The Kinetics for the Solution of Silica in Aqueous Solutions

O'Connor, T. L.; Greenberg, S. A.

doi:10.1021/j150568a008

Cited by 74 publications

(34 citation statements)

References 2 publications

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“…From hereon, this behaviour is described as non-linearity in the O'Connor and Greenberg (1958) Equation. In kinetics, fractional orders suggest a complex mechanism. The well-known idea (Bunnett, 1974a) that it arises from a dimer in an equilibrium prior to a rate determining step was dismissed because we are not aware of any evidence for an appreciable proportion of silicic acid dimer at the pH of seawater.…”

Section: Our Modelmentioning

confidence: 96%

The Rate-equation for Biogenic Silica Dissolution in Seawater – New Hypotheses

2005

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This paper investigates the kinetics of biogenic silica dissolution in seawater, through batch dissolution, where the reaction is observed as the increase in dissolved silicic acid concentration with time. It utilises new data from dissolution of the marine diatom Cyclotella cryptica, and the freshwater diatom C. meneghiniana, as well as literature results. The sum of exponentials form: C t ¼ A 1 ð1 À e Àkat Þ þ B 1 ð1 À e Àkbt Þ, is hypothesised as the most general rate equation, with the single exponential form occurring in a minority of cases. The consistency of this behaviour with a near-exponential decay of surface area with time, an appropriate mathematical integration, and surface heterogeneity, is discussed. (Serious errors in some existing integrations are identified.) The rate of dissolution at constant surface area is shown to decrease non-linearly as the ambient concentration of silicic acid increases. A fractional order with respect to silicic acid in the back reaction, close to 0.5, leads to a mechanism in which an intermediate is formed from the surface and an, as yet, unidentified molecule, probably water. Good preliminary fits are found between the model and literature results found using entirely different methods. A parallel treatment of hydrogen ion dependency is suggested. The likely distortion of full reaction curves from exponential behaviour imposed by the back reaction, is considered in detail.

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Section: Our Modelmentioning

confidence: 96%

The Rate-equation for Biogenic Silica Dissolution in Seawater – New Hypotheses

2005

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“…7a from Tester et al (1994): (1) Similar equations have been used by many previous investigators (O'Connor and Greenberg, 1958;van Lier et al, 1960;Tester et al, 1977;Rimstidt and Barnes, 1980;Robinson, 1982). The mass of water Mw is calculated as the product of the reactor liquid volume and the density of the water at reaction conditions.…”

Section: Dissolution Rate Determinationmentioning

confidence: 99%

Quartz dissolution kinetics from 100–200°C as a function of pH and ionic strength

1996

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“…Van Lier, de Bruyn, and Overbeek (1960) reported that as rnuch as about 11 ppm quartz was soluble in water at 25°0 and that saturation was attained slowly. The rate of silica solution also was studied by O'Connor and Greenberg (1958) and reported to be proportional to t4e surface area of solid exposed.…”

Section: F3 Chemistry Of Individual Constituents Ffionmentioning

confidence: 99%