20344-49-4

reddish-brown crystalline solid

In purifying water; as absorbent in chemical processing; as pigment; as catalyst.

Iron(III) hydroxide, γ-phase is used in purifying water and as an absorbent in chemical processes. It is involved in the preparation of iron oxide-hydroxides nanoparticles, which is used as a very good adsorbent for lead removal from aquatic media. It is also used as a pigment, as a catalyst and in aquarium water treatment as a phosphate binder. Further, it is employed in the paints-lacquers-varnishes industry.

A cold solution of 810 g of Fe(NO3)3?9H2O in two liters of water is poured slowly, with vigorous stirring, into an ammonia solution prepared by dissolving 120 g of gaseous NH3 in two liters of water (cooling necessary). The hydroxide which precipitates is amorphous to x-ray analysis. It is washed by stirring at least five times with eight-liter portions of cold water, each portion being decanted as completely as possible. The residual slurry is then stirred with sufficient cone. KOH solution to give a mixture approximately 2N and allowed to stand for 3-4 hours. Finally 100℃ steam is bubbled through for two hours. The precipitate is thereby transformed completely into bright-yellow α-FeO(OH), which shows a crystalline x-ray diffraction pattern.