Gas-liquid flows are abundant in industrial applications, viz. aeration, hydrogenation processes, etc. Within MRF we study the flow and transport phenomena in these flows with the aid of numerical models and experimental techniques. We focus on two particular aspects: i) manipulating the bubbly flow as to maximize the mass transfer rate and ii) understanding how surface active species influence the bubbly flow behavior. For the former we use meshes made of thin wires that cut the bubbles in smaller pieces. The latter requires the development of novel tools to quantitatively characterize the presence of surfactants on the gas-liquid interface.