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Isotopic exchange measurements in batch adsorption and desorption experiments

  • H. A. Das
  • R. D. van der Weyden
Article

Abstract

The systematics of isotopic exchange in a heterogeneous batch system between a dilute aqueous solution and an adsorbate or the solid adsorbent are discussed. In particular, the influence of the experimental precision on the detection of an eventual non-reactive fraction of the adsorbate is considered, down to ~ 5% of which is detectable. The exchange with the solid adsorbent is illustrated by the case of45Ca2+ and calcite. The minimum layer thickness observable in surface exchange is ~ 0.05 μm. The same formalism can be applied to uptake due to recrystallization of the solid. It enables distinction between this phenomenon and diffusion into the solid.

Keywords

Physical Chemistry Aqueous Solution Inorganic Chemistry Calcite Recrystallization 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

List of symbols

aL

specific activity of liquid, Bq·ml−1

as

specific activity of adsorbate, Bq·g−1

CL

concentration of exchanging constituent in liquid, g·ml−1

Cs

concentration of exchanging constituent in solid, g·g−1

De

effective diffusion coefficient in the pores of the solid, cm2·s−1

Ds

diffusion coefficient in the solid, cm2·s−1

f

fraction of solid that has partaken in isotopic exchange

G

mass of solid, g

k

rate constant for isotopic exchange, (g·ml−1)−1·h−1

ke

experimentally deduced value ofk, (g·ml−1)−1·h−1

p

ratio (mass in solid/mass in liquid) of exchanging constituent for an adsorbate

ps

ratiop in case of isotopic exchange of the solid matrix

Q0

total activity of the added radioactive spike

q

relative (residual) specific activity of the liquid

q

equilibrium value ofq

r

ratio between the rate constants for isotopic exchange of the two fractions of the adsorbate

S

surface area of the solid matrix, cm2

t

time, h

V

volume of the liquid, cm3

Vs

volume of the solid matrix, cm3

x

ratio between the masses of the two fractions of the adsorbate

ϱ

density of the solid matrix, g·cm−3

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References

  1. 1.
    H. A. C. McKAY, Principles of radiochemistry. Butterworths, London, 1971, p. 296.Google Scholar
  2. 2.
    R. BYRON BIRD, W. E. STEWART, E. N. LIGHTFOOT, Transport Phenomena, Wiley International Edition, New York, 1960, p. 621.Google Scholar
  3. 3.
    N. LAHAV, G. H. BOLT, Soil Sci., 97 (1964) 293.Google Scholar
  4. 4.
    P. MÖLLER, C. S. SASTRI, Z. Phys. Chem. Neue Folge, 89 (1974) 80.Google Scholar
  5. 5.
    Measurements performed at the Institute for Earth Sciences, State University at Utrecht.Google Scholar

Copyright information

© Akadémiai Kiadó 1995

Authors and Affiliations

  • H. A. Das
    • 1
    • 2
  • R. D. van der Weyden
    • 2
  1. 1.ECNNetherlands Energy Research FoundationPetten(The Netherlands)
  2. 2.Institute for Earth SciencesUniversity UtrechtUtrecht(The Netherlands)

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