Hyperbranched Polymer Induced Antibacterial Tree-Like Nanofibrous Membrane for High Effective Air Filtration.

The air filtration materials with high efficiency, low resistance, and extra antibacterial property are crucial for personal health protection. Herein, a tree-like polyvinylidene fluoride (PVDF) nanofibrous membrane with hierarchical structure (trunk fiber of 447 nm, branched fiber of 24.7 nm) and high filtration capacity is demonstrated. Specifically, 2-hydroxypropyl trimethyl ammonium chloride terminated hyperbranched polymer (HBP-HTC) with near-spherical three-dimensional molecular structure and adjustable terminal positive groups is synthesized as an additive for PVDF electrospinning to enhance the jet splitting and promote the formation of branched ultrafine nanofibers, achieving a coverage rate of branched nanofibers over 90% that is superior than small molecular quaternary ammonium salts. The branched nanofibers network enhances mechanical properties and filtration efficiency (99.995% for 0.26 µm sodium chloride particles) of the PVDF/HBP-HTC membrane, which demonstrates reduced pressure drop (122.4 Pa) and a quality factor up to 0.083 Pa-1 on a 40 µm-thick sample. More importantly, the numerous quaternary ammonium salt groups of HBP-HTC deliver excellent antibacterial properties to the PVDF membranes. Bacterial inhibitive rate of 99.9% against both S. aureus and E. coli is demonstrated in a membrane with 3.0 wt% HBP-HTC. This work provides a new strategy for development of high-efficiency and antibacterial protection products.

Characterizing phosphorus removal from polluted urban river water by steel slags in a vertical flow constructed wetland.

Phosphorus (P) removal in constructed wetlands (CWs) is often low unless special substrates with high sorption capacities are used. However, the use of special substrates in vertical flow (VF) CWs has not been proved to enhance P sorption. Thus, two VF wetlands were designed to evaluate the potential for enhanced P removal from polluted urban river water, one with slag as substrate and the other as a control with gravel as substrate. Findings from batch experiments showed P sorption capacities of 3.15 gP/kg and 0.81 gP/kg, respectively, for steel slag and gravel. Different organic matter fractions played different roles in P sorption, the effects of which were significant only at high concentrations. Over a 220 days' operation, the VF-slag removed 76.0% of the influent total phosphorus (TP) at 0.159 g/m(2)·d and PO4-P of 70.9% at 0.063 g/m(2)·d, whereas the VF-gravel removed 65.0% at 0.136 g/m(2)·d and 48.6% at 0.040 g/m(2)·d, respectively. Therefore, the merit of using a steel slag substrate in VF wetlands can be significant for the removal of PO4-P.

Nitrogen removal performance of bioretention cells under polyethylene (PE) microplastic stress.

The use of bioretention cells as a stormwater control measure allows stormwater runoff to be collected and filtered, effectively removing microplastics and other pollutants from stormwater. This study investigated the effect of polyethylene microplastics (PE-MPs) retention on the bioretention cell, in terms of denitrification performance and microbial community structure. Four PE-MP exposures were compared at different concentrations of 0, 250, 500 and 1000 mg/L under alternating dry and wet period conditions. Results showed that the removal efficiency reduced by 14.99%, 28.37% and 18.59% with PE-MP concentrations of 250, 500 and 1000 mg/L. The NO3--N removal efficiency increased by 36.19%, 20.19% and 35.39%. After 8 days of dry conditions, the NO3--N removal efficiencies of the bioretention cells were reduced by 36.66%, 46.86% and 31.11% compared to those after 2 days of dry conditions. Microbial sequencing results indicated that the accumulation of PE-MPs changed the microbial community structure within the bioretention cell filler material, promoting the growth of bacteria such as Actinobacteria, Bacteroidetes and Firmicutes. Furthermore, PE-MPs reduced the relative abundance of nitrifying bacteria (e.g. Nitrospira) within the bioretention cell and promoted denitrifying bacteria (e.g. Dechloromonas and Hydrogenophaga), along with numerous other genera such as Azotobacter and Nocardia.

Effects of inorganic ions with different concentrations on the nanofiltration separation performance of perfluorobutane sulfonic acid (PFBS).

Perfluorobutane sulfonic acid (PFBS) is a kind of anthropogenic recalcitrant contaminant that has posed a threat to drinking water safety and brought widespread public health concerns. Nanofiltration (NF) is an effective way to remove PFBS from drinking water, while the removal is influenced by coexisting ions. To investigate the effects and intrinsic mechanisms of coexisting ions on the rejection of PFBS, poly(piperazineamide) NF membrane was utilized in this work. Results showed that most cations and anions in the feedwater could effectively improve PFBS rejection and simultaneously reduce NF membrane permeability. In most cases, the decrease in NF membrane permeability corresponded to an increase in the valence of cations or anions. When cations (Na+, K+, Ca2+, and Mg2+) were present, the rejection of PFBS was effectively improved from 79% to more than 91.07%. Under these conditions, electrostatic exclusion was the dominant NF rejection mechanism. This was also the leading mechanism for 0.1 mmol/L Fe3+ coexisted condition. As the concentration of Fe3+ increased to 0.5-1 mmol/L, intensified hydrolyzation would accelerate the formation of the cake layers. The differences in the cake layer characteristics led to the different rejection trends of PFBS. For anions (SO42- and PO43-), both sieving effects and electrostatic exclusion were enhanced. As anionic concentration raised, the NF rejection of PFBS increased to above 90.15%. By contrast, the effect of Cl- on PFBS rejection was also affected by coexisting cations in the solution. The dominant NF rejection mechanism was electrostatic exclusion. Accordingly, it is suggested that the usage of negatively charged NF membranes could facilitate the efficient separation of PFBS under ionic coexisting conditions, thereby ensuring the safety of drinking water.

Sustainable Natural Bio-Origin Materials for Future Flexible Devices.

Flexible devices serve as important intelligent interfaces in various applications involving health monitoring, biomedical therapies, and human-machine interfacing. To address the concern of electronic waste caused by the increasing usage of electronic devices based on synthetic polymers, bio-origin materials that possess environmental benignity as well as sustainability offer new opportunities for constructing flexible electronic devices with higher safety and environmental adaptivity. Herein, the bio-source and unique molecular structures of various types of natural bio-origin materials are briefly introduced. Their properties and processing technologies are systematically summarized. Then, the recent progress of these materials for constructing emerging intelligent flexible electronic devices including energy harvesters, energy storage devices, and sensors are introduced. Furthermore, the applications of these flexible electronic devices including biomedical implants, artificial e-skin, and environmental monitoring are summarized. Finally, future challenges and prospects for developing high-performance bio-origin material-based flexible devices are discussed. This review aims to provide a comprehensive and systematic summary of the latest advances in the natural bio-origin material-based flexible devices, which is expected to offer inspirations for exploitation of green flexible electronics, bridging the gap in future human-machine-environment interactions.

Applying a dynamic membrane filtration (DMF) process for domestic wastewater preconcentration: Organics recovery and bioenergy production potential analysis.

Wastewater is increasingly recognized as a valuable resource rather than as a waste, motivating a shift in the perspective of wastewater treatment from pollution control to resource recovery. This study proposes the recovery of organic matter from domestic wastewater for the production of bioenergy through a novel process of wastewater preconcentration based on dynamic membrane filtration (DMF). The selection of a dynamic membrane (DM) supporting material, the preconcentration performance of organics, and the biomethane production potential (BMP) of the organic concentrate were investigated. The process optimization results indicated that a DM module with a supporting material of a 25 µm stainless steel mesh with a three-layer structure, assisted by internal suspended particles derived from raw wastewater, enabled the rapid DM layer formation within 1 h. The DMF process operated under a constant high flux of 30-60 L/m2 h at a trans-membrane pressure (TMP) of less than 40 kPa. During the continuous DMF operation, the average chemical oxygen demand (COD) of the influent, effluent and concentrate was 305, 113 and 2000-2500 mg/L, respectively, while the removal performance of other pollutants(such as nitrogen and phosphorus) varied, indicating differential retention effects for the various pollutants by the DM layer. Air back-flushing can effectively regenerate the DM layer and maintain long-term stable operation, but higher rates of TMP increase were observed for later filtration cycles, probably due to the accumulation of physically irremovable fouling. The BMP of the DMF concentrate was 0.20 L CH4/g COD, which was comparable to the ordinary biogas yield from municipal wastewater by anaerobic digestion. The DMF process integrated with anaerobic digestion can be a promising alternative for energy-sufficient wastewater treatment.

Vitamin E TPGS coated liposomes enhanced cellular uptake and cytotoxicity of docetaxel in brain cancer cells.

The aim of this work was to develop a drug delivery system of liposomes, which are coated with D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS), a PEGylated vitamin E, with docetaxel as a model drug for enhanced treatment of brain tumour in comparison with the nude liposomes as well as with the so-called stealth liposomes, i.e. those coated with polyethylene glycol (PEG), which have been intensive investigated in the literature. Docetaxel or coumarin-6 loaded liposomes were prepared by the solvent injection method and characterized for their particle size, polydispersity, zeta potential and drug encapsulation efficiency. C6 glioma cells were employed as an in vitro model to access cellular uptake and cytotoxicity of the drug or coumarin-6 loaded liposomes. The particle size of the PEG or TPGS coated liposomes was ranged between 126 and 191nm. High-resolution field-emission transmission electron microscopy (FETEM) confirmed the coating of TPGS on the liposomes. The IC50 value, which is the drug concentration needed to kill 50% cells in a designated time period, was found to be 37.04±1.05, 31.04±0.75, 7.70±0.22, and 5.93±0.57µg/ml for the commercial Taxotere(®), the nude, PEG coated and TPGS coated liposomes, respectively after 24h culture with C6 glioma cells. The TPGS coated liposomes showed great advantages in vitro than the PEG coated liposomes.