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991.
Effects of particle composition and environmental parameters on catalytic hydrodechlorination of trichloroethylene by nanoscale bimetallic Ni-Fe 总被引:1,自引:0,他引:1
Jianjun Wei Yajing Qian Wenjuan Liu Lutao Wang Yijie Ge Jianghao Zhang Jiang Yu Xingmao Ma 《环境科学学报(英文版)》2014,26(5):1162-1170
Catalytic nickel was successfully incorporated into nanoscale iron to enhance its dechlorination efficiency for trichloroethylene (TCE), one of the most commonly detected chlorinated organic compounds in groundwater. Ethane was the predominant product. The greatest dechlorination efficiency was achieved at 22 molar percent of nickel. This nanoscale Ni-Fe is poorly ordered and inhomogeneous; iron dissolution occurred whereas nickel was relatively stable during the 24-hr reaction. The morphological characterization provided significant new insights on the mechanism of catalytic hydrodcchlorination by bimetallic nanoparticles. TCE degradation and ethane production rates were greatly affected by environmental parameters such as solution pH, temperature and common groundwater ions. Both rate constants decreased and then increased over the pH range of 6.5 to 8.0, with the minimum value occurring at pH 7.5. TCE degradation rate constant showed an increasing trend over the temperature range of 10 to 25℃. However, ethane production rate constant increased and then decreased over the range, with the maximum value occurring at 20℃, Most salts in the solution appeared to enhance the reaction in the first half hour but overall they displayed an inhibitory effect. Combined ions showed a similar effect as individual salts. 相似文献
992.
Mitsuhiko Hat Jiraporn Chomanee Thunyapat Thongyen Linfa Bao Surajit Tekasakul Perapong Tekasakul Yoshio Otani Masami Furuuchi 《环境科学学报(英文版)》2014,26(9):1913-1920
The characteristics of the particles of the smoke that is emitted from the burning ofbiomass fuels were experimentally investigated using a laboratory-scale tube furnace and different types of biomass fuels: rubber wood, whole wood pellets and rice husks. Emitted amounts of particles, particle-bound polycyclic aromatic hydrocarbons (PAHs) and water-soluble organic carbon (WSOC) are discussed relative to the size of the emitted particles, ranging to as small as nano-size (〈70 nm), and to the rate of heating rate during combustion, differential thermal analysis (DTA) and thermogravimetric analysis (TG) techniques were used to examine the effect of heating rate and biomass type on combustion behaviors relative to the characteristics of particle emissions. In the present study, more than 30% of the smoke particles from the burning ofbiomass fuel had a mass that fell within a range of 〈 100 nm. Particles smaller than 0.43 μm contributed greatly to the total levels of toxic PAHs and WSOC. The properties of these particles were influenced by the fuel component, the combustion conditions, and the particle size. Although TC--DTA results indicated that the heating rate in a range of 10-20℃did not show a significant effect on the combustion properties, there was a slight increase in the decomposition temperature as heating rate was increased. The nano-size particles had the smallest fraction of particle mass and particle-bound PAHs, but nonetheless these particles registered the largest fraction of particle-bound WSOC. 相似文献
993.
Mohammad Shahi Ibrahim El Saliby Andrew McDonagh Leonard D. Tijing Jong-Ho Kim Ho Kyong Shon 《环境科学学报(英文版)》2014,26(11):2348-2354
Potassium titanate nanostructures were synthesised by hydrothermal treatment of TiO2 (P25) in KOH and H2O2. As-produced powders were characterised by scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, and nitrogen adsorption-desorption methods. Longitudinally-oriented-wire-like structures with a length up to several micrometres and diameters ranging from 10 to 30 nm were obtained. Larger size fibrous nanowires resulting from the hydrotherrnal treatment showed high affinity in adsorbing crystal violet (CV), which was mainly due to their high surface area. The photocatalytic bleaching of CV solution revealed that the wires are photoactive under ultraviolet light irradiation. Macroporous nanowires are considered as effective adsorbents of CV, capable of photocatalvtic degradation, and they can be easily separated from the solution by settling. 相似文献
994.
A series of graphene–TiO2photocatalysts was synthesized by doping TiO2 with graphene oxide via hydrothermal treatment. The photocatalytic capability of the catalysts under ultraviolet irradiation was evaluated in terms of sodium pentachlorophenol(PCP-Na) decomposition and mineralization. The structural and physicochemical properties of these nanocomposites were characterized by X-ray diffraction, N2adsorption–desorption, transmission electron microscopy, scanning electron microscopy, Ultraviolet–visible diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectra, and Fourier-transform infrared spectroscopy. The graphene–TiO2nanocomposites exhibited higher photocatalytic efficiency than commercial P25 for the degradation of PCP-Na, and 63.4% to 82.9% of the total organic carbon was fully mineralized. The improved photocatalytic activity may be attributed to the accelerated interfacial electron-transfer process and the significantly prolonged lifetime of electron-hole pairs imparted by graphene sheets in the nanocomposites. However,excessive graphene and the inhomogeneous aggregation of TiO2 nanoparticles may decrease photodegradation efficiency. 相似文献
995.
Perfluorooctanoic acid (PFOA), a persistent organic pollutant, receives increasing concerns due to its worldwide occurrence and resistance to most conventional treatment processes. The photochemical decomposition by 185 nm vacuum ultraviolet (VUV) is one of the efficient methods for PFOA decomposition. The effects of pH on PFOA decomposition in nitrogen atmosphere or oxygen atmosphere were investigated. At its original pH (4.5) of PFOA aqueous solution, PFOA decomposed efficiently both in nitrogen and in oxygen atmosphere. However, when the pH increased to 12.0, PFOA decomposition was greatly inhibited in oxygen atmosphere, while it was greatly accelerated in nitrogen atmosphere with a very short half-life time (9 rain). Furthermore, fluorine atoms originally contained in PFOA molecules were almost completely transformed into fluoride ions. Two decomposi- tion pathways have been proposed to explain the PFOA decomposition under different conditions. In acidic and neutral solutions, PFOA predominantly decomposes via the direct photolysis in both atmospheres; while in the alkaline solution and in the absence of oxygen, the decomposition of PFOA is mainly induced by hydrated electrons. 相似文献
996.
研究了两种不同浓度CuO NPs(1 mg/L和10 mg/L)长期暴露对SBR反应器出水水质的影响。结果表明,在进水CuO NPs浓度为1 mg/L和10 mg/L,长期运行120 d后,SBR1(1 mg/L)和SBR2(10 mg/L)反应器出水的COD、氨氮(NH4+-N)和亚硝态氮(NO2--N)浓度与对照组(SBR0)相比没有明显变化,出水COD、NH4+-N基本被完全去除。然而,出水总磷(TP)和硝态氮(NO3--N)的浓度发生明显变化,SBR1和SBR2出水TP浓度相较于SBR0的0.20 mg/L分别升高到1.07 mg/L和1.65 mg/L,而出水NO3--N浓度相较于SBR0的5.86 mg/L分别降低为3.86 mg/L和3.01 mg/L。 相似文献
997.
998.
999.
纳米复合水凝胶的制备及其对重金属离子的吸附 总被引:1,自引:0,他引:1
以N-羟甲基丙烯酰胺(HMAm)和2-丙烯酸羟乙酯(HEA)为共聚单体,采用60Co-γ射线低温辐照法,制备了具酰胺基和羟基的新型聚合物水凝胶p(HMAm/HEA),运用原位沉淀法制备了纳米复合水凝胶HMO-p(HMAm/HEA),用于对重金属离子Pb~(2+)和Cu~(2+)的去除.应用SEM、TEM、FTIR等方法对水凝胶进行表征,表征结果证明p(HMAm/HEA)是HMAm和HEA的共聚产物,且纳米水合氧化锰(HMO)成功负载.探讨了溶液初始p H值、反应温度、重金属初始浓度、反应时间、竞争性Ca~(2+)和Na+浓度等因素对纳米复合水凝胶吸附过程的影响,研究表明HMO-p(HMAm/HEA)对Pb~(2+)和Cu~(2+)的吸附过程不受温度的影响;吸附量随着溶液初始p H的升高而增加;吸附过程属于Langmuir单分子层吸附;吸附动力学过程符合准二级动力学吸附;高浓度的Ca~(2+)和Na~+对吸附过程影响不大.XPS图谱进一步证明吸附机制是重金属离子与羟基间的离子交换作用.采用0.05 mol·L~(-1)的HCl溶液为脱附剂,经过4次吸附-脱附循环再生后,纳米复合水凝胶重复利用性好. 相似文献
1000.
生物法回收贵金属铂纳米颗粒及其机制 总被引:1,自引:1,他引:0
利用自行分离的粪肠球菌Z5(Enterococcus faecalis Z5)菌株(保藏号CCTCC M2012445)回收贵金属铂,探讨了其在外源电子供体条件下以纳米颗粒形式回收溶液中化合态铂的可能性,研究了铂初始浓度、生物量、温度以及p H值对回收过程的影响,探讨了粪肠球菌Z5回收铂纳米颗粒过程的可能机制.结果表明,粪肠球菌Z5菌株可以回收铂纳米颗粒,回收过程主要包括生物吸附和生物还原.铂初始浓度为286.46 mg·L~(-1)、生物量为3.2 g·L~(-1)、温度50℃以及p H值为6时为其最佳回收条件.X射线衍射(XRD)和透射电镜(TEM)分析表明,回收产物为5 nm左右粒径的铂纳米颗粒,主要分布于细胞周质.X射线电子能谱(XPS)分析显示,Pt(Ⅳ)首先被还原为Pt(Ⅱ),然后被还原为Pt(0),且从Pt(Ⅱ)还原成Pt(0)为限制步骤,傅里叶红外(FTIR)分析显示菌体表面的羟基和酰胺基官能团可能在回收过程中起作用. 相似文献