Особенности синтеза ферратов(VI) из сульфата железа(II)
Ключові слова:
ferrate(VI) synthesis, ferrous sulfate, hypochlorite method, potassium and sodium ferratesАнотація
High cost of ferrates(VI) – new promising oxidants – stimulates enhancement of Fe(VI) derivatives obtaining technology based on usage of available cheap raw materials. In present paper peculiarities of ferrates(VI) of alkaline and alkaline-earth metals synthesis based on hypochlorite method have been investigated:
FeSO4(s) + 2ClO–+ 4OH–® FeO42–+ 2Cl– + SO42–+ 2Н2О.
This reaction should be quantitative based on thermodynamic analysis. Nevertheless it was found during carried out experiments that yield of Fe(VI) compounds less than 100%. Influence of operating parameters (hydroxide and hypochlorite concentrations, temperature, molar ratio [ClO−]/[Fe(II)]) on yield of product has been investigated. It was found out than generation of ferrate decreases with increase of temperature so it is advisable to carry out synthesis in low temperature field (0-5 0C). It is necessary at least twice greater excess of oxidant comparing to stoichiometry to achieve the completeness of the conversion raw material to wanted product. It was found that degree of conversion ferrous salts to ferrates during hypochlorite oxidation increases in row ferrous sulfate - ferrous chloride - ferrous nitrate. It was stated by experiment that magnetite formation occurs (no more 7% of total Fe) during ferrate synthesis from FeSO4·7H2O by hypochlorite way. It was demonstrated solid ferrates (K2FeО4, CaFeO4 и BaFeO4) have been wasted by sulfate anions during synthesis, lowest (<4%) content of it ones has been fix in potassium ferrate, highest (~18%) – in barium salt. New technological decisions for synthesis efficiency improvements and decreasing impurities content (mainly sulfates) have been proposedПосилання
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