Sonocatalytic degradation of C.I. Reactive Red 198 in H2O2-based Systems

This study elucidated the effects of pH on the decolorization of C.I. Reactive Red 198 (RR198) in US, UV/H₂O₂, US/H₂O₂ and UV/US/H₂O₂ systems. The synergistic effects in US/H₂O₂ and UV/US/H₂O₂ systems were also evaluated. At pH 4, 7 and 10, the decolorization rates of RR198 followed the order UV/US/H₂O₂ > UV/H₂O₂ > US > US/H₂O₂.     

Kinetics and products of ozonation of C.I. Reactive Red 195 in a semi-batch reactor

Textile wastewater shows great threats to the environment if not well pretreated before discharge. A promising technique, ozonation, was applied to remove the color in dye solutions containing C.I. Reactive Red 195 (RR195) in a semi-batch reactor. The decolorization of RR195 by the ozone process followed pseudo-first-order kinetics. Several factors which influenced the efficiency of decolorization were studied and the reaction rate constant (k) obtained with different operational parameters was compared. Our results showed that RR195 was more easily degraded in acidic than in alkaline conditions. The dyeing auxiliaries (sodium carbonate and sodium chloride) that acted as radical scavengers could enhance the decolorization process, and the ozonation time for total color removal lengthened if the initial dye concentration was higher. The analysis of the ozonation products was performed by liquid chromatography-tandem mass spectrometer and a possible degradation pathway was predicted according to the ozonation products and structure of RR195. Our results indicated that ozonation was effective in the color removal of dyes, but further treatment might be necessary since the ozonation products are high toxic.     

Comparison of the performances of Ti/SnO2-Sb, Ti/SnO2-Sb/PbO2, and Nb/BDD anodes on electrochemical degradation of azo dye

In this paper, the preparation conditions of antimony-doped SnO₂ and PbO₂ electrode were optimized for the degradation activity of AO7 dye solution. The results showed that when the doping content of Sb is 8 mol %(SnO₂-Sb(0.08)), the SnO₂ electrode exhibited best activities for the decolorization and mineralization of AO7. The concentration of NaF in electroplating solution had a noticeable effect on PbO₂ electrode for the decolorization of AO7 solution, but little influence on the COD removal rate. The anodic stability tests showed that the electrode prepared in the solution containing 0.10 g l⁻¹ NaF (PbO₂-F(0.10)) was best for environmental application. The comparison of SnO₂-Sb(0.08), PbO₂-F(0.10) and Boron-doped Diamond (BDD) electrodes revealed that a more rapid decolorization rate was obtained on SnO₂-Sb(0.08) and PbO₂-F(0.10) electrodes in dilute AO7 solutions, while higher COD removal rate of concentrated AO7 solutions was on BDD and SnO₂-Sb(0.08) electrodes. The effect of concentration of Na₂SO₄ on the degradation rate of AO7 was very notable on BDD electrode for its highest overpotential of oxygen evolution reaction. In the chloride-containing medium, the decolorization was accelerated greatly but the completed mineralization of AO7 was inhibited with the increasing of chloride ions concentration when these high-overvoltage anodes were used Published in Russian in Elektrokhimiya, 2008, vol. 44, No. 7, pp. 865–875. The text was submitted by the authors in English.     

Solid-solid interactions in pure and Li2O-doped manganese and magnesium mixed oxides system

The solid-solid interactions between manganese and magnesium oxides in absence and in presence of small amounts of Li₂O have been investigated. The molar ratios between manganese and magnesium oxides in the form of Mn₂O₃ and MgO were varied between 0.05:1 to 0.5:1. The mixed solids were calcined in air at 400-1000°C. The techniques employed were DTA, XRD and H₂O₂ decomposition at 20-40°C.The results obtained revealed that solid-solid interactions took place between the reacting solids at 600-1000°C yielding magnesium manganates (Mg₂MnO₄, Mg₆MnO₈, MgMnO₄ besides unreacted portions of MgO, Mn₂O₃ and Mn₃O₄). Li₂O-doping (0.75-6 mol%) of the investigated system followed by calcination at 600 and 800°C decreased progressively the intensity of the diffraction lines of Mn₂O₃ (Bixbyite) with subsequent increase in the lattice parameter 'a' of MgO to an extent proportional to the amount of Li₂O added. This finding might suggest that the doping process enhanced the dissolution of Mn₂O₃ in MgO forming solid solution. This treatment led also to the formation of Li₂MnO₃. Furthermore, the doping with 3 and 6 mol% Li₂O conducted at 800°C resulted in the conversion of Mn₂O₃ into Mn₃O₄, a process that took place at 1000°C in absence of Li₂O. The produced Li₂MnO₃ phase remained stable by heating at up to 1000°C. Furthermore, Li₂O doping of the investigated system at 400-1000°C resulted in a progressive measurable increase in the particle size of MgO.The catalytic activity measurements showed that the increase in the molar ratio of Mn₂O₃ in the samples precalcined at 400-800°C was accompanied by a significant increase in the catalytic activity of the treated solids. The maximum increase in the catalytic activity expressed as reaction rate constant measured at 20°C (k _20°C) attained 3.14, 2.67 and 3.25-fold for the solids precalcined at 400, 600 and 800°C, respectively. Li₂O-doping of the samples having the formula 0.1 Mn₂O₃/MgO conducted at 400-600°C brought a progressive significant increase in its catalytic activity. The maximum increase in the value of k _20°C due to Li₂O attained 1.93 and 2.75-fold for the samples preheated at 400 and 600°C, respectively and opposite effect was found for the doped samples preheated at 800°C.This revised version was published online in November 2005 with corrections to the Cover Date.     

吸附相反应技术制备MnOx/CeO2/SiO2催化剂及其低温选择性催化还原Nox

采用吸附相反应技术制备得到了MnO_x/CeO₂/SiO₂催化剂,通过X 射线衍射（XRD）、透射电子显微镜（TEM）、高分辨透射电子显微镜（HRTEM）、紫外激光拉曼（Raman）等手段对催化剂进行了表征. HRTEM分析表明活性组分MnO_x与CeO₂都均匀分布在载体SiO₂表面;XRD分析表明Mn₃O₄特征峰随着CeO₂含量的增加逐渐减小至完全消失,CeO₂的加入降低了MnO_x的结晶程度,增加了MnO_x的分散性;Raman光谱表明催化剂表面的Mn离子能够进入CeO₂晶格,激发出空穴氧,随着CeO₂负载量的增加,催化剂氧空穴浓度先升高后降低.以NH₃为还原剂,考评催化剂的NO_x低温选择性催化还原（SCR）性能,催化剂催化活性随CeO₂负载量增加先升高后降低,与催化剂氧空穴浓度变化规律一致,说明催化剂活性受氧空穴浓度影响,氧空穴浓度升高,催化剂催化活性升高.     

Photocatalytic activity of TiO2/SnO2/Pt prepared by the sol-gel method

This investigation compares the photodegradation performance of C.I. Reactive Red 2 (RR2) in single- and coupled-photocatalyst systems. The photocatalysts were produced via the sol-gel method. PEG and Pt addition increases the decolorization rate (1.6–2.12 h⁻¹), the amount of sulfate released and the DOC reduction percentage in coupled photocatalyst systems the cause of PEG improving the homogeneity of the final product and incorporating Pt into the lattice reduced the band gap of photocatalysts.     

Preparation of trifluoroiodomethane via vapor-phase catalytic reaction between hexafluoropropylene oxide and iodine

Based on our previous investigation on the reaction mechanism to produce difluorocarbene and subsequent CF₃I starting with CHF₃ and I₂, a new route for preparing CF₃I at a relative low temperature, 200 °C, has been developed via a vapor-phase catalytic reaction between hexafluoropropylene oxide with I₂ in the presence of KF supported on activate charcoal as a catalyst. The influence of reaction temperature and reaction time on the amount of CF₃I was investigated. In the reaction process, coke-formation was suggested on the surface of catalysts by means of BET, XPS and TG-DTA analysis. The process for the formation of CF₃I and by-products is also discussed.     

MnO_2/NiCo_2O_4的静电自组装合成及其电化学性能

通过带负电荷的MnO2纳米片与带正电荷的Co-Ni层状双氢氧化物(LDHs)纳米片的静电自组装外加后续热处理合成了异质层状结构的MnO2/NiCo2O4复合物.采用X射线衍射(XRD)、傅里叶变换红外(FTIR)光谱、拉曼光谱、原子吸收光谱(AAS)、场发射扫描电镜(FESEM)和透射电子显微镜(TEM)对其结构和形貌进行了表征.用循环伏安(CV)、恒流充放电和电化学交流阻抗技术对其电化学性能进行了测试.研究结果表明,该方法制得的异质复合物具有多孔层状堆垛结构,这种特殊的结构不仅增大了电解液离子的接触面积,而且还为其嵌入-脱出提供了有效途径.该复合物在1 A·g-1电流密度时,-0.6-0.45 V电位窗口内的比电容达482 F·g-1,优于纯组分MnO2和NiCo2O4的电容性能.     

CoAl_2O_4/蜂窝陶瓷催化剂的制备及其催化臭氧化性能

采用涂覆法制备了CoAl_2O_4/蜂窝陶瓷催化剂。利用X射线衍射、N_2吸附-脱附和透射电镜等方法对所制备的催化剂进行了表征,并分析了其催化臭氧化降解对苯二酚的效能。结果表明,CoAl_2O_4/蜂窝陶瓷的晶相属于典型的尖晶石结构,具有较大的比表面积、孔容和孔径,分别达到77 m~2·g~(-1)、0.001 7 cm~3·g~(-1)和3.9 nm。CoAl_2O_4/蜂窝陶瓷催化臭氧化对苯二酚的去除率高达81.2%,COD去除率可达47.7%。在叔丁醇存在的条件下,对苯二酚的去除率显著下降,说明CoAl_2O_4/蜂窝陶瓷催化臭氧化遵循羟基自由基机理。     

CoAl2O4/蜂窝陶瓷催化剂的制备及其催化臭氧化性能

采用涂覆法制备了CoAl₂O₄/蜂窝陶瓷催化剂。利用X射线衍射、N₂吸附-脱附和透射电镜等方法对所制备的催化剂进行了表征,并分析了其催化臭氧化降解对苯二酚的效能。结果表明,CoAl₂O₄/蜂窝陶瓷的晶相属于典型的尖晶石结构,具有较大的比表面积、孔容和孔径,分别达到77 m²·g^-1、0.001 7 cm³·g^-1和3.9 nm。CoAl₂O₄/蜂窝陶瓷催化臭氧化对苯二酚的去除率高达81.2%,COD去除率可达47.7%。在叔丁醇存在的条件下,对苯二酚的去除率显著下降,说明CoAl₂O₄/蜂窝陶瓷催化臭氧化遵循羟基自由基机理。     

纯相Li2MnO3薄膜的制备及作为锂离子电池正极材料的电化学行为

采用固相烧结法制备了纯相Li₂MnO₃正极材料及靶材,采用脉冲激光沉积（PLD）法在氧气气氛、不同温度下沉积了Li₂MnO₃薄膜. 通过X射线衍射（XRD）和拉曼（Raman）光谱表征了薄膜的晶体结构,采用扫描电镜（SEM）观察薄膜形貌及厚度,利用电化学手段测试了Li₂MnO₃薄膜作为锂离子电池正极材料性能. 结果表明,PLD 方法制备的纯相Li₂MnO₃薄膜随着沉积温度升高薄膜结晶性变好. 25 ℃沉积的薄膜难以可逆充放电,400 ℃沉积的薄膜具有较高的电化学活性和循环稳定性. 相对于粉末材料,400与600 ℃制备的Li₂MnO₃薄膜电极平均放电电位随着循环次数的衰减速率明显低于相应的粉体材料.     

Monolith Manganese-Based Catalyst Supported on ZrO2-TiO2 for NH3-SCR Reaction at Low Temperature

Monolith catalysts were prepared using TiO₂ and ZrO₂-TiO₂ as supports with MnO₂ as active component and Fe₂O₃ as promoter. The catalytic activities at low temperature and stability at high temperature for selective catalytic reduction of NO_x with NH₃ (NH₃-SCR) in the presence of excessive O₂ were studied after the catalysts calcined at different temperatures. The catalysts were characterized by X-ray diffraction (XRD), specific surface area measurements (BET), oxygen storage capacity (OSC), and temperature programmed reduction (H₂-TPR). The results indicated that the catalyst supported on ZrO₂-TiO₂ had excellent stability at high temperature, and possessed high specific surface area and oxygen storage capacity, and had strong redox property. The results of the catalytic activities indicated that the monolith manganese-based catalyst using ZrO₂-TiO₂ as support had evidently improved the activity of NH₃-SCR reduction reaction at low temperature, and it showed great potential for practical application.     

MnO2 nanozyme induced the chromogenic reactions of ABTS and TMB to visual detection of Fe2+ and Pb2+ ions in water

In this study, we used a simple and rapid colourimetric reaction for visual sensing of Fe²⁺ and Pb²⁺ ions in water by employing nano-MnO₂ as a natural oxidase mimic to respectively catalyse ABTS and TMB in citrate-phosphate buffer solution (C-PBS) at 25°C and pH 3.8. It was found that nano-MnO₂ possessed highly oxidase-mimicking activity with the K_m values of 0.030 and 0.027 toward ABTS and TMB, respectively, indicating TMB had a stronger affinity on nano-MnO₂ than ABTS. Interestingly, the presence of 0.01 mmol·L^?1 Fe²⁺/Pb²⁺ ion was able to significantly down-regulate the activity of MnO₂ nanozyme in nano-MnO₂-mediated ABTS reaction processes (P < 0.01), which mainly due to the strong adsorption of metal ion toward nano-MnO₂ surface via the electrostatic attractions, thus leading to the passivation and inactivation of MnO₂ nanozyme catalytic activity. Thereinto, Fe²⁺ reacted with multivalent manganese by oxidation-reduction, while Pb²⁺ was specifically adsorbed onto the surface of MnO₂ nanozyme and formed complexes. Notably, only Fe²⁺ ion inhibited the activity of MnO₂ nanozyme-TMB with a detection limit as low as 1.0 μmol·L^?1. In MnO₂ nanozyme-ABTS sensing systems, Fe²⁺ and Pb²⁺ ions detection limit of 0.5 and 2.0 μmol·L^?1 were, respectively, achieved with a linear response range of 0–0.02 and 0–0.8 mmol·L^?1, implying the developed MnO₂ nanozyme-ABTS sensor was potentially applicable for the visual determination of Fe²⁺ and Pb²⁺ ions in water. In the real water samples, MnO₂ nanozyme-ABTS achieved high accuracy (relative errors: 3.4?10.5%) and recovery (96?110%) for respective detection of Fe²⁺ and Pb²⁺ ions. The simple and rapid MnO₂ nanozyme-ABTS sensing systems might provide a practical assay for visual detection of Fe²⁺ and Pb²⁺ ions in the environmental water samples.     

The Kinetics of Oxidation of L-Tryptophan by Water-Soluble Colloidal Manganese Dioxide

The kinetics of the oxidation of L-tryptophan by water-soluble colloidal MnO₂ (prepared from potassium permanganate and sodium thiosulfate solutions) has been carried out in aqueous perchloric acid medium at different temperatures. Monitoring the disappearance of the MnO₂ spectrophotometrically at 390 nm was used to follow the kinetics. The first-order kinetics with respect to [L-tryptophan] at low concentrations shifted to zero-order at higher concentrations. The reaction followed first-order with respect to [MnO₂] but fractional-order with respect to [HClO₄]. Adding trapping agents enhanced the rate of the reaction. The Arrhenius and Eyring equations were found valid for the reaction between 35°C and 55°C and different activation parameters (E_a, ΔH^#, ΔS^#) have been evaluated. On the basis of various observations and product characterization a plausible mechanism has been envisaged for the reaction taking place at the colloid surface. The results suggest formation of an adsorption complex between L-tryptophan and MnO₂. The complex decomposes in a rate-determining step, leading to the formation of free radical, which again reacts with the colloidal MnO₂ in a subsequent fast step to yield products. Freundlich isotherm is used to explain the adsorption of L-tryptophan on the colloidal MnO₂.     

焙烧温度对MnOx-CeO2-WO3-ZrO2催化剂上NH3选择性还原NO的影响

采用共沉淀法制备了MnO_x-CeO₂-WO₃-ZrO₂催化剂,考察了催化剂焙烧温度对O₂和H₂O存在下NH₃选择性催化还原（NH₃-SCR） NO的影响,并利用低温N₂吸附、X射线衍射（XRD）、透射电镜（TEM）、X射线光电子能谱（XPS）、NH₃程序升温脱附（NH₃-TPD）和CO脉冲反应对催化剂进行了表征. 结果表明在NH₃-SCR反应中,催化剂的低温活性随焙烧温度的提高而降低,这是由于催化剂表面化学吸附氧和酸性位减少引起的;催化剂的高温活性随焙烧温度的提高先增加后减小,这与催化剂表面最易释放氧数量的变化趋势相反. 700 ℃焙烧的催化剂具有良好的低温活性和最宽的反应温度窗口,在空速为90000 h^-1的条件下,该催化剂的起燃温度（50% NO转化率）为189 ℃,且反应温度在218-431 ℃范围内,NO转化率可达到80%-100%.     

Ag/Ag2MoO4/Bi2MoO6复合光催化剂的制备及其光催化性能

采用水热、化学沉积和原位光还原的方法成功制备了新型Ag/Ag₂MoO₄/Bi₂MoO₆三元复合光催化剂。通过X射线粉末衍射（XRD）、扫描电子显微镜（SEM）、X射线光电子能谱（XPS）和紫外可见漫反射光谱（UV-Vis DRS）等技术对材料的组成、形貌、光吸收特性和光电化学性能等进行系统分析。以四环素为目标污染物,研究Ag/Ag₂MoO₄/Bi₂MoO₆在可见光下的光催化性能。研究结果表明,相比于纯Ag₂MoO₄和Bi₂MoO₆,Ag的表面等离子体共振（SPR）效应显著拓宽了催化体系对可见光的吸收能力及响应范围。当Ag₂MoO₄理论负载量（质量分数）为24.6%时,Ag/Ag₂MoO₄/Bi₂MoO₆复合材料在20 min内可将四环素完全降解,且5次循环使用后仍保持较高的催化活性,表现出良好的循环稳定性。     

Influence of MnO<Subscript>2</Subscript> on the photocatalytic activity of P-25 TiO<Subscript>2</Subscript> in the degradation of methyl orange

Influences of α-MnO₂, β-MnO₂, and δ-MnO₂ on the photocatalytic activity of Degussa P-25 TiO₂ have been investigated through the photocatalytic degradation of methyl orange. The TiO₂ photocatalyst, before and after being contaminated by MnO₂, was characterized by UV-visible diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS). The results showed that photocatalytic activity of TiO₂ could be inhibited significantly or completely deactivated due to the presence of even a small amount of MnO₂ particles. It was found that the poisoning effect varied with the crystal phases of MnO₂ and the effect was in the order δ-MnO₂ >α-MnO₂ >β-MnO₂. The poisoning effect was attributed to the formation of heterojunctions between MnO₂ and TiO₂ particles. The heterojunctions changed the chemical state of Ti⁴⁺ and O²⁻ sites in the crystalline phase of TiO₂. MnO₂ in contact with TiO₂ particles also broadens the band-gap of TiO₂, which decreases UV absorption of TiO₂. It can also create some deep impurity energy levels serving as photoelectron-photohole recombination center, which accelerates the electron-hole recombination. Supported by the National Natural Science Foundation of China (Grant No. 20477009) and the Natural Science Foundation of Hebei Province (Grant No. E2005000183)     

Synthesis and crystal structure of the novel Pb5Sb2MnO11 compound

The new Pb₅Sb₂MnO₁₁ compound was synthesized using a solid-state reaction in an evacuated sealed silica tube at 650°C. The crystal structure was determined ab initio using a combination of X-ray powder diffraction, electron diffraction and high-resolution electron microscopy (a=9.0660(8)Å, b=11.489(1)Å, c=10.9426(9)Å, S.G. Cmcm, R_I=0.045, R_P=0.059). The Pb₅Sb₂MnO₁₁ crystal structure represents a new structure type and it can be considered as quasi-one-dimensional, built up of chains running along the c-axis and consisting of alternating Mn⁺²O₇ capped trigonal prisms and Sb₂O₁₀ pairs of edge sharing Sb⁺⁵O₆ octahedra. The chains are joined together by Pb atoms located between the chains. The Pb⁺² cations have virtually identical coordination environments with a clear influence of the lone electron pair occupying one vertex of the PbO₅E octahedra. Electronic structure calculations and electron localization function distribution analysis were performed to define the nature of the structural peculiarities. Pb₅Sb₂MnO₁₁ exhibits paramagnetic behavior down to T=5 K with Weiss constant being nearly equal to zero that implies lack of cooperative magnetic interactions.     

Determination of heats of aluminothermic redox reaction of V2O5 and MnO2

Differential thermal analysis has been used for quantitative determination of heats of aluminothermic redox reaction of MnO₂ and V₂O₅ over a wide range of temperatures. Heat of reaction V₂O₅?Al and MnO₂?Al systems have been determined using the calibration plot established. The experimentally determined values compare well with those predicted from thermodynamic data available in the literature. It has been found that V₂O₅?Al system involves a higher heat of reaction in comparison to the MnO₂?Al system.     

Preparation and characterization of mesoporous TiO2-CeO2 nanopowders respond to visible wavelength

Mesoporous TiO₂-CeO₂ nanopowders responding to visible wavelength were synthesized by using a surfactant assisted sol-gel technique. They were obtained using metal alkoxide precursors modified with acetylacetone (ACA) and laurylamine hydrochloride (LAHC) as surfactant. The samples were characterized by XRD, nitrogen adsorption isotherm, SEM, TEM, and selected area electron diffraction (SAED), respectively. The 95 mol% TiO₂-5 mol% CeO₂ system yielded single anatase phase, however, further addition of the CeO₂ formed cubic CeO₂ structure while anatase TiO₂ decreased. Additions of 5 and 10 mol% CeO₂ increased the surface area, but those of 25, 50, and 75 mol% CeO₂ did not affect it very much. By using this mixed metal oxides system, TiO₂ can be modified to respond to the visible wavelength. The mixed metal oxides had catalytic activity (evaluating the formation rate of I₃⁻) about 2-3 times higher than pure CeO₂, while nanosize anatase type TiO₂ materials had no catalytic activity under visible light. The catalytic activity was almost proportional to the specific surface area. The formation rate of I₃⁻ was much improved by changing the calcination temperature and calcination period. Highest catalytic activity in this study was obtained for the 50 mol% TiO₂-50 mol% CeO₂ nanopowders calcined at 250 °C for 24 h.