Microwave Absorption Properties of Magnetite Particles Extracted from Nickel Slag.

The utilization of nickel slag has attracted much attention due to its high-content of valuable elements. As a part of these efforts, this work focuses on whether magnetite crystals, obtained from nickel slag via molten oxidation, magnetic separation, and ball-milling can be used as a microwave absorber. The composition, morphology, microstructure, magnetic properties, and microwave absorption performance were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM), and vector network analysis (VNA). The results reveal that the magnetite crystals exhibit excellent microwave absorption properties because of the synergistic action between dielectric loss and magnetic loss. The minimum reflection loss (RL) of the particles obtained after 6 h ball-milling reaches -34.0 dB at 16.72 GHz with thickness of 5 mm. The effective frequency bandwidth (RL ≤ -10 dB) is 4.8-5.4 GHz and 15.9-17.6 GHz. Interfacial polarization of the particles could play a crucial role in improving absorbing properties because several components contained in the particles can dissipate electromagnetic wave effectively. The current study could show great potential in the preparation of magnetite crystals and utilization of nickel slag.

Ultrathin 2D Ti3C2Tx MXene membrane for effective separation of oil-in-water emulsions in acidic, alkaline, and salty environment.

Layered Ti3C2Tx MXene is a two-dimensional (2D) metal carbide based material with high adsorption capacity and hydrophilicity, which is beneficial for oil/water separation. Herein, the Ti3C2Tx (T represents O, OH, and/or F) MXene membrane was obtained by depositing Ti3C2Tx MXene 2D nanosheets carbides onto porous polyvinylidene fluoride (PVDF) membranes by vacuum filtration. The as-prepared Ti3C2Tx MXene membrane exhibits excellent underwater superoleophobicity with oil contact angles (OCAs) close to 158° and oil sliding angles (OSAs) lower than 7°. In addition, the layered Ti3C2Tx MXene membrane can separate a series of stable emulsions even emulsified crude oil-in-water mixtures, and displays excellent separation efficiency over 99.4% and high permeation flux of 887 L m-2 h-1 bar-1. Furthermore, the Ti3C2Tx membrane displays superior durability to the corrosive liquids such as acidic, alkaline and salty, and can also effectively remove oil droplets from water in corrosive environment. This work provides a promising approach to prepare the ultrathin and layered 2D MXene Ti3C2Tx membrane for separation of stable emulsified oil-in-water mixtures separation.

Robust superhydrophobic attapulgite meshes for effective separation of water-in-oil emulsions.

Special-wetting materials have been broadly studied in various oil/water separation processes. However, there are granted numerous challenges in extremely durable materials with mechanical robustness, especially considering the great requirements in purifying emulsified oil/water mixtures. Herein, we present a facile route to prepare robust superhydrophobic surface by spraying Octadecyltrimethoxys modified attapulgite suspension combined with inorganic adhesive on mesh. The as-prepared meshes show eminent superhydrophobicity and acquire a gravity driven water-in-oil emulsion separation with efficiency above 99.7% and flux above 106.7 L m-2h-1 even after multiple cycles. In addition, the meshes exhibit robust and stable superhydrophobicity with water contact angles above 150° after 200 sandpaper abrasion (transverse shear force) and harsh sand impact (longitudinal impact force) cycles, and meanwhile, still maintain outstanding emulsion separation performance during tests. This study is meaningful for the development of fabricating low-energy separating materials with high efficiency and mechanical robustness for harsh chemical engineering.

Underliquid Superlyophobic Copper-Coated Meshes for the Separation of Immiscible Organic Liquid Mixtures.

Superwettable materials have been studied extensively and successfully applied in various forms liquid separation. However, because of low surface tension differences, organic liquids (OLs) exhibit approximate wettability on most of the material surfaces, and the separation of OL mixtures remains a challenge. The current separation method for OL mixtures is mainly dependent on covalent modification to precisely control the surface energy of the membranes, which is extremely complicated. Herein, we demonstrate a novel concept of underliquid superlyophobicity for the separation of immiscible OLs mixtures, which only depend on a relatively stable liquid-repellent interface. Furthermore, the minimum system's free-energy principle was used to explain this wetting behavior. Different from the previous reports, the method of separation of OL mixtures does not involve various low-surface-energy materials, thus it is facile and eco-friendly. Our research provides a general strategy for the efficient separation of immiscible OLs mixtures and is expected to promote the development of superwettable materials for multiphase liquid separation.

Waste cigarette filter as nanofibrous membranes for on-demand immiscible oil/water mixtures and emulsions separation.

The rapid industrial growth and the frequent oil spill accidents have led to the large production of oily wastewater. Thus, it is urging to develop a low-cost and eco-friendly material to purify the oily wastewater. In our work, the waste cigarette filter as the raw material was used to prepare cigarette filter coated meshes (CFCMs) by a facile electrospinning approach. The as-prepared CFCMs prewetted with water or oil achieved the special wetting performance of underwater superoleophobicity or underoil superhydrophobicity without any further chemical modification. Hence, the cigarette filter coated meshes with larger or smaller pore size can be applied to on-demand immiscible oil/water mixtures (light or heavy oil/water mixtures) and oil/water emulsions separation (water-in-oil or oil-in-water emulsions), respectively. Moreover, the CFCMs still exhibited high separation efficiency larger than 99.9% for immiscible oil/water mixtures and emulsions after many cyclic testing. The work provides an application in oil/water separation for waste cigarette filters and contributes to reduce the pollution for environment from the waste cigarette filters.

On the origin of the "giant" electroclinic effect in a "de Vries"-type ferroelectric liquid crystal material for chirality sensing applications.

W415 is a chiral smectic compound with a remarkably weak temperature dependence of its giant electroclinic effect in the liquid crystalline smectic A* phase. Furthermore it possesses a high spontaneous polarization in the smectic C* phase. The origin of this striking electroclinic effect is the co-occurrence of a de Vries-type ordering with a weak first-order tilting transition (see the synchroton X-ray scattering profiles).