UV/Fe0/H2O2降解乙苯气体的工艺研究

以零价铁(Fe⁰)代替Fe²⁺作Fenton试剂催化剂,考察H₂O₂浓度、[H₂O₂]/[Fe⁰]摩尔比和pH值对UV/Fe⁰/H₂O₂技术降解乙苯气体的影响,分析了反应过程中H₂O₂和铁物质的浓度变化,通过GC-MS检测不同时间段的液体中间产物。结果表明,以48μm工业级Fe⁰作催化剂,在H₂O₂浓度为100 mmol/L、[H₂O₂]/[Fe⁰]摩尔比为40和pH值为3的优化条件下,UV₃₆₅/Fe⁰/H₂O₂体系中乙苯气体降解率在45 min内达到67.5%。检测到不同时间段的液体中间产物,如甲苯、苯乙醇...     

Cu2+和Co2+促进芬顿氧化处理垃圾渗滤液的研究

通过在传统芬顿体系中加入Cu²⁺、Co²⁺,研究Cu²⁺/Co²⁺/Fe²⁺/H₂O₂、Cu²⁺/Fe²⁺/H₂O₂、Co²⁺/Fe²⁺/H₂O₂和Fe²⁺/H₂O₂四种芬顿体系对垃圾渗滤液的处理效果,发现当初始pH分别为2、3、4、5、6时,各体系去除CODCr的效果排序为Cu²⁺/Co²⁺/Fe²⁺/H₂O₂>Cu²⁺/Fe²⁺/H₂O₂>Co²⁺/Fe^2...     

CuCe氧化物催化剂的制备及CWPO降解双酚A废水研究

为解决Fenton法存在活性组分流失及通常在pH 2～3条件下运行的局限性,采用柠檬酸络合法制备了CuCe氧化物催化剂,建立了双酚A非均相催化湿式过氧化氢氧化（CWPO）反应体系。考察了焙烧温度、Cu/Ce摩尔比、H₂O₂用量、双酚A初始浓度和pH对催化剂物化结构和CWPO性能的影响。并分析了可能的降解路径。结果表明：催化剂具有良好的高温稳定性和pH适应性,在pH 1.6～7.9范围内对双酚A都具有较高的降解性能,不需要调节pH。在焙烧温度450℃、Cu/Ce摩尔比1.0、催化剂用量1 g·L^-1、H₂O₂用量196 mmol·L^-1、BPA浓度152 mg·L^-1、pH 6.6、反应温度75℃、反应95 min后,BPA和TOC去除率分别为91.8%和84.5%,Cu²⁺析出浓度为19.3 mg·L^-1。推测了双酚A可能的降解路径。     

载Ni2+/Fe3+海泥催化污泥蒸汽气化制富氢燃气

以滩涂海泥(SM)为催化剂载体，通过共浸渍法制备了Fe³⁺、Ni²⁺、Ni-Fe基低负载催化剂并进行表征分析。考察了负载金属、负载率、温度等因素对污泥蒸汽气化效果的影响。结果表明：所制备催化剂的催化性能为SM-Ni-Fe-6%> SM-Ni-6%> SM-Ni-Fe-12%>SM-Fe-6%。Ni-Fe低负载SM催化剂具有优异的催化活性：在相同气化条件下，可有效提高合成气产率、H₂纯度及H₂产率；在相同H₂产率条件下，可显著降低气化温度。t=850℃,催化剂Ni-Fe负载率为6%时，获得最大合成气产率(0.38 m³/kg)、H₂纯度(49.34%)和H₂产率(8.40 mol/kg),相比无催化剂(对照组)分别提高了74.77%、17.45%和105.73%。Ni-Fe基催化剂中NiFe₂O₄的形成可有效协同Fe³⁺裂解C—O和...     

抗坏血酸对Fe2+/H2O2体系氧化NO的促进作用

采用实验方法研究了低成本环境友好型添加剂抗坏血酸(AA)对Fe²⁺/H₂O₂体系氧化NO气体及其对体系内H₂O₂分解的影响,分析了AA对体系氧化NO能力及H₂O₂分解的影响机制。研究结果表明:AA通过加速Fe³⁺向Fe²⁺的转化而促进Fe²⁺/H₂O₂体系对NO的氧化。[AA]₀:[Fe²⁺]₀对体系氧化NO的能力及H₂O₂的分解具有重要影响。综合考虑NO氧化脱除量及H₂O₂消耗量,合理的[AA]₀:[Fe²⁺]₀为1/3~1/2。AA的分次添加方式可大幅度提升体系氧化NO气体的能力。研究结果可望为发展基于H₂O₂为氧化剂的烟气NO绿色氧化技术提供理论基础。     

H2O2改性稻杆作为Pb2+吸附剂的工艺优化

H₂O₂改性稻杆作为Pb²⁺吸附剂,具有改性工艺环保、简单、成本低,以及对Pb²⁺吸附率高等特点,是一种优良的改性剂。优化改性工艺,制备优良吸附性能的H₂O₂改性稻杆具有较强的实用价值。详细探讨了改性工艺的影响因素如pH值、H₂O₂用量、Fe²⁺/H₂O₂物质的量之比、改性温度、改性时间、稻杆颗粒度和稻杆用量等对改性效果的影响,在单因素实验的基础上,通过正交实验和对比实验对改性工艺进行了进一步优化。得出最适宜的改性工艺为：在100 mL的溶液中,不加FeSO₄的情况下,稻杆用量为3 g,改性pH值为8,H₂O₂用量为稻秆用量的30%,稻杆颗粒度为40目,改性温度为20℃,改性时间为4 h。用2 g H₂O₂改性稻秆处理100 mL 200 mg/L的Pb²⁺废水时,对Pb²⁺的吸附率为94.45%,吸附容量为9.445 mg/g,表明H₂O₂改性稻秆具有优良的吸附性能。     

添加剂改性Fenton体系中Fe2+再生过程及机制的对比

Fe²⁺的再生直接决定Fenton体系产生的能力。选取羟胺、对苯二酚、对苯醌、亚硫酸钠4种典型添加剂,通过分析不同改性Fenton体系中Fe²⁺浓度、H₂O₂浓度、氧化还原电极电位（ORP）,揭示了Fe²⁺再生机制的差异,并进一步分析了不同添加剂与体系中H₂O₂及·OH的反应情况。结果表明：NH₂OH能快速使Fe²⁺再生,但伴随其消耗,Fe²⁺浓度不断降低。对苯二酚、对苯醌具有相似效果,两者均可大大强化Fe²⁺的再生。与NH₂OH不同,两者在体系中可迅速建立醌循环,持续还原Fe³⁺,且以两种物质或其组合均可建立循环。与上述机理均不同,Na₂SO₃会先与·OH及H₂O₂反应,因而不能有效还原Fe³⁺。实验还发现添加剂均存在与·OH的反应,其中Na₂SO₃还会消耗H₂O₂。     

UV-Fenton工艺的研究进展及其在水环境微污染处理领域的应用

近年来，水环境中的新型难降解污染物受到广泛关注，催生了该领域大量降解、还原及吸附等处理技术的相关研究，尤其是基于强氧化性自由基的高级氧化法(AOPs),典型工艺就是Fenton法。但在传统Fenton氧化体系中，H₂O₂的利用效率较低，铁泥产量高，且pH限制范围较窄，影响了Fenton反应的整体降解效果及应用。因此，引入了紫外光以提高H₂O₂的分解效率，即UV-Fenton体系，较传统Fenton可以有效减少Fe²⁺用量，促进Fe³⁺向Fe²⁺的转化，加速H₂O₂分解，并提高H₂O₂利用率，进而使有机物矿化更彻底。文章详细对比了传统Fenton与UV-Fenton工艺，介绍UV-Fenton工艺的反应原理，并讨论其影响因素(例如光照强度、Fe²⁺和H₂O₂用量等),同时，文章总结了U...     

Fe2+/H2O2体系O2生成路径

掌握Fe²⁺/H₂O₂体系O₂的生成路径,可为避免H₂O₂无效分解,开发经济高效的Fe²⁺/H₂O₂体系利用技术指明方向。采用添加自由基捕获剂的方法,探究Fe²⁺/H₂O₂体系内各种自由基对O₂生成速率的影响,进而确定O₂的生成路径。结果表明:Fe²⁺/H₂O₂体系内不会产生大量O₂^-·,O₂^-·不是生成O₂的主要反应物质;O₂^-·被全部捕获后,体系中仍产生大量O₂^-·,但此时无O₂生成,证明生成O₂的反应由·OH和HO₂·两种自由基直接参与。分析认为反应·OH+HO₂·-H₂O+O₂是体系内O₂生成的主要路径。控制Fe²⁺/H₂O₂体系定向生成·OH,抑制HO₂·的产生,是提高Fe²⁺/H₂O₂体系中H₂O₂利用率的有效手段。     

电芬顿工艺对垃圾渗滤液纳滤浓缩液的处理性能研究

本研究采用电芬顿工艺处理垃圾渗滤液纳滤浓缩液,系统考察电流密度、n(H₂O₂):n(Fe²⁺)、pH等工艺参数对渗滤液纳滤浓缩液COD的去除性能,运用响应曲面法推算最优工艺条件。结果表明,电芬顿处理渗滤液纳滤浓缩液的最优工艺参数反应时间为2h,电流密度为6.471 mA/cm²,n(H₂O₂):n(Fe²⁺)为12,pH为3.78,COD去除率可达到80.7%。     

Comparison of a new immobilized Fe3+ catalyst with homogeneous Fe3+–H2O2 system for degradation of 2,4‐dinitrophenol

BACKGROUND: Heterogeneous Fenton catalysts have been used to treat various organic pollutants in an aqueous environment. The present study has investigated the degradation of 2,4‐dinitrophenol (2,4‐DNP), a priority pollutant generated by such industries as pharmaceuticals, pesticides, pigments and dyes. Degradation of 2,4‐DNP (100 mg L^?1) was studied using Fe³⁺ loaded on Al₂O₃ as a heterogeneous catalyst in the presence of H₂O₂, and the efficiency compared with the homogeneous Fe³⁺/H₂O₂ based Fenton‐like process. The effect of different parameters for both processes, such as catalyst loading, H₂O₂ concentration, initial solution pH, initial substrate concentration and temperature were investigated and the optimum operating conditions determined. RESULTS: Under optimal operating conditions of the homogeneous system ([Fe³⁺] 125 mg L^?1; [H₂O₂] 250 mg L^?1; pH 3; room temperature), 92.5% degradation was achieved in 35 min for an initial 2,4‐DNP concentration of 100 mg L^?1. In the case of immobilized Fe (Fe³⁺–Al₂O₃ catalyst), degradation improved to 98.7% under the condition 10 wt% [Fe³⁺–Al₂O₃] 1 g L^?1 catalyst loading; [H₂O₂] 250 mg L^?1; pH 3; at room temperature for the same duration. CONCLUSIONS: This study demonstrated the stability and reusability of the prepared heterogeneous catalyst. This process is a viable technique for treatment of aqueous solutions containing contaminants. Copyright © 2012 Society of Chemical Industry     

Photoassisted Fenton mineralisation of Acid Violet 7 by heterogeneous Fe(III)–Al2O3 catalyst

Photoassisted Fenton mineralisation of an azo dye Acid Violet 7 was studied in detail using a Fe(III) loaded Al₂O₃ as a heterogeneous catalyst in the presence of H₂O₂ and UV-A light. The catalyst ferrioxalate–Al₂O₃ is more efficient than ferricnitrate–Al₂O₃. 35% Fe³⁺ loaded Al₂O₃ shows maximum efficiency in the degradation. The effects of reaction parameters such as catalyst loading, H₂O₂ concentration, initial solution pH and initial dye concentration on photodegradation were investigated and the optimum conditions are reported.     

Degradation of C.I. Acid Orange 7 by heterogeneous Fenton oxidation in combination with ultrasonic irradiation

BACKGROUND: A mesoporous alumina supported nanosized Fe₂O₃ was prepared through an original synthesis procedure and used as a heterogeneous catalyst for the Fenton process degradation of the model azo dye C.I. Acid Orange 7 enhanced by ultrasound irradiation (US/Fe₂O₃‐Al₂O₃‐meso/H₂O₂ system). The effect of various operating conditions was investigated, namely hydrogen peroxide concentration, initial pH, ultrasonic power and catalyst loading. RESULTS: The results indicated that the degradation of C.I. Acid Orange 7 followed a pseudo‐first‐order kinetic model. There exists an optimal hydrogen peroxide concentration, initial pH, ultrasonic power and catalyst loading for decolorization. The aggregate size of the spent catalyst was reduced after dispersion in water by ultrasonic irradiation. A very low level of iron leaching was observed ranging from < 0.1 to 0.23 mg L^?1. The intermediate products of C.I. Acid Orange 7 degradation were identified using gas chromatography–mass spectrometry (GC‐MS). CONCLUSION: The optimal conditions for efficient C.I. Acid Orange 7 degradation were pH close to 3, hydrogen peroxide concentration 4 mmol L^?1, catalyst loading 0.3 g L^?1, and ultrasonic power 80 W. Copyright © 2011 Society of Chemical Industry     

Synthesis and Characterization of Magnetically Retrievable Fe3O4/Polyvinylpyrrolidone/Polystyrene Nanocomposite Catalyst for Efficient Catalytic Oxidation Degradation of Dyes Pollutants

Recently, the application of metal oxides such as Fe₃O₄ nanoparticles have wide interest for environmental remediation and treatment of wastewater especially contaminated with azo dyes owing to its high degradation efficacy and low toxicity. The recovery of magnetic catalysts without losing their efficiency is an essential feature in the catalytic applications. The aim of this article is to investigate and synthesis of magnetically retrievable Fe₃O₄/polyvinylpyrrolidone/polystyrene (Fe₃O₄/PVP/PS) nanocomposite for the catalytic degradation of azo dye acid red 18 (AR18). Fe₃O₄/PVP/PS nanocomposite was prepared in two steps. Firstly, PVP/PS microsphere was synthesized by γ-irradiation polymerization of styrene in presence of PVP solution. Secondly, deposition of Fe₃O₄ nanoparticles on PVP/PS microsphere was achieved by the alkaline co-precipitation of Fe³⁺/Fe²⁺ ions. The chemical structural and morphological properties of PVP/PS microsphere and Fe₃O₄/PVP/PS nanocomposite were examined by XRD, TEM, DLS, FTIR, EDX and VSM techniques. TEM results showed homogeneous morphology, spherical shaped and well-dispersed Fe₃O₄ nanoparticles with average particle size of 26 nm around PVP/PS microspheres. The VSM measurements of Fe₃O₄/PVP/PS nanocomposite exhibit excellent magnetic response of saturation magnetization 26.38 emu/g which is suitable in magnetic separation. The effect of the synthesized Fe₃O₄/PVP/PS nanocomposite on the catalytic degradation of AR18 in presence of hydrogen peroxide (H₂O₂) as a heterogeneous Fenton-like catalyst was examined. The catalyst Fe₃O₄/PVP/PS/H₂O₂ played basic role in promoting the oxidation degradation efficiency of AR18 of initial concentration 50 mg/L to 94.4% in 45 min with excellent recyclability till the sixth cycles under the best conditions of pH 3, 2% v/v H₂O₂ and 0.3 g catalyst amount. Furthermore, the Fe₃O₄/PVP/PS/H₂O₂ hybrid catalyst system supports high capability for oxidation degradation of mixture of different dyes. The Fe₃O₄/PVP/PS nanocomposite catalyst had high magnetic and recyclability characters which are acceptable for the treatment of wastewater contaminated by various dyes pollutants.

     

Catalytic Ozonation of Oxalic Acid in the Presence of Fe2O3-Loaded Activated Carbon

ABSTRACT

The activity and optimum condition of metal-loaded activated carbon catalyst (Me/AC) for oxalic acid (OA) ozonation were evaluated. Results showed that Fe-loaded activated carbon (Fe/AC) showed better activity in five kinds of Me/AC catalysts prepared by a dipping method. Fe catalyst, crystallizing as γ-Fe₂O₃, dispersed well on AC surface. Fe₂O₃/AC, with 1.12% Fe weight ratio and 450°C calcination temperature and showed better activity for OA ozonation. 89.2% of OA was removed in the Fe₂O₃/AC/O₃ process, which was higher than those in AC/O₃ (79.6%) and O₃ (3.2%) processes. The calcination process helped to promote adsorption capability and catalytic activity of AC. In addition, Surface hydroxyl groups played a key role in Fe₂O₃/AC’s catalytic activity. Acidic condition was more favorable for OA removal in the Fe₂O₃/AC/O₃ process. A hydroxyl radical (?OH) oxidation mechanism was proven in Fe₂O₃/AC/O₃. The catalytic activity of Fe₂O₃/AC remained satisfactory after several cycles, indicating that Fe₂O₃/AC had a good reusability property.     

Investigating the Influence of Fe Speciation on N<Subscript>2</Subscript>O Decomposition Over Fe–ZSM-5 Catalysts

The influence of Fe speciation on the decomposition rates of N₂O over Fe–ZSM-5 catalysts prepared by Chemical Vapour Impregnation were investigated. Various weight loadings of Fe–ZSM-5 catalysts were prepared from the parent zeolite H-ZSM-5 with a Si:Al ratio of 23 or 30. The effect of Si:Al ratio and Fe weight loading was initially investigated before focussing on a single weight loading and the effects of acid washing on catalyst activity and iron speciation. UV/Vis spectroscopy, surface area analysis, XPS and ICP-OES of the acid washed catalysts indicated a reduction of ca. 60% of Fe loading when compared to the parent catalyst with a 0.4 wt% Fe loading. The TOF of N₂O decomposition at 600 °C improved to 3.99?×?10³ s^?1 over the acid washed catalyst which had a weight loading of 0.16%, in contrast, the parent catalyst had a TOF of 1.60?×?10³ s^?1. Propane was added to the gas stream to act as a reductant and remove any inhibiting oxygen species that remain on the surface of the catalyst. Comparison of catalysts with relatively high and low Fe loadings achieved comparable levels of N₂O decomposition when propane is present. When only N₂O is present, low metal loading Fe–ZSM-5 catalysts are not capable of achieving high conversions due to the low proximity of active framework Fe³⁺ ions and extra-framework ɑ-Fe species, which limits oxygen desorption. Acid washing extracts Fe from these active sites and deposits it on the surface of the catalyst as Fe_xO_y, leading to a drop in activity. The Fe species present in the catalyst were identified using UV/Vis spectroscopy and speculate on the active species. We consider high loadings of Fe do not lead to an active catalyst when propane is present due to the formation of Fe_xO_y nanoparticles and clusters during catalyst preparation. These are inactive species which lead to a decrease in overall efficiency of the Fe ions and consequentially a lower TOF.     

Photo Assisted Fenton in a Batch and a Membrane Reactor for Degradation of Drugs in Water

Abstract

Some advanced oxidation processes (AOP's) such as Fenton H₂O₂/Fe²⁺, photo assisted Fenton UV/H₂O₂/Fe²⁺, UV photolysis, and photo assisted Fenton—like UV/O₂/Fe²⁺ have been tested for the degradation of Gemfibrozil in aqueous solution in a batch system and then in a membrane reactor. A nanofiltration/reverse osmosis type cross‐linked polyamide, UTC‐60 (Toray) membrane (19 cm²) was used. In the batch degradation tests, the gemfibrozil, used at 5 mg/L, was degraded by employing the four AOP's but numerous peaks of intermediates were observed at the HPLC. Indeed DOC analyses showed poor mineralization in the case of photolysis (3.1%) and UV/O₂/Fe (10%), while it was 62% using the photo assisted Fenton and 24% using the Fenton. Thus in the membrane reactor only the Fenton and the photo assisted Fenton were tested. Obtained results showed a drug degradation higher than 92%, a mineralization higher than 55%, and a membrane retention of the catalyst in solution higher than 95%.     

Modeling dye degradation kinetic using dark- and photo-Fenton type processes

Dark- and photo-Fenton type processes, Fe²⁺/H₂O₂, Fe³⁺/H₂O₂, Fe⁰/H₂O₂, UV/Fe²⁺/H₂O₂, UV/Fe³⁺/H₂O₂ and UV/Fe⁰/H₂O₂, were applied for the treatment of model colored wastewater containing two reactive dyes, C.I. Reactive Blue 49 and C.I. Reactive Blue 137, and degradation kinetics were compared. Dye degradation was monitored by the means of UV/VIS, adsorbable organic halides (AOX) and total organic carbon (TOC) analysis, thus determining decolorization and dechlorination of triazine structure, as well as mineralization of model colored wastewater. Both dark- and photo-Fenton type processes were proven to be very efficient for color removal; ≥98% was achieved in all cases. Significant improvements in the mineralization of studied dyes were achieved by the assistance of UV light, as it was expected. It was demonstrated that the degradation kinetic of applied dyes depended on the presence of UV light, as well as type of iron catalyst and dye structure. On bases of the obtained experimental results, the mathematical models were developed describing dye degradation kinetics in all studied systems. Since UV light was used in order to enhance the efficiency of dark-Fenton type processes, mathematical model describing dye degradation by UV photolysis providing the values of quantum yields for each of the dye was developed and incorporated in model for photo-Fenton type processes. A sensitivity analysis for the evaluation of importance of each reaction used in mathematical models was also performed.     

The Mechanism of N2O Decomposition on Fe-ZSM-5: An Isotope Labeling Study

The role of Fe promoters has been investigated on Pd/ceria, Pt/ceria and Rh/ceria catalysts for the water–gas shift (WGS) reaction in 25 torr of CO and H₂O under differential reaction conditions. While no enhancement was observed with Pt and Rh, the activity of Pd/ceria increased by as much as an order of magnitude upon the addition of an optimal amount of Fe. Similarly, the addition of 1 wt% Pd to an Fe₂O₃ catalyst increased the WGS rate at 453 K by a factor of 10 over that measured on Fe₂O₃ alone, while the addition of Pt or Rh to Fe₂O₃ had no effect on rates. The amount of Fe that was necessary to optimize the rates increased with Pd loading but was independent of the order in which Fe and Pd were added to the ceria. Increased WGS activity was also observed upon the addition of Fe to Pd supported on Ce_0.5Zr_0.5O₂. XRD measurements, performed after running the catalyst under WGS conditions, show the formation of a Fe–Pd alloy, even though similar measurements on an Fe/ceria catalyst showed that Fe₃O₄ was the stable phase for Fe in the absence of Pd. Possible implications of these results on the development of new WGS catalysts are discussed.     

3D rectangular WO3 hybridized by PrFeO3 nanoparticles with efficient dual charge transfer for enhanced photo-Fenton-like activity

In this work, zero-dimensional (0D) high crystalline PrFeO₃ worm nanocrystals were loaded over a three-dimensional (3D) rectangular WO₃ to construct a 0D/3D PFO/W Z-scheme heterojunction by an in situ ultrasonic synthetic process. This heterojunction exhibited excellent photocatalytic activities towards the degradation of organic pollutants such as rhodamine B (RhB), Methylene blue (MB), and tetracycline hydrochloride (TC) in the presence of small amounts of H₂O₂ under visible-light irradiation. For example, the k value of PFO/W + H₂O₂ was about 67, 107, 45, 27, 11 and 14 times higher than pure H₂O₂, PrFeO₃, WO₃, PFO/W nanocomposite, PrFeO₃+ H₂O₂ and WO₃+H₂O₂ respectively during the degradation of MB. The trapping experiments and ESR measurements identified that the generated ·OH, ·O₂⁻, and h⁺ were the active species involved in the catalysis. Further, the ·OH radical could be continuously generated by Fe³⁺/Fe²⁺ and W⁶⁺/W⁵⁺ conversion and played the dominant role in the degradation of organic pollutants. The superior photocatalytic performance of the PFO/W + H₂O₂ system was derived from the synergistic effect of the Z-scheme heterostructure and dual photo-Fenton-like oxidation (Fe³⁺/Fe²⁺ and W⁶⁺/W⁵⁺). A possible mechanism was postulated based on the results obtained. In summary, this study provided new insights into synthesizing an effectively heterogeneous 0D/3D Z-scheme dual photo-Fenton-like catalyst for water clarification.