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Rapid reaction rates between water and a calcareous clay as observed by specific-ion electrodes

Journal of Research of the U.S. Geological Survey
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Abstract

Specific-ion electrodes were used to simultaneously determine the activity changes of calcium, hydrogen, sodium, fluoride, and divalent ions when 50 g of a natural, untreated material containing calcium-rich mixed-layer illite-montmorillonite clay, quartz sand, and calcium carbonate was added to 250 ml of natural Canadian River water containing 220 mg/1 Na. Calcium and magnesium were displaced from the clay by the sodium; the exchanged and dissolved noncarbonate calcium precipitated as calcium carbonate, and the magnesium remained in solution. Fluoride entered into both a rapid reaction and a long-term reaction, indicating solution from the material. The pH decreased rapidly. The reactions for all observed ions, other than fluoride, were faster than the response time of their respective electrodes and were complete in less than one minute. Rapid solution of material containing calcium, magnesium, sodium, and fluoride was also observed when a duplicate sample of the earth material was added to distilled water; pH also changed rapidly in this mixture. These results suggest that many important water-rock reactions can be considered nearly instantaneous for purposes of digital modeling of the geochemical changes during artificial recharge.

Publication type Article
Publication Subtype Journal Article
Title Rapid reaction rates between water and a calcareous clay as observed by specific-ion electrodes
Series title Journal of Research of the U.S. Geological Survey
Volume 1
Issue 2
Year Published 1973
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Description 4 p.
First page 237
Last page 241
Country United States of America
Online Only (Y/N) N
Additional Online Files (Y/N) N
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