%0 Journal Article
%T Formation and Morphology Evolution from Ferrihydrite to Hematite in the Presence of Tartaric Acid
%J -
%D 2019
%R https://doi.org/10.1021/acsearthspacechem.8b00186
%X Hematite, with ferrihydrite as the common precursor, is the most stable iron oxide in soils and sediments and has many applications in environmental systems. As a common reducing agent in soils, tartaric acid (L-TA) can reduce Fe3+ to Fe2+ and template the formation of hematite from ferrihydrite. Here, the formation of hematite in the presence of L-TA was investigated under different L-TA concentrations, initial suspension pH, and aging time. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high- resolution transmission electron microscopy (HRTEM). Both the transformation process and the particle morphology of hematite were affected by the initial suspension pHi at which the L-TA was added to the suspension. Optimal pHi values at a L-TA/Fe(III) molar ratio of 1.0% and an aging time of 10 h at 100 ˇăC were pHi 7 and pHi 11. At pHi 7, the optimal L-TA/Fe(III) molar ratio for the transformation was 1.0% and aging at 100 ˇăC was completed after about 20 h. The transformation occurred through a dissolution¨Ccrystallization process. Crystalline corn-like particles (84 m2/g) were obtained through an oriented attachment mechanism. At a L-TA/Fe(III) molar ratio of 3.0% the ferrihydrite surface was saturated with L-TA and the transformation was inhibited. At pHi 11, L-TA/Fe(III) of 1.0% and aging for 10 h (100 ˇăC), subrounded crystalline particles (24 m2/g) were obtained by solid-phase transformation, oriented attachment, and Ostwald ripening mechanism
%U https://pubs.acs.org/doi/10.1021/acsearthspacechem.8b00186