| Because of the widely application of nanosized iron oxides in many aspects,such ascatalysis,antisepsis,pigments and magnetic recording materials,the preparation of thenanosized iron oxides attracts much attention．Fe2O3 and FeOOH are also component ofcorrosion products of steel．The FeOOH phase and morphology have been shown to beinfluenced by many factors such as the concentration of iron salt,the type of anion,pH,temperature,the oxidizing agent and the presence of organic compounds．A variety oftransformations between different species of iron oxides can take place underγ-ray irradiation．Andthe Photo-Fenton reaction system has been successfully applied to the decomposition oforganic pollutants under light irradiation．However,to the best of our knowledge,theinfluence of visible light on the synthesis of iron oxyhydroxides has not been reported．This article described the preparation of nanosized iron oxides,using FeSO4 as the rawmaterial by air oxidation of Fe(OH)2 under irradiation by visible light in the presence of traceEDTA,and investigated the oxidation mechanisms of Fe(OH)2 suspension at differentconditions．Subsequently,we give primary discuss on solid phase transformation of products．This research can provide some data for the preparation of iron oxides using FeSO4 as the rawmaterial,and it is also benefit for the investigate of corrosion mechanisms．This syntheticmethod which is low cost and zero pollution,will have a bright and widely applicationprospect．The main results of the thesis are as follows:1．Variety influential factors effect on the oxidation of Fe(OH)2 suspension by air:Iron oxides were prepared,using FeSO4 as the raw material by air oxidation of Fe(OH)2under irradiation by visible light in the presence of trace EDTA．Many factors were discussedsuch as the initial pH,temperature,air flow rate,light and EDTA．The result revealed that theproducts wereγ-FeOOH,α-FeOOH and Fe3O4 respectively with increasing the pH value (pH=8．0～12．0)．When pH>12．0,the main product was goethite．Meanwhile,it was in favor oftheα-FeOOH and Fe3O4 with the increasing of temperature．And it was bencfited to formlepidocrocite with the increasing of air flow rate．The oxidation rate could be significantlyaccelerated by visible light in the presence of EDTA．Moreover,the rapid reaction rate isfavorable for the formation ofγ-FeOOH．The productsα-FeOOH andγ-FeOOH were bothamorphous under irradiation by visible light in the presence of trace EDTA．2．Research on the oxidation mechanisms of light-induced in the presence of EDTAThe initial pH has an important effect on the products．According to the experimentresults,Fe(Ⅱ)EDTA was the inducible precursor for the formation ofγ-FeOOH under lightirradiation．Green rust can be transformed rapidly to amorphousγ-FeOOH with the increasingof EDTA．The Fe(Ⅱ)-EDTA complex could bring O2·-,HO2·and H2O2 under lightirradiation,which further oxidizes Fe(Ⅱ)to Fe(Ⅲ)．Thus,the oxidation of Fe(Ⅱ)to Fe(Ⅲ)was accelerated by both visible light and EDTA．So the rate of the oxidation reaction iscertainly accelerated．Because the reaction rate was very fast,the crystal seeds ofγ-FeOOHwere formed too rapidly and too many to grow in a short time．Consequently,amorphousγ-FeOOH was obtained．3．Preparation of Fe3O4 by liquid phase methodsIn the light irradiation system,Fe3O4 was successfully synthesized by air oxidation．Theinfluences of pH value and reaction temperature were studied,and the effect of light intensityand illuminating on the particle size were discussed．The results demonstrate that the particlediameter of Fe3O4 decreases,with increasing pH．In this paper,the pH should be 9-11．Theincrease in temperature corresponds to the increase of the size of Fe3O4,and the pure phaseFe3O4 can be obtained at 20℃．With the increasing of light intensity,the particle diameter ofFe3O4 is accordingly decreased．And different particle size of Fe3O4 has different magneticproperties．4．solid transformationEffect of various factors such as the calcination temperature,calcination time,crystallinityof precursor and phosphate,etc．on the solid transformation ofα-FeOOH,γ-FeOOH andFe3O4 were studied in detail．Compared with the good crystallinity,the phase transformation' temperature of amorphousα-FeOOH,γ-FeOOH were very low,about 200℃．When thecalcination temperature was 300℃,the particle size ofα-Fe2O3 was about 10nm．Thephosphate could depress the growing of crystal．And during the calcinations process of Fe3O4,phosphate inhibited the phase transformation ofγ-Fe2O3 and adjusted the morphology ofproductα-Fe2O3．...
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