engleski

Precipitation of hematite from dense beta-FeOOH suspensions with ammonium amidosulfonate adding

Precipitation of hematite (alpha-Fe2O3) from aqueous solutions has been the subject of many investigations. The hydrolysis of aqueous Fe(III)-salt solutions, microemulsion hydrolysis, sol-gel or crystallization from ferrihydrite were used in the synthesis of alpha-Fe2O3. Some precipitation methods are limited due to small yield and they can be only of academic interest. On the other hand, the crystallization from concentrated aqueous Fe(III)-salts solutions yields alpha-Fe2O3 in high quantities. However, in the later case it is more difficult to control the size and shape of alpha-Fe2O3 particles. In the present work we have investigated precipitation of alpha-Fe2O3 particles from dense beta-FeOOH suspensions in the presence of amidosulfonate anion in hydrothermal conditions at 160 oC. The samples were characterized with 57Fe Mössbauer, FT-IR, XRD, FE-SEM and EDS. The kinetics of crystallization of alpha-Fe2O3, geometrical shape and size of alpha-Fe2O3 particles were depending on the concentration of ammonium amidosulfonate added at the start of the precipitation process. Aggregation effect plays an important role in the formation of alpha-Fe2O3 particles. It was also concluded that geometrical shape and size of primary as well as secondary particles were influenced by the preferential adsorption of sulfonate groups at acidic conditions in dense suspension.

alpha-Fe2O3; beta-FeOOH; 57Fe Mossbauer; FT-IR; XRD; FE SEM

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