engleski

Forced hydrolysis of FeCl3 solutions in the presence of Cr3+ ions in acidic medium

Forced hydrolyses of FeCl3 solutions in the presence of Cr3+ ions without alkali addition were investigated at 200°C. These precipitation systems were compared to corresponding reference systems. The isolated precipitates were characterized with XRD, 57Fe Mössbauer, FT-IR, FE SEM and photocatalytic measurements. Although chromium was not detected by EDS (Energy Dispersive X-ray Spectroscopy), the analysis of samples precipitated in the presence of Cr3+ ions showed several effects which can be attributed to the presence of these ions in the starting solutions. Autoclaving of FeCl3 solutions in the presence of Cr3+ impeded the transformation kinetics -FeOOH to a-Fe2O3. Relative intensities of prominent diffraction lines 104 and 110 of a-Fe2O3 changed as a result of the presence of Cr3+ ions. Changes in the size and formation of lemon-like particles instead of cube-like a-Fe2O3 particles were also noticed. The presence of Cr3+ ions in hydrolysing FeCl3 solution influenced the photocatalytic degradation of rhodamine B. Since no specific adsorption of Cr3+ ions occurred in the acidic pH medium, it was inferred that traces of Cr3+ ions enter into the structural tunnels of b-FeOOH crystals. It can be assumed that a-Fe2O3 crystals start to grow on very fine and thin b-FeOOH crystallites which were not completely dissolved, but were previously affected by Cr3+ ions.

forced hydrolysis ; hematite

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