(The) effects of adsorbed polymer on the dispersion stability of alumina suspension

Abstract

In this study, the adsorption behavior of polymeric stabilizers on the alumina particles and effects of adsorbed polymer on the alumina suspension stability were investigated. The stability of suspension was measured using the UV absorbance and viscosity of suspension. And the IR spectroscopy studies were performed for one kind of polymers. The adsorption experiment was performed at 28.5± 0.5℃ for about 24 hours. In the adsorption of poly(acrylic acid) (PAA), this polymer shows high affinity for alumina. The adsorbed amount of PAA increases abruptly and then increases gradually. The adsorbed amount increased as the pH of suspension decreased. But the stability of PAA-adsorbed suspension increased with decreasing pH due to the electrostatic repulsion forces between the particles. The amount of adsorbed poly(ethylene oxide)(PEO) and poly(vinylpyrollidone)(PVP) is rather small compared with the adsorbed PAA. And the adsorbed amount is nearly independent of pH for these polymers. The amount of adsorbed poly(vinyl alcohol)(PVA) was more than the PEO and PVP but still less than PAA. However, the adsorption behavior of PVA showed a contrary trend with PAA. That is, the adsorbed amount of PVA increased as pH increased. The stability increased as the pH increased regardless of the adsorbed amount of PAA in the stability measurements of PAA-adsorbed suspension. This is because the adsorption of PAA makes the IEP of particle shift into near pH 3. Therefore, the alumina particle has a high |ξ| value at high pH. Bridging flocculation occurred in low concentration range, but this phenomenon was overcome as the concentration increased. In the case of PEO and PVP, low molecular weight polymers have little effect on the stability. But, when polymers with high molecular weight are added, it can be observed that the stability of suspension increases as polymer concentration increases at low pH. When PVA, which is usually used as a binder, was added to alumina suspension, rapid se...