Sedimentation studies have been carried out to optimize the dispersion conditions of aqueous alumina nanopowder suspensions with or without dispersants (ammonium salt of polymethacrylic acid or rhamnolipids at 15%). Different dispersant dosages, solid loadings, pulp densities and pH values were examined. The iso-electric point (IEP) of the alumina nanopowder was found to be pHiep= 9.2. The experiments revealed that the polymethacrylic acid was more effective as dispersant than rhamnolipids in a wide range of pH at all solid-loading conditions tested. Optimum dispersant dosages for polymethacrylic acid and rhamnolipids to achieve maximum stability of alumina nanodispersion at iso-electric point were found to be 9.25 mg/g and 57.75 mg/g solids, respectively.
alumina nanoparticles; sedimentation; iso-electric point; bio-surfactant JBR215; darvan C.
