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Rates of dissolution of aluminosilicates in seawater

A. Lerman·F.T. MacKenzie·O.P. Bricker
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Abstract

Dissolution of eight clay minerals, four zeolites, and quartz in seawater has been monitored for 8 1 2 years. For most of the minerals, dissolution can be described as a first-order reaction in which dissolved silica approaches from undersaturation steady concentration values with time. Characteristic reaction rate constants (k 1 ) are of the order of 10 -7 sec -1 . One of the zeolites, clinoptilolite, shows a different dissolution behavior: SiO 2 concentration in solution reaches a high value within one year, followed by a decline to a lower value, suggestive of precipitation of another silicate phase (possibly sepiolite). A mathematical solution is given for a kinetic equation combining the parabolic-rate and first-order rate processes. It is shown that in a wide range of silicate dissolution reactions taking place over long periods of time, the presence of the parabolic-rate dissolution processes cannot be detected, thereby making its inclusion in the kinetic equations unnecessary. The experimental rates of dissolution are comparable to the SiO 2 - dissolution rates in oceanic sediments near the sediment/water interface. But deeper in the sediment, the calculated dissolution rates are significantly lower than the near-interface and experimental values. © 1975.

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A. Lerman, F.T. MacKenzie, O.P. Bricker. 1975. Rates of dissolution of aluminosilicates in seawater. https://doi.org/10.1016/0012-821x(75)90213-7

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