Precipitation of Ferrous Oxalate from Ferrous Ammonium Sulfate in Oxalic Acid Solution

A kinetic study was conducted experimentally for the precipitation of ferrous oxalate. The ferrous oxalate, in the form of dihydrate (FeC2O4·2H2O), was produced by the acidic dissolution of ferrous ammonium sulfate (Fe(NH4)2(SO4)2) in an aqueous solution of oxalic acid, and then precipitated by nucleation and particle growth from supersaturated solution. The effect of the concentration of ferrous ammonium sulfate and oxalic acid as raw materials was investigated on the kinetics of the ferrous oxalate precipitation. Temperature was kept constant at 25 °C. The surface morphology, atomic compositions, and crystal phase were characterized for the ferrous oxalate precipitate collected. As the initial concentration of ferrous ammonium sulfate increased, the initial precipitation of ferrous oxalate occurred faster. The concentration of oxalic acid did not significantly affect the rate of precipitation of ferrous oxalate. The experimental behavior of ferrous oxalate precipitation was modeled with first-order models of reaction kinetics.