The Role Of Surfactant Polymer Interactions With The Solid Liquid Interface In Fine Particle Flotation PDF Download

Environmental pressures are driving detergent formulations to become ever-more so- phisticated blends of stabilisers; probing the interactions occurring in complex systems of hydrosoluble polymers with surfactants and their adsorption onto particles is key for the understanding of the mechanism of colloidal stability. In this thesis, the polymer-polymer and polymer-surfactant interactions have been investigated both in bulk and at the solid/liquid interface. The main techniques used were solvent relaxation NMR, photon correlation spectroscopy, small angle neutron scattering, diffusion NMR and optical reflectometry. The majority of experiments involved polyvinyl pyrrolidone, PVP, adsorbed on silica. Addition of sodium dodecyl sulfate, SDS, decreased the adsorbed amount but increased the layer thickness, leaving the remaining adsorbed polymer in an extended conformation caused by repulsive interactions amongst adsorbed surfactant aggregates and the silica interface. The introduction of a nonionic alcohol ethoxylate surfactant to this system prevented the desorption of the polymer layer as it formed mixed micelles with SDS reducing the total charges per micelle and lowering repulsions between the surface and the surfactant micelles. The effect of a non-adsorbing polymer, sodium polystyrene sulfonate, aPSS, on the stability of silica particles was also investigated, showing that addition of the polyelec- trolyte to the silica dispersion modifies the interparticles interactions. Small roughly spherical clusters were formed, followed by larger, less spherical aggregates resulting in the formation of a dense gel network. Exploring the PVP /N aPSS system showed that these polymers interact in bulk forming NaPSS-rich complexes; interfacial investigations revealed that adding aPSS to PVP previously adsorbed on silica led to surface complexes formation. Finally exposing PVP to sodium polyacrylate revealed some polymer interactions at high pH. These interactions were favoured by increasing molecular weights; adding this polymer to PVP adsorbed onto silica lead to a small decrease in adsorbed amount and some particle aggregation.