. The precipitation of jarosite in AMD systems and metallurgical processes is of interest due to the potential for jarosite to scavenge heavy metals. More recently, jarosite has been identified at the Terra Meridiani locality on Mars, by the Opportunity Exploration Rover.

The stability of jarosite in terrestrial environments is fairly well established. In general, stability is limited to oxidizing and acidic systems. Moreover, literature data shows that hydronium jarosite ((H3O)Fe3(SO4)2(OH)6) is significantly more soluble than end-member potassium jarosite. However, only a few jarosite dissolution studies have been completed. These studies were completed in pure water, for limited time periods. Thermodynamic data for the solubility of jarosite are, therefore, somewhat limited; making it difficult to evaluate the stability of the mineral under potential Martian conditions.

This presentation will summarize our solubility experiments performed at 50C, using synthetic jarosite that was reacted for over 900 days. Jarosite was synthesized following the procedure outlined by Baron et al. (GCA, v.60, 1996); then characterized extensively. The solubility experiments were completed in tetramethyl ammonium-chloride (TMA-Cl) and TMA-nitrate media, at ionic strengths of 0.1 and 0.3 m, over a pH range of 1.5 to 3.5. TMA was selected as the cation-electrolyte ion because of its large size, thus preventing substitution into the jarosite structure. Two anion electrolyte ions were selected to examine the effect of possible ion-pairing with Fe3+ on the solubility. Samples were withdrawn from the experimental solutions at regular intervals and analyzed for Fe, K, and SO4, and pH was recorded at 50C. Both ionic strength and solution pH had a significant effect on the solubility. Moreover, at low pH an iron-oxy(hydr)oxide phase precipitated

2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM
General Information for this Meeting
Session No. 141--Booth# 7
Geochemistry; Geochemistry, Organic (Posters)
George R. Brown Convention Center: Exhibit Hall E
8:00 AM-4:45 PM, Sunday, 5 October 2008

Geological Society of America Abstracts with Programs, Vol. 40, No. 6, p. 131

© Copyright 2008 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.