Fe2+/H2O2体系内各种自由基在氧化NO中的作用

Fe²⁺/H₂O₂体系可分解产生多种氧化性自由基, 主要包括O₂^-·、·OH和HO₂·。本文实验研究了O₂^-·、·OH及HO₂·在Fe²⁺/H₂O₂体系氧化NO气体过程中的作用。结果表明:在本实验条件下, O₂^-·对NO气体的氧化作用不明显;·OH及HO₂·是该体系氧化NO气体的主要活性物质, 其中·OH的氧化作用更大。加快自由基的生成速率可以增强Fe²⁺/H₂O₂体系对NO气体的氧化能力, 但O₂的生成速率同时加快。只有少量·OH及HO₂·参与NO的氧化, ·OH与HO₂·之间的快速反应是Fe²⁺/H₂O₂体系氧化NO过程中H₂O₂利用率低的主要原因。     

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...     

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。     

Fe2+/H2O2体系降解MB机制及影响因素研究

以亚甲基蓝（MB）作为目标污染物，实验研究了Fe²⁺/H₂O₂体系降解MB的活性物质，明确了主要反应条件对MB降解的影响特性。结果表明：HO₂?没有直接降解MB的能力；Fe²⁺/H₂O₂体系对MB的降解能力主要来自于?OH；Fe²⁺/H₂O₂体系降解MB可分为快速反应阶段和匀速反应阶段。快速反应阶段的MB降解率随温度升高而下降。体系对MB降解能力随H₂O₂初始浓度增加呈现先升高后减弱的趋势，本实验条件下，最佳H₂O₂初始浓度为5 mmol·L^-1。体系对MB降解能力随Fe²⁺初始浓度的增加而单调增加。MB降解速率随MB初始浓度的增加而增加，但MB降解率随其初始浓度呈现先增大后减小的趋势。保证?OH生成速率及其有效利用是提高体系氧化能力及H₂O₂利用率的关键。     

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...     

H2O2/Fe2(MoO4)3体系中H2O2吸附分解及NO氧化行为的DFT研究

为阐明H₂O₂/Fe₂(MoO₄)₃体系脱硝过程中H₂O₂吸附分解及NO氧化行为，基于DFT方法首次计算了H₂O₂和NO分子单独及二者同时在Fe₂(MoO₄)₃表面的吸附构型，并通过考察吸附能、Mulliken电荷及氧化路径等特性揭示H₂O₂催化分解和NO氧化的微观机制。结果表明：H₂O₂在Fe₂(MoO₄)₃表面易分解为活性自由基，而NO则以分子形式吸附；H₂O₂和NO共吸附时，H₂O₂优先吸附于催化剂表面并随后分解，NO则分别被H₂O₂分解产...     

不同尺寸反应器内H2O2热分解氧化NO特性与氧化产物分析

采用实验方法研究了不同尺寸滴管炉反应器内H₂O₂热分解氧化NO特性。对比了不同H₂O₂蒸发条件对NO氧化率的影响规律。分析了气体温度、H₂O₂溶液浓度、H₂O₂：NO摩尔比、NO初始浓度及气体流量对NO氧化率的影响。检测了氧化产物并分析了产物的生成路径。结果表明：H₂O₂的快速蒸发是其热分解氧化NO的前提。减小H₂O₂液滴尺寸或液膜厚度可加速H₂O₂蒸发与分解,提高NO氧化率,扩宽NO氧化的温度范围。保证蒸发速率可削弱H₂O₂浓度对NO氧化率的影响。当H₂O₂：NO < 10时,NO氧化率随H₂O₂：NO的增加而增加;当H₂O₂：NO>10时,NO氧化率几乎不随H₂O₂：NO变化。H₂O₂热分解对于较高浓度的NO具有更高的氧化效率。H₂O₂热分解氧化NO的主要产物为NO₂。HO₂·直接将NO氧化为NO₂,·OH则先将NO转化为HONO,然后进一步氧化为NO₂。     

UV/H2O2氧化联合Ca(OH)2吸收同时脱硫脱硝

在小型紫外光-鼓泡床反应器中,对UV/H₂O₂氧化联合Ca(OH)₂吸收同时脱除燃煤烟气中NO与SO₂的主要影响因素[H₂O₂浓度、紫外光辐射强度、Ca(OH)₂浓度、NO浓度、溶液温度、烟气流量以及SO₂浓度]进行了考察。采用烟气分析仪和离子色谱仪分别对尾气中的NO₂和液相阴离子作了检测分析。结果显示:在本文所有实验条件下,SO₂均能实现完全脱除。随着H₂O₂浓度、紫外光辐射强度和Ca(OH)₂浓度的增加,NO的脱除效率均呈现先大幅度增加后轻微变化的趋势。NO脱除效率随烟气流量和NO浓度的增加均有大幅度下降。随着溶液温度和SO₂浓度的增加,NO脱除效率仅有微小的下降。离子色谱分析表明,反应产物主要是SO₄^2-和NO₃^-,同时有少量的NO₂^-产生。尾气中未能检测到有害气体NO₂。     

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...     

二乙烯三胺五亚甲基膦酸/Fenton体系氧化脱除NO

针对当前Fenton氧化法脱除燃煤烟气中NO的过程中H₂O₂大量无效分解生成氧气的缺点,本文采用二乙烯三胺五亚甲基膦酸(DTPMPA)/Fenton系统进行氧化脱除NO的实验研究。结果表明：该系统在NO脱除效率为95.1%的情况下,H₂O₂无效分解占比降低至15.5%。DTPMPA浓度的增加抑制了H₂O₂无效分解,其浓度较低时促进NO脱除而浓度较高时抑制NO脱除;H₂O₂及Fe²⁺浓度的增加均对NO脱除及H₂O₂无效分解有一定的促进作用,但二者浓度过高时亦均对脱除NO有一定抑制作用;降低反应温度对NO脱除影响较小,但会削弱H₂O₂无效分解;SO₂对NO的脱除及H₂O₂无效分解影响甚小。电子自旋共振技术和淬灭剂添加实验结果表明：DTPMPA的...     

The kinetics of phenol decomposition under UV irradiation with and without H2O2 on TiO2, Fe–TiO2 and Fe–C–TiO2 photocatalysts

H₂O₂ used in the photo-Fenton reaction with iron catalyst can accelerate the oxidation of Fe²⁺ to Fe³⁺ under UV irradiation and in the dark (in the so called dark Fenton process). It was proved that conversion of phenol under UV irradiation in the presence of H₂O₂ predominantly produces highly hydrophilic products and catechol, which can accelerate the rate of phenol decomposition. However, while H₂O₂ under UV irradiation could decompose phenol to highly hydrophilic products and dihydroxybenzenes in a very short time, complete mineralization proceeded rather slowly. When H₂O₂ is used for phenol decomposition in the presence of TiO₂ and Fe–TiO₂, decrease of OH radicals formed on the surface of TiO₂ and Fe–TiO₂ has been observed and photodecomposition of phenol is slowed down. In case of phenol decomposition under UV irradiation on Fe–C–TiO₂ photocatalyst in the presence of H₂O₂, marked acceleration of the decomposition rate is observed due to the photo-Fenton reactions: Fe²⁺ is likely oxidized to Fe³⁺, which is then efficiently recycled to Fe²⁺ by the intermediate products formed during phenol decomposition, such as hydroquinone (HQ) and catechol.     

Partial oxidation of propane on Nafion supported catalytic membranes

Nafion supported catalytic membranes were found to be effective in the partial oxidation of propane to oxygenates with H₂O₂ in the presence of Fe²⁺ under mild conditions. The influence of [Fe²⁺] and [H₂O₂] on the reaction rate and product distribution in the temperature range 80–110°C has been ascertained. A reaction pathway involving the electrophilic activation of propane on superacid sites and subsequent reaction of the activated propane molecules with OH radicals generated by Fe²⁺/H₂O₂ Fenton system is discussed.     

Comparative evaluation of Fe and TiO2 photoassisted processes in solar photocatalytic disinfection of water

A lost of culturability of bacteria Escherichia coli K12 was observed after exposition to a solar simulator (UV–vis) in a laboratory batch photoreactor. The bacterial inactivation reactions have been carried out using titanium dioxide (TiO₂) P25 Degussa and FeCl₃ as catalysts. At the starting of the treatment, the suspensions were at their “natural” pH. An increase in the efficiency in the water disinfection was obtained when some advanced oxidation processes such as UV–vis/TiO₂, UV–vis/TiO₂/H₂O₂, UV–vis/Fe³⁺/H₂O₂, UV–vis/H₂O₂ were applied. The presence of H₂O₂ accelerates the rate of disinfection via TiO₂. The addition of Fe³⁺ (0.3 mg/l) to photocatalytic system decreases the time required for total disinfection (<1 CFU/ml), for TiO₂ concentrations ranging between 0.05 and 0.5 g/l. At TiO₂ concentrations higher than 0.5 g/l the addition of Fe³⁺ does not significantly increase the disinfection rate. The systems: Fenton (H₂O₂/Fe³⁺/dark), H₂O₂/dark, H₂O₂/TiO₂/dark showed low disinfection rate. The effective disinfection time (EDT₂₄) was reached after 60 and 30 min of illumination for the Fe³⁺ and TiO₂ photoassisted systems, respectively. EDT₂₄ was not reached for the system in the absence of catalyst (UV–vis). The effect on the bacterial inactivation of different mixture of chemical substance added to natural water was studied.     

Degradation of 4-chloro-2-methylphenol in aqueous solution by electro-Fenton and photoelectro-Fenton processes

Degradation of 4-chloro-2-methylphenol (PCOC), a refractory toxic chemical emitted to the environment from the industrial production of phenoxy herbicides was studied in aqueous solution. Electro-Fenton and photoelectro-Fenton processes were used as the degradation methods. H₂O₂, produced by the reduction of oxygen at carbon cathode reacted with dissolved metal ions to form hydroxyl radicals, which in turn reacted with PCOC sequentially to degrade the aromatic ring. The effects of using different [Fe²⁺]/[PCOC]₀ and the effect of replacing Fe²⁺ by Mn²⁺ ion have been examined. It was found that degradation rate was increased with increasing [Fe²⁺]/[PCOC]₀ ratio from 2 to 4. However, the total charge utilized during the treatment was also increased. The efficiency of PCOC degradation was observed to be higher when Mn²⁺ was used as the catalyst. The mineralization of aqueous solutions of PCOC, withdrawn from the reactor at certain time interval, has been followed by total organic carbon (TOC) decay and dechlorination. A fast and complete degradation of the aromatic ring was achieved in photoelectro-Fenton system. 41.7% TOC decay and complete dechlorination were observed by consuming only 141.4 C electrical charge during a 300 min photoelectron-Fenton treatment. In the case of electro-Fenton system, 280.7 C electrical charge was consumed during 450 min of electrolysis to attain a similar degradation of PCOC. 14.9% TOC removal and 89.3% dechlorination have been obtained in this system under the applied conditions.     

Fe/Fe cycling promoted by Ta3N5 under visible irradiation in Fenton degradation of organic pollutants

Ta₃N₅ was synthesized by nitridation of Ta₂O₅ under NH₃ flow at 700 °C. The catalyst was pure Ta₃N₅ according to X-ray diffraction (XRD), and was about 5 nm in size with a BET specific surface area 52.8 m²/g. When Ta₃N₅ was added to Fe³⁺/H₂O₂ solution (known as Fenton-like system), most Fe³⁺ were adsorbed on the Ta₃N₅ surface and could not react with H₂O₂ in the dark, which is different from the general Fenton reaction. Under visible light irradiation, adsorbed Fe³⁺ ions were reduced to Fe²⁺ rapidly and Fe²⁺ were reoxidized by H₂O₂ on the Ta₃N₅ surface, thus a fast Fe³⁺/Fe²⁺ cycling was established. Kinetics and ESR measurements supported this mechanism. The Ta₃N₅/Fe³⁺/H₂O₂ system could efficiently decompose H₂O₂ to generate hydroxyl radicals driven by visible light, which could accelerate significantly the degradation of organic molecules such as N,N-dimethylaniline (DMA), and 2,4-dichlorophenol (DCP). A mechanism was proposed for iron cycling on the basis of experimental results.     

Co3O4 with ordered pore structure derived from wood vessels for efficient Hg0 oxidation

Catalytic oxidation of Hg⁰ to HgO is an efficient way to remove Hg⁰ from coal-fired flue gas. The catalyst with ordered pore structure can lower mass transfer resistance resulting in higher Hg⁰ oxidation efficiency. Therefore, in the present work, wood vessels were used as sacrificial template to obtain Co₃O₄ with ordered pore structure. SEM and BET results show that, when the mass concentrations of Co(NO₃)₂·6H₂O was 20%, the obtained catalyst (Co₃O₄ [20%Co(NO₃)₂]) possesses better pore structure and higher surface area. It will expose more available surface active sites and lower the mass transfer resistance. Furthermore, XPS results prove that Co₃O₄ [20%Co(NO₃)₂] has the highest ratio of chemisorbed oxygen which plays an important role in Hg⁰ oxidation process. These results lead to a better Hg⁰ oxidation efficiency of Co₃O₄ [20%Co(NO₃)₂], which is about 90% in the temperature range of 200 to 350 ℃. Furthermore, Co₃O₄ [20%Co(NO₃)₂] has a stable catalytic activity, and its Hg⁰ oxidation efficiency maintains above 90% at 250 ℃ even after 90 h test. A probable reaction mechanism is deduced by the XPS results of the fresh, used and regenerated catalyst of Co₃O₄ [20%Co(NO₃)₂]. Chemisorbed oxygen can react with Hg⁰ forming HgO with the reduction of Co³⁺ to Co²⁺. And lattice oxygen and gaseous oxygen can supplement the consumption of chemisorbed oxygen to oxidize Co²⁺ to Co³⁺.