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Adsorption of polyvinyl alcohol on silica at various ph values and its effect on the flocculation of the dispersion

1978; Elsevier BV; Volume: 64; Issue: 1 Linguagem: Inglês

10.1016/0021-9797(78)90332-6

1095-7103

Th. F. Tadros,

Polymer Surface Interaction Studies

The adsorption of polyvinyl alcohol (PVA) from water onto various forms of silica and the flocculation of the dispersions by the polymer were found to depend on the nature and history of the silica sample, and the pH of the solution. Maximum adsorption of PVA, accompanied by maximum flocculation, occurs at the point of zero charge (pzc) of the oxide, above which there is a progressive decrease of adsorption and flocculation with increasing pH. The adsorption of PVA also increases as the temperature of the heat pretreatment of the silica is increased, reaching a maximum at ∼700°C; thereafter the adsorption decreases progressively with increasing temperature. This maximum and the marked pH influence indicate that both "isolated" silanols and siloxane bonds are adsorption sites for PVA adsorption, an optimum ratio for maximum adsorption being obtained by heating silica at 700°C.