Transition metal tungstates (MWO4), a well-performed electrode material for supercapacitors thanks to their intrinsically outstanding electrochemical property, has recently emerged and drawn great attention. Herein, we synthesized bimetallic Ni4-xCoxWO4 (x=0.5,...

Layered perovskites have attracted considerable attention in optoelectronic applications due to their excellent electronic properties and stability. In this work, the quasi-2D aurivillius halide perovskites are investigated using density functional theory. The single-layer aurivillius perovskite Ba2PbI6 is predicted to have a direct bandgap of 1.89 eV, which is close to that of the Ruddlesden–Popper perovskite Cs2PbI4. The electronic structures near the Fermi level are mainly governed by the [PbX6] octahedra, which leads to similar electronic properties to that of Cs2PbI4. Decomposition energies reveal that these aurivillius perovskites exhibit thermal instability. Increasing the number of [PbX6] octahedra layer can enhance the stability and reduce the bandgap. Bi- and In-based aurivillius perovskites are also calculated to evaluate the Pb-free alternatives. These calculations can serve as a theoretical support in exploring novel layered perovskites.<br>

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Dealkalization is the necessary step for the multipurpose use of red mud (RM), and acid leaching is a productive method to realize the dealkalization of RM. Most researches focus on recovering metals from the highly alkaline waste by pure acid leaching or stabilization by dealkalization. In this study, according to the strong alkalinity of RM and strong acidity of the waste acid from titanium dioxide production, the waste acid was used for the dealkalization of RM. The effects of leaching temperature, reaction time, the concentration of waste acid, liquid–solid ratio (L/S), and stirring rate on the dealkalization of RM were investigated, and the main metal ions in the dealkalization solution were analyzed. The results show that the leaching ratio of sodium can reach 92.3591% when the leaching temperature is 30 °C, the reaction time is 10 min, the concentration of waste acid is 0.6238 mol/L, the L/S is 4:1, and the stirring rate is 300 rpm. The residual alkali content in the treated RM is 0.2674%, which is a reduction to less than 1%. The phase analysis results show that the sodalite and cancrinite in RM are dissolved, decomposed, and transformed after acid leaching. Therefore, RM meets the requirements of building materials after dealkalization, which provides further development as building material products.

Layered perovskites have attracted considerable attention in optoelectronic applications due to their excellent electronic properties and stability. In this work, the quasi-2D aurivillius halide perovskites are investigated using density functional theory. The single-layer aurivillius perovskite Ba2PbI6 is predicted to have a direct bandgap of 1.89 eV, which is close to that of the Ruddlesden–Popper perovskite Cs2PbI4. The electronic structures near the Fermi level are mainly governed by the [PbX6] octahedra, which leads to similar electronic properties to that of Cs2PbI4. Decomposition energies reveal that these aurivillius perovskites exhibit thermal instability. Increasing the number of [PbX6] octahedra layer can enhance the stability and reduce the bandgap. Bi- and In-based aurivillius perovskites are also calculated to evaluate the Pb-free alternatives. These calculations can serve as a theoretical support in exploring novel layered perovskites.<br>