不同盐沼湿地类型脱氮除磷效能及影响因素分析

采用沉水植物表面流湿地(沉水组)、挺水植物表面流湿地(挺水组)和浮床湿地(浮床组)3种盐沼湿地对长江口近岸低污染水体进行脱氮除磷效能的研究。结果表明,HRT为3 d时,水组、挺水组、浮床组对NO3^--N的去除率在高温时段分别为79.9%±13.2%、71.8%±15.2%、77.2%±13.2%,中温时段分别为39.4%±13.7%、31.5%±8.5%、18.4%±16.6%,低温时段分别为15.6%±14.6%、19.7%±8.6%、2.%5±8.6%。沉水组和挺水组对TP的去除率受温度影响较小,分别为66.4%±32.4%、55.5%±29.4%;而浮床组除磷效果受温度影响较大。当HRT缩短为1.5 d时,3组湿地系统在高温时段仍可达到相近的脱氮除磷效果,在中低温时段脱氮除磷效果都有不同程度的下降。     

变压吸附制氮(PSA)设备在炼油生产中的应用

针对某炼油装置氮气供需矛盾突出的问题,提出采用变压吸附(PSA)制氮设备,利用空压站净化风生产氮气方案,(1)降低空压站多余风量放空,减少浪费;(2)正常生产情况下,利用PSA设备生产氮气,对供氮管网压力调节。针对上述方案,结合空压站供风现状进行分析,得出结论:利用PSA制氮设备满足炼油装置高峰用氮是可行的,并提出了具体措施和运行过程中应注意的问题。     

Flexible Osteogenic Glue as an All-In-One Solution to Assist Fracture Fixation and Healing

Osteogenic glue that reproduces the natural bone composition represents the final frontier of orthopedic adhesives with the potential to revolutionize surgical strategies against comminuted fractures. However, it is difficult to achieve an all-in-one formula, which could provide flexible and reliable adhesiveness while avoiding interfering with or even promoting the healing of glued fractures. Herein, an osteogenic glue characterized by inorganic-in-organic integration between amine-modified mesoporous bioactive glass nanoparticles (AMBGN) and bioadhesive gelatin-dextran network (GelDex) is introduced as an all-in-one tool to flexibly adhere and splice bone fragments and subsequently guide fracture healing during degradation. Relying on such integration, a 4-fold improvement in cohesiveness is presented, followed by a nearly 5-fold enhancement in adhesive strength in ex vivo porcine bone samples. The reversible and re-adjustable adhesiveness also enables glue to effectively splice intricate fragments from highly comminuted fractures in the rabbit radius in an in vivo environment. Moreover, well-preserved organic–inorganic integrity during degradation of the glue guides sustained interfacial osteogenesis and achieve satisfying healing outcomes in glued fractures, as observed by the 2-fold improvement in biomechanical and radiological performance compared with commercially available cyanoacrylate adhesives. The current findings propose an all-in-one solution for the fixation of bone fragments during surgery.     

Iron-based sulfur and nitrogen dual doped porous carbon as durable electrocatalysts for oxygen reduction reaction

The widespread use of fuel cell technology is hampered by the use of expensive and scarce platinum metal in electrodes which is required to facilitate the sluggish oxygen reduction reaction (ORR). In this work, a viable synthetic approach was developed to prepare iron-based sulfur and nitrogen dual doped porous carbon (Fe@SNDC) for use in ORR. Benzimidazole, a commercially available monomer, was used as a precursor for N doped carbon and calcined with potassium thiocyanate at different temperatures to tune the pore size, nitrogen content and different types of nitrogen functionality such as pyridinic, pyrrolic and graphitic. The Fe@SNDC–950 with high surface area, optimum N content of about 5 at% and high amount of pyridinic and graphitic N displayed an onset potential and half-wave potential of 0.98 and 0.83 V vs RHE, respectively, in 0.1 M KOH solution. The catalyst also exhibits similar oxygen reduction reaction performance compared to Pt/C (20 wt%) in acidic media. Furthermore, when compared to commercially available Pt/C (20 wt%), Fe@SNDC–950 showed enhanced durability over 6 h and poison tolerance in case of methanol crossover with the concentration up to 3.0 M in oxygen saturated alkaline electrolyte. Our study demonstrates that the presence of N and S along with Fe-N moieties synergistically served as ORR active sites while the high surface area with accessible pores allowed for efficient mass transfer and interaction of oxygen molecules to the active sites contributing to the ORR activity of the catalyst.     

Magnetic field-enhanced photocatalytic nitrogen fixation over defect-rich ferroelectric Bi2WO6

Photocatalytic N₂ fixation is a promising and sustainable manufacturing process of ammonia (NH₃); however, the NH₃ production rate by this method is very low, thus severely restricting further application of this sustainable technology. Therefore, developing an efficient photocatalyst for N₂ fixation under mild conditions is urgently required. Herein, ferroelectric Bi₂WO₆ materials with different surface oxygen defects were prepared, and the concentration of corresponding defects was controlled by adjusting the thermal reduction time. The abundant oxygen defects in Bi₂WO₆ can provide more reactive sites to promote the effective adsorption of N₂, and the photogenerated charge carrier can be efficiently separated benefiting from the internal electric field. These would weaken the N₂ triple bond and reduce the activation energy barrier for the conversion of N₂ to NH₃ under mild conditions. In the absence of sacrificial agents and cocatalysts, the optimized Bi₂WO₆ with oxygen defects shows an indigenous NH₃ yield of 132.175 μmol·g^-1·L^-1·h^-1, which is more than two times higher than that of the original Bi₂WO₆. Surprisingly, the Bi₂WO₆ with oxygen defects produced more than eight times NH₃ (471.13 μmol·g^-1·L^-1·h^-1) than that of the original Bi₂WO₆ when assisted by an external magnetic field, thus providing a new perspective for further enhancing the N₂ fixation performance.     

Preparation of faceted TaN grains by heating Ta-containing oxides in BN crucible with Na

Single-crystal grains of TaN were synthesized by heating Ta₂O₅, FeTa₂O₆, or FeTaO₄ in a BN crucible together with Na metal in an Ar atmosphere at 1100 °C. The BN crucible acted a solid source of nitrogen. Aggregates of columnar ε-TaN single crystals 10–150 μm in size were formed on the inner wall of the BN crucible when either Ta₂O₅ or FeTa₂O₆ was used. On the other hand, platelet-like single crystals of θ-TaN 1–50 μm in size were obtained from FeTaO₄. The results of wavelength-dispersive X-ray spectrometry indicated that the compositions of the ε-TaN and θ-TaN crystals were close to the stoichiometric ideal.     

Fe(III) grafted MoO3 nanorods for effective electrocatalytic fixation of atmospheric N2 to NH3

Electrocatalytic nitrogen reduction reaction (ENRR) offers a carbon-neutral process to fix nitrogen into ammonia, but its feasibility depends on the development of highly efficient electrocatalysts. Herein, we report that Fe ion grafted on MoO₃ nanorods synthesized by an impregnation technique can efficiently enhance the electron harvesting ability and the selectivity of H⁺ during the NRR process in neutral electrolyte. In 0.1 M Na₂SO₄ solution, the electrocatalyst exhibited a remarkable NRR activity with an NH₃ yield of 9.66 μg h^?1 mg^?1_cat and a Faradaic efficiency (FE) of 13.1%, far outperforming the ungrafted MnO₃. Density functional theory calculations revealed that the Fe sites are major activation centers along the alternating pathway.     

Oxidation State Modulation of Bismuth for Efficient Electrocatalytic Nitrogen Reduction to Ammonia

Electrocatalytic nitrogen reduction reaction (NRR) is a promising strategy for ammonia (NH₃) production under ambient conditions. However, it is severely impeded by the challenging activation of the NN bond and the competing hydrogen evolution reaction (HER), which makes it crucial to design electrocatalysts rationally for efficient NRR. Herein, the rational design of bismuth (Bi) nanoparticles with different oxidation states embedded in carbon nanosheets (Bi@C) as efficient NRR electrocatalysts is reported. The NRR performance of Bi@C improves with the increase of Bi⁰/Bi³⁺ atomic ratios, indicating that the oxidation state of Bi plays a significant role in electrochemical ammonia synthesis. As a result, the Bi@C nanosheets annealed at 900  ° C with the optimal oxidation state of Bi demonstrate the best NRR performance with a high NH₃ yield rate and remarkable Faradaic efficiency of 15.10  ± 0.43% at − 0.4 V versus RHE. Density functional theory calculations reveal that the effective modulation of the oxidation state of Bi can tune the p-filling of active Bi sites and strengthen adsorption of *NNH, which boost the potential-determining step and facilitate the electrocatalytic NRR under ambient conditions. This work may offer valuable insights into the rational material design by modulating oxidation states for efficient electrocatalysis.     

低温等离子体用于柴油机尾气脱硝的实验

柴油机作为卡车、重型机械以及船舶的主动力装置仍被广泛采用，其尾气中氮氧化物的脱除技术也是目前的研究热点。本文搭建了模拟柴油机尾气的配气系统，采用介质阻挡放电产生低温等离子体（non-thermal plasma，NTP）的方法对模拟柴油机尾气进行了脱硝的实验研究。实验结果表明：针对本系统，电源效率和能量密度随着输入电压的增大而升高，当输入电压高于60V时，电源效率在90%以上；在O₂/N₂条件下，随着O₂浓度以及能量密度的增加，NO生成量逐渐增加，NO₂生成量先增加后降低最终趋于稳定；在NO/N₂条件下，低温等离子体对NO的脱除率接近100%；在NO/O₂/N₂条件下，随着NO浓度的增加，临界O₂浓度升高，O₂体积分数为1%时脱硝效率在90%以上，O₂体积分数高于14%时低温等离子体的脱硝率为负值，且随着能量密度的增加，生成的NO _x 浓度也更高，O₂浓度对低温等离子体的脱硝性能起决定性作用；在低能量密度时，加入NH₃会提高脱硝性能，高能量密度时NH₃会略微降低NTP的脱硝性能，当加入H₂O模拟真实柴油机尾气成分且喷氨时，获得的脱硝率最高为40.6%。