Magnetic double-core@shell MnO2@NiFe@DE as a multifunctional scavenger for efficient removal of tetracycline, anionic and cationic dyes.

Design and fabrication of core-shell nanomaterials with excellent properties such as multifunctionality, tunability, and stability for the removal of recalcitrant pollutants from wastewater is highly valued. In this work, magnetic MnO2@NiFe@DE nanocomposites with double-core@shell structures were obtained via a two-step hydrothermal method for efficiently removing tetracycline, anionic and cationic dyes through the synergistic effect of oxidation and adsorption. The novel nanomaterial displayed superior removal of methyl orange, methylene blue, and tetracycline in low pH solutions with 100%, 100%, and 83%, respectively. The effects of solution pH, adsorption time, and contaminant concentration on the performance of the nanocomposite were also investigated, and the pseudo-second-order kinetic model well described the data. Physical adsorption including electrostatic adsorption, anion exchange, and hydrogen bonding are the predominant mechanisms for contaminant removal. The oxidation mechanism is mainly hydroxyl radical action. Through the use of permanent magnets, the recovery process of the adsorbent and the adsorbed dyes and antibiotics is energetically and economically sustainable. This as-synthesized nanocomposite as multifunction material has a high removal rate, low cost, and easy separation, and the applicability in treating the solutions with low pH, which is promised to be an efficient organic wastewater remover in practical applications.

Microwave Absorption of α-Fe2O3@diatomite Composites.

A neoteric round sieve diatomite (De) decorated with sea-urchin-like alpha-type iron trioxide (α-Fe2O3) synthetics was prepared by the hydrothermal method and further calcination. The results of the electromagnetic (EM) parameters of α-Fe2O3-decorated De (α-Fe2O3@D) showed that the minimum reflection loss (RLmin) of α-Fe2O3@D could reach -54.2 dB at 11.52 GHz and the matched absorber thickness was 3 mm. The frequency bandwidth corresponding to the microwave RL value below -20 dB was up to 8.24 GHz (9.76-18 GHz). This indicates that α-Fe2O3@D composite can be a lightweight and stable material; because of the low density of De (1.9-2.3 g/cm3), the density of α-Fe2O3@D composite material is lower than that of α-Fe2O3 (5.18 g/cm3). We found that the combination of the magnetic loss of sea-urchin-like α-Fe2O3 and the dielectric loss of De has the most dominant role in electromagnetic wave absorption and loss. We focused on comparing the absorbing properties before and after the formation of sea-urchin-like α-Fe2O3 and explain in detail the effects of the structure and crystal shape of this novel composite on the absorbing properties.

2D-3D graphene-coated diatomite as a support toward growing ZnO for advanced photocatalytic degradation of methylene blue.

In this work, a diatomite@graphene@ZnO (ZGD) photocatalyst was synthesized by chemical vapor deposition and hydrothermal methods and used for the photocatalytic degradation of methylene blue. The characterization of the prepared nanocomposite was performed by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray diffraction (XRD), and N2 adsorption-desorption techniques. Ultraviolet-visible diffuse reflectance spectroscopy (DRS) showed that the prepared ZGD photocatalyst enhanced the absorption of visible light and induced a red-shift. Photoluminescence spectroscopy (PL) revealed that the recombination of electron and hole pairs can be effectively suppressed. Besides, the synergistic effect of diatomite and graphene avoids the agglomeration of ZnO, increases the number of surface adsorption sites, and limits the electron transport, consequently improving the photocatalytic activity of ZnO. When ZGD-3 was UV-irradiated (λ = 663 nm) for 90 minutes, the degradation effectiveness of methylene blue (MB) was 100%. After the fifth repetition, the photocatalytic degradation efficiency was always greater than 95%. Simply put, the ZGD nanocatalyst can be used as an efficient photocatalyst for dye wastewater treatment.