In this work, graphene oxide (GO) and its reduced graphene oxide-zinc oxide nanocomposite (rGO-ZnO) was used for the removal of Cr (VI) from aqueous medium. By employing a variety of characterization techniques, morphological and structural properties of the adsorbents were determined. The adsorption study was done by varying concentration, temperature, pH, time, and amount of adsorbent. The results obtained confirmed that rGO-ZnO is a more economical and promising adsorbent for removing Cr (VI) as compared to GO. Kinetic study was also performed, which suggested that sorption of Cr (VI) follows the pseudo-first-order model. For equilibrium study, non-linear Langmuir was found a better fitted model than its linearized form. The maximum adsorption capacity calculated for GO and rGO-ZnO nanocomposite were 19.49 mg/g and 25.45 mg/g, respectively. Endothermic and spontaneous nature of adsorption was detected with positive values of ΔS (change in entropy), which reflects the structural changes happening at the liquid/solid interface.

The search for new multiferroic materials is on the rise due to their potential applications in an advanced generation of highly efficient multifunctional devices. Here we report a series of PbTi_1−xFe_xO₃ (0 ≤ x ≤ 0.5) samples prepared by a solid-state reaction method. Structural analysis suggests that doping of Fe introduces oxygen vacancies along the c-axis (aliovalent substitution; Fe³⁺ → Ti⁴⁺), local distortions and microstrains in the PbTiO₃ lattice which triggered the partial structural transformation from tetragonal to cubic. This has been confirmed using structural analysis tools such as X-ray diffraction, Fourier Transform Infrared Spectroscopy, Raman spectroscopy, and Mössbauer spectroscopy. The presence of oxygen vacancies was further confirmed by refining the site occupancies through Rietveld refinement. Mössbauer measurements confirmed that Fe ions exist in the 3+ state and change in coordination of some Fe³⁺ ions from octahedral to tetrahedral points towards the oxygen deficiency in the system. Raman studies confirm the presence of all ordinary and quasi phonon modes in Fe doped PbTiO₃ samples. The overlapping and weakening of modes are related to the structural changes/transformation. The modes’ shifting to lower wavenumbers is ascribed to the increase in the average atomic mass at Ti-sites. The induced ferromagnetism in the system increases with an increase in the Fe content and can be explained on the basis of the F-center exchange mechanism. Moreover, we found an anomalous temperature-dependent trend in the magnetic coercivity (decrease in coercivity as the temperature is decreased) which can be explained in terms of a low-temperature decrease in an effective magnetic anisotropy when the effects of magneto-electric coupling are included. The existence of well-developed ferroelectric and ferromagnetic hysteresis loops confirmed the multiferroic nature of the system. The increase in the value of the dielectric constant at 1 MHz with an increase in the Fe content is attributed to the increase in resistivity of the system due to the formation of immobile defect dipole complexes.

A significant waste, including dyes in water, is generated during textile industrial processes, which causes environmental challenges. Herein, various nanocomposites (NC) of nickel oxide (NiO) and zinc oxide (ZnO) were prepared by solvothermal assisted green method where ethanolic extract of spinach leaves were used as a green source. The ultraviolet-visible (UV–vis) spectroscopy revealed that the band gap energies and absorption maxima of NiO/ZnO were 2.25 eV and 371 nm for 1:1 NC, 2.07 eV and 380 nm for 5:1 NC, and 2.02 eV and 385 nm for 1:5 NC. Ultraviolet-visible (UV–vis) spectroscopy, x-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were employed to investigate the optical and structural characteristics of the NCs. The XRD patterns of NiO/ZnO NCs (i.e., 1:1, 5:1, 1:5) displayed crystallite sizes of 44.6, 52.17, and 42.5 nm, respectively. Associations of different functional groups with the surfaces of NC was confirmed by FTIR. Batch method was used to conduct the NCs-mediated adsorption of methylene blue (MB), methyl red (MR), and methyl orange (MO). Furthermore, several factors, including dye concentration, contact time, and temperature that affected the sorption, are reported. Pseudo-first order and pseudo-second order kinetic models were utilized to examine the adsorption kinetics. For all the dyes studied, pseudo-first order is the one which fitted best to the kinetic data, based on regression coefficient (R²). Indeed, experimental data were found to follow the Langmuir model. The maximum uptake capacity (q_m) of MB adsorbed on NiO/ZnO NC (1:1) was 370 mg g⁻¹ which is higher compared to that of values reported in the literature. These findings report a dual method (i.e., solvothermal-green chemistry) contribute to the development of efficient and cost-effective methods for wastewater treatment and environmental remediation.