22nd International Symposium on Analytical and Environmental Problems 334 OBTAINING OF FeCO 3 MICROPARTICLES Marius Chirita 1 , Mihaela Luminita Kiss 1 , Adrian Ieta 2 1 Department of Nanocrystal Synthesis, National Institute for Research and Development in Electrochemistry and Condensed Matter, Timisoara, Plautius Andronescu Str. No. 1, RO- 300224, Timisoara, Romania; tel. 0040256494413 2 Department of Physics, State University of New York at Oswego, Oswego, NY e-mail: chirifiz@yahoo.com Abstract Usinghydrothermal decomposition of the Fe(III)-EDTA complex in the presence of urea, we developed a new procedure for synthesizing highly crystalline FeCO 3 starting from Ferric Ammonium Sulfate and Na 4 EDTA as main precursors. Single phase FeCO 3 microcrystals with size in the range of 50µm-200µm have been obtained after high pressure-temperature treatment time between 15 hours and 26 hours at 230ºC and 250ºC. Keywords: FeCO 3 , iron carbonate, hydrothermal decomposition, Fe-EDTA complex. Introduction Due to its implications upon the geological sequestration of CO 2 [1], the thermodynamics of iron carbonate (FeCO 3 ) has been studied in many research fields, such as geology [2, 3], oceanography [4, 5] and sedimentology [6, 7]. A very interesting application in crystallography is the potential of the iron carbonate to be used as precursor to prepare Fe 3 O 4 and Fe 2 O 3 crystals [8] by partial or total oxidation of Fe 2+ ions to Fe 3+ ions, respectively. Continuing our previous studies [9], the present experimental procedure is focused on the hydrothermal synthesis of iron carbonate microparticles in a pure crystalline structure, by hydrothermal decomposition of the Fe(III)-EDTA complex in the presence of urea, starting from Fe(III)-Ferric Ammonium Sulfate (FAS) and Na 4 EDTA as main precursors. Experimental methods Synthesis The following procedure of chemical preparation was followed: An aqueous solution of 1.05x10 -1 M of FAS, an aqueous solution of 1.05x10 -1 M Na 4 EDTA, and an aqueous solution of 9.71∙10 -1 M of urea were mixed under continuous stirring. This solution was transferred into a number of Teflon-lined stainless-steel autoclaves and was heated up to 230°C and 250ºC by a rate of 1.7ºC/min. The autoclaves were removed, one by one, every two hours in the range between 15 and 26 hours. All the pH measurements indicated a value between 9.4 and 9.5 for the final solutions. The obtained microparticles were filtrated, washed with bidistilled water and dried at 60C in air. Results The crystalline structure of the FeCO 3 microparticles synthesized between 15 and 26 hours of high pressure-temperature treatment time is confirmed by XRD analysis spectra (Figures 1.a) in agreement with the respective ICSD (Inorganic Crystal Structure Database) reference code: 01- 083-1764. The high purity of FeCO3 microcrystals synthesized between 16 and 24 hours of high