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Water environment conditions directly support aquatic life. It is important to maintain a suitable water environment to improve the efficient use of water resources. Supersaturation of total dissolved gas (TDG) in the water will cause fish suffer from gas bubble disease and even mortalities. Measures should be taken to mitigate the adverse effect of supersaturated TDG. Considering the adsorption effect of porous medium, activated carbon (AC) was utilized in this experiment to explore the effect of AC on supersaturated TDG removal. The effects of AC properties, AC dosage, and initial TDG saturation were investigated. The results showed that adding AC in the water could effectively accelerate the supersaturated TDG removal rate, which was positively correlated with the AC specific surface area and dosage. Meanwhile, the average dissipation rate of TDG increased and then decreased with increasing initial TDG saturation. The adsorption characteristics of AC on supersaturated TDG were also explored. The maximum equilibrium adsorption capacity and removal rate were 0.262 mg/g and 48.5% respectively. It was concluded that the adsorption process of AC on supersaturated TDG conformed to the Langmuir equation and pseudo-first-order kinetic model. Recycling test indicated that the used AC could be reused after drying. It was hoped that this research could contribute to improving water environment and ensuring the healthy development of the aquatic livings. [ABSTRACT FROM AUTHOR]

Magnesium-enriched magnesium slag particles (MSPs) can be used as an adsorption substrate as well as the magnesium source for struvite precipitation. In this study, an HCl treatment was used to enhance MSPs for phosphorus removal. After soaking in 1 mol/L HCl, an 11.27% decrease in median diameter (D50) and a 6.73% increase in specific surface area were observed when compared with the original MSPs. The improvement of the MSP surface properties resulted in 188.96 mg/kg increase in the PO43− adsorption capacity. Irrespective of HCl treatment, the phosphorus adsorption process followed the Dubinin–Radushkevich (D–R) model much more accurately than the Langmuir and Freundlich equations with correlation coefficients higher than 0.94. The adsorption free energy obtained through the D–R model revealed a 9.75% decrease after HCl treatment. Sequential fraction extraction results indicated that 96% of the Mg2+ released from the HCl-treated MSPs came from acid-soluble magnesium (exchangeable and carbonate-bound). Mg2+ obtained from HCl-treated solutions provided a reliable magnesium source for struvite precipitation. The PO43− removal rate can reach 53.63% with the optimal pH value of 10.0 and molar ratio of NH4+ to PO43− of 1:1. Struvite precipitation and adsorption can simultaneously occur in HCl-treated MSP solution. It contributed 63.19% to the overall PO43− removal and is a major contributor compared with adsorption. Thus, HCl treatment greatly enhanced the potential of MSPs for phosphorus removal due to an improved adsorption capacity and is a reliable Mg2+ source for struvite precipitation. [ABSTRACT FROM AUTHOR]

Phosphorus recovery from wastewater not only reduces the unbearable impacts of excessive nutrient discharge on environmental systems but also favor the reuse of phosphorus resource. Based on the mechanism as well as technical analysis for major phosphorus recovery techniques including struvite precipitation and wetland substrate adsorption, a novel magnesium slag-packed wetland filter and corresponding operational procedures are proposed, which aim to reduce the dependence of using magnesium-containing chemical reagent as magnesium sources for struvite precipitation, and improve the accumulation and recovery performance for struvite precipitation within porous wetland substrate. Results from preliminary experiments indicated that magnesium slag particles with approximately 2 mm in diameter can recover 43.20-72.39% phosphorus from 1-25 mol/L PO solution, and the presence of 5-50 mol/L NH contributed to 11.71-29.11% enhancement of phosphorus recovery mainly due to struvite precipitation. The detected generation of struvite via XRD spectrum analysis partly demonstrated the potential of phosphorus recovery in magnesium slag-packed wetland filter. The proposed phosphorus recovery technology is free of secondary pollution and solid waste generation; phosphorus-saturated (mainly due to struvite precipitation and adsorption) magnesium slag particles can be potentially used as phosphorus fertilizer and thus partly solved the traditional shortages of disposing phosphorus-saturated substrate due to low phosphorus contents. [ABSTRACT FROM AUTHOR]

Investigation of phosphorus (P) sorption-desorption characteristics of drainage ditch sediments is important for better understanding on sediment P transport behaviors in ditches. Surface ditch sediment samples were collected from headwater subcatchment of forestland, sloping cropland, paddy field, and residential area in a representative catchment in the central Sichuan Basin. These sediment samples were used for determination of P sorption-desorption characteristics by a batch equilibrium technique. Results showed that the maximum P sorption capacities (Q) in the sediments ranged from 159.7 to 263.7 mg/kg, while higher Q were observed in the ditch sediments from the paddy fields. The Q was significantly and positively correlated with oxalate-extractable Fe and Al oxides ( r=0.97 and 0.98, p < 0.01), clay fraction ( r = 0.78, p < 0.05) and organic matter ( r = 0.95, p < 0.01). Sediment pH, clay and organic matter influenced the P sorption through amorphous Fe and Al oxides. CaCO content was negatively correlated with the Q ( r = −0.83, p < 0.05), implying that saturated CaCO (> 50 g/kg) would not increase P sorption capacity in the ditch sediments. The ditch sediments featured a linear desorption curve, suggesting that P release risk would be enhanced with the increase of the P adsorption. The P desorption rate was positively correlated with Olsen P ( r = 0.94, p < 0.01), but negatively related to the fine particle-size fractions ( r = −0.92, p < 0.01), the sum of the amorphous Fe and Al oxides ( r = −0.67, p < 0.05) and the P sorption capacity ( r = −0.59, p < 0.05). The ditch sediments from residential area had a higher P release risk than that from the other ditches of forestland, sloping cropland and paddy field. The P sorption index (PSI) derived from single-point measurement was significantly correlated with the P sorption capacity ( r = 0.99, p < 0.01), and could be used for estimating Q as 1.64 times PSI plus 24.0 (Q = 1.64 PSI + 24.0) for similar sediments with highly calcareous soils and sediments. Ditch cleaning and sediment removal for the ditch in residential area were recommended in this area to reduce the P release risk. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have been widely employed for metal ion adsorption owing to their inherent advantages, encompassing low crystal density, well-organized organic unit structures, adjustable pore size, and remarkable structural stability. However, it is still a great challenge to design excellent COFs with high adsorption and advanced purification capabilities for Pb2+ and Cd2+ ions. Herein, hydrazine-linked COFs (COF-TCH) were prepared for effective adsorption and advanced purification of metal ions. The adsorption capacity of COF-TCH for Pb2+ and Cd2+ ions are 395.3 and 153.5 mg/g, respectively. Moreover, the Pb2+ and Cd2+ ions in water can be treated from 75 and 30 mg L−1 to less than 0.01 and 0.003 mg L−1, respectively, indicating the excellent adsorption and advanced purification capability of COF-TCH. This is a rare example of COFs adsorbent that deeply purify water to meet the guideline values in drinking water for the World Health Organization. FT-IR, XPS and quantum mechanics calculation were performed to understand the adsorption mechanism. The remarkable adsorption and advanced purification capability of COF-TCH for Pb2+ and Cd2+ ions can be attributed to the synergistic interaction between the amine and thione groups, which can easily complex with Pb2+ and Cd2+ ions to form stable five-membered ring structure in COF-TCH. In addition, COF-TCH still remains an adsorption capacity of over 90% after ten adsorption-desorption cycles, indicating its excellent reusability and stability. COF-TCH with high adsorption and advanced purification capability, high stability, low cost and reusability has enormous practical application potential in high-performance remediation of Pb2+ and Cd2+ contaminated water. [Display omitted] [ABSTRACT FROM AUTHOR]

A sulfur composite active material for lithium-sulfur batteries with a highly active interface structure can display excellent electrochemical performances. For this reason, in this paper, we design a type of V 2 O 5-x /TiO 2 active interface structure with high polysulfide adsorption energy as a high-performance sulfur-wrapped matrix. Physical property characterization indicates this interface is constructed from circular anatase structure TiO 2 and anoxic vanadium oxide structure composed of V4+ and V5+. After sulfur wrapping, Ti-S and S-S bond structures are produced by chemical and physical adsorption. Density functional theory calculations show that the V 2 O 5-x /TiO 2 interface has very high adsorption energy (-5.93 eV) with lithium polysulfide (Li 2 S 6). After sulfur wrapping as a cathode active material, it displays low electrochemical charge transfer resistance (31.89 Ω) and high lithium-ion transfer efficiency (3.50 × 10−12). In addition, it has rather high discharge specific capacities of 1466.47, 963.84 and 801.16 mAh.g−1 at 0.1, 0.2 and 0.5 C, respectively. After 500 cycles, the discharge capacity retention at 0.5 C is up to 76.11% corresponding to 0.048% capacity decay rate per cycle. This is the reason that the V 2 O 5-x /TiO 2 active interface has very strong adsorption to polysulfide and can effectively suppress the shuttle effect (Q low /Q high =1.44 at 0.2 C). [ABSTRACT FROM AUTHOR]

• CNT@Co 3 O 4-x -P with dual defects of O-vacancy and P-doping is developed. • The construction of O-vacancy mainly promotes polysulfide conversion kinetics. • The phosphorus doped atoms mainly contribute to polysulfide adsorption. • CNT@Co 3 O 4-x -P/S based cell shows excellent specific capacity and cycling stability. Lithium-sulfur (Li-S) battery is considered as a burgeoning energy storage device owing to its high theoretical energy density. However, the shuttle effect and sluggish kinetics of sulfur species during conversion reactions lead to the challenges in attaining commercial application of high-performance Li-S battery. Herein, a double-defect engineering strategy is developed to endow CNT@Co 3 O 4 with favorable effects on Li-S chemistry by introducing oxygen vacancies and phosphorus doped atoms (CNT@Co 3 O 4-x -P). Experimental and theoretical investigations indicate that both enhanced adsorption and conversion of polysulfides can be realized on the surface of CNT@Co 3 O 4-x -P. Taking advantage of the superb adsorption-conversion property of CNT@Co 3 O 4-x -P, the cell achieves a specific capacity of 903 mAh/g with splendid cyclability at 2 C and a high areal capacity of 7.3 mAh cm−2 under the lean electrolyte (E/S = 6 μL E mg−1 S) condition. This work offers a creative approach to implement high-performance Li-S batteries and promotes the application of Li-S batteries. [ABSTRACT FROM AUTHOR]

A strategy of regulating the basicity of perovskite oxygen ions by cation doping is proposed to design cathode materials with high catalytic activity for solid oxide electrolysis cells (SOECs). Specifically, a series of Sr 2 Fe 1.5- x Zr x Mo 0.5 O 6−δ (SFZ x M) perovskites are developed and characterized for its electrocatalytic activity and oxygen ions basicity to investigate the effect on electrochemical performance. The experimental results show that the single cell prepared with the Sr 2 Fe 1.3 Zr 0.2 Mo 0.5 O 6−δ (SFZ2M) cathode reaches a current density of 1.85 A cm−2 at 1.8 V and 800 °C and exhibits good stability over 120 h under CO 2 atmosphere. Combined with first-principles calculations, it is further confirmed that the introduction of low-electronegativity ions can improve the oxygen ions basicity and also increase the oxygen vacancy concentration of the cathode, thereby realizing the improvement of electrochemical performance. Thus, this strategy provides new insights into designing electrodes for direct CO 2 electrolysis as well as other electrochemical catalysis. [Display omitted] • Zr-doped Sr 2 Fe 1.5 Mo 0.5 O 6-δ (SFZxM) perovskites are firstly evaluated as SOEC cathode. • SFZxM materials greatly enhance the chemisorption of CO 2 by increasing the oxygen vacancies concentration. • The introduction of Zr4+ can improve the oxygen ion basicity of SFZxM cathodes. • The improved electrochemical performance is facilitated by the double regulation of oxygen ion basicity and oxygen vacancies. [ABSTRACT FROM AUTHOR]

Herein, we report a facile and effective adsorption strategy to improve the performance of Lithium-Sulfur (Li-S) batteries. MnO 2 nanosheets grown on the surface of highly conductive graphene resulted in a coupled composite bilayer electrode when coated onto a sulfur cathode. In this way, a high initial specific capacity of 1395 mA h g −1 at a rate of 0.5C, a coulombic efficiency approaching 100% and steady cyclic efficiency with a fade rate of 0.3% per cycle from 10 to 100 cycles has been achieved. This hybrid electrode not only shows enhanced electrochemical performance but can also be easily controlled and scaled thereby aiding future commercialization of high-performance Li-S batteries. [ABSTRACT FROM AUTHOR]

• Cu-doped (La 0.2 Sr 0.8) 0.95 Ti 0.65- x Mn 0.35 Cu x O 3- δ(LSTMC)are firstly evaluated as SOEC cathode. • LSTMC greatly enhances the catalytic activity by enhancing the chemisorption of CO 2. • The catalytic reaction mechanisms of LSTMC are discussed. • A max electrolytic current density of 2.33 A cm−2 is obtained under 1.8 V at 800 °C. Solid oxide electrolysis cell (SOEC) is a promising technology to efficiently convert carbon dioxide. However, the lack of suitable cathode, with desirable catalytic activity, limits the advancement of SOEC. Herein, we report a novel (La 0.2 Sr 0.8) 0.95 Ti 0.65- x Mn 0.35 Cu x O 3-δ (LSTMC x , x = 0, 0.05, 0.1 and 0.15) as a high-performance cathode, co-doped with hetero-valent Cu and Mn ions at B-site synergistically regulates the surface environment of LST. Cu doping significantly improved the catalytic activity by enhancing the chemisorption of CO 2 , and Mn doping increased the concentration of oxygen vacancies, resulting in abundant electrochemically active sites. Moreover, the as-prepared LSTMC render a higher electrocatalysis performance (2.33 A cm−2 at 1.8 V and 800 °C) than the previously reported perovskite-based cathodes. In addition, the LSTMC-based single cell did not exhibit any significant performance degradation after long-term stability test (100 h) under pure CO 2. Therefore, this newly developed perovskite is considered as a promising cathode for SOEC. [ABSTRACT FROM AUTHOR]