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Polybrominated diphenyl ethers (PBDEs) are recognized as a new class of widely-distributed and persistent contaminants for which effective treatment and remediation technologies are needed. In this study, two kinds of commercially available nanoscale Fe0 slurries (Nanofer N25 and N25S), a freeze-dried laboratory-synthesized Fe0 nanoparticle (nZVI), and their palladized forms were used to investigate the effect of particle properties and catalyst on PBDE debromination kinetics and pathways. Nanofers and their palladized forms were found to debrominate PBDEs effectively. The laboratory-synthesized Fe0 nanoparticles also debrominated PBDEs, but were slower due to deactivation by the freeze-drying and stabilization processes in the laboratory synthesis. An organic modifier, polyacrylic acid (PAA), bound on N25S slowed PBDE debromination by a factor of three to four compared to N25. The activity of palladized nZVI (nZVI/Pd) was optimized at 0.3 Pd/Fe wt% in our system. N25 could debrominate selected environmentally-abundant PBDEs, including BDE 209, 183, 153, 99, and 47, to end products di-BDEs, mono-BDEs and diphenyl ether (DE) in one week, while nZVI/Pd (0.3 Pd/Fe wt%) mainly resulted in DE as a final product. Step-wise major PBDE debromination pathways by unamended and palladized Fe0 are described and compared. Surface precursor complex formation is an important limiting factor for palladized Fe0 reduction as demonstrated by PBDE pathways where steric hindrance and rapid sequential debromination of adjacent bromines play an important role. 相似文献
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Solid phase reactions of Cr(Ⅵ) with Fe(0) were investigated with spherical-aberration-corrected scanning transmission electron microscopy(Cs-STEM) integrated with X-ray energy-dispersive spectroscopy(XEDS). Near-atomic resolution elemental mappings of Cr(Ⅵ)–Fe(0) reactions were acquired. Experimental results show that rate and extent of Cr(Ⅵ) encapsulation are strongly dependent on the initial concentration of Cr(Ⅵ) in solution. Low Cr loading in nZⅥ(1.0 wt%) promotes the electrochemical oxidation and continuous corrosion of n ZⅥ while high Cr loading(1.0 wt%) can quickly shut down the Cr uptake. With the progress of iron oxidation and dissolution, elements of Cr and O counter-diffuse into the nanoparticles and accumulate in the core region at low levels of Cr(Ⅵ)(e.g., 10 mg/L). Whereas the reacted n ZⅥ is quickly coated with a newly-formed layer of 2–4 nm in the presence of concentrated Cr(Ⅵ)(e.g., 100 mg/L). The passivation structure is stable over a wide range of pH unless pH is low enough to dissolve the passivation layer. X-ray photoelectron spectroscopy(XPS) depth profiling reconfirms that the composition of the newly-formed surface layer consists of Fe(Ⅲ)–Cr(Ⅲ)(oxy)hydroxides with Cr(Ⅵ) adsorbed on the outside surface. The insoluble and insulating Fe(Ⅲ)–Cr(Ⅲ)(oxy)hydroxide layer can completely cover the n ZⅥ surface above the critical Cr loading and shield the electron transfer. Thus, the fast passivation of nZⅥ in high Cr(Ⅵ) solution is detrimental to the performance of nZⅥ for Cr(Ⅵ) treatment and remediation. 相似文献
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We explored the feasibility and removal mechanism of removing 2-chlorobiphenyl(2-Cl BP)from soil–water system using granular activated carbon(GAC) impregnated with nanoscale zerovalent iron(reactive activated carbon or RAC).The RAC samples were successfully synthesized by the liquid precipitation method.The mesoporous GAC based RAC with low iron content(1.32%) exhibited higher 2-Cl BP removal efficiency(54.6%) in the water phase.The result of Langmuir–Hinshelwood kinetic model implied that the different molecular structures between 2-Cl BP and trichloroethylene(TCE) resulted in more difference in dechlorination reaction rates on RAC than adsorption capacities.Compared to removing2-Cl BP in the water phase,RAC removed the 2-Cl BP more slowly in the soil phase due to the significant external mass transfer resistance.However,in the soil phase,a better removal capacity of RAC was observed than its base GAC because the chemical dechlorination played a more important role in total removal process for 2-Cl BP.This important result verified the effectiveness of RAC for removing 2-Cl BP in the soil phase.Although reducing the total RAC removal rate of 2-Cl BP,soil organic matter(SOM),especially the soft carbon,also served as an electron transfer medium to promote the dechlorination of 2-Cl BP in the long term. 相似文献
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双表面活性剂修饰下纳米零价铁对水中Cr(Ⅵ)污染去除研究 总被引:1,自引:0,他引:1
为解决纳米级零价铁(nZVI)在环境中易团聚、易氧化的问题,强化其去除水中Cr(VI)的能力,选择非离子型表面活性剂聚乙烯吡咯烷酮(PVP)和阴离子表面活性剂油酸钠(NaOA)同时对nZVI进行修饰.同时,通过对比不同pH值、材料干湿状态、初始浓度及共存离子条件下的反应效果,结合材料的XRD和XPS表征、动力学实验和25℃等温线的拟合进行机理分析.结果表明:酸性条件有利于Cr(VI)的去除;材料的干湿状态对去除效率影响较大;材料去除水中Cr(VI)可在3 h内达到反应平衡,去除效率在90%以上,实验条件下最大去除量为183.1 mg·g-1,反应过程符合准二级动力学模型及Langmuir模型;反应过程中Cr(VI)大部分转化为Cr(Ⅲ). 相似文献
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Toxicity studies considering both the bare and stabilized forms of zero valent iron nanoparticles (nZVI) could be timely, given that ecological risks identified are minimized through modification or with substitution of approaches in the synthesis, development and environmental application of the nanoparticles before succeeding to volume production. This review is focused on the fate, transport and toxicological implications of the bare nZVI and surface modified particles used for environmental applications. 相似文献
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本研究系统分析了不同初始砷浓度和不同nZVI投加量等条件下,nZVI去除As(III)和As(V)的动力学过程和除砷性能.结果表明,nZVI可快速有效地去除As(III)和As(V),除砷过程均符合准二级动力学模型,且As(III)的去除速率明显快于As(V).在砷浓度为5 mg·L-1时,As(III)去除速率常数达最大值0.30 g·mg-1·min-1,为As(V)去除速率(0.034 g·mg-1·min-1)的8.8倍.Weber-Morris粒子内扩散模型拟合结果表明,nZVI除砷速率是由外扩散和颗粒内扩散共同控制的.分析反应平衡时砷浓度测定结果,发现不同砷浓度条件下nZVI对As(III)的去除量为As(V)的1.5~2.6倍,nZVI对砷的去除量随初始砷浓度增加而降低,随nZVI投加量增加而增加.砷浓度为50.0 mg·L-1时,As(III)和As(V)去除量达到最高,分别为152.14 mg·g-1和62.02 mg·g-1,均高于传统(羟基)氧化铁对As(III)和As(V)的去除量.因此,nZVI可高效去除水中As(III)和As(V),且用于修复以As(III)污染为主的地下水更具有优势. 相似文献
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Rong Cheng Yingying Zhang Tao Zhang Feng Hou Xiaoxin Cao Lei Shi Peiwen Jiang Xiang Zheng Jianlong Wang 《Frontiers of Environmental Science & Engineering》2022,16(8):108
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通过向厌氧氨氧化反应器(ASBR)中投加纳米单质铁(nZVI),考察了其对厌氧氨氧化反应(ANAMMOX)脱氮性能的影响.结果表明,在温度为(25±0.5)℃,pH值为7.5±0.5,进水NH4+-N和NO2--N浓度分别为30.35mg/L和37.89mg/L条件下,分别投加0,10,50,100.200,500,1000mg/L nZVI时,总氮去除率(NRE)分别达到70.27%、74.25%、83.45%、90.16%、68.59%、57.18%、50.93%.用修正的Boltzmann、Gompertz、Logistic模型对其进行动力学分析,R2值分别为0.9963、0.9944、0.9851,总氮(TN)出水浓度和NRE的预测值与实际值比较,其均方误差值分别为2.13、6.31、8.48和6.93、7.47、10.95. 相似文献
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Graphene-supported nanoscale zero-valent iron:Removal of phosphorus from aqueous solution and mechanistic study 总被引:1,自引:0,他引:1
Fenglin Liu JingHe Yang Jiane Zuo Ding M Lili Gan Bangmi Xie Pei Wang Bo Yang 《环境科学学报(英文版)》2014,26(8):1751-1762
Excess phosphorus from non-point pollution sources is one of the key factors causing eutrophication in many lakes in China,so finding a cost-effective method to remove phosphorus from non-point pollution sources is very important for the health of the aqueous environment. Graphene was selected to support nanoscale zero-valent iron(nZVI)for phosphorus removal from synthetic rainwater runoff in this article. Compared with nZVI supported on other porous materials,graphene-supported nZVI(G-nZVI) could remove phosphorus more efficiently. The amount of nZVI in G-nZVI was an important factor in the removal of phosphorus by G-nZVI,and G-nZVI with 20 wt.% nZVI(20% G-nZVI)could remove phosphorus most efficiently. The nZVI was very stable and could disperse very well on graphene,as characterized by transmission electron microscopy(TEM) and scanning electron microscopy(SEM). X-ray photoelectron spectroscopy(XPS),Fourier Transform infrared spectroscopy(FT-IR) and Raman spectroscopy were used to elucidate the reaction process,and the results indicated that Fe-O-P was formed after phosphorus was adsorbed by G-nZVI. The results obtained from X-ray diffraction(XRD) indicated that the reaction product between nZVI supported on graphene and phosphorus was Fe3(PO4)2·8H2O(Vivianite). It was confirmed that the specific reaction mechanism for the removal of phosphorus with nZVI or G-nZVI was mainly due to chemical reaction between nZVI and phosphorus. 相似文献