H. Kumazawa et F. Sezaki, FORMATION OF SPINDLE-SHAPE GOETHITE FINE PARTICLES BY AIR OXIDATION OF AQUEOUS SUSPENSION OF FERROUS CARBONATE IN A BUBBLE-COLUMN, Chemical engineering communications, 159, 1997, pp. 39-50
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.