Bimetallic nickel molybdate supported Pt catalyst for efficient removal of formaldehyde at low temperature

Efficient removal of formaldehyde from indoor environments is of significance for human health.In this work,a typical binary transition metal oxide that could provide various oxidation states,β-NiMoO_4,was employed as a support to immobilize the active Pt component(Pt/NiMoO_4) for catalytic formaldehyde elimination at low ambient temperature(15℃).The results showed that the hydrothermal preparation temperature and time had a noticeable impact on the morphology and catalytic activity of the samples.The catalyst prepared with hydrothermal temperature of 150℃ for 4 hr(Pt-150-4) exhibited superior catalytic activity and stability mainly due to its distinctly porous structure,relative abundance of adsorbed surface hydroxyls/water,and high oxidation ability,which resulted from the interaction of Pt with Ni and Mo of the bimetallic NiMoO_4 support.Our results might shed light on the rational design of multifunctional catalysts for removal of indoor air pollutants at low ambient temperature.     

Environmental fate and behavior of silver nanoparticles in natural estuarine systems

Silver nanoparticles (AgNPs) are widely used in many consumer products, whereas their environmental behaviors in natural aquatic systems remain unknown, especially in natural brackish media. Therefore, it is urgent to investigate the environmental fate of AgNPs in natural brackish waters. Here, we investigated the stability of citrate-coated AgNPs in natural brackish water collected from 6 different sites with distinct salinities in the Xinglinwan Reservoir, located in Xiamen City, southeast China. The obtained results showed that AgNP colloids remained stable in low-salinity waters, which was mainly determined by the effects of dissolved organic matter (DOM) promoting the stability of the nanoparticles. However, the environmental fate of AgNPs in high-salinity waters was dominated by the salinity or ionic strength, especially the free ion concentrations of Cl^?, SO₄^2?, or S^2?, resulting in rapid sedimentation and dissolution. In addition, both DOM and salinity contributed to the environmental behavior of AgNPs in moderate-salinity waters, ultimately resulting in either colloidal stability or sedimentation. Overall, these results may reveal that AgNPs remain relatively stable for a long period in low-salinity natural waters, and that the stability might gradually decrease as AgNPs are transferred from freshwaters through brackish waters and eventually end up in seawater along the bay. Our findings also further indicate that the toxicity and potential risks of AgNPs may present more serious threats to the environment and organisms in natural freshwaters than in natural estuarine systems or seawater.     

nZVI@mesoSiO2的可控合成及应用性能研究

采用改进的两步法在原位基础上合成了以纳米零价铁(nano Zero Valent Iron,nZVI)为核芯的核壳型介孔二氧化硅(nZVI@mesoSiO_2).同时,通过简单地调控铁源用量得到具有单一nZVI核芯和不同壳层厚度的核壳型纳米复合材料.结果发现,铁源用量的增加会导致核芯尺寸减小、壳层厚度增加及颗粒比表面积下降.当铁源用量为2.78 g时,得到的nZVI@mesoSiO_2不仅具有较高的比表面积和单一且均匀的孔径分布,而且对2,4,6-三氯苯酚(2,4,6-Trichlorophenol, 2,4,6-TCP)的去除表现出很高的性能.影响因素实验表明,材料的最佳投加量为1.0 g·L~(-1),体系适宜初始pH为5.0,污染物初始浓度升高会导致去除效果下降,并且反应体系内乙二胺四乙酸(EDTA)的存在可以提高2,4,6-TCP的去除率.材料的重复利用实验结果表明,经过多次循环反应后会导致材料nZVI核芯的失活和孔道的堵塞.本研究不仅为制备可控壳层厚度的核壳型介孔材料提供了理论指导,而且为进一步改性合成对2,4,6-TP具有高选择性的复合材料提供了依据.     

腐殖酸作用下酸性多孔介质中纳米TiO2的迁移与滞留机制

探讨了富里酸（FA）和胡敏酸（HA）存在条件下饱和石英砂填充柱中纳米二氧化钛（nTiO₂）的迁移和滞留机制.结果表明,pH 4.0条件下,不存在FA和HA时,nTiO₂不发生迁移;FA和HA吸附到nTiO₂表面,改变nTiO₂电动性质,促进其在饱和多孔介质柱中迁移.随着FA和HA浓度由1mg/L升高至10mg/L,nTiO₂的流出率（填充柱流出液与进液中nTiO₂总量的比值）分别由0.01和0.88升高至0.91和0.94;相同条件下,HA在nTiO₂表面的吸附量比FA大,对nTiO₂迁移性的促进作用也更大.离子抑制nTiO₂的迁移,且CaCl₂影响大于NaCl.相同NaCl浓度,与FA相比,HA作用下nTiO₂的迁移性更强,并且7%~56%的nTiO₂沉降在第二极小势能区,高于FA作用下的4%~17%,更易被重新释放.nTiO₂与石英砂之间的高势垒促进nTiO₂的迁移,而低势垒、第二最小势能、阻塞作用、扩散和重力沉降是nTiO₂滞留的主要原因.     

纳米银对聚磷菌吸磷和释磷的影响及毒性效应

利用硼氢化钠还原硝酸银,并使用聚乙烯醇（PVA）作为分散剂,制备出分散良好、粒径为（14±3）nm的纳米银颗粒,考察了其对聚磷菌（Microlunatus phosphovorus）好氧吸磷和厌氧释磷的影响,以及产生的毒性效应.结果表明,在好氧状态下,7mg/L的纳米银能够完全抑制聚磷菌的生长（P <0.01）,达到10mg/L时才能完全抑制聚磷菌的吸磷能力（P=0.01）;在厌氧状态下,大于20mg/L的纳米银才使聚磷菌释磷能力受到部分抑制（P <0.05）.活性氧簇（ROS）和扫描电子显微镜（SEM）的检测结果表明,纳米银使细菌体内ROS水平降低,部分细菌菌体表面塌陷,这说明,纳米银不但可以毒害聚磷菌菌体表面,还可以降低菌内ROS水平.     

Interactions between engineered nanoparticles and dissolved organic matter: A review on mechanisms and environmental effects

Dissolved organic matter (DOM) is ubiquitous in the environment and has high reactivity. Once engineered nanoparticles (ENPs) are released into natural systems, interactions of DOM with ENPs may significantly affect the fate and transport of ENPs, as well as the bioavailability and toxicity of ENPs to organisms. However, because of the complexity of DOM and the shortage of useful characterization methods, large knowledge gaps exist in our understanding of the interactions between DOM and ENPs. In this article, we systematically reviewed the interactions between DOM and ENPs, discussed the effects of DOM on the environmental behavior of ENPs, and described the changes in bioavailability and toxicity of ENPs caused by DOM. Critical evaluations of published references suggest further need for assessing and predicting the influences of DOM on the transport, transformation, bioavailability, and toxicity of ENPs in the environment.     

纳米Fe3O4/H2O2降解诺氟沙星

采用纳米Fe3O4催化H2O2氧化降解水环境中的诺氟沙星.考察了溶液酸度、温度、催化剂和H2O2浓度对诺氟沙星降解的影响,对比不同底物在Fe3O4/H2O2体系中的降解情况,并进一步探讨了其反应机制.结果表明,溶液酸度显著影响诺氟沙星的降解率,在酸性条件下（pH=3.5）诺氟沙星的降解效率最高.诺氟沙星的降解率随纳米F...     

Silver nanoparticles tolerant bacteria from sewage environment

Silver nanoparticle (SNP) is a threat to soil, water and human health. Protection of environment from silver nanoparticles is a major concern. A sewage isolate, Bacillus pumilus treated with SNPs showed similar growth kinetics to that without nanoparticles. A reduction in the amount of exopolysaccharides was observed after SNPs – B. pumilus culture supernatant interaction. The Fourier transform infrared spectroscopy (FT-IR) peaks for the exopolysaccharides extracted from the bacterial culture supernatant and the interacted SNPs were almost similar. The exopolysaccharide capping of the SNPs was confirmed by UV-Visible, FT-IR and X-ray di raction analysis. The study of bacterial exopolysaccharides capped SNPs with E. coli, S. aureus and M. luteus showed less toxicity compared to uncoated SNPs. Our studies suggested that the capping of nanoparticles by bacterially produced exopolysaccharides serve as the probable mechanism of tolerance.     

介孔磁性微球的制备表征及其在环境中的应用

文章在Fe3O4(magnetite)纳米粒子的表面包覆一层SiO2(silica),再以十六烷基三甲基溴化铵(CTAB)表面活性剂作为结构导向剂,包覆一层介孔SiO2,形成一种核壳式介孔磁性二氧化硅材料(MS),然后在其表面引进巯基(mercapto)从而成为一种新型巯基修饰的磁性二氧化硅载体(MMS).这种材料是介...     

长江口水环境中纳米颗粒物初探

利用抽滤及切向超滤（cross-flow ultrafiltration,CFUF）技术对长江口水环境中的纳米级颗粒物（NP）进行了有效地分离,对其理化性质进行表征,进而初步探讨了水环境因子对NP理化特性的影响机制.结果表明,长江口水环境中NP粒径变化范围为69.5～263.5 nm,平均值为157.3 nm;Zeta...