Articles | Volume 6, issue 1
Regular research article
23 May 2017
Regular research article |  | 23 May 2017

Simultaneous in situ characterisation of bubble dynamics and a spatially resolved concentration profile: a combined Mach–Zehnder holography and confocal Raman-spectroscopy sensor system

Jajnabalkya Guhathakurta, Daniela Schurr, Günter Rinke, Roland Dittmeyer, and Sven Simon

Abstract. For a reaction between a gaseous phase and a liquid phase, the interaction between the hydrodynamic conditions, mass transport and reaction kinetics plays a crucial role with respect to the conversion and selectivity of the process. Within this work, a sensor system was developed to simultaneously characterise the bubble dynamics and the localised concentration measurement around the bubbles. The sensor system is a combination of a digital Mach–Zehnder holography subsystem to measure bubble dynamics and a confocal Raman-spectroscopy subsystem to measure localised concentration. The combined system was used to investigate the chemical absorption of CO2 bubbles in caustic soda in microchannels. The proposed set-up is explained and characterised in detail and the experimental results are presented, illustrating the capability of the sensor system to simultaneously measure the localised concentration of the carbonate ion with a good limit of detection and the 3-D position of the bubble with respect to the spot where the concentration was measured.