Production of nanoscale maghemite powder involves precipitation from solution of ferrous and ferric sulfates in oxygen-free deionized water with sodium hydroxide, washing, acidification, quantitative oxidation and dialysis

摘要

Production of nanoscale maghemite powder comprises: (a) dissolving iron(II) and iron(III) sulfates in oxygen-free deionized water to a total iron concentration of 0.1-1.1 mole/l and Fe2+/Fe3+ molar ratio of about 1:2; (b) adding sodium hydroxide; (c) washing the precipitate; (d) adding acid to pH 0.5-3; (e) quantitative oxidation of Fe2+ to Fe3+ with air; and (f) removing salts from the precipitate. Production of nanoscale maghemite powder comprises (a) preparing a solution of iron(II) sulfate, FeSO4, and iron(III) sulfate, Fe2(SO4)3, in deionized water, freed from oxygen, so that the total iron (Fe) concentration is 0.1-1.1 mole/l and the molar ratio of Fe2+/Fe3+ ions is about 1:2; (b) adding sodium hydroxide (NaOH) to a molar ratio of NaOH to total Fe of 2.7-3; (c) washing the resultant precipitate with deionized water; (d) adjusting the pH of the precipitate to 0.5-3 by adding acid; (e) quantitative conversion of the Fe2+ present to Fe3+ by oxidation with air at 60-100 deg C; and (f) separating the precipitate, taking it up in water and freeing it from salts by dialysis.