Adsorption of hydroxypropyl methyl cellulose in an aqueous system containing multicomponent oxide particles

The adsorption behavior of a hydroxypropyl methyl cellulose (HPMC) polymer in aqueous suspensions of alumina, silica, kaolin, and talc powders, two-co mponent combinations, and one three-component combination was determined. P owders were well characterized by chemical analysis, XRD, DRIFT, SEM, parti cle size, surface area, and density analyses. The zeta-potential of each po wder in aqueous suspension was determined over a range of pH to determine p article charging and the isoelectric point for each material. Alumina and s ilica powders having heavily hydroxylated surfaces were observed not to ads orb the HPMC polymer over a range of pH. The Layer-type minerals talc, whic h was noticeably hydrophobic, and kaolin, which had differently hydrated ba sal planes, adsorbed the HPMC polymer but in different amounts per unit of surface area. In the two-component systems, HPMC polymer adsorption for sys tems of dispersed particles of Like electrical charge (kaolin + silica, tal c + silica or alumina, and kaolin + talc) was proportionate to the sum of t he fraction x specific surface area x adsorption capacity for each particle type. In systems where particles had an opposite electrical charge (kaolin + alumina, kaolin + talc + alumina), the HPMC polymer adsorption was signi ficantly lower than that calculated for a dispersed system. SEM analysis sh owed very fine, nonadsorbing alumina particles predominantly on the faces o f the adsorbing kaolin particles that apparently masked polymer adsorption. Results suggested a hydrophobic mechanism for the HPMC polymer adsorption and adsorption on only one face of the kaolin particles.