Contamination of water with organic dyes is a major environmental concern as it causes serious life-threatening environmental problems. The present research was designed to evaluate the potential of three different natural inorganic clays (NICs) i.e., Pakistani bentonite clay (PB), bentonite purchased from Alfa Aesar (BT), and Turkish red mud (RM) for malachite green (MG) dye removal from an aqueous solution. Various analytical techniques, namely X-ray fluorescence spectrometry (XRF), X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), Brunauer–Emmett–Teller surface area measurement (BET), and thermogravimetric analysis (TGA), were used to investigate the physicochemical properties of the NICs samples. The effect of adsorption operational parameters such as contact time, aqueous phase pH, dye concentration, and amount of NICs on the adsorption behavior of MG onto NICs samples were investigated under the batch adsorption system. The equilibrium and kinetic inspection reflected the best description of MG adsorption behavior by the Langmuir isotherm model and pseudo-first-order kinetic model, respectively. The results indicated that the adsorption was favorable at higher pH. The maximum adsorption capacities calculated by Langmuir isotherm for PB, BT, and RM were found to be 243.90 mg/g, 188.68 mg/g, and 172.41 mg/g, respectively. It can be concluded that natural inorganic clays with a higher surface area can be used as an effective adsorbent material to remove the MG dye from an aqueous solution.

First-principles calculations based on density-functional theory were performed to investigate heterostructures of group-III monochalcogenides (GaS, GaSe, InS, and InSe) and the effects of incommensurability on their electronic structures. We considered two heterostructures: GaS/GaSe, which has a lattice mismatch of 4.7%, and GaSe/InS, with a smaller mismatch of 2.1%. We computed the cost of having commensurate structures, and we also examined the potential energy landscape of both heterostructures in order to simulate the realistic situation of incommensurate systems. We found that a commensurate heterostructure may be realized in GaSe/InS as the interaction energy of this system with the monolayers assuming the average lattice constant is smaller than the interaction energy of an incommensurate system in which each layer keeps its own lattice constant. For GaS/GaSe, on the other hand, we found that the incommensurate heterostructure is energetically more favorable than the commensurate one, even when taking into account the energetic cost due to the lack of proper registry between the layers. Since the commensurate condition requires that one (or both) layer(s) is (are) strained, we systematically investigated the effect of strain on the band gaps and band-edge positions of the monolayer systems. We found that, in all monolayers, the conduction-band minimum is more than two times more sensitive to applied strain than the valence-band maximum; this was observed to strongly affect the band alignment of GaS/GaSe, as it can change from type-I to type-II with a small variation in the lattice constant of GaS. The GaSe/InS heterostructure was found to have a type-II alignment, which is robust with respect to strain in the range of $-2\%$ to $+2\%$.

The need for new and better semiconductor materials for use in renewable energy devices motivates us to study KRuF₃ and KOsF₃ fluoride materials. In the present work, we computationally studied these materials and elaborate their varied properties comprehensively with the assistance of density functional theory-based techniques. To find the structural stability of these under-consideration materials, we employed the Birch-Murnaghan fit, while their electronic characteristics were determined with the usage of modified potential of Becke-Johnson. During the study, it became evident from the band-structure results of the KRuF₃ and KOsF₃ materials that both present an indirect semiconductor nature having the band gap values of 2.1 and 1.7 eV, respectively. For both the studied materials, the three essential elastic constants were determined first, which were further used to evaluate all the mechanical parameters of the studied materials. From the calculated values of Pugh's ratio and Poisson's ratio for the KRuF₃ and KOsF₃ materials, both were verified to procure the nature of ductility. During the study, we concluded from the results of absorption coefficient and optical conduction in the UV energy range that both the studied materials proved their ability for utilization in the numerous future optoelectronic devices.