Tetracycline removal via adsorption and metal-free catalysis with 3D macroscopic N-doped porous carbon nanosheets: Non-radical mechanism and degradation pathway

Recently, metal-based carbon materials have been verified to be an effective persulfate activator, but secondary pollution caused by metal leaching is inevitable. Hence, a green metalfree 3D macroscopic N-doped porous carbon nanosheets（NPCN） was synthesized successfully. The obtained NPCN showed high adsorption capacity of tetracycline（TC） and excellent persulfate（PS） activation ability, especially when calcined at 700 °C（NPCN-700）. The maximum adsorption capacity of NPCN-700 was 121.51 mg/g by ...     

透水路面-生物滞留池组合道路的城市面源污染控制效果评估

不同低影响开发(LID)技术组合对于控制城市面源污染具有重要应用价值,但是其对城市面源污染形成过程(污染物累积-冲刷-输送)的影响及污染负荷削减效果的评估鲜见报道.本研究以深圳市国际低碳城为例,分析了6场降雨事件下透水路面-生物滞留池组合对城市面源晴天污染物累积量、降雨径流冲刷量、不同LID设施的削减量、溢流的负荷量的影响.结果表明,研究区地表颗粒物平均累积量为(15.80±3.79)g·m~(-2),粒径250μm的颗粒物质量占比约为65.14%;6场不同强度降雨对地表颗粒物的平均冲刷率为17.15%,粒径105μm的颗粒物冲刷率为62.71%~74.94%;降雨冲刷地表径流污染物SS、TN、TP的平均污染负荷分别为2.02、0.025、0.001 3 g·m~(-2);透水路面下渗、过滤作用对污染物SS、TN、TP的去除率分别为70.26%、46.29%、19.27%;生物滞留池对径流二次净化去除率分别为85.25%、20.22%、70.27%;入河径流污染物SS、TN、TP的平均污染负荷分别为0.08、0.011、0.000 3 g·m~(-2),是地表冲刷污染负荷的4.05%、43.47%、24.39%.透水路面-生物滞留池组合应用对道路径流中污染物的净化效果显著.通过定量化表征透水路面-生物滞留池组合应用道路的城市面源污染形成过程,以期为城市面源污染形成过程的污染负荷估算及LID工程绩效评估提供科学依据,为LID在国内的推广应用和海绵城市设计提供参考.     

乳化纳米铁浆液在含水层中的迁移特征研究

本文主要研究地下水修复试剂乳化纳米铁（EZVI）在含水层中的迁移特性和影响因素.一维模拟柱实验考察EZVI的穿透曲线和模拟柱中分布情况.结果表明：乳化植物油对纳米铁的改性显著提高了纳米铁在含水层中的迁移能力,EZVI的迁移距离为未改性纳米铁的2~3倍;EZVI中的乳化植物油会随水流迁移,分别形成纳米铁反应带和植物油反应带;岩性对迁移的影响表现为介质粒径越大,越有利于EZVI的迁移,且EZVI在粗砂中的迁移能力是细砂的1.9倍;注入速率通过影响纳米铁迁移到含水层介质表面的几率影响迁移行为,注入速率越大,迁移距离越长;共存离子对乳化纳米铁的迁移性能影响不大,会引起微量的铁的损失.最佳迁移效果的条件是3cm/min的注入速度,2g/L的注入浓度.     

露天堆场防风抑尘网的动力学数值模拟

开放性露天堆场的散尘是大气颗粒物的重要来源. 来流空气在棱形物料堆的上部绕流,使其表面的空气流动结构逐点不同,而料堆表面的空气动力学结构又决定着堆场的散尘机理及散尘量. 分析了典型单一棱形料堆周围空气湍流结构,并应用三维标准k-ε紊流模型对其流场进行了数值模拟;计算了来流方向抑尘网前后不同断面处风速的垂直分布;分析了不同孔隙率(0、0.2、0.3、0.4、0.5、0.6和1.0)抑尘网后料堆迎风面和背风面沿高度方向、平顶面沿水平方向的剪切应力特性和分布规律. 结果表明:抑尘网前3倍网高距离处的风速较无网工况(孔隙率为1.0)略有减小,降幅随孔隙率增大而减小, 孔隙率为0时最大降幅为5.1%;网前2倍网高距离处与抑尘网之间区域的风速廓线与无网工况相差甚远,孔隙率为0时近网区域风速最高降幅达92.8%. 抑尘网和料堆迎风面之间区域,从地面至网顶高度,不同孔隙率抑尘网工况下的风速均较无网工况小,最小处为无网工况风速的18.5%;抑尘网以上区域的风速较无网工况的大,最大处为无网工况风速的128.0%,并且差距随抑尘网孔隙率的减小而增大. 料堆剪切力分布显示,其迎风面和平顶面为主要散尘面,背风面被涡旋卷起的扬尘量较前两者小得多. 防风抑尘网的设置改变了料堆周围空气的流动结构和受力分布,对不同孔隙率的抑尘网数值模拟结果可知,0.2和0.3为最佳孔隙率.      

过渡金属负载γ-Al2O3对HCN催化水解性能的影响

为高效催化水解净化废气中的HCN,采用等体积浸渍法改性γ-Al₂O₃制备HCN水解催化剂,考察不同金属组分及其负载量对HCN催化水解效率的影响. 结果表明:不同金属对HCN的催化水解活性依次为Cu>Cr>Fe>Zn>Ni>Co,Cu/γ-Al₂O₃系催化剂中Cu的最佳负载量为15.0%,添加1.0%的Ni有助于增加该催化剂对HCN的催化水解性能. 空速为18 000 h-1时,Cu/Ni/γ-Al₂O₃型催化剂在6 h内净化效率均能保持在91%以上,尾气中ρ(NH₃)为16.6 mg/m3. 采用X线衍射(XRD)、扫描电镜与能量色谱(SEM/EDS)、N₂物理吸附(N₂-BET)对Cu/Ni/γ-Al₂O₃系催化剂表征可知,CuO是Cu/Ni/γ-Al₂O₃系催化剂的主要活性成分,与未改性γ-Al₂O₃相比,Cu、Ni改性后催化剂微孔和中孔(孔宽为1.7~15.0 nm)的孔体积有所降低,其中直径较小的中孔对HCN的催化水解起主导作用.      

Decomposition of hexachlorobenzene over Al2O3 supported metal oxide catalysts

Decomposition of hexachlorobenzene (HCB) was investigated over several metal oxides (i.e., MgO, CaO, BaO, La₂O₃, CeO₂, MnO₂, Fe₂O₃, and Co₃O₄) supported on Al₂O₃, which was achieved in closed system at a temperature of 300°C. Catalysts were prepared by incipient wetness impregnation with different metal oxides loading and impregnating solvents. The decomposition efficiency of different catalysts for this reaction depends on the nature of the metal oxide used, and Al₂O₃ supported La₂O₃ was found to be the most active one. Pentachlorobenzene (PeCB), and all tetrachlorobenzene (TeCB), trichlorobenzene (TrCB), and dichlorobenzene (DCB) isomers were detected after the decomposition reaction, indicating that the decomposition was mainly a dechlorination process. The detection of all lower chlorinated benzenes suggested the complexity of decomposition and the presence of more than one dechlorination pathway.     

Analytical solutions of three-dimensional contaminant transport in uniform flow field in porous media: A library

The purpose of this study is to present a library of analytical solutions for the three-dimensional contaminant transport in uniform flow field in porous media with the first-order decay, linear sorption, and zero-order production. The library is constructed using Green’s function method (GFM) in combination with available solutions. The library covers a wide range of solutions for various conditions. The aquifer can be vertically finite, semi-infinitive or infinitive, and laterally semi-infinitive or infinitive. The geometry of the sources can be of point, line, plane or volumetric body; and the source release can be continuous, instantaneous, or by following a given function over time. Dimensionless forms of the solutions are also proposed. A computer code FlowCAS is developed to calculate the solutions. Calculated results demonstrate the correctness of the presented solutions. The library is widely applicable to solve contaminant transport problems of one- or multiple- dimensions in uniform flow fields.     

多孔TiO2薄膜电极/泡沫镍硬模板制备及其光电催化性能

以泡沫镍为载体,活性炭为造孔剂,采用硬模板法制备泡沫镍负载多孔TiO2薄膜(Porous TiO,films/foam nicel,PTFN)电极,并利用XRD和SEM等测试手段对其结构进行表征.同时,通过亚甲基蓝溶液的光电催化降解反应,对其光电催化活性进行评价,并探讨阳极偏压、通气速率、亚甲基蓝初始溶液浓度和活性炭造孔剂量对降解效率的影响规律.结果表明:相对于未加模板造孔剂的TiO2薄膜电极的光电催化性能,泡沫镍负载多孔TiO2薄膜具有更好的光电催化性能,原因是高比表面积电极有利于为光电催化提供高浓度的亚甲基蓝分子,使反应速率加快;另外,存在最佳的光电催化降解条件,即当外加阳极偏压为3 V,通气速率为40 L·h-1,n(活性炭造孔剂最):n(前驱体中钛)(即C/Ti)为10％,亚甲基蓝溶液初始浓度为1mg·L-1时,光电催化降解效率最高.同时,研究发现,亚甲基蓝在光电催化降解过程中,通过自由基的氧化发生了C=N键的断裂去甲基化,最后被降解为H2O、CO2和SO42-、NO3-、Cl-离子.     

Efficient nitrogen doped porous carbonaceous CO2 adsorbents based on lotus leaf

In this work, the waste biomass lotus leaf was converted into N-doped porous carbonaceous CO₂ adsorbents. The synthesis process includes carbonization of lotus leaf, melamine post-treatment and KOH activation. For the resultant sorbents, high nitrogen content can be contained due to the melamine modification and advanced porous structure were formed by KOH etching. These samples were carefully characterized by different techniques and their CO₂ adsorption properties were investigated in detail. These sorbents hold good CO₂ adsorption abilities, up to 3.87 and 5.89 mmol/g at 25 and 0°C under 1 bar, respectively. By thorough investigation, the combined interplay of N content and narrow microporous volume was found to be responsible for the CO₂ uptake for this series of sorbents. Together with the high CO₂ adsorption abilities, these carbons also display excellent reversibility, high CO₂/N₂ selectivity, applicable heat of adsorption, fast CO₂ adsorption kinetics and good dynamic CO₂ adsorption capacity. This study reveals a universal method of obtaining N-doped porous carbonaceous sorbents from leaves. The low cost of raw materials accompanied by easy synthesis procedure disclose the enormous potential of leaves-based carbons in CO₂ capture as well as many other applications.     

N-doped mesoporous alumina for adsorption of carbon dioxide

N-doped mesoporous alumina has been synthesized using chitosan as the biopolymer template. The adsorbent has been thoroughly investigated for the adsorption of CO₂ from a simulated flue gas stream (15% CO₂ balanced with N₂) and compared with commercially available mesoporous alumina procured from SASOL, Germany. CO₂ adsorption was studied under different conditions of pre-treatment and adsorption temperature, inlet CO₂ concentration and in the presence of oxygen and moisture. The adsorption capacity was determined to be 29.4 mg CO₂/g of adsorbent at 55℃. This value was observed to be 4 times higher in comparison to that of commercial mesoporous alumina at a temperature of 55℃. Basicity of alumina surface coupled with the presence of nitrogen in template in synthesized sample is responsible for this enhanced CO₂ adsorption. Adsorption capacity for CO₂ was retained in the presence of oxygen; however moisture had a deteriorating effect on the adsorption capacity reducing it to nearly half the value.