Cobalt chromium-layered double hydroxide, α- and β- Co(OH)2 and amorphous Cr(OH)3: synthesis, modification and characterization

Cobalt-chromium layered double hydroxide (CoCr LDH), α- and β- Co(OH)2 and amorphous Cr(OH)3 have been synthesized under different reaction conditions. The obtained CoCr LDH was modified by stearic acid (SA) and sodium stearate (SS). The obtained samples have been characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Ultraviolet-visible- (UV-Vis), Fourier transform infrared- (FTIR) and Energy-dispersive X-ray- (EDX) spectroscopy. The influence of reaction conditions on product composition, structural and optical properties of the samples have been discussed in detail. The basal spacing of CoCr-LDH increased from 7.366 Å to 7.428 Å and 25.214Å after the intercalation by stearic acid and sodium stearate, respectively. The average particles size by SEM analyze was estimated to be approximately 100-150 nm and 30-50 nm for CoCr-LDH0.6M(90°C) and CoCr-LDH0.6M(90°C)/SS nanostructures, respectively. Mixed hydroxides like α- and β- Co(OH)2 have been obtained along with LDH at lower pH value (pH ∼ 7). The number of diffraction peaks corresponding to β-Co(OH)2 has increased with relatively decreasing of Co2+ ions in the reaction medium. At high chromium concentrations (Co2+:Cr3+ = 1:3 and 1:5), amorphous Cr(OH)3 were formed in the experiment.