Formation, properties and reactivity of coprecipitates and organomineral complexes in soil environments

In soil environments the formation of simple coprecipitates formed by the interaction of two or more cations and/or anions are the rule and not the exception. In this review we describe the formation, the nature and the reactivity of coprecipitates formed by the interaction between cations (Fe, Al, Mg, Mn, Zn) with the formation of mixed oxides or layered double hydroxides (LDHs) and of coprecipitates formed by the interactions of inorganic and low molecular mass organic (LMMOLs) ligands with OH-Al and/or OH-Fe species both in the absence or presence of phyllosilicates. The presence of anions within these samples strongly affect the sorption of other ligands on the surfaces of the coprecipitates. Furthermore, the anions coprecipitated with Al and/or Fe hydrolytic products are only partially replaced even by ligands with strong affinity for the surfaces of the final samples, clearly because they are also incorporated into the network of the precipitates. We also describe the formation, surface properties and reactivity of binary complexes obtained by the interaction of hydrolytic products of Al and Fe with clay minerals and of ternary OH-Al(-Fe)-organics-phyllosilicates (organics included also large anions as tannate or proteins). The effect of the sequence of addition of the components of the final organomineral complexes influenced the physicochemical and mineralogical properties of the samples. Attention was also devoted to the stabilization of organic substances in organo-mineral coprecipitates and soils.