Hydrogen Utilization in Electroflotation of Silica at Varying Solids Concentration

This study investigated the flotation of silica particles using electrolytically-generated hydrogen gas bubbles-the oxygen was not utilised in the recovery process. Two experimental apparatuses were constructed, to determine: (1) The rate of hydrogen gas production as a function of current density, solids concentration, mechanical agitation, and presence of dissolved gases; and (2) The rate of flotation recovery as a function of solids concentration. A steel wire mesh, with wire diameter 0.4 mm, was used as the cathode, while 0.2M sodium sulphate was used as the electrolyte. It was found that approximately 98 percent of the (theoretical) hydrogen produced by the electrolysis process resulted in gas bubbles. This is a positive result, in that almost all of the electrical power is being converted to hydrogen (and oxygen) bubbles that can be used for flotation recovery. For a given current density, the rate of hydrogen gas production was largely independent of the concentration of the suspended solids. There was a very small increase in the gas production rate with the introduction of mechanical agitation. Conversely, gas production rate decreased slightly for degassed electrolyte solution, although this effect is expected to disappear once the dissolved gas(es) concentration reaches a steady state. Finally, following the modelling approach of Koh and Schwarz (2006), and using the measured hydrogen gas generation rates and bubble sizes, flotation recovery was reasonably predicted for a batch wise system.