Preparation of MgCr2O4 from waste tannery solution and effect of sulfate, chloride, and calcium on leachability of chromium

Structural, Optical, and Catalytic Properties of MgCr2O4 Spinel-Type Nanostructures Synthesized by Sol–Gel Auto-Combustion Method

“…The absorption bands recorded around 1630 cm −1 (scissors-bending of H 2 O) indicate adsorption of water during the cooling of the samples and hydrophilic nature of the obtained particles [27]. The absence of the bands associated with the Cr(VI)-O bond vibrations suggests that the spinel form of MgCr 2 O 4 _HMTA nanoparticles were already formed after the thermal treatment at 500 • C, which confirmed the reduction of Cr (VI) to Cr (III) [26]. However, for the other two samples, the Cr(VI)-O bands disappeared only after the thermal treatment at 750 • C. Figure 1a-d shows the FTIR spectra recorded at various annealing temperatures on the three samples.…”

“…Figure 1 shows the IR spectra recorded on the three series of samples synthesized by using HMTA, FS, and TA as chelating/fuel agents after thermal treatment at various temperatures: 500 • C, 700 • C, 750 • C, and 900 • C. The vibrational bands recorded at 638 cm −1 , 640 cm −1 , and 640 cm −1 on the three samples correspond to the lattice vibrations of the Cr 3+ -O 2− from the tetrahedral positions. The markers recorded at 492 cm −1 , 498 cm −1 , 496 cm −1 , 418 cm −1 , 410 cm −1 , and 415 cm −1 were attributed to the lattice vibrations of Mg 2+ , Cr 3+ -O 2− from tetrahedral and octahedral positions [26]. The vibration bands recorded at about 940-950 cm −1 were attributed to the presence of Cr(VI)-O bond vibrations [26].…”

“…The markers recorded at 492 cm −1 , 498 cm −1 , 496 cm −1 , 418 cm −1 , 410 cm −1 , and 415 cm −1 were attributed to the lattice vibrations of Mg 2+ , Cr 3+ -O 2− from tetrahedral and octahedral positions [26]. The vibration bands recorded at about 940-950 cm −1 were attributed to the presence of Cr(VI)-O bond vibrations [26]. The absorption bands recorded around 1630 cm −1 (scissors-bending of H 2 O) indicate adsorption of water during the cooling of the samples and hydrophilic nature of the obtained particles [27].…”

MgCr2O4-Modified CuO/Cu2O for High-Temperature Thermochemical Energy Storage with High Redox Activity and Sintering Resistance

“…The detailed FTIR spectra at 400–4000 cm –1 are shown in Figure S6. The peaks at 423, 499, 534, and 652 cm –1 on the MC samples could be attributed to the lattice vibrations of Mg 2+ –O 2– and Cr 3+ –O 2– at the tetrahedral and octahedral sites of the spinel structure. − With the increase in the MgCr 2 O 4 doping content, the Mg 2+ and Cr 3+ –O 2– peak intensities increased gradually. Bands were observed at 616–631 cm –1 , arising from the vibrations of Cu + –O 2– at the samples after reduction .…”

Enrichment Characteristics of Cr in Chromium Slag after Pre-Reduction and Melting/Magnetic Separation Treatment

“…Chromium slag is the waste residue generated by the industrial process of extracting chromium (Cr) from chromite ore. Due to different needs for chromite quality in the target product, the extraction processes for chromium (Cr) are also different, leading to diverse compositions and properties for chromium slag [ 1 , 2 , 3 ]. Chromium salt manufacturing is a typical extraction process, which takes chromite, sodium carbonate, and dolomite as raw materials.…”