Surfactant behavior in the mechanisms of ink removal from secondary fiber in flotation deinking.

Abstract

To date, the majority of the research into ink removal from secondary fiber by the flotation deinking method has centered about empirical research, and the fundamental mechanisms have not been well understood. In this study, the underlying mechanisms of "collector chemistry" are elucidated and found to be complex combinations of the ink particle interactions stemming from the nature of the surfactant/calcium relationship. While previous investigators employed long chain fatty acid surfactants typically used in industrial applications, this study focuses on two medium chain-length fatty acids (sodium octanoate and sodium dodecanoate) and a comparable chain-length sulfate (sodium dodecyl sulfate) so as to be able to observe the system behavior below the K$\rm\sb{sp}$ of the surfactant/calcium complex. By investigating the adsorption isotherms of the surfactants on both model inks and fibers, the associated zeta potentials, the aggregation characteristics of the model ink, and the flotation of the ink and fibers, the fundamental mechanisms were found to be adsorptive rather than precipitative. This mechanistic understanding could translate into more efficient surfactant formulations for the flotation deinking process. In addition to the aforementioned investigations, a new technique was developed to simultaneously measure paper brightness and dirt count using an image analyzer. Also, a new class of polymeric reverse phase high performance liquid chromatography (HPLC) packings was developed.