ABSTRACT
In the present work, based on the stable phase of alpha-FeOOH and beta-FeOOH easily formed in ferric solutions of Fe (NO3)3 and FeCl3 at the appropriate pH values, respectively, the phase and crystallizability, morphologies and sizes for the particles of FeOOH minerals prepared under the conditions of heating at 40 and 70 degreeC, and magnetic stirring at 25 degreeC were identified and examined by X-ray diffraction (XRD), transmission/scanning electron microscopy (TEM/SEM) and laser scattering particle analyzer. Meanwhile the surface chemistry properties were also detected and analyzed by Fourier transform infrared spectrometer (FTIR). Investigation results showed that the prepared minerals Gth-T70 (alpha-FeOOH), Aka-T40 and Aka-T70 (beta-FeOOH) have good properties of nanocrystallity, homogeneous particles and higher specific surface areas, which induced that the above alpha, beta-FeOOH are potentially excellent adsorbent materials for removal of some contaminants in circumstances.
ABSTRACT
In the present work, the iron oxyhydroxides were prepared by hydrolysis and neutralization of ferric ion from FeCl3, Fe(NO3)3 and Fe2 (SO4)3 salts, under the conditions of various pH values and aging for about 6 days at 60 degrees C. These iron minerals were identified and characterized using X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). In addition, particle size distributions of FeOOH suspension were also determined by LS-230 model laser grainsize analyzer. Results showed that ferrihydrite formed in the ferric solutions containing Cl-, NO3- and SO4(2-) at pH values of 8 and 10. It was testified that the presence of Cl- was favorable for the formation of akaganéite. Meanwhile, the poor crystalline goethite phase was observed to be formed in FeCl3 or Fe(NO3)3 solution, but not be formed in Fe2 (SO4)3 solution at pH 12. It indicated that the presence of SO4(2-) obviously inhibited the formation of goethite. However, the goethite phase formed in Fe2 (SO4)3 solution with addition of ferrous ion, indicating that ferrous ion could promote the formation of goethite in SO4(2-) -rich solution. In addition, it was usually easy for the crystalline goethite to be transformed from the above generated ferrihydrite precipitates by aging at 60 degrees C. Furthermore, the phase of akaganéite also was obtained in the Cl(-) -rich acid (pH < or = 5) solution by aging at 60 degrees C. In conclusion, the prepared FeOOH samples show some differences in their properties such as the phase, surface properties, morphology structures and particle size.
ABSTRACT
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.
