Ferric oxy hydroxides

Hsi, C.K., Langmuir, D., 1985. Adsorption of uranyl onto ferric oxy-hydroxides application to the surface complexation site-binding model. Geochim. Cosmochim. Acta 49, 1931-1941. 

As pH rises, the metal content of drainage water tends to decrease. Some metals precipitate directly from solution to form oxide, hydroxide, and oxy-hydroxide phases. Iron and aluminum are notable is this regard. They initially form colloidal and suspended phases known as hydrous ferric oxide (hfo, FeOOH n O) and hydrous aluminum oxide (HAO, AlOOH nH.2O), both of which are highly soluble under acidic conditions but nearly insoluble at near-neutral pH. 

Hydrolysis reactions and the precipitation of iron oxyhydroxide phases also play a key role in the corrosion of metallic iron. Corrosion reactions can involve both ferrous and ferric iron hydrolysis species and the formation of surface coatings of either iron(ll) or iron(lll) (oxy)hydroxide phases. The understanding of corrosion and its effects has received a considerable amount of attention. 

Ferric hydroxide is readily soluble in mineral acids yielding the corresponding ferric salt, and in ferric chloride solution yielding oxy compounds which are acidic in their behaviour, decomposing carbonates, and can therefore hardly be termed basic chlorides.3 It dissolves in aqueous oxalic acid to an extent directly proportional to the concentration of the acid, no definite basic oxalate being formed at 25° C. from solution.4 It does not combine with carbon dioxide when freshly precipitated and suspended in water.5... 

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