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水中药物新污染物与腐殖酸共存的氧化偶联强化去除机理研究
No full text含有苯胺、硫醇等活性基团的药物新污染物释放到水环境中会对生态环境和人体健康造成潜在风险。通常在水环境或污/废水体系中，药物新污染物浓度仅为常规污染物（例如腐殖酸类污染物）浓度的数十分之一，甚至更低。常规的无选择性氧化会将大量能量和氧化剂消耗在降解浓度更高的常规污染物上，无法实现药物新污染物的低成本、低碳、高选择性去除。自然水体的腐殖化自净化通过氧化偶联将新污染物与腐殖酸结合实现无害化处理，这为新污染物的低成本去除提供了新思路。但目前尚未有针对药物新污染物，深入探索腐殖酸共存环境下的氧化偶联机理的研究。
本文根据不同药物与不同氧化态腐殖酸的结构特点，开展了药物新污染物与腐殖酸类共存环境下氧化偶联反应机理研究，重点考察了不同药物新污染物的亲核结构与氧化过程不同腐殖酸中间体对氧化偶联反应的作用影响，提出了氨基和硫醇类药物通过氧化偶联途径强化去除的差异化调控方法。
主要研究包括：
（1）研究了31种不同亲核结构的药物污染物与氯醌类氧化型腐殖酸发生直接偶联反应的机理，发现了氯醌的偶联反应途径与解毒机理受药物污染物的最大局部亲核指数Nk,max显著影响的规律。对于具有硫醇类官能团的药物（Nk,max>0.75），硫醇易与醌类物质直接亲核偶联形成稳定产物，显著降低氯醌毒性；对于具有氨基类官能团的药物（Nk,max<0.75），由于氨基亲核指数小于水，醌类物质发生水解转化。反之，硫醇类药物可以通过直接和氧化态腐殖酸偶联转化，而氨基类药物与腐殖酸发生氧化偶联的机理还需要进一步探索。
（2）建立了电子顺磁共振结合循环伏安有效识别半醌自由基类腐殖酸氧化活性中间体的分析方法，通过鉴别氧化锰氧化过程16种腐殖酸模拟物产生的半醌自由基、醌等活性中间体，探明了这些活性中间体与磺胺类药物的氧化偶联反应途径，揭示了腐殖酸半醌自由基在氨基类药物新污染偶联转化的主导途径，提出了腐殖酸通过单电子氧化诱导磺胺类药物发生“半醌自由基交叉偶联”的作用机理，进一步建立了半醌自由基活性与磺胺类药物去除速率之间的定量构效关系QSAR模型。
（3）探索了氧化锰、空气、过氧化氢等不同弱氧化体中，8种不同的金属阳离子通过络合稳定腐殖酸半醌自由基活性中间体的效果。发现了金属离子络合通过降低腐殖酸中间体的ESOMO提高半醌自由基稳定性强化“半醌自由基交叉偶联”的机理，揭示了络合稳定腐殖酸中间体促进氨基类药物氧化偶联转化的机理。提出了“金属耦合电子转移“强化氨基类药物的新去除方法，显著提高了磺胺的氧化偶联反应速率常数。
（4）针对头孢抗生素废水中高浓度硫醇类特征污染物，研究了11种氧化态腐殖酸通过预偶联强化硫醇氧化去除的反应机理，揭示了预偶联在氧化过程中显著改变硫醇电子结构特性、降低硫醇偶联产物氧化开环能垒的关键作用。提出了一种“腐殖酸预偶联-强化氧化”的处理方法，与芬顿氧化和臭氧氧化法相比，在总有机物去除率和成本方面均具有明显优势。</p
Effect of Zn Transition Layer on Properties of Vacuum Deposited Zn-Mg Coating
No full textAbstract
Zinc coatings have been served as a barrier and a galvanic protection for steel products for over a century. However, with the depletion of zinc resources, it becomes an urgent issue to obtain a new type of zinc coating that uses less zinc and has higher corrosion resistance. In order to develop Zn/ZnMg coatings with better corrosion resistance than traditional galvanized steel and suitable for advanced high strength steel, the vacuum thermal evaporation technique was used to simultaneously deposit Zn/ZnMg coating onto interstitial free steel plates and single-crystal silicon wafers in a high vacuum environment. The microstructure, morphology, adhesion and corrosion resistance behavior of the Zn/ZnMg coating were studied by scratch test, salt spray test and electrochemical method. The results shows that the grain size in the Zn/ZnMg coating tended to increase with the increase of the substrate temperature. After deposited the pure Zn transition layer, the adhesion of the coating has been obviously improved. When the substrate temperature was increased to 200°C, the obtained coating exhibited strong corrosion resistance
Dynamic behaviors of bubble formation on submerged micro-capillary under constant flow conditions
No full textBubble column offers various advantages compared to other devices in the chemical process industry, which was used as a fine particulate and sulfuric acid mist control device. Bubble formation behaviors, including volume, diameter and velocity, were systematically investigated in the single submerged micro-capillary test bed under constant flow conditions by using the high-speed optical camera in this paper. Besides, force model of the bubble forming process was established based on the experimental results. It was found that the formed bubble turned to be elliptical and bubble shape was independent of the gas flow rate under the conditions of this study. In addition, bubble velocity was found quickly reached the highest level, then decreased, and eventually tended to be stable (0.02-0.1 m/s). By analyzing the bubble forces, it was found that pressure force FP, surface tension force FS and buoyancy force FB played different roles in different bubble formation process. These results can provide detailed parameters for the modeling of bubble formation process under the test conditions
Data-driven discovery of the governing equation of granular flow in the homogeneous cooling state using sparse regression
No full textWith the arrival of the era of big data and the rapid development of high-precision discrete simulations, a wealth of high-quality data is readily available, but discovering physical laws from these data remains a great challenge. In this study, an attempt is made to discover the governing equation of the granular flow for the homogeneous cooling state from discrete element method (DEM) data through sparse regression. It is shown that not only the governing equation but also the energy dissipation rate can be obtained accurately from DEM data for systems having different physical properties of particles and operating conditions. The present work provides the evidence that the macroscopic governing equation and the constitutive relation of granular flow can be discovered from microscopic data using a purely data-driven method
Molecular-Layer-Deposited Zincone Films Induce the Formation of LiF-Rich Interphase for Lithium Metal Anodes
No full textLithium metal anodes suffer from low Coulombic efficiency and dendritic growth owing to an unstable solid electrolyte interphase (SEI), which limit the practical applications of lithium metal anodes. Here, zincone (ZnHQ) is conformally fabricated on 3D copper nanowires (CuNWs) via a molecular layer deposition (MLD) technology. Upon polarization, the terminal oxygen of ZnHQ serves as a strong nucleophilic agent to attack Li bis(trifluoromethanesulfonyl)imide, yielding a LiF-rich SEI. This SEI facilitates the Li transport, shuts off the electron conduction, and inhibits the growth of lithium dendrites. In addition, the zinc atoms of ZnHQ induce favorable Li deposition owing to their lithiophilicity. These advantages enabled by MLD make the ZnHQ-modified CuNW (CuNW@ZnHQ) an ideal Li metal anode, which demonstrates excellent cyclability. A symmetrical cell of CuNW@ZnHQ shows high cycling stability for more than 7000 h at the current density of 1 mA cm(-2). When pairing with a Ni/Co/Mn ternary oxide cathode (NCM523), the resultant CuNW@ZnHQ||NCM full cell is cycled for 1000 cycles with a 90% capacity retention at an areal capacity of 3.2 mAh cm(-2). The MLD technology brings new opportunities for next-generation high-energy Li metal batteries
A review on facilitated transport membranes based on z-complexation for carbon dioxide separation
No full textThe emission of CO2 from human activities is the principal reason for global warming. Membrane separation technology has been extensively regarded as a tremendous potential option for mitigating CO2 emissions when utilizing fossil fuels as a major source of energy. As an important group of CO2 separation membranes, the fixed CO2 carrier-facilitated transport membrane guided by z-complexation reactions is a rising research field and has attracted much attention in the last ten years due to its desirable CO2 separation performance in the dry state and high resistance to oxidation. In this review, facilitated transport theories derived from z-complexation reactions are discussed for an in-depth understanding, rational design and tunable fabrication of facilitated transport membranes. According to the different fixation methods of metal ions (CO2 active carrier), polymer electrolyte membranes and mixed matrix membranes are discussed in detail as two strategies for fabricating CO2-facilitated transport membranes. Future perspectives toward z-complexation reaction-facilitated transport membranes are proposed
Special Project for Trans-formation of Major Technological Achievements in HeBei Province[22293601Z]
No full text
Achieving efficient pretreatment of corn straw at elevated temperatures via constraining cellulose degradation
No full textGreatly reducing the cellulose crystallinity and lignin content of lignocellulose can substantially improve the enzymatic hydrolysis efficiency, dramatically reducing the enzyme dosage; however, it is difficult to be simultaneously achieved. A solution was put forward - biomass pretreatment was carried out with the binary system consisted of 1-n-butyl-3-methylimidazole chloride (BMIMCl) and arginine (Arg) at temperatures higher than the glass transition temperature of lignin (Tg-lignin). The cellulose crystallinity decreased because of hydrogen bonding with BMIMCl. Delignification was promoted via raising the temperature higher than the Tg-lignin, while cellulose degradation was constrained by Arg. The delignification rate reached 90.36 %. The yield of cellulose remained at a level of 88.89 %, while the Crystallinity Index (CI) of cellulose decreased from 36.13 % (raw corn straw) to 13.50 % (regenerated material, RM). It was found that the average molecular weight (Mw) of lignin decreased from 1632 g/mol to 584 g/mol after pretreatment, indicating the lignin was depolymerized; the 2DHSQC result showed the beta-O-4 ' bond of lignin was broken. Because the cellulose crystallinity and the lignin content of the regenerated material were reduced greatly at the same time, the RM was easily hydrolyzed by cellulase. The enzymatic hydrolysis glucose yield of the RM was 3.75 times that of raw corn straw when the enzyme dosage was only 0.41 FPU/g sample, reaching 99.5 %. The IL was successfully recycled four times, and the recovery rate was higher than 93 % each time. RM obtained in four cycles maintained high lignin removal rate and enzymatic hydrolysis glucose yield. The degradation products of hemicellulose and lignin were the main impurities in the recovered IL. This work may provide a new solution for green and efficient biomass pretreatment