还原氧化石墨烯负载零价铁的合成及对TNT废水处理

选取比表面积大且导电性能优良的还原氧化石墨烯(rGO)作为支撑材料,负载还原性强但极易团聚的纳米零价铁(nZVI),制得还原氧化石墨烯负载零价铁(nZVI/rGO)复合材料.通过X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、扫描电子显微镜(SEM)与X射线光电子能谱(XPS)等测试手段对零价铁的负载情况、材料表面微观形貌与反应前后nZVI/rGO材料表面铁元素的含量与组成进行表征.考察了溶液初始pH值、材料投加量和理论零价铁负载量等因素对nZVI/rGO去除2,4,6-三硝基甲苯(TNT)的影响,研究了nZVI/rGO材料去除TNT的反应机理.通过正交实验可知, nZVI/rGO对含TNT废水的处理在较宽的反应条件范围内都可达到处理要求,在理论零价铁的负载量为3.0 g/g rGO,溶液初始pH为6,材料投加量为40 g/L时效果最佳,可将废水中TNT处理到检出限0.1 mg/L以下.     

负载零价铁膨胀石墨的合成及对水中NO3-去除的效果与机制

以网络状孔型结构发达的膨胀石墨（EG）为载体,采用化学沉积法制备了负载零价铁（ZVI）的膨胀石墨（EG-ZVI）.利用扫描电子显微镜（SEM）、X射线衍射（XRD）仪及X射线光电子能谱仪（XPS）等对负载及反应前后的EG-ZVI进行表征,探究了EG-ZVI对硝酸根（NO₃^-）的去除效果并对其反应产物及机理进行了分析.结果表明,亚微米级零价铁已负载到EG石墨表面,且分布均匀;与EG相比,EG-ZVI对NO₃^-的去除能力显著提升,其去除率是EG的2.3倍.得益于铁碳原电池效应,EG-ZVI对pH依赖性比零价铁低,即使在pH=9的条件下,NO₃^-去除率依然能达到65%以上,是单独用零价铁处理时的1.83倍;EG-ZVI去除NO₃^-是吸附和还原过程共同作用的结果,符合三级动力学模型,其还原过程由负载在EG表面的零价铁发生腐蚀提供电子,从而还原NO₃^-产生以NH₄⁺-N为主的含氮化合物;EG-ZVI对NO₃^-具有较强的还原吸附作用,并能解决零价铁在反应过程中生成惰性层或金属氢氧化物导致去除效率低的缺陷,使其在含NO₃^-废水的处理中具有较高的应用潜力.     

制备高活性纳米零价铁的甘露醇改性机理

纳米零价铁(Nano zero-valent iron,nZVI)被广泛应用于水污染治理,高纯度且分散性良好的nZVI的制备方法一直是研究热点.本文采用含不同羟基数目的醇(乙醇、乙二醇、赤藓糖醇、甘露醇和山梨醇)作为改性剂,分别制备得到n ZVI-EA,nZVI-EG,nZVI-ER,nZVI-M和nZVI-S样品.将上述样品应用于水中微囊藻毒素(Microcystin-LR,MC-LR)的还原去除.结果表明,随着改性剂羟基数目的增多,改性nZVI的抗氧化能力和分散性增强,对MC-LR的降解反应速率也随之提高.nZVI-M去除MC-LR的表面积校正特征速率常数(79.35×10^-5L·m^?2·min^?1)是nZVI-S(8.55×10^-5 L·m^?2·min^?1)的9.3倍,是未改性样品nZVI₀(1.30×10^-5 L·m^?2·min^?1)的61.0倍.通过X射线衍射...     

纳米零价铁复合材料制备、稳定方法及其水处理应用

纳米零价铁(nZVI/Fe⁰)因极高的催化活性和经济适用性备受关注,但实际推广中受团聚性和空气不稳定性等限制。为解决这些问题,近年来国内外学者研究开发了系列纳米零价铁的复合材料和稳定方法,在制备方法、基体材料和环境修复方面均有了较大进展。本文对近五年的研究成果进行汇总,从复合载体研究、稳定方法和水环境应用三个方面对纳米零价铁复合材料研究进行较全面的综述和展望。在纳米零价铁负载方面,本文对聚合物载体、黏土矿物、碳材料和金属氧化物载体的相关研究进行了总结;在颗粒稳定性方面着重讨论了复合金属、表面涂层、硫化方面的新成果;在水环境应用方面,本文指出纳米零价铁主要通过吸附、还原、络合、共沉淀、电化学反应、(类)芬顿氧化等过程实现水中的重金属以及有机物的去除,光、热、电、超声、微波的引入可显著增强水体中污染物的处理效果。     

功能性纳米零价铁的构筑及其对环境放射性核素铀的富集应用研究进展

随着核能的广泛应用和核技术的快速发展,环境中放射性核素铀的污染日益严峻.纳米零价铁（Nanoscale Zero Valent Iron：nZVI）因其具有廉价、制备简便、高表面活性及对铀高效的吸附性能等特性而逐渐成为环境中铀污染处理的良好材料.采用可行的方法制备纳米零价铁复合材料,借助单体材料之间的协同效应可进一步提高材料对铀酰的吸附性能.因此,纳米零价铁复合材料的制备以及应用成为近期环境科学领域的研究热点之一.针对纳米零价铁及其复合材料对环境中铀酰的去除研究进行了概述和展望,包括纳米零价铁及其复合材料的制备方法、去除效果及去除机理,并且简要探讨了纳米零价铁及其复合材料在环境放射性污染治理的应用前景,以期为今后的深入研究和实际应用提供参考依据.     

生物炭负载纳米零价铁的制备及其在环境修复中的研究进展[1]

纳米零价铁（nZVI）作为一种高效还原性修复材料被广泛应用于多种污染物的去除,但易团聚、易被氧化失活的缺陷使其应用受到局限。近年来,研究者们通过将nZVI负载在多孔生物炭（BC）上来改善其本身缺陷,以期提高其应用潜力。本文综述了近年来nZVI/BC的制备方法及优缺点,总结分析了nZVI/BC对水体、土壤和沉积物中多种有机和无机污染物的去除效果和机理。同时综述了不同老化方法对nZVI/BC稳定性和反应活性的影响。在此基础上,在改进nZVI/BC制备技术、应用范围的拓展、潜在的生态和健康风险、探索老化过程和老化机制等方面进行了展望,旨在为nZVI/BC的理论研究和工程实践提供借鉴和参考。     

纳米零价铁去除水体中砷的效能与机理

全球超过一亿人受到高毒性、难处理的砷污染引发的饮用水安全的威胁,解决砷污染问题迫在眉睫而又任重道远。纳米零价铁(nZVI)能高效去除重(类)金属、硝酸盐、磷酸盐、高氯酸盐、卤代物、多环芳烃、偶氮染料和苯酚等污染物,成为广泛应用的工程纳米材料之一,在全球已有近60例的环境原位修复和废水处理工程案例。其独特的纳米级核壳结构和表面性质使其能够通过吸附、还原和沉淀等多种作用高效去砷。本文综述了近年来nZVI及其改性材料去除水中砷的研究进展,探讨了nZVI去除水中As(Ⅲ)和As(Ⅴ)的反应机理,归纳了不同反应条件(初始pH值、反应时间、nZVI投加量、砷初始浓度、共存离子和有机质)对去除效果的影响,总结了nZVI改性材料(多孔材料负载改性nZVI、金属掺杂改性nZVI、表面稳定剂改性nZVI和绿色合成nZVI)对砷的去除效率,展望了纳米零价铁去除砷的发展方向和所面临的挑战。     

纳米零价铁对水中砷和硒去除的比较研究

采用纳米零价铁去除水中的砷和硒,考察了不同溶解氧、纳米零价铁投加量、接触时间以及溶液初始pH值等条件下纳米零价铁去除水中砷和硒的效果,并比较了反应前后固体的形貌、组成、溶液pH值及反应机制.结果表明,纳米零价铁可广泛用于去除水中的砷/硒污染,去除效果顺序依次为Se（IV）> As（Ⅲ）> Se（VI）> As（V）;水中溶解氧（DO）对As（Ⅲ）和Se（IV）的去除没有显著的影响,而高浓度的DO对As（V）和Se（VI）的去除产生了一定的抑制作用;增加纳米零价铁投加量可促进砷和硒的去除;溶液初始pH值对纳米零价铁去除As（Ⅲ）,As（V）和Se（VI）的影响较大,而对Se（IV）的去除几乎没有影响;反应后固体的形貌、组成及溶液pH值存在差异.纳米零价铁与砷、硒反应机理的不同造成了去除效果及反应后固液两相的差异.     

氢气热处理活性炭表面模板法生长立方多孔银

通过氢气高温处理调控成型活性炭（MAC）的表面官能团及孔结构,然后先后吸附Cl^-和Ag⁺,以形成的立方AgCl作为牺牲模板,经MAC表面官能团还原制备出立方多孔银.用扫描电子显微镜（SEM）和X射线衍射（XRD）表征了产物的形貌和相结构,并用X射线光电子能谱（XPS）分析了成型活性炭不同处理阶段的表面官能团.研究了制备过程中氢气处理温度、Cl^-预吸附液的浓度、Ag⁺浓度及Ag⁺前驱体种类等对MAC表面生长银形貌的影响.结果表明,氢气预处理一方面可降低MAC表面含氧官能团的数量,调控MAC还原能力;另一方面可提高MAC比表面积,有利于Cl^-的吸附及AgCl模板的形核.通过氢气预处理,在合适的Cl^-,Ag⁺浓度及Ag⁺前驱体条件下,可在成型活性炭表面获得外形规整的立方多孔银.     

Ag+/Ag/ZnO多孔纳米结构纤维材料的制备及可见光催化性能

借助棉花纤维模板, 采用两步法制备了Ag⁺/Ag/ZnO多孔纳米结构纤维材料, 并利用X射线衍射(XRD)、 X射线光电子能谱(XPS)、 扫描电子显微镜(SEM)和紫外-可见光谱(UV-Vis)等对其进行了表征. 以亚甲基蓝(MB)的脱色降解为模型反应, 考察了银修饰量(摩尔分数, 0~1.50%)对ZnO纳米结构纤维材料光催化性能的影响. 结果表明, 利用模板辅助的两步法制备了Ag⁺-Ag共修饰的ZnO多孔纳米结构纤维材料Ag⁺/Ag/ZnO, Ag⁺和Ag通过改变ZnO的晶胞结构、 光吸收特性及形貌等影响其光催化性能; 在可见光条件下, Ag⁺/Ag/ZnO的催化性能优于纯ZnO, 且与修饰量有关.     

银元素的循环实验

设计并完成了由5步构成的银元素的循环实验,从银粉出发,经过银在硝酸中溶解,银离子与氯离子反应生成氯化银沉淀,氯化银溶解于氨水,银氨络离子与乙炔反应生成乙炔银,水合肼将乙炔银还原为单质银等化学反应,完成了银的循环实验。     

Idiosyncratic Ag7Pt2O7: An Electron Imprecise yet Diamagnetic Small Band Gap Oxide

The seminal qualitative concepts of chemical bonding, as presented by Walter Kossel and Gilbert Newton Lewis back in 1916, have lasting general validity. These basic rules of chemical valence still serve as a touchstone for validating the plausibility of composition and constitution of a given chemical compound. We report on Ag₇Pt₂O₇, with a composition that violates the basic rules of chemical valence and an exotic crystal structure. The first coordination sphere of platinum is characteristic of tetravalent platinum. Thus, the electron count corresponds to Ag₇Pt₂O₇*e⁻, where excess electrons are associated with the silver substructure. Such conditions given, it is commonly assumed that the excess electrons are either itinerant or localized in Ag−Ag bonds. However, the material does not show metallic conductivity, nor does the structure feature Ag-Ag pairs. Instead, the excess electrons organize themselves in 2e−4c bonds within the silver substructure. This subvalent silver oxide reveals a new general facet pertinent to silver chemistry.     

Influence of Temperature and Time on the Stability of Silver in Silica Sol-Gel Glasses

The darkening of silica sol-gel glasses doped with 0.05 mol% silver was studied. Six sols were prepared from TEOS and silver nitrate. Different additives were used, to influence the chemical and physical states of silver: oxidizing or reducing agents (H₂O₂, As₂O₅), colloid stabilizer (sodium citrate) and network modifiers (Li₂O, CaO). Sols were gelified at 60°C and densified at 600°C. The samples without additives and those prepared with H₂O₂ at room temperature even if they were protected from light. With increased temperature, the darkening became samples were heated above, 400°C, reversible bleaching took place. This darkening-bleaching is of thermal nature (“thermochromic effect”) and seems to be determined by a reversible aggregation-disaggregation of tiny silver particles. The presence of sodium citrate, as an additive delayed the darkening effect and the presence of CaO delayed it even further. Lithium oxide inhibited it totally.     

In-Situ Formation of AgCl Nanocrystallites in Films Prepared by the Sol-Gel and Silver Nanoparticles in Silica Glass Films

We are reporting on a novel preparation of silver chloride in sol-gel silica films as a precursor for nanoparticles of silver. The precipitation of silver chloride particles in-situ was achieved by the reaction of silver nitrate with trichloroacetic acid. The reaction leads to a slow release of chloride leading to a controlled precipitation of AgCl. The existence of an isotropic crystalline AgCl phase in the glass films was demonstrated by X-rays Diffraction Analysis (XRD) and Scanning Electron Microscope and Energy Dispersive Analysis of X-rays (SEM-EDAX). The resulting films are of good optical quality and exhibit a strong coloration upon irradiation with sunlight or heating to 600°C, due to the reduction of AgCl to silver nanoparticles. The absorption spectra of the films before and after irradiation are shown.     

银/聚合物纳米复合材料

银/聚合物纳米复合材料是一种典型的聚合物基复合材料, 其结构和性能依赖于合成方法,因此开发材料的优异性能必须以深入研究纳米材料的先进合成技术为前提。本文综述了纳米银粒子及其与聚合物形成的纳米复合材料的最新合成进展, 重点介绍了基于液相化学还原方法合成纳米银粒子的新方法, 如溶胶-凝胶法、沉淀法、微乳液法和离子液体法, 以及纳米银粒子的分散技术和原位法合成银/聚合物纳米复合材料的新技术, 并介绍了纳米银复合材料的电绝缘性、表面增强拉曼散射性能、抗菌性及其在生物医学等领域中的应用。     

单分散性银纳米粒子的可控制备

以卤化银或氧化银作为前驱体,室温下以水为溶剂,在较高溶液浓度下,利用化学还原法制备了单分散性银纳米粒子,并通过改变前驱体的种类,实现了粒径可控制备。采取扫描电子显微镜（SEM）、紫外-可见光谱仪（UV-Vis）、X射线-粉末衍射仪（XRD）、X射线-光电子能谱仪（XPS）等对所制备的银纳米粒子的形貌及成分进行了表征。结果显示,所制备的银纳米粒子具有较高的单分散性,粒径在40~150 nm之间,具有面心立方多晶结构。该方法制备的银纳米粒子可用于喷墨打印RFID天线。     

Resonance Light Scattering Spectra of Silver Thiocyanate System and its Application in Analysis

A novel determination method of Ag^＋ was established. In acetic acid-sodium acetate buffer （pH 5.0） medium, Ag^＋ reacts with SCN^- to form AgSCN in the presence of TritonX-100,which results in an increase of resonance light scattering （RLS）and giving a new RLS spectrum.The maximum RLS peak was at 585 nm,The enhancement of resonance light scattering at 585 nm was proportional to the concentration of Ag^＋ ranging from 0.0045-4.00μg mL^-1 （r=9991）,and the detection limit was 1.37 ng mL^-1 with the recovery of 97.70%- 104.80%。     

Fabrication of a Simple and Cheap Screen-printed Silver/Silver Chloride (Ag/AgCl) Quasi-reference Electrode

In this work, a silver/silver chloride ink is fabricated using two steps. First the silver ink is prepare using silver, nail polish and acetone. Then the silver ink is painted in a paper substrate and a silver chloride layer is deposited using a bleach solution. The result is the silver/silver chloride conductive ink. The silver ink is cheap ($2.49/g), well-dispersive and very easy to fabricate. The materials were characterized by SEM and XRD. The Ag ink showed the formation of a continuous network throughout the silver ink film with fewer agglomeration. The effective chlorination process was also observed in the Ag/AgCl characterization. Since the Ag/AgCl substrate will be used as a quasi-reference electrode, it is important to investigate the electrical properties. The Ag ink showed an average ohmic resistance of 2.27 Ω. The addition of the AgCl layer decreases the conductivity, as expected. In summary, the Ag/Ag/Cl ink developed is simple, well-dispersed, cheap and with good conductivity. Therefore, it can be used as a conductive ink in the fabrication of quasi-reference electrodes.     

银纳米微球和银纳米棒自组装膜的制备及SERS研究

采用硼氢化钠还原硝酸银,用振荡器在不同转速下振荡得到单分散的银纳米微球和银纳米棒,再将银纳米微球及银纳米棒自组装于被3-氨丙基-三甲氧基硅烷(APTMS)修饰的玻璃基片上,制得了具有表面增强拉曼(SERS)活性的基底,分别以罗丹明6G(R6G)和罗丹明B(RB)为探针分子对这两种基底进行SERS活性检测,结果发现这两种基底均为较理想的SERS衬底。     

A study of the silver form of a natural zeolitic material of the clinoptilolite type

The silver forms of a natural zeolitic material (from the East Slovakian deposit) on the clinoptilolite type has been prepared. The silver forms of the natural zeolitic material were investigated by X-ray powder diffractometry, IR spectroscopy, ESCA measurements, scanning electron microscopy and conductivity measurements. Depending on the preparation conditions, the content of silver ions in the zeolitic products was found to be in the range from 16 to 24%. In the sample with a silver loading of 18.6%, the silver uptake is due to an ion exchange process, mostly involving Na(I), Ca(II) and Mg(II) ions.