The ability of constructed wetlands with different plants in nitrate removal were investigated. The factors promoting the rates of denitrification including organic carbon, nitrate load, plants in ...wetlands, pH and water temperature in field were systematically investigated. The results showed that the additional carbon source （glucose） can remarkably improve the nitrate removal ability of the constructed wetland. It demonstrated that the nitrate removal rate can increase from 20% to more than 50% in summer and from 10% to 30% in winter, when the nitrate concentration was 30-40 rag/L, the retention time was 24 h and 25 mg/L dissolved organic carbon （DOC） was ploughed into the constructed wetland. However, the nitrite in the constructed wetland accumulated a little with the supply of the additional carbon source in summer and winter, and it increased from 0.15 to 2 mg/L in the effluent. It was also found that the abilities of plant in adjusting pH and temperature can result in an increase of denitrification in wetlands. The seasonal change may also impact the denitrification.
Trihalomethanes (THMs) and haloacetonitriles (HANs), most common disinfection by-products in drinking water, pose adverse environmental impacts and potential risks to human health. There is a ...pressing need to develop innovative, economically feasible, and environmentally benign processes to control these persistent contaminants. In this paper, visible-light-responsive graphitic carbon nitride (g-C3N4) samples were synthesized to degrade the THMs and HANs and the photocatalytic degradation mechanism was explored. The results indicated that a carbon-doped g-C3N4 with an optimum dopant content (MCB0.07) displayed the best photocatalytic activity for the total trihalomethanes (TTHM) and total haloacetonitriles (THAN), with the reaction rate constant of 11.6 and 10.4 (10−3 min−1), respectively. MCB0.07 demonstrated a high THMs and HANs removal efficiency under visible light irradiation and could be reused. According to scavenger tests of the selected reactive species and X-ray photoelectron spectroscopy, holes play a dominant role for both THMs and HANs degradation on the MCB0.07. The degradation of HANs by holes proceeded mainly through breakage of the CC bond in the CCN group. The THMs degradation was achieved through hydrogen abstraction or/and dehalogenation. The brominated-THMs/HANs were more photosensitive than their chlorinated analogous and were less stable than bromo-chloro-THMs/HANs. This study sheds light on the mechanism of the photocatalytic degradation of THMs and HANs under visible light irradiation by carbon-doped g-C3N4. Furthermore, it could provide insights for engineering applications and contaminant control in drinking water purification.
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•A carbon-doped g-C3N4 displayed high photocatalytic activity for TTHM and THAN.•Holes played dominant roles for THMs and HANs degradation.•THMs degradation was achieved through hydrogen abstraction or/and dehalogenation.•The photocatalysis removed HANs mainly through CC bond breakage.
Airborne pathogens constitute a growing threat to global public health. Wastewater treatment plants (WWTPs) are important sources of airborne bacteria, which pose great health risks to the employee ...and nearby residents. In this study, the distribution, transmission and health risk of the airborne culturable and inhalable bacteria carried by PM2.5 in a semiunderground WWTP were evaluated. The concentrations of culturable bacteria in the air were 21.2–1431.1 CFU/m3, with the main contributions of primary and biological treatments. The relative abundances of culturable and total inhalable bacterial taxa were positively correlated (p < 0.05). However, certain bacteria, including Bacillus, Acinetobacter and Enterococcus, exhibited high reproductive capacity despite their low concentration in the air, suggesting that they can survive and regrow in suitable environments. Transmission modeling revealed that the concentrations of airborne bacteria exponentially decreased with distance from 18.67 to 24.12 copies /m3 at the source to 0.06–0.14 copies /m3 at 1000 m downwind. The risks of 8-h exposure in this WWTP except the outlet exceeded the reference value recommended by WHO, which were primarily dependent on P. aeruginosa, Salmonella, and E. coli. Management practices should consider improved controls for bioaerosols in order to reduce the risk of disease transmission.
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•Airborne bacteria exhibited site- and seasonal-relative variations in this WWTP.•The relative abundances of culturable and inhalable bacteria were positively correlated.•Certain airborne bacteria exhibited high reproductive capacity despite low concentrations.•The risk of airborne pathogens in this WWTP was higher than the limits of WHO.
Antiferromagnetic spintronics actively introduces new principles of magnetic memory, in which the most fundamental spin‐dependent phenomena, i.e., anisotropic magnetoresistance effects, are governed ...by an antiferromagnet instead of a ferromagnet. A general scenario of the antiferromagnetic anisotropic magnetoresistance effects mainly stems from the magnetocrystalline anisotropy related to spin–orbit coupling. Here magnetic field driven contour rotation of the fourfold anisotropic magnetoresistance in bare antiferromagnetic Sr2IrO4/SrTiO3 (001) thin films hosting a strong spin–orbit coupling induced Jeff = 1/2 Mott state is demonstrated. Concurrently, an intriguing minimal in the magnetoresistance emerges. Through first principles calculations, the bandgap engineering due to rotation of the Ir isospins is revealed to be responsible for these emergent phenomena, different from the traditional scenario where relatively more conductive state is obtained usually when magnetic field is applied along the magnetic easy axis. These findings demonstrate a new efficient route, i.e., via the novel Jeff = 1/2 state, to realize controllable anisotropic magnetoresistance in antiferromagnetic materials.
Controllable anisotropic magnetoresistance and concurrent magnetoresistance minimal are evidenced in Sr2IrO4 thin film, which is antiferromagnetic with strong spin–orbit coupling. First‐principles calculations reveal that bandgap engineering due to rotation of the Ir's isospins in the films is responsible for these two emergent phenomena.
The exploration of new rare-earth (RE)-based triangular-lattice materials plays a significant role in motivating the discovery of exotic magnetic states. Herein, we report a family of hexagonal ...perovskite compounds Ba
RE
Ti
O
(RE = Nd, Sm, Gd, Dy-Yb) with a space group of
6
/
, where magnetic RE
ions are distributed on the parallel triangular-lattice layers within the
-plane and stacked in an 'AA'-type fashion along the
-axis. The low-temperature magnetic characterizations indicate that all synthesized Ba
RE
Ti
O
compounds exhibit dominant antiferromagnetic (AFM) interactions and the absence of magnetic order down to 1.8 K. The isothermal magnetization and electron spin resonance results reveal the distinct magnetic anisotropy for the compounds with different RE ions. Moreover, the as-grown Ba
Nd
Ti
O
single crystals exhibit Ising-like magnetic anisotropy with a magnetic easy-axis perpendicular to the triangle-lattice plane and no long-range magnetic order down to 80 mK, as the quantum spin liquid candidate with dominant Ising-type interactions.
The exploration of new rare-earth (RE)-based triangular-lattice materials plays a significant role in motivating the discovery of exotic magnetic states. Herein, we report a family of hexagonal ...perovskite compounds Ba6RE2Ti4O17 (RE = Nd, Sm, Gd, Dy–Yb) with a space group of P63/mmc, where magnetic RE3+ ions are distributed on the parallel triangular-lattice layers within the ab-plane and stacked in an ‘AA’-type fashion along the c-axis. The low-temperature magnetic characterizations indicate that all synthesized Ba6RE2Ti4O17 compounds exhibit dominant antiferromagnetic (AFM) interactions and the absence of magnetic order down to 1.8 K. The isothermal magnetization and electron spin resonance results reveal the distinct magnetic anisotropy for the compounds with different RE ions. Moreover, the as-grown Ba6Nd2Ti4O17 single crystals exhibit Ising-like magnetic anisotropy with a magnetic easy-axis perpendicular to the triangle-lattice plane and no long-range magnetic order down to 80 mK, as the quantum spin liquid candidate with dominant Ising-type interactions.
Strain at CoMo1.14O4/CoOOH interface induces reversible reconstruction evolution. CoMo1.14O4 anode in AEM water-splitting device can endure current shock without decay.
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•CoMoxO4/CoOOH ...interfaces with an optimizing strain to facilitate structural reversibility during fluctuating oxygen evolution.•Fluctuating OER of CoMo1.14O4 with favorable durability is demonstrated by the lower current fluctuation of 1.7% relative to 4.3% in CoMo0.82O4 and 13.8% in CoMoO4.•An AEM water splitting electrolyzer made of CoMo1.14O4 anode can endure current shock, with negligible decay at 800 mA cm−2 after 9 shocks.
Transition metal oxide usually suffers from reconstruction into metal oxyhydroxide during oxygen evolution reaction (OER), while irreversible evolution between metal oxyhydroxides and intermediate species cannot agilely response to the fluctuating power of renewable energy. Herein, an individual CoMoxO4 phase with a tunable Co/Mo stoichiometry is reconstructed into CoOOH skin as active material for OER. Compressive strain induced by CoMo1.14O4/CoOOH interface, downshifting the d-band center of CoOOH, is an effective strategy to not only accelerate the sluggish kinetics of OER, but also enable inspiring the expeditious evolution and the reversibility between CoOOH and intermediate species. The reversibility is an applicable demand for OER in case of fluctuating potential. Reaction current on CoMo1.14O4 at constant potential is demonstrated by the lower fluctuation of 1.7 %, relative to 13.8 % in CoMoO4 after 12 cycles. Meanwhile, an anion exchange membrane water splitting electrolyzer made of CoMo1.14O4 anode can endure current shock of 50 ∼ 800 mA cm−2 in 0.2 s, which has negligible decay at 800 mA cm−2 after 9 shocks. Designing strategy of interfacial strain modulated by stoichiometry can be universally extended into the other oxide electrocatalysts including NiMoO4 and their derivatives.
Polymer-based nanocomposite capacitors for energy storage with high discharged energy density and charge-discharge efficiency are of great importance to modern electronic devices and electrical ...systems. Herein, the energy storage properties are improved by applying double-layered core-shell nanoparticles as fillers. The dopamine was adopted as the outermost layer to improve the dispersibility and compatibility between the fillers and matrix. The high resistance of SiO2 works as a barrier to limit the movement of space charge over the BaTiO3 (BT) surface when a high electric field is applied, leading to an enhancement of breakdown strength as well as a decreased space charge polarization, so that an enhancement of discharged energy density and charge-discharge efficiency are achieved. The SiO2@BT/P(VDF-CTFE) also shows weaker frequency dependence, indicating the reduction of space charge polarization. A possible mechanism of reduced space charge polarization was proposed to explain the effects of SiO2. This work demonstrates that constructing a core-shell structure with high resistance is an effective way to improve the energy properties of nanocomposite capacitors.
Abstract
Antiferromagnetic spintronics actively introduces new principles of magnetic memory, in which the most fundamental spin‐dependent phenomena, i.e., anisotropic magnetoresistance effects, are ...governed by an antiferromagnet instead of a ferromagnet. A general scenario of the antiferromagnetic anisotropic magnetoresistance effects mainly stems from the magnetocrystalline anisotropy related to spin–orbit coupling. Here magnetic field driven contour rotation of the fourfold anisotropic magnetoresistance in bare antiferromagnetic Sr
2
IrO
4
/SrTiO
3
(001) thin films hosting a strong spin–orbit coupling induced
J
eff
= 1/2 Mott state is demonstrated. Concurrently, an intriguing minimal in the magnetoresistance emerges. Through first principles calculations, the bandgap engineering due to rotation of the Ir isospins is revealed to be responsible for these emergent phenomena, different from the traditional scenario where relatively more conductive state is obtained usually when magnetic field is applied along the magnetic easy axis. These findings demonstrate a new efficient route, i.e., via the novel
J
eff
= 1/2 state, to realize controllable anisotropic magnetoresistance in antiferromagnetic materials.
Electrochemical carbon dioxide reduction meditated by metallic catalysts suffers from restricted selectivity and competition from hydrogen evolution, which sensitively depends on ambiguous ...contributions of alloying and strain state in bimetallic catalysts. Herein, nanoporous Au-Sn (NPAS) containing trace tin solute in Au lattices is delicately designed to convince real strain effect, while eliminating other undesirable factors, such as alloying, crystal facets and surface composition. Compared with nanoporous gold (NPG), the NPAS with a solute strain of ∼2.2 % enables more efficient CO2-to−CO conversion, with an efficiency as high as 92 % at -0.85 V versus reversible hydrogen electrode (vs. RHE), and the high activity can retain for more than 8 h. The combination of HRTEM and surface valence band photoemission spectra reveals that the tensile strain on the surface of 3D nanoporous structure promotes the catalytic activity by shifting up the d-band center and strengthening the adsorption of key intermediate *COOH. A small amount of Sn solute in the nanoporous alloy can prevent ligament coarsening effectively and improve the electrochemical stability.
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