FORMATION OF SPINDLE-SHAPE GOETHITE FINE PARTICLES BY AIR OXIDATION OF AQUEOUS SUSPENSION OF FERROUS CARBONATE IN A BUBBLE-COLUMN

Spindle-shape goethite (alpha-FeOOH) fine particles which can be used as a starting material for maghemite (gamma-Fe2O3) were produced by ai r oxidation of aqueous suspension of ferrous carbonate at an alkali mo lar ratio of 2 and temperatures of 40 to 55 degrees C using a bubble c olumn, The oxidation rate can be expressed apparently as zero-order in the concentration of total Fe(II) and first-order in the concentratio n of dissolved oxygen up to the fractional oxidation of 0.8 as in case of the formation of acicular goethite particles by a similar reaction method. The particle size based on major axis decreased with increasi ng reaction rate. At an initial loading of Fe(II), the particle size c ould be correlated well with the reaction rate alone.