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Water-in-oil emulsion foaming by thiourea nitrosation: Reaction and mass transfer
Journal article   Peer reviewed

Water-in-oil emulsion foaming by thiourea nitrosation: Reaction and mass transfer

G. da Silva, B.Z. Dlugogorski and E.M. Kennedy
AIChE Journal, Vol.52(4), pp.1558-1565
2006
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Abstract

A study has been undertaken into the chemical production of gas bubbles within a concentrated water-in-oil emulsion, typical of those used as emulsion explosives. Chemical foaming was initiated by the introduction of a concentrated sodium nitrite solution to the emulsion, and the measurement of the decreasing emulsion density with time served to estimate the rate of nitrogen production. A conversion of emulsion density to nitrite ion concentration facilitated a kinetic analysis of the data. The change in nitrite ion concentration follows a rate equation which indicates that the rate-limiting reaction step corresponds to the N-nitrosation of thiourea by ON+, with an apparent rate constant of 0.22 M-1 s-1 at 25°C. Tests over a temperature range of 25 to 50°C yielded an activation energy of 59 kJ mol-1. A mass-transfer model describing the rate of diffusion between aqueous droplets is presented. This model suggests that chemical kinetics, rather than molecular diffusion, is the rate-limiting phenomenon in the foaming of emulsions. Supporting this finding, the kinetic experiments in emulsion returned very similar results to previous experiments performed in aqueous media under similar conditions.

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Citation topics
1 Clinical & Life Sciences
1.254 Ultrasound in Medicine
1.254.976 Microbubbles
Web Of Science research areas
Engineering, Chemical
ESI research areas
Chemistry
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