Effect of adsorption of surfactants on stability of suspension of alumina powders

The adsorption of sodium dodecyl sulfonate (SDBS), tetradecyl pyridine chloride (TPC) and Triton X-100 (TX-100) onto the alumina powders at various pH was studied. The ??-potential of the particles and the stability of the suspension in water were determined. The main results are as follows. (1) At suitable pH, the adsorption isotherms are LS type for SDBS and TPC. At higher concentration of surfactants, association on the surface occurs to form a close-packed monolayer. The orientation of hydrophilic group to water phase was inferred from values of adsorption limit, surface area and molecular dimensions. The sign of ??-potential of alumina powder was opposite to the original one in lower concentration of SDBS or TPC, and the values of ??-potential increased with increasing concentration. The stability of suspension of alumina powders is a function of SDBS or TPC concentration and displays an V-shaped curve with increasing concentration at lower concentration. (2) At pH 6.9 and higher concentration, monolayer on the surface of alumina was formed by adsorption of TX-100. In the monolayer the hydrophilic EO group interact with the hydroxy of surface and the hydrophilic group is in water phase. Then the stability of the suspension of alumina powders is lower than that of the suspension at lower concentration of TX-100.EI06735-7403