Cu/Fe双金属负载PAN非织造布催化降解甲醛气体研究

采用偕胺肟改性聚丙烯腈(PAN)非织造布作为载体材料,将其与Cu~(2+)和Fe~(3+)的混合溶液进行反应制备双金属负载PAN非织造布催化剂。采用XPS和UV-Vis对催化剂的分子结构进行了表征,然后考察了其在甲醛气体氧化降解反应中的催化作用。结果表明,Cu~(2+)和Fe~(3+)均是通过与偕胺肟基团中的羟基和氨基的配位作用负载于PAN非织造布上,而且两种金属离子可能通过配体发生了相互作用。此外,与Fe~(3+)的单金属催化剂相比,适量掺杂Cu~(2+)能够有效提高催化体系在甲醛降解反应中的催化活性,尤其有利于其在暗反应时催化降解甲醛气体,这主要归因于Cu~(2+)/Cu~+价态转化促进了强氧化性中间体Fe(Ⅳ)=O的生成。     

Comparative study of different Fe(III)-carboxylic fiber complexes as novel heterogeneous Fenton catalysts for dye degradation

Three carboxylic fibers including alginate fiber, polyacrylic acid-grafted polypropylene (PP), and polytetrafluoroethylene (PTFE) fibers were coordinated with Fe(III) ions, respectively, to prepare the different Fe(III)-carboxylic fiber complexes. On the basis of investigating their coordination with Fe(III) ions, the coordination number, surface morphology, and light adsorption property of the formed Fe(III)-carboxylic fiber complexes were characterized and compared. And the catalytic performance of the three complexes was then evaluated as the heterogeneous Fenton catalysts in the degradation of a typical azo dye, Reactive Red 195 in water. The results indicated that alginate fiber could react with Fe(III) ions more easily than the grafted PP or PTFE fibers containing similar amount of carboxyl groups to form Fe(III)-carboxylic fiber complexes. Higher concentration of Fe(III) ions led to a proportional increase in Fe content of the obtained complexes. Fe(III)-alginate fiber complex has the more unsaturated configuration than Fe(III)-grafted PP or PTFE fiber complex due to the changes in its coordination number. Moreover, the light adsorption of the complexes was affected by nature of fiber used. The incorporation of hydrophobic synthetic fiber, especially grafted PTFE fiber reduced the visible light absorption of the obtained complexes. Three Fe(III)-carboxylic fiber complexes could catalyze the dye degradation in the dark or under light irradiation. Fe(III)-alginate fiber complex showed better catalytic activity and reuse stability than the other two complexes with similar Fe content.     

Comparative study on the mechanical and thermal properties of two different modified PAN fibers and their Fe complexes

The polyacrylonitrile (PAN) fibers were modified with hydroxylamine and its mixture with hydrazine to prepared the amidoximated PAN fibers (denoted as AO-PAN) and mixing modified PAN fibers (denoted as M-PAN) respectively, and then both of which were reacted with Fe³⁺ ions to form two modified PAN fiber–Fe complexes (denoted as Fe–AO-PAN for AO-PAN and Fe–M-PAN for M-PAN). Their mechanical properties were evaluated and compared with respect to the breaking strength and elongation at break in both dry and wet conditions, and two important effecting factors including weight gain rate of the PAN fiber after modification and Fe content remained in the PAN fiber were investigated. Besides, thermal behavior of the modified PAN fibers and their Fe complexes was also examined by DSC and DMA methods. The results indicated that higher weight gain rate imparts the reduced breaking strength to two modified PAN fibers, and which is found to be further lower in wet state. The mechanical properties of the modified PAN fibers-Fe complexes, especially Fe–AO-PAN varied with Fe content (C_Fe–PAN). Moreover, two critical C_Fe–PAN values are observed to be 79.75 mg/g for Fe–AO-PAN and 28.35 mg/g for Fe–M-PAN, respectively, at which they show a minimum values of breaking strength and elongation at break. Also, Fe–AO-PAN is much higher than Fe–M-PAN in terms of the critical C_Fe–PAN value, which is mainly attributed to the difference in molecular structure between them. Thermal behavior of the modified PAN fibers and their Fe complexes is also greatly affected by their modification methods.     

A novel biomimetic catalyst constructed by axial coordination of hemin with PAN fiber for efficient degradation of organic dyes

A novel biomimetic catalyst was synthesized by supporting hemin onto the amidoximated polyacrylonitrile (PAN) fiber and then used for the oxidative degradation of organic dyes by H₂O₂ activation. SEM, FTIR and XPS results suggested that the OH and NH₂ in amidoxime groups were responsible for hemin immobilization through axial coordination bonds. The fibrous support significantly enhanced the catalytic activity and pH tolerance of pure hemin, and the prepared catalyst also exhibited excellent recycling capability. In addition, the effect of axial ligands on the catalytic mechanism was clarified by employing the modified PAN fiber with amidrazones groups as the support of hemin, and the possible catalytic mechanism was proposed and discussed based on the ESR measurement combined with a series of designed experiments. It is found that OH and NH₂ as axial ligands of hemin might induce H₂O₂ activation through two different pathways, corresponding to the generation of Fe(IV)=O and ^·OH species, respectively.     

Photo degradation of methyl orange an azo dye by advanced Fenton process using zero valent metallic iron: influence of various reaction parameters and its degradation mechanism

Advanced Fenton process (AFP) using zero valent metallic iron (ZVMI) is studied as a potential technique to degrade the azo dye in the aqueous medium. The influence of various reaction parameters like effect of iron dosage, concentration of H(2)O(2)/ammonium per sulfate (APS), initial dye concentration, effect of pH and the influence of radical scavenger are studied and optimum conditions are reported. The degradation rate decreased at higher iron dosages and also at higher oxidant concentrations due to the surface precipitation which deactivates the iron surface. The rate constant for the processes Fe(0)/UV and Fe(0)/APS/UV is twice compared to their respective Fe(0)/dark and Fe(0)/APS/dark processes. The rate constant for Fe(0)/H(2)O(2)/UV process is four times higher than Fe(0)/H(2)O(2)/dark process. The increase in the efficiency of Fe(0)/UV process is attributed to the cleavage of stable iron complexes which produces Fe(2+) ions that participates in cyclic Fenton mechanism for the generation of hydroxyl radicals. The increase in the efficiency of Fe(0)/APS/UV or H(2)O(2) compared to dark process is due to continuous generation of hydroxyl radicals and also due to the frequent photo reduction of Fe(3+) ions to Fe(2+) ions. Though H(2)O(2) is a better oxidant than APS in all respects, but it is more susceptible to deactivation by hydroxyl radical scavengers. The decrease in the rate constant in the presence of hydroxyl radical scavenger is more for H(2)O(2) than APS. Iron powder retains its recycling efficiency better in the presence of H(2)O(2) than APS. The decrease in the degradation rate in the presence of APS as an oxidant is due to the fact that generation of free radicals on iron surface is slower compared to H(2)O(2). Also, the excess acidity provided by APS retards the degradation rate as excess H(+) ions acts as hydroxyl radical scavenger. The degradation of Methyl Orange (MO) using Fe(0) is an acid driven process shows higher efficiency at pH 3. The efficiency of various processes for the de colorization of MO dye is of the following order: Fe(0)/H(2)O(2)/UV>Fe(0)/H(2)O(2)/dark>Fe(0)/APS/UV>Fe(0)/UV>Fe(0)/APS/dark>H(2)O(2)/UV approximately Fe(0)/dark>APS/UV. Dye resisted to degradation in the presence of oxidizing agent in dark. The degradation process was followed by UV-vis and GC-MS spectroscopic techniques. Based on the intermediates obtained probable degradation mechanism has been proposed. The result suggests that complete degradation of the dye was achieved in the presence of oxidizing agent when the system was amended with iron powder under UV light illumination. The concentration of Fe(2+) ions leached at the end of the optimized degradation experiment is found to be 2.78 x 10(-3)M. With optimization, the degradation using Fe(0) can be effective way to treat azo dyes in aqueous solution.     

The effect of a catecholate chelator as a redox agent in Fenton-based reactions on degradation of lignin-model substrates and on COD removal from effluent of an ECF kraft pulp mill

We evaluated the effect of a catecholate chelator as a redox agent in Fenton-based reactions (known as chelator-mediated Fenton reaction-CMFR), in the presence of three different transition metals ions (Fe(2+), Fe(3+) and Cu(2+)) by determining the oxidative capability of CMFR towards lignin-model substrates. The potential application of mediated Fenton-based reactions as a novel process to treat pulp mill effluent was evaluated and monitored by chemical oxygen demand (COD) and total phenol removals from a combination of the effluents generated during an ECF bleaching stage. The catecholate chelator 3,4-dihydroxiphenilacetic acid (DOPAC) reduced both Fe(3+) and Cu(2+), in addition, the maximum Cu(2+) reduction activity was reached in a shorter time than for Fe(3+) reduction, however, the highest metal reduction activity was observed with Fe(3+). When DOPAC was added to Fenton-based reactions (Fe(3+)/H(2)O(2), Fe(2+)/H(2)O(2), Cu(2+)/H(2)O(2)) an increase in oxidative activities of these reactions were found as they resulted in great degradation improvement of the lignin-model substrates azure B, phenol red and syringaldazine. The same increase in oxidative capability of Fenton-based reactions in the presence of DOPAC was observed after effluent treatment, expressed by the increase in COD removal, namely, an increase in the range of about 70% in COD removal when Fe(2+) or Fe(3+) was the catalytic metal and about 25% for Cu(2+). However CMFR lead to an increase in total phenol content. As COD removal by CMFR system using Fe(3+) and Fe(2+) was not significantly different and that Fe(3+) ions promoted lesser increase in total phenol content, Fe(3+) was chosen for experimental optimization. At optimum conditions, 75% of COD and 30% of total phenol removal were achieved.     

AOPAN/RC纳米纤维膜的制备及对金属离子吸附性能

采用静电纺丝技术制备聚丙烯腈/醋酸纤维素(PAN/CA)纳米纤维膜,通过化学改性制备偕胺肟化聚丙烯腈/再生纤维素(AOPAN/RC)纳米纤维膜,研究了纳米纤维膜对单一金属离子(Fe~(3+))和混合金属离子(Cu~(2+)、Cd~(2+)、Fe~(3+))的吸附性能。通过扫描电镜、红外光谱、X射线能谱仪等测试对纳米纤维膜进行了表征,并通过静态接触角测定纳米纤维膜亲水性能。研究表明,改性后制备的AOPAN/RC纳米纤维膜的亲水性能得到较大改善,同时纳米纤维膜能够高效吸附溶液中的金属离子,纳米纤维膜对单一组分Fe~(3+)的饱和吸附可达411.21mg/g,对于混合金属离子溶液,纳米纤维膜对其吸附能力顺序为Fe~(3+)Cu~(2+)Cd~(2+),而且纳米纤维膜具备优良的重复使用能力。     

Adsorption and aggregation of Fe(III)-hydroxy complexes during the photodegradation of phenol using the iron-added-TiO(2) combined system

The behavior of Fe(III) aquacomplexes in TiO(2) suspensions in the degradation of phenol has been investigated. The most active Fe(OH)(2+) species adsorbed on the surface of TiO(2) retards the conversion of Fe(OH)(2+) into oligomers and therefore increases the percentage of Fe(OH)(2+) with irradiation time, with a consequent enhancement in the catalytic cycle of Fe(III)/Fe(II) and excited charge traps by Fe(III) in the iron-TiO(2) system. The influence of iron addition on TiO(2) was obtained when the regeneration of [Fe(OH)(2+)] remained continuous with irradiation time. In an optimum TiO(2) suspension (0.5g/L) with the addition of 0.1mM Fe(III), the measured k(obs) values for phenol degradation were enhanced for the higher adsorption of Fe(OH)(2+) on the reactive surface of TiO(2) at a specified irradiation time.     

Studies on nanosized iron based modified catalyst for Fischer-Tropsch synthesis application

To improve catalytic performance iron based catalyst, the effects of some metal promoters, especially potassium, copper and other transition metal oxides as well as different supports have been reported. A series of Fe/K/Cu catalysts promoted with magnesium and ceria by precipitation method, followed by impregnation method; keeping Cu and K content same. The catalysts were characterized by XRD, N2 physisorption, TPR and TEM techniques. From XRD, the presence of hematite (Fe2O3) phase was detected in all precipitated iron catalysts and CFe2.5 phase in all used catalysts. TPR results showed that addition of Mg facilitated the reduction of Fe2O3 and decrease in reduction temperature. The catalytic performance was investigated in a fixed-bed reactor at 250 degrees C, 2 MPa pressure and H2/CO molar ratio of 2. Concentration of Mg was found to affect the CO conversion and product distribution. It was found that precipitated iron catalyst Fe/Mg/Cu/K with Mg/Fe ratio of 0.1 showed highest conversion (60.6%) and C5(+) selectivity (92.4%) among all catalysts tested.     

In situ incorporation of well-dispersed Cu–Fe oxides in the mesochannels of AMS and their utilization as catalysts towards the Fenton-like degradation of methylene blue

Multi-components active metal oxide-supported catalysts are highly promising in heterogeneous catalysis due to some special promoting effects. In this study, by the controllable amount of Cu, Cu–Fe decorated anionic surfactant-templated mesoporous silica (Cu _x Fe/AMS) was directly prepared. The obtained catalysts were characterized by X-ray diffraction, N₂ adsorption–desorption, inductively coupling plasma emission spectroscopy, scanning electron microscopy, transmission electron microscopy, UV–visible, hydrogen temperature-programmed reduction, and X-ray photoelectron spectroscopy techniques. The results revealed that bimetallic Cu–Fe oxides were directly formed and highly dispersed in the mesochannels during the calcinations and the introduction of Cu²⁺ and Fe²⁺ on the micelles has influence on the structure properties. As compared to the monometallic Fe-modified AMS, the presence of Cu promotes the effects between Fe species and silica wall, leading to the better dispersion of Fe in the mesochannels of AMS. Finally, a series of Cu–Fe-modified AMS were used as Fenton-like catalysts and exhibited good catalytic activity in the degradation of methylene blue (MB), which resulted from high dispersion of Fe species and synergetic effect between Cu and Fe active sites. 1.0 was the optimum molar ratio of Cu²⁺ to Fe²⁺ ions to achieve the best catalytic activity and stability.     

铁铝柱撑二硫化钼的合成与表征

采用取代反应获得了具有Keggin结构的聚合羟基铁铝离子,并通过单分子层技术将聚合羟基离子嵌入到二硫化钼的层间,制得了层间距1.394至1.513nm的柱撑二硫化钼复合材料.研究表明,随着Fe/Al比的增加,层间距逐渐下降,颗粒度逐渐增大,比表面积逐渐降低.催化实验表明,柱撑材料将S2-催化氧化为S2O3^2-,其催化活性是2H-MoS2的4～5倍,且光催化活性大于催化活性.这与材料比表面积增加所导致催化活性部位的增多,以及光致电子-空穴对的产生有关.     

Degradation of commercial azo dye reactive Black B in photo/ferrioxalate system

The photolysis and photo-catalysis of ferrioxalate in the presence of hydrogen peroxide with UV irradiation (UV/ferrioxalate/H(2)O(2) process) for treating the commercial azo dye, reactive Black B (RBB), is examined. An effort is made to decolorize textile effluents at near neutral pH for suitable discharge of waste water. pH value, light source, type of initial catalyst (Fe(3+) or Fe(2+)) and concentration of oxalic acid (Ox) strongly affected the RBB removal efficiency. The degradation rate of RBB increased as pH or the wavelength of light declined. The optimal molar ratio of oxalic acid to Fe(III) is three, and complete color removal is achieved at pH 5 in 2h of the reaction. Applying oxalate in such a photo process increases both the RBB removal efficiency and the COD removal from 68% and 21% to 99.8% and 71%, respectively.     

铜掺杂纳米 TiO2 的制备及其抗菌性能研究

目的制备铜掺杂纳米二氧化钛抗菌材料,测定其金属溶出率,研究该材料的光催化活性及抗菌性能。方法通过水热合成法制备掺铜二氧化钛(TiO_2Cu)纳米材料,采用催化动力学法测定该材料Cu~(~(2+))溶出率,以亚甲蓝为光催化降解材料测定其光催化活性,以金黄色葡萄球菌为目标物,研究在紫外光和非光条件下TiO_2Cu纳米材料的抗菌性能。结果 TiO_2Cu纳米材料Cu~(2+)溶出率最大值为72.36%,在自然光和紫外灯光照下对亚甲蓝光催化降解率分别为95.06%和85.08%,光照下TiO_2Cu材料质量浓度达到10 mg/m L,与细菌共培养90 min后,抑菌率可达94%。结论采用冷冻干燥法制备的含铜量为0.2%的TiO_2Cu材料具有良好的光催化活性,在暗光和紫外光照下均具有一定的抗菌性能。     

不同组成Cu(I)配合物的光催化性能

以有机膦配体双二苯基膦甲烷与溴化亚铜不同比例合成2种不同结构的Cu(I)配合物,通过X-射线单晶衍射的测定其结构发现在1∶1的比例下生成的配合物由内界配离子[Cu3(μ3-Br)2(dppm)3]十和外界阴离子Br-组成的,2∶1的比例下生成的配合物是一个中性配分子。以甲基橙的降解对其光催化性能进行测试,结果表现出配合物的结构与催化性能之间有关系。     

基于铝热反应Cu-Fe二元合金的微观组织与摩擦性能研究EI北大核心CSCD

基于铝热法制备含2%(质量分数)Al的Cu-Fe合金,采用XRD,SEM,EDS和EBSD技术对Cu-Fe合金的相结构、微观组织进行表征,同时采用HVS-1000A维氏硬度仪和CFT-1材料表面性能测试仪测试Cu-Fe合金的硬度及抗磨损性能。结果表明:利用铝热反应可高效地制备Cu-Fe合金,成分可控,组织致密无夹杂,其中Fe相均匀地分布在Cu基体中,Cu和Fe的相界面结合良好;Fe相的硬度为322.2HV,基体Cu相的硬度为169.3HV,Cu-Fe合金的电导率为40.8 MS/m。铝热法制备的Cu-Fe合金具有较低的摩擦因数,平均摩擦因数为0.124,磨损率为2.17×10^(-3) mm 3·N^(-1)·m^(-1)。     

聚丙烯腈纤维改性条件优化及其对模拟电镀废水的净化作用

为了寻求低价、环保的电镀废水处理方案,将廉价的聚丙烯腈(PAN)纤维与羟胺试剂反应对PAN纤维进行改性,使其上氰基螯合获得偕胺肟基纤维。通过改变各种改性条件,探讨了改性条件对PAN改性纤维在重金属单离子溶液和多离子混合溶液中吸附性能的影响。结果表明:最佳改性条件为21.2 g/L PAN纤维,27.0 g/L盐酸羟胺,pH值为7.0,70℃下反应2 h;改性PAN纤维对模拟电镀废水中的Cu2+,Zn2+,Ni2+,Pb2+,Cd2+等重金属离子均有较好吸附性能,其中对Cd2+吸附效果最好,吸附量为55 mg/g;在多离子混合溶液中优先选择吸附Cd2+;改性PAN纤维再生效果优良,可重复利用。     

Applicability of boron-doped diamond electrode to the degradation of chloride-mediated and chloride-free wastewaters

The degradation of diphenylamine (DPA) in aqueous solution by persulfate is investigated. Effects of pH, persulfate concentration, ionic strength, temperature and catalytic ions Fe(3+) and Ag(+) on the degradation efficiency of DPA by persulfate are examined in batch experiments. The degradation of DPA by persulfate is found to follow the pseudo-first-order kinetic model. Increasing the reaction temperature or persulfate concentration may significantly accelerate the DPA degradation. Fe(3+) and Ag(+) ions can enhance the degradation of DPA, and Ag(+) ion is more efficient than Fe(3+) ion. However, the increase of either the pH value or ionic strength will decrease the rate of DPA degradation. N-Phenyl-4-quinoneimine, N-carboxyl-4-quinoneimine, 4-quinoneimine and oxalic acid are identified as the major intermediates of DPA degradation, and a primary pathway for the degradation of DPA is proposed. The degradation of DPA in surface water, groundwater and seawater is also tested by persulfate, and more than 90% of DPA can be degraded at room temperature in 45min at an initial concentration of 20mgL(-1).     

Zinc oxide nanorod mediated visible light photoinactivation of model microbes in water

The inactivation of model microbes in aqueous matrix by visible light photocatalysis as mediated by ZnO nanorods was investigated. ZnO nanorods were grown on glass substrate following a hydrothermal route and employed in the inactivation of gram-negative Escherichia coli and gram-positive Bacillus subtilis in MilliQ water. The concentration of Zn(2+) ions in the aqueous matrix, bacterial cell membrane damage, and DNA degradation at post-exposure were also studied. The inactivation efficiencies for both organisms under light conditions were about two times higher than under dark conditions across the cell concentrations assayed. Anomalies in supernatant Zn(2+) concentration were observed under both conditions as compared to control treatments, while cell membrane damage and DNA degradation were observed only under light conditions. Inactivation under dark conditions was hence attributed to the bactericidal effect of Zn(2+) ions, while inactivation under light conditions was due to the combined effects of Zn(2+) ions and photocatalytically mediated electron injection. The reduction of pathogenic bacterial densities by the photocatalytically active ZnO nanorods in the presence of visible light implies potential ex situ application in water decontamination at ambient conditions under sunlight.     

Ferric ion mediated photochemical decomposition of perfluorooctanoic acid (PFOA) by 254nm UV light

The great enhancement of ferric ion on the photochemical decomposition of environmentally persistent perfluorooctanoic acid (PFOA) under 254nm UV light was reported. In the presence of 10microM ferric ion, 47.3% of initial PFOA (48microM) was decomposed and the defluorination ratio reached 15.4% within 4h reaction time. While the degradation and defluorination ratio greatly increased to 80.2% and 47.8%, respectively, when ferric ion concentration increased to 80microM, and the corresponding half-life was shortened to 103min. Though the decomposition rate was significantly lowered under nitrogen atmosphere, PFOA was efficiently decomposed too. Other metal ions like Cu(2+) and Zn(2+) also slightly improved the photochemical decomposition of PFOA under irradiation of 254nm UV light. Besides fluoride ion, other intermediates during PFOA decomposition including formic acid and five shorter-chain perfluorinated carboxylic acids (PFCAs) with C7, C6, C5, C4 and C3, respectively, were identified and quantified by IC or LC/MS. The mixture of PFOA and ferric ion had strong absorption around 280nm. It is proposed that PFOA coordinates with ferric ion to form a complex, and its excitation by 254nm UV light leads to the decomposition of PFOA in a stepwise way.     

Electro-Fenton and photoelectro-Fenton degradations of the drug beta-blocker propranolol using a Pt anode: identification and evolution of oxidation products

The beta-blocker propranolol hydrochloride has been degraded by electrochemical advanced oxidation processes like electro-Fenton (EF) and photoelectro-Fenton (PEF) using a single cell with a Pt anode and an air diffusion cathode (ADE) for H(2)O(2) electrogeneration and a combined system containing the above Pt/ADE pair coupled in parallel to a Pt/carbon-felt (CF) cell. Organics are mainly oxidized with hydroxyl radical (OH) formed from Fenton's reaction between added Fe(2+) and electrogenerated H(2)O(2). The PEF treatment in Pt/ADE-Pt/CF system yields almost total mineralization because OH production is enhanced by Fe(2+) regeneration from Fe(3+) reduction at the CF cathode and Fe(III) complexes with generated carboxylic acids are rapidly photodecarboxylated under UVA irradiation. Lower mineralization degree is found for PEF in Pt/ADE cell due to the little influence of UVA light on Fe(2+) regeneration. The homologous EF processes are much less potent as a result of the persistence of Fe(III)-carboxylate complexes. Aromatic intermediates such as 1-naphthol, 1,4-naphthoquinone and phthalic acid and generated carboxylic acids such as pyruvic, glycolic, malonic, maleic, oxamic, oxalic and formic are identified. While chloride ion remains stable, NH(4)(+) and NO(3)(-) ions are released to the medium. A reaction sequence for propranolol hydrochloride mineralization is proposed.