In this study the hydrogen bubble electroflotation of 3-15 mu m diameter silica particles was investigated. Experiments were conducted to determine the influence of current density, solids concentration, mechanical agitation and the presence of dissolved gases on the rate of hydrogen gas production. It was found that approximately 98% of the theoretical hydrogen production resulted in gas bubbles. There was a very small increase in the hydrogen bubble production rate with the introduction of mechanical agitation, while the opposite trend was observed for the degassed electrolyte solution. Hydrogen gas production was found to be largely independent of the concentration of the suspended solids. Batchwise flotation experiments were also undertaken to determine the influence of particle diameter and solids concentration on flotation recovery. The experimental results were inputted into a recovery model, based largely on the work of Koh and Schwarz [1], that was applied to gain insight into the factors that influence the fractional coverage of the bubble surface by the particles. From the analysis it was found that, for this study at least, flotation recovery was controlled by either the bubble-particle aggregate rise velocity being greater than zero or the bubble-particle aggregate projected area being less than that of just the bubble. (C) 2011 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.