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Spinel oxides are a type of material that can be used in a wide range of applications, such as photocatalysis, hydrogen production and environmental protection. In this respect, calcium aluminate (CaAl2O4) and chromate (CaCr2O4) spinels were synthesized in this study by the coprecipitation method using potash solution as a precipitant. CaAl2O4 and CaCr2O4 spinels were annealed at 900 and 1100°C, respectively, for different periods. The obtained spinels were first characterized by thermal analysis, and the phase composition of the oxides was analysed using X-ray diffraction. Hydroxyl groups and absorbed water in the obtained precipitates disappeared after calcination and were observed via Fourier transform infrared spectroscopy. BET and SEM/EDS analyses were also used to determine the total surface area of the powder particles, the size of the grains and the morphology of the powders of the synthesized nanoparticles, respectively. The structural and morphological analyses revealed the formation of single-phase CaAl2O4 and dual-phase CaCr2O4, with specific surfaces for each spinel of 44.2165 and 5.7190 m2 g−1, respectively. Moreover, DFT calculations were performed on the materials, and the direct bandgaps of these spinels were found to be 4.365 eV for CaAl2O4 and 2.256 eV for CaCr2O4. The results indicated that different compositions led to different optical bandgaps. Finally, the results indicate that due to the suitable characteristics and properties of the produced spinel oxides, they are among the promising materials that may be employed as semiconductors for various applications. [ABSTRACT FROM AUTHOR]

An electro-electrodialysis process (EED) is used to generate HCl and NaOH from trade NaCl. The key phenomenon limiting the current efficiency of this process is proton leakage through the anion selective membrane. Two new low proton leakage membranes: the ARA and ACM were used. NaOH and HCl solutions with purity higher than 99.9% are obtained. The experimental values of the fluxes for HCl and NaOH are compared with values calculated from integration of the Nernst–Planck electrodiffusion equations. This calculation requires several experimentally determined parameters: ionic diffusion coefficients, membrane conductance and amount of sorbed electrolyte. Algerian rock salt from El Outaya is used to compare electro-electrodialysis and electrodialysis using bipolar membranes. [ABSTRACT FROM AUTHOR]