[Preparation of nanocrystalline goethite (alpha-FeOOH) by gel-network precipitation method and spectral properties].

Iron oxyhydroxides (FeOOH), as an environmental mineral material, can adsorb and coprecipitate the contamination from the medium. The ability of removing contamination is decided by the morphology and structural characteristic and the synthesis methods of the obtained mineral. In the present, the used synthesis methods of iron oxyhydroxides (FeOOH) include ferric iron hydrolyzation and ferrous chemical oxidation. But the products of iron oxyhydroxides prepared by these two chemical methods are easily agglomerated and form bigger particles. Thus, in the present study, a novel gel-network precipitation method was developed to synthesize the nanoparticles of goethite (alpha-FeOOH) as environmental mineral material. During formation of alpha-FeOOH nanoparticles by this method, FeCl3 acted as the reaction material and glutin played a role of the reaction medium, which prevents the presence of agglomeration of precipitate particles. So the obtained alpha-FeOOH nanoparticles had smaller size, no aggregation and basic monodispersity, compared with that prepared by the coprecipitation method. At the same time, we introduced the spectrum analysis measures, and studied the effect of different concentration of glutin and FeCl3 solution on the crystallizability and morphology of products. The structure and morphology of alpha-FeOOH nanocrystallites were determined by means of XRD, FTIR and SEM. The results of the spectrum analysis showed that the particle sizes and shapes and crystallizability of the obtained alpha-FeOOH precipitate products were highly related to the network structure of gelatin. And the goethite particles with better monodispersity, prepared by the optimum concentrations of glutin (12%) and FeCl3 solution (0.6 mol x L(-1)), had a short rod-type shape approximately 110 nm in length with an average diameter of about 35 nm.