Flame Retardancy, Thermal and Mechanical Properties of Novel Intumescent Flame Retardant/MXene/Poly(Vinyl Alcohol) Nanocomposites

Poly(vinylphosphonic acid) (PVPA) and polyethylenepolyamine (PEPA) are used as novel intumescent flame retardants to improve the properties of MXene (2D Ti3C2Tx)/poly(vinyl alcohol) (PVA) nanocomposites. We investigated the flame-retardant properties, thermal stability, and mechanical properties of MXene/PVA nanocomposites. The results show that MXene was homogeneously dispersed in the PVA matrix containing PVPA and PEPA. PVPA and PEPA effectively improved the flame-retardant properties of MXene/PVA nanocomposites and they did not obviously change the thermal degradation of the MXene/PVA nanocomposites. Moreover, MXene improved the thermal stability of the PVA matrix. The elongation at break of MXene/PVA nanocomposites reached its maximum when the MXene mass fraction was 1.0 wt.%, regardless of whether PVPA and PEPA were present in the PVA matrix, whereas the tensile strength and Young’s modulus of MXene/PVA nanocomposites increased with the increase in MXene content in the PVA matrix

Determination of nine emerging pesticides at trace level in aqueous samples using fully automated on-line solid phase extraction coupled with liquid chromatography-mass spectrometry

MEL Visiting Fellowship Program [MELRS1116]; CAS/SAFEA International Partnership Program for Creative Research Teams [KZCX2-YW-T08]On-line solid phase extraction (SPE) coupled to liquid chromatography-mass spectrometry (LC-MS) offers an easy and fast strategy to analyze the organic contaminants in environmental samples with high sensitivity and selectivity. This paper described an in-house designed on-line SPE system and an on-line SPE-LC-MS method for the determination of pesticides at trace levels in water samples. The system was assembled from an eight-position valve, a piston pump, a six-port valve and a C18 SPE column, and significantly reduced analysis time by achieving full automation. Moreover, the use of a large enrichment volume (50mL) significantly enhanced method sensitivity. Using this on-line SPE system, an on-line SPE-LC-MS method was developed for the determination of nine pesticides at trace levels in lake water and seawater sample. Under optimized conditions, method detection limits (MDLs) were 1.00-10.0ngL(-1)

Ab Initio Study of Gas Adsorption in Metal–Organic Frameworks Modified by Lithium: The Significant Role of Li-Containing Functional Groups

Metal–organic frameworks (MOFs) are promising materials for gas adsorption. Introducing metal cations, for example, lithium cations (Li⁺), in the framework is an effective way to alter the gas adsorption features of MOFs. In this work, Li⁺ carried by different functional groups was incorporated onto a benzene linker, which is one type of the most common liker used in MOF synthesis. The interactions between the Li-modified linkers and various gas molecules were studied using MP2 method. Compared to the original benzene ring, the structures and orbitals of Li-modified linkers were significantly changed toward the direction of enhancing gas adsorption. For nonpolar gas species (CH₄, H₂, N₂, and CO₂), the induced polarizations greatly enhance the interactions between gas molecules and MOF linkers. Particularly, the expanded binding energy differences of H₂/N₂, CH₄/CO₂, and N₂/CO₂ will make them easier to get separated. For polar gas species (H₂O, H₂S, SO₂, and CO), the electrostatic interactions between gas molecules and Li⁺ play a significant role in enhancing gas adsorption. The strong affinities between polar gases and Li-modified linkers denote that the binding sites around Li⁺ can be first occupied by polar molecules such as H₂O and SO₂ during the practical adsorption process. This can result in the reduced adsorption capacities of other gases, such as CO₂

Insights into efficient removal and mechanism for ammonium from aqueous solution on tricalcium aluminate

Ammonium (NH4+) has been causing severe environmental pollution while the development of material with high capacity for ammonium removal remains a challenge. Herein, the cement-based material tricalcium aluminate (C3A) was employed to remove NH4+ from digested piggery wastewater. The conditions influencing the removal capacity were investigated, including contact time, initial ammonium concentration, temperature, dosage and initial co-existing phosphate concentration. The physicochemical structure of C3A and the resultant were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and N2 adsorption–desorption isotherms. The maximum removal capacity of NH4+ by C3A was 155.4 mg·g−1 at 298 K. The characterization revealed that the resultant was CaAl-Cl-LDH. The hydroxyl groups and Al(OH)4− from the C3A hydration played an important role in ammonium removal. High alkalinity could enhance the removal capacity. This work presents an efficient solution for ammonium removal, thus providing new insight into the mechanism of cement-based materials for water pollutant removal

Customized Electrolyte and Host Structures Enabling High-Energy-Density Anode-Free Potassium–Metal Batteries

Potassium shows great potential to replace lithium in energy storage for its high abundance and comparable energy density. However, issues including an unstable interphase, dendrite growth, and volume change restrict the development of potassium metal batteries, and so far, there is no single cure that works once and for all. Here an anode-free potassium metal battery is demonstrated by introducing a customized electrolyte and host structures that simultaneously promote efficiency, reversibility, and energy density. First, a diluted high-concentration electrolyte with fast kinetics and high stability triggers an inorganic-rich durable interphase. Meanwhile, a carbonaceous host containing narrowly distributed mesopores (MCNF) favors reduced surface area but enough inner space. Together, they achieve a high average Coulombic efficiency (CE) of 99.3% and an initial CE of 95.9% at 3 mA cm–2–3 mA h cm–2. Anode-free MCNF||Prussian blue (PB) potassium cells are delivered with 100 reversible cycles and a high energy density of 362 W h kg–1