Rheology of colloidal gas aphrons (microfoams)

Abstract

This paper reports on the effect of surfactant concentration and pipe shape and size on the rheological properties of colloidal gas aphrons (CGA) or microfoams. CGA consists of closely packed spherical gas bubbles with diameter ranging from 10 to 100 microns surrounded by a surfactant shell. It is produced by stirring an aqueous surfactant solution at high speed in a baffled beaker. Pipe flow experiments were performed in cylindrical pipes with diameter ranging from 1.0 to 3.0 mm under adiabatic laminar flow conditions. The porosity, bubble size distribution, surface tension, and pH were systematically measured. First, it is established that there was no slip velocity at the wall and CGA did not change morphology and porosity between the inlet and outlet of the pipes less than 2 mm in diameter. Compressibility effects were accounted for through the volume equalization approach. Then, pipe shape and diameter have no

Drainage mechanism of microbubble dispersion and factors influencing its stability

“…The hypothesized structure of a microbubble comprises of a gas core encapsulated by multiple layers of surfactant molecules, which retard coalescence of the microbubbles, thereby giving it remarkable stability compared to conventional bubbles [4]. This feature coupled with a large interfacial area arising from the small bubble size has resulted in its applications in separation processes [5][6][7][8][9]. It has been suggested that microbubble dispersions can enhance bioremediation by effectively increasing mass transfer of oxygen and nutrients in the subsurface [10][11][12].…”

The role of surfactant type and bubble surface mobility in foam rheology

“…In parallel, the effects of surfactants on dynamic phenomena in foams were studied by several other research groups. 25,[47][48][49][50] In the current review we summarise the progress achieved so far in these studies. Comparison with the results of the various research groups is made, and some open questions, deserving further investigation, are discussed.…”

Dispersion characteristics of ionic microbubble suspension in continuous plant prototype developed for mineral beneficiation

“…The constant n is called flow index and gives a measure of degree of departure from Newtonian behaviour. The parameter n and K are independent of shape of the column [26]. The value of n and K is calculated experimentally in a horizontal pipe from the wall shear stress (t) and the apparent shear rate (g a ).…”

“…The parameter K 0 and the flow consistency index (K) of the microbubble suspension are related as [26] …”