Better contaminant removal is a key barrier to the expansion of the use of recycled fiber in papermaking. Dirt, inks, filler, coatings and stickies must all be removed from the repulped slurry prior to use. A key step in this process is deinking flotation. Flotation is a separation process used to remove particulates from a suspension. Bubbles are introduced into the suspension; as they rise through the fluid, contaminant particles adsorb to the bubble surface and may then be removed from the froth. Successful flotation depends upon the surface chemistry of the particulates and bubbles and the fluid mechanics of the system.

The fundamental phenomena in flotation deinking are the interactions between a particle and a bubble. Our work uses high-speed imaging techniques to study these interactions for stationary bubbles and bubbles in a flow field. Results can be used to quantify the effect of surfactant chemistry, particle & bubble size, and other parameters on the degree of particle adsorption. This talk will present results of our studies and how they can be applied to flotation deinking unit operations. The relative effect of fatty acid and sulfate based surfactant chemistries on particle adsorption will be discussed, as will the role of calcium ions.