共查询到20条相似文献,搜索用时 15 毫秒
1.
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Fe 2+/H 2O 2体系氧化NO气体及其对体系内H 2O 2分解的影响,分析了AA对体系氧化NO能力及H 2O 2分解的影响机制。研究结果表明:AA通过加速Fe 3+向Fe 2+的转化而促进Fe 2+/H 2O 2体系对NO的氧化。[AA] 0:[Fe 2+] 0对体系氧化NO的能力及H 2O 2的分解具有重要影响。综合考虑NO氧化脱除量及H 2O 2消耗量,合理的[AA] 0:[Fe 2+] 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H 2O 2为氧化剂的烟气NO绿色氧化技术提供理论基础。 相似文献
2.
Ta 3N 5 was synthesized by nitridation of Ta 2O 5 under NH 3 flow at 700 °C. The catalyst was pure Ta 3N 5 according to X-ray diffraction (XRD), and was about 5 nm in size with a BET specific surface area 52.8 m 2/g. When Ta 3N 5 was added to Fe 3+/H 2O 2 solution (known as Fenton-like system), most Fe 3+ were adsorbed on the Ta 3N 5 surface and could not react with H 2O 2 in the dark, which is different from the general Fenton reaction. Under visible light irradiation, adsorbed Fe 3+ ions were reduced to Fe 2+ rapidly and Fe 2+ were reoxidized by H 2O 2 on the Ta 3N 5 surface, thus a fast Fe 3+/Fe 2+ cycling was established. Kinetics and ESR measurements supported this mechanism. The Ta 3N 5/Fe 3+/H 2O 2 system could efficiently decompose H 2O 2 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. 相似文献
3.
H 2O 2 used in the photo-Fenton reaction with iron catalyst can accelerate the oxidation of Fe 2+ to Fe 3+ 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 H 2O 2 predominantly produces highly hydrophilic products and catechol, which can accelerate the rate of phenol decomposition. However, while H 2O 2 under UV irradiation could decompose phenol to highly hydrophilic products and dihydroxybenzenes in a very short time, complete mineralization proceeded rather slowly. When H 2O 2 is used for phenol decomposition in the presence of TiO 2 and Fe–TiO 2, decrease of OH radicals formed on the surface of TiO 2 and Fe–TiO 2 has been observed and photodecomposition of phenol is slowed down. In case of phenol decomposition under UV irradiation on Fe–C–TiO 2 photocatalyst in the presence of H 2O 2, marked acceleration of the decomposition rate is observed due to the photo-Fenton reactions: Fe 2+ is likely oxidized to Fe 3+, which is then efficiently recycled to Fe 2+ by the intermediate products formed during phenol decomposition, such as hydroquinone (HQ) and catechol. 相似文献
4.
掌握Fe 2+/H 2O 2体系O 2的生成路径,可为避免H 2O 2无效分解,开发经济高效的Fe 2+/H 2O 2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Fe 2+/H 2O 2体系内各种自由基对O 2生成速率的影响,进而确定O 2的生成路径。结果表明:Fe 2+/H 2O 2体系内不会产生大量O 2-·,O 2-·不是生成O 2的主要反应物质;O 2-·被全部捕获后,体系中仍产生大量O 2-·,但此时无O 2生成,证明生成O 2的反应由·OH和HO 2·两种自由基直接参与。分析认为反应·OH+HO 2·-H 2O+O 2是体系内O 2生成的主要路径。控制Fe 2+/H 2O 2体系定向生成·OH,抑制HO 2·的产生,是提高Fe 2+/H 2O 2体系中H 2O 2利用率的有效手段。 相似文献
5.
Fe 2+/H 2O 2体系可分解产生多种氧化性自由基, 主要包括O 2-·、·OH和HO 2·。本文实验研究了O 2-·、·OH及HO 2·在Fe 2+/H 2O 2体系氧化NO气体过程中的作用。结果表明:在本实验条件下, O 2-·对NO气体的氧化作用不明显;·OH及HO 2·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Fe 2+/H 2O 2体系对NO气体的氧化能力, 但O 2的生成速率同时加快。只有少量·OH及HO 2·参与NO的氧化, ·OH与HO 2·之间的快速反应是Fe 2+/H 2O 2体系氧化NO过程中H 2O 2利用率低的主要原因。 相似文献
6.
以亚甲基蓝(MB)作为目标污染物,实验研究了Fe 2+/H 2O 2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:HO 2?没有直接降解MB的能力;Fe 2+/H 2O 2体系对MB的降解能力主要来自于?OH;Fe 2+/H 2O 2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H 2O 2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H 2O 2初始浓度为5 mmol·L -1。体系对MB降解能力随Fe 2+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H 2O 2利用率的关键。 相似文献
7.
Fe 2+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Fe 2+浓度、H 2O 2浓度、氧化还原电极电位(ORP),揭示了Fe 2+再生机制的差异,并进一步分析了不同添加剂与体系中H 2O 2及·OH的反应情况。结果表明:NH 2OH能快速使Fe 2+再生,但伴随其消耗,Fe 2+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Fe 2+的再生。与NH 2OH不同,两者在体系中可迅速建立醌循环,持续还原Fe 3+,且以两种物质或其组合均可建立循环。与上述机理均不同,Na 2SO 3会先与·OH及H 2O 2反应,因而不能有效还原Fe 3+。实验还发现添加剂均存在与·OH的反应,其中Na 2SO 3还会消耗H 2O 2。 相似文献
8.
Alachlor, atrazine and diuron dissolved in water at 50, 25 and 30 mg/L, respectively were photodegraded by Fe 2+/H 2O 2, Fe 3+/H 2O 2, TiO 2 and TiO 2/Na 2S 2O 8 treatments driven by solar energy at pilot-plant scale using a compound parabolic collector (CPC) photoreactor. All the advanced oxidation processes (AOPs) employed mainly compared the TOC mineralisation rate to evaluate treatment effectiveness. Parent compound disappearance, anion release and oxidant consumption are discussed as a function of treatment time. The use of Fe 2+ or Fe 3+ showed no influence on the reaction rate under illumination and the reaction using 10 or 55 mg/L of iron was quite similar. TiO 2/Na 2S 2O 8 showed a quicker reaction rate than TiO 2 and a similar rate compared to photo-Fenton. The main difference found was between TiO 2/Na 2S 2O 8 and photo-Fenton, detected during atrazine degradation, where pesticide transformation into cyanuric acid was confirmed only for TiO 2/Na 2S 2O 8. 相似文献
9.
在浸没式循环撞击流反应器中,以氨水为沉淀剂,用七水合硫酸亚铁和六水合三氯化铁为原料,采用共沉淀法制备了纳米四氧化三铁粒子。考察了搅拌转速、亚铁与三价铁物质的量比、反应温度和溶液pH对所得纳米四氧化三铁的分散性和粒径的影响。采用傅里叶红外光谱仪、透射电镜、X射线衍射仪等对制得的纳米粒子的结构和性能进行了表征。结果表明:用撞击流反应器制备纳米四氧化三铁粒子的最佳工艺条件:亚铁与三价铁物质的量比为1 ∶1,反应温度为40 ℃,搅拌转速为1 600 r/min,以氨水作沉淀剂,最佳pH控制在11.0左右。在上述条件下,可以制备出分散性好、纯度高、平均粒径为10 nm的四氧化三铁粒子。 相似文献
10.
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 (TiO 2) P25 Degussa and FeCl 3 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/TiO 2, UV–vis/TiO 2/H 2O 2, UV–vis/Fe 3+/H 2O 2, UV–vis/H 2O 2 were applied. The presence of H 2O 2 accelerates the rate of disinfection via TiO 2. The addition of Fe 3+ (0.3 mg/l) to photocatalytic system decreases the time required for total disinfection (<1 CFU/ml), for TiO 2 concentrations ranging between 0.05 and 0.5 g/l. At TiO 2 concentrations higher than 0.5 g/l the addition of Fe 3+ does not significantly increase the disinfection rate. The systems: Fenton (H 2O 2/Fe 3+/dark), H 2O 2/dark, H 2O 2/TiO 2/dark showed low disinfection rate. The effective disinfection time (EDT 24) was reached after 60 and 30 min of illumination for the Fe 3+ and TiO 2 photoassisted systems, respectively. EDT 24 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. 相似文献
11.
Highly ordered iron-containing mesoporous material, Fe-MCM-41, with 0.5–4 Fe/Si mol% loading was prepared and characterization was performed using XRD, SEM/TEM, EDS, N 2-sorption, and FT-IR and UV–vis spectroscopies. Fe-MCM-41 exhibited high catalytic activity in phenol hydroxylation using H 2O 2 as oxidant, giving phenol conversion of ca. 60% at 50 °C [phenol:H 2O 2 = 1:1, water solvent]. Effects of Fe contents in Fe-MCM-41 and catalyst concentration, temperature, solvent used, phenol/H 2O 2 mole ratios and H 2O 2 feeding method, and catalyst calcination temperature on conversion profiles were examined. Catalyst recycling was performed to investigate the extent of potential metal leaching. Comparisons in performance were also made using nano-sized Fe 2O 3 particles and Fe-salt impregnated MCM-41 as catalyst. Catechol to hydroquinone in product ratio was close to 2:1 in accordance with a free radical reaction scheme involving Fe 2+/Fe 3+ redox pair and the larger amount of Fe species always achieved the given phenol conversion at a shorter reaction time. As the calcination temperature increases from 400 to 800 °C increasing amount of Fe species came out from the MCM-41 framework. Both tetrahedral Fe and extra-framework Fe species were found catalytically active, but high dispersion of Fe species achieved in Fe-MCM-41 was an advantage. 相似文献
12.
The catalytic behavior of the Fe 3+/Fe 2+ system in the electro-Fenton degradation of the antimicrobial drug chlorophene has been studied considering four undivided electrolytic cells, where a Pt or boron-doped diamond (BDD) anode and a carbon felt or O 2-diffusion cathode have been used. Chlorophene electrolyses have been carried out at pH 3.0 under current control, with 0.05 M Na 2SO 4 as supporting electrolyte and Fe 3+ as catalyst. In these processes the drug is oxidized with hydroxyl radical (OH) formed both at the anode from water oxidation and in the medium from electrochemically generated Fenton's reagent (Fe 2+ + H 2O 2, both of them generated at the cathode). The catalytic behavior of the Fe 3+/Fe 2+ system mainly depends on the cathode tested. In the cells with an O 2-diffusion cathode, H 2O 2 is largely accumulated and the Fe 3+ content remains practically unchanged. Under these conditions, the chlorophene decay is enhanced by increasing the initial Fe 3+ concentration, because this leads to a higher quantity of Fe 2+ regenerated at the cathode and, subsequently, to a greater OH production from Fenton's reaction. In contrast, when the carbon felt cathode is used, H 2O 2 is electrogenerated in small extent, whereas Fe 2+ is largely accumulated because the regeneration of this ion from Fe 3+ reduction at the cathode is much faster than its oxidation to Fe 3+ at the anode. In this case, an Fe 3+ concentration as low as 0.2 mM is required to obtain the maximum OH generation rate, yielding the quickest chlorophene removal. Chlorophene is poorly mineralized in the Pt/O 2 diffusion cell because the final Fe 3+–oxalate complexes are difficult to oxidize with OH. These complexes are completely destroyed using a BDD anode at high current thanks to the great amount of OH generated on its surface. Total mineralization is also achieved in the Pt/carbon felt and BDD/carbon felt cells with 0.2 mM Fe 3+, because oxalic acid and its Fe 2+ complexes are directly oxidized with OH in the medium. Comparing the four cells, the highest oxidizing power regarding total mineralization is attained for the BDD/carbon felt cell at high current due to the simultaneous destruction of oxalic acid at the BDD surface and in the bulk solution. 相似文献
13.
Oxidative reactions of phenol and chlorobenzene with electrogenerated Fenton's reagent, Fe 2+ + H 2O 2, were investigated. The electrogeneration of H 2O 2 and the regeneration of Fe 2+ were performed at a graphite cathode. Results are compared for conventional vs. electrogenerated Fenton's reagent. It was found that the conversion of chlorobenzene was substantially greater by the electrochemical method than the conventional system. The rates of H 2O 2 generation were dependent on solution pH; electrogeneration was favored at low pH, while the opposite was the case for the hydroxylation of the organics. The hydroxylation products of phenol with electrogenerated Fenton's reagent included hydroquinone, catechol and resorcinol. For chlorobenzene, a hydroxylated product (p-chlorophenol) and a dehalogenated product (phenol) were obtained. The rates of phenol and chlorobenzene hydroxylation were dependent on pH, and concentrations of F 2+ and H 2O 2. Results indicated that the electrochemical system provided an efficient way to regenerate Fe 2+ 相似文献
14.
This work shows that aqueous solutions of clofibric acid (2-(4-chlorophenoxy)-2-methylpropionic acid), the bioactive metabolite of various lipid-regulating drugs, up to saturation at pH 3.0 are efficiently and completely degraded by electrochemical advanced oxidation processes such as electro-Fenton and photoelectro-Fenton with Fe 2+ and UVA light as catalysts using an undivided electrolytic cell with a boron-doped diamond (BDD) anode and an O 2-diffusion cathode able to electrogenerate H 2O 2. This is feasible in these environmentally friendly methods by the production of oxidant hydroxyl radical at the BDD surface from water oxidation and in the medium from Fenton's reaction between Fe 2+ and electrogenerated H 2O 2. The degradation process is accelerated in photoelectro-Fenton by additional photolysis of Fe 3+ complexes under UVA irradiation. Comparative treatments by anodic oxidation with electrogenerated H 2O 2, but without Fe 2+, yield much slower decontamination. Chloride ion is released and totally oxidized to chlorine at the BDD surface in all treatments. The decay kinetics of clofibric acid always follows a pseudo-first-order reaction. 4-Chlorophenol, 4-chlorocatechol, hydroquinone, p-benzoquinone and 2-hydroxyisobutyric, tartronic, maleic, fumaric, formic and oxalic acids, are detected as intermediates. The ultimate product is oxalic acid, which is slowly but progressively oxidized on BDD in anodic oxidation. In electro-Fenton this acid forms Fe 3+–oxalato complexes that can also be totally destroyed at the BDD anode, whereas in photoelectro-Fenton the mineralization rate of these complexes is enhanced by its parallel photodecarboxylation with UVA light. 相似文献
15.
Field disinfection of water in a large solar compound parabolic collector (CPC) photoreactor (35–70 l) was conducted at 35 °C by different photocatalytic processes: sunlight/TiO 2, sunlight/TiO 2/Fe 3+, sunlight/Fe 3+/H 2O 2 and compared to the control experiment of direct sunlight alone. Experiments were carried out using a CPC and natural water spiked with E. coli K 12. Under these conditions, total disinfection by bare sunlight irradiation was not reached after 5 h of treatment; and bacterial recovery was observed during the subsequent 24 h in the dark. The addition of TiO2, TiO2/Fe3+ or Fe3+/H2O2 to the water accelerates the bactericidal action of sunlight, leading to total disinfection by solar-photocatalysis. No bacterial regrowth was observed during 24 h after stopping sunlight exposure. For some samples, the decrease of bacteria continues in the dark. A “residual disinfection effect” was observed for these samples before reaching the total inactivation. The effective disinfection time (EDT24), defined as the treatment time required to prevent any bacterial regrowth during the subsequent 24 h in the dark, after stopping the phototreatment, was reached in the presence but not in the absence of different photocatalytic systems. EDT24 was 2 h 30 min, 2 h and 1 h 30 min for sunlight/TiO2, sunlight/TiO2/Fe3+ and sunlight/Fe3+/H2O2 systems, respectively. The post irradiation events observed when the phototreated water is poured into an optimal growth medium are also discussed. 相似文献
16.
Metal ions including Fe 3+, Ca 2+, Mg 2+, Ni 2+, Co 2+ and Cu 2+ are commonly found in the leaching solution of laterite-nickel ores, and the pre-removal of Fe 3+ is extremely important for the recovery of nickel and cobalt. Di(2-ethylhexyl)phosphate acid (D2EHPA) showed high extraction rate and selectivity of Fe 3+ over other metal ions. The acidity of the aqueous solution is crucial to the extraction of Fe 3+, and the stoichiometry ratio between Fe 3+ and the extractant is 0.86:1.54. The enthalpy for the extraction of Fe 3+ using D2EHPA was 19.50 kJ/mol. The extraction of Fe 3+ was ≥99% under the optimized conditions after a three-stage solvent extraction process. The iron stripping effects of different reagents showed an order of H 2C 2O 4>NH 4HCO 3>HCl>NaCl>NaHCO 3>Na 2SO 3. The stripping of Fe was ≥99% under the optimized conditions using H 2C 2O 4 as a stripping reagent. 相似文献
17.
Decolorization of reactive brilliant red X-3B was studied by using an Fe–Ce oxide hydrate as the heterogeneous catalyst in the presence of H 2O 2 and UV. The decolorization rate was in the order of UV–Fe–Ce–H 2O 2 > UV–Fe 3+–H 2O 2 > UV–H 2O 2 > UV–Fe–Ce ≥ Fe–Ce–H 2O 2 > Fe–Ce. Under the conditions of 34 mg l −1 H 2O 2, 0.500 g l −1 Fe–Ce, 36 W UV and pH 3.0, 100 mg l −1 X-3B could be decolorized at efficiency of more than 99% within 30 min. The maximum dissolved Fe during the reaction was 1 mg l −1. From the fact that the decolorization rate of the UV–Fe–Ce–H 2O 2 system was significantly higher than that of the UV–Fe 3+–H 2O 2 system at Fe 3+ = 1 mg l −1, it is clear that the Fe–Ce functioned mainly as an efficient heterogeneous catalyst. UV–vis, its second derivative spectra, and ion chromatography (IC) were employed to investigate the degradation pathway. Fast degradation after adsorption of X-3B is the dominant mechanism in the heterogeneous catalytic oxidation system. The first degradation step is the breaking down of azo and CN bonds, resulting in the formation of the aniline- and phenol-like compounds. Then, the breaking down of the triazine structure occurred together with the transformation of naphthalene rings to multi-substituted benzene, and the cutting off of sulphonic groups from the naphthalene rings. The last step includes further decomposition of the aniline structure and partial mineralization of X-3B. 相似文献
18.
具有复杂分子结构的三苯甲烷类染料孔雀石绿是一种典型的较难降解染料,是工业废水处理的难点之一。本文根据Goldschmidt半径容差规则法,设计了用于孔雀石绿降解的ABO 3型SrFe (1-x)Co xO 3催化剂,并选择出活性较高的SrFe 0.6Co 0.4O 3催化剂。通过XRD、SEM、BET吸附及XPS分析表明:该催化剂是纯净钙钛矿结构,颗粒形貌为无规则堆叠的“蜂窝”片状;吸附等温线没有明显的回滞环,说明没有“墨水瓶”类孔结构;XPS谱中,B位离子同时存在Fe 2+/Fe 3+和Co 2+/Co 3+ 4种价态离子,且反应前后,4种离子的分布比例有较大变化。根据实验结果,推测该催化反应机理为:催化剂B位Co 3+与溶解氧形成活性氧[O 2] +和Co 2+;活性氧[O 2] +完成氧化反应后其正电荷转移到B位Fe 2+上形成Fe 3+,Fe 3+的正电荷可再转移到Co 2+形成Co 3+,完成催化过程的电荷转移与循环。 相似文献
19.
采用二(2-乙基己基)磷酸酯(P204)-磺化煤油萃取体系从高硫酸氰化尾渣矿浆电解液中富集铁离子,重点研究了P204浓度、相比(O/A)、振荡时间、振荡频率及温度等对Fe 3+萃取率的影响及其萃取过程。研究表明,在P204体积分数为25%、电解液pH为1.5、温度25℃、O/A=1∶1、振荡时间10 min、振荡频率180r/min的条件下,电解液中Fe 3+的单级萃取率可达97.73%以上,饱和萃取容量可达到21.57g/L。Fe 3+在有机相中的萃取富集主要归因于其与P204分子结构中羟基的阳离子交换反应以及磷酰基的配位反应,形成的配合物为FeSO 4A(HA) 3与FeA 3(HA) 3。在草酸1mol/L、O/A=1∶1、振荡时间10min、振荡频率190r/min的条件下,负载有机相中Fe 3+的单级反萃率可达82.64%以上,反萃液中铁主要以[Fe(C 2O 4) 3<... 相似文献
20.
The room temperature wet catalytic oxidation was conducted in a batch reactor with Fe/MgO catalyst. Fe/MgO catalyst was prepared by the dissolution–precipitation method. XRD and temperature-programmed reductions (TPR) indicate that Fe oxide in the Fe/MgO is finely dispersed in the MgO support. The high H 2S removal capacities of Fe/MgO can be explained by the finely dispersed iron oxide MgO. The H 2S removal capacities of Fe/MgO are dependent on oxygen partial pressure (1.0 g H 2S/g cat in air and 2.6 g H 2S/g cat in oxygen). The valence state analysis of Fe/MgO catalyst suggests that the H 2S oxidation on Fe/MgO can occur by a redox couple reaction, reducing Fe 3+ into Fe 2+ by H 2S and oxidizing Fe 2+ to Fe 3+ by O 2. 相似文献
|