Measuring induction period for calcium sulfate dihydrate precipitation
- Univ. di Napoli Federico II (Italy). Dipt. di Ingegneria Chimica
- CNR, Napoli (Italy). Istituto di Ricerche sulla Combustione
- Univ. di L`Aquila (Italy). Dipt. di Chimica, Ingegneria Chimica e Materiali
Homogeneous nucleation of CaSO{sub 4}{center_dot}2H{sub 2}O (gypsum) based on an optical diagnostic technique was studied within a supersaturation range of 1--4 at 25--90 C. The experiments were carried out using an experimental apparatus consisting of a batch crystallizer with the related measurement devices. Signals of scattered and transmitted light coming from a He-Ne laser source were analyzed to measure the induction period (t{sub ind}), that is, the time delay necessary for homogeneous nucleation to take place. As expected from theory, it was found that t{sub ind} decreases when either temperature or supersaturation increase; from the dependence of t{sub ind} on supersaturation, it was possible to distinguish between the mechanisms of homogeneous and heterogeneous nucleation. From the experimental data relative to homogeneous nucleation, the interfacial tension ({gamma}{sub s}) between CaSO{sub 4}{center_dot}2H{sub 2}O and the surrounding aqueous solution and the activation energy (E{sub att}) for CaSO{sub 4}{center_dot}2H{sub 2}O crystallization were evaluated. In particular, the dependence of t{sub ind} on temperature made it possible to evaluate E{sub att} at 30 kJ/mol and the dependence of t{sub ind} on supersaturation offered the value of {gamma}{sub s} to be about 37 mJ/m{sup 2}, which does not vary with temperature in the interval explored.
- OSTI ID:
- 329250
- Journal Information:
- AIChE Journal, Journal Name: AIChE Journal Journal Issue: 2 Vol. 45; ISSN 0001-1541; ISSN AICEAC
- Country of Publication:
- United States
- Language:
- English
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