Abstract: The kinetics of α-FeO(OH) formation in weak acidic medium was studied.The effects of the initial concentration,temperature,pH value,partial pres- sure of oxygen,air flow rate and agitating intensity on the oxidation rate of Fe(OH)_2 suspensions have been investigated.It is confirmed that the reaction order for Fe(Ⅱ) is zero at the stage of α-FeO(OH) seeds formation,and about 0.5 at the stage of the seeds growth,and in the whole process partial pres- sure of oxygen appears in first order.The activation energy is determined.The dissolution-oxidation equilibrium which exists in the process of seeds formation has been suggested,by which the zero order reaction for Fe(Ⅱ) and the plateau in the pH-t curve were explained.Physical process is the rate-determining step of the heterogeneous reaction.The study on the kinetics of α-FeO(OH) formation may provide some fundamental informa- tion for the reactor design,the engineering amplifi- cation and the optimization control in the industrial process.

Key words: kinetics, α-FeO(OH), heterogeneous reaction, growth of crystalline