Electrochemical degradation of azo dye C.I. Reactive Red 195 by anodic oxidation on Ti/SnO2-Sb/PbO2 electrodes

This study investigated the electrochemical degradation of C.I. Reactive Red 195 (RR195) in aqueous solution on a Ti/SnO₂-Sb/PbO₂ electrode. The influence of operating variables on the mineralization efficiency was studied as a function of the current density, the initial pH, the initial concentration of the dye and the addition of NaCl. The efficiency of RR195 mineralization decreased with increased initial concentration, from 100 mg L⁻¹ to 400 mg L⁻¹. The current density had both a positive and a negative effect on degradation rates, and no significant effect of initial pH on RR195 mineralization was observed. Measurement of absorbance was used to discriminate the effect of NaCl in the electro-oxidation process. We found that the decolouring efficiency increased whereas the mineralization efficiency decreased with the increasing concentration of NaCl. The intermediates formed during the degradation were detected by gas chromatography-mass spectrometry, and the major aromatic intermediates identified were 1-(3,6,8-trihydroxy-1-naphthyl)urea, nitrobenzene, benzo-1,4-quinone, (3,6,8-trihydroxy-1-naphthyl)carbamic acid and phthalic acid. Quantitative measurement of organic and inorganic ions was done by ion chromatography. On the basis of the reaction products identified, a possible degradation pathway for the anodic oxidation of RR195 in aqueous solution is proposed.     

SnO_2-MnO_2-Sb_2O_3体系固溶体相图初探

采用化学共沉淀方法制备了SnO2-MnO2-Sb2O3三元固溶体并对其相图进行了初步研究,绘制了固相线下SnO2-MnO2-Sb2O3三元体系相图,确定该类固溶体的类型及其形成机制。实验结果表明:该三元体系的相关系图中含有2个单相区、8个两相区和3个三相区。金红石型SnO2为主要化合物的1区和锡锑共存互溶形成的(Sn,Sb)O2ss化合物为主的2区这两个单相区中的氧化物可以作为耐腐蚀性强、导电性良好的阳极材料中间层。     

Low temperature oxidation of methane over Pd/SnO2 catalyst

Catalytic activities of supported Pd were investigated for low temperature oxidation of methane. Pd/SnO₂ catalysts demonstrated excellent activity for methane oxidation in spite of their low surface area. The catalytic activity of Pd/SnO₂ was strongly affected by the preparation procedure. Impregnation of Pd on SnO₂ using aqueous solution of Pd(CH₃COO)₂ was most effective in enhancing the catalytic activity. The catalytic activity was also improved when well-crystallized SnO₂ was employed as a support material. TEM observations revealed that catalytic activity is strongly influenced by the dispersion state of Pd. For the active catalysts, strong interaction between Pd and SnO₂ support was observed in the adsorption of oxygen.     

Physico-chemical characteristics and CO oxidation studies over Pd/(Mn2O3 + SnO2) catalyst

The mixed oxide catalyst (Mn₂O₃ + SnO₂) prepared by the coprecipitation method has been impregnated with Pd metal and it's catalytic behaviour for CO oxidation reaction has been investigated. In the coprecipitated material, Mn₂O₃ and SnO₂ were found to crystallise at 875 K and 1175 K, respectively, which are significantly higher than the crystallisation temperatures of individual oxides prepared under similar conditions. Results of catalytic oxidation of CO, carried out using the pulse method for the mixed oxide system and the individual oxides, suggest significant synergistic effects between these two oxides. The impregnation of palladium metal facilitated CO oxidation and the catalyst Pd/(Mn₂O₃ + SnO₂) was found to be quite effective for CO oxidation even at room temperature. Further, the CO disproportionation has been observed on palladium sites in the temperature range 350 to 400 K for the individual oxide systems.     

Characterization of SnO2 nanowires synthesized from SnO by carbothermal reduction process

In this paper, single-crystalline SnO₂ nanowires have been successfully prepared by a carbothermal reduction process employing SnO as the starting material and CuO as the catalyst. Their morphologies, purity and sizes of the products were characterized by transmission electron microscopy (TEM), selected area electron diffraction, X-ray diffraction, field emission scanning electron microscopy (FESEM) and Raman spectroscopy, respectively. The FESEM images reveal wire-like and rod-shaped nanowires of about 100–800 μm in length and 30–200 nm in the transverse dimensions. The three observed Raman peaks at 474, 634 and 774 cm⁻¹ indicate the typical rutile phase of the SnO₂ which is in agreement with the X-ray diffraction results. The influence of some reaction parameters, including the temperature and the reaction duration, on the forming, morphology and particle size of SnO₂ crystallize is discussed.     

Investigation of formic acid oxidation on Ti/IrO2 electrodes

A model has been proposed according to which the voltammetric charge involved in the Ti/IrO₂ electrodes is due to two contributions: a faradaic contribution due to surface redox activities at the IrO₂ coating and a non-faradaic contribution due to the charging of electrical double layer (). The later has been proposed as a tool for the estimation of the relative surface area of the Ti/IrO₂ electrodes.Differential electrochemical mass spectrometry (DEMS) measurements using H₂¹⁸O has demonstrated that we are dealing with an active electrode in which the surface redox couple IrO₃/IrO₂ acts as mediator in the oxidation of formic acid (FA).From the voltammetric measurements using different IrO₂ loading and FA concentrations, the kinetic parameters of FA oxidation via the surface redox couple IrO₃/IrO₂ have been determined.Finally a model has been proposed considering that FA oxidation at Ti/IrO₂ anodes is controlled by mass transfer. The good agreement between the experimental results and the model indicates that the surface reaction between FA and the electrogenerated IrO₃ is a fast reaction.     

微流控反应器中苯酚在Ti/SnO2-Sb2O5电极上的阳极氧化分析

目前在电化学氧化处理法降解苯酚废水的研究过程中,研究者多将重心放在活性电极的探索及制备上,而对于反应器的开发鲜有报道。就这一问题,本文研究了新型微流控反应器中苯酚的电化学降解效果。电化学氧化实验在装有Ti/SnO₂-Sb₂O₅阳极的微型流通池中操作进行,实验对循环体系的体积流率Φ_V、电极间距h的影响进行了考察。结果表明,当流通电解槽中的阴阳极间距采用微米级尺寸时,苯酚的阳极氧化反应取得了较快的氧化速度。在 em= 20 mA/cm²、Φ_V= 0.54 mL/min的电解条件下,电解2~3h苯酚去除率即可达到90%以上,相同流速下电极间距h越小降解速率越快。且由数据回归得到了苯酚的一系列随h的减小而增大的准一级反应的反应速率常数。这一结论表明微流控电解槽内的苯酚降解过程主要传质控制过程。     

Degradation of azo dye C.I. Acid Red 18 in aqueous solution by ozone-electrolysis process

In this paper, the degradation of azo dye C.I. Acid Red 18 (AR18) with initial concentration of 100 mg L⁻¹ in aqueous solution by ozone-electrolysis process (OEP) as hybrid method of advance oxidation process was investigated. All experiments were performed in a 450 mL mixed semi-batch reactor to obtain the optimal conditions. The effects of NaCl concentration as supporting electrolyte, current density and initial pH on the removal efficiency of AR18 solution were investigated. The efficiency of color and TOC removal were compared as functional of degradation and decolorization of AR18. The results of UV/vis spectra showed that the AR18 structures were destroyed under ozone-electrolysis reaction. This investigation revealed ozone-electrolysis presents good efficiency for both solution decolorization and total organic carbon (TOC) removal. Results of experiments indicated that ozone-electrolysis process has a synergistic effect on decolorization rate of AR18.     

Catalytic activity and solid acidity of vanadium oxide thin layer loaded on TiO2, ZrO2, and SnO2

Vanadium oxide spread highly on TiO₂ (anatase, A) and SnO₂, and rather densely on TiO₂ (rutile, R) and ZrO₂ to make the monolayer in less than 4–5 V nm⁻². Profile of acid site of the monolayer was measured by temperature programmed desorption of ammonia, and its relation with the surface oxidation state was studied. The acid site density was high on the V₂O₅/TiO₂ (A) independent of the degree of oxidation. On the other hand, that of V₂O₅/TiO₂ (R) and V₂O₅/ZrO₂ depended on the oxidation state, and the high value of the concentration was observed on the oxidized one. The strength of acid site generated on the V₂O₅ monolayer on TiO₂ was as high as on the HZSM-5 zeolite. Turnover frequency (TOF) of propane conversion, and product selectivity were measured in propane oxidation. Among tested oxides, the V₂O₅/TiO₂ (A) showed the high TOF and selectivity to form propylene, while those loaded on TiO₂ (R) and ZrO₂ the small TOF and poor selectivity. Therefore, the reaction profile of activity and selectivity could be related with the extent of spreading and solid acidity. An idea of limit of the acid site density ca. 1.5 nm⁻² on the monolayer was elucidated.     

On the performance of Ti/SnO2 and Ti/PbO2 anodesin electrochemical degradation of 2-chlorophenolfor wastewater treatment

Electrochemical oxidation of 2-chlorophenol was studied at Ti/PbO2 and Ti/SnO2 anodes. The performance of the electrodes was evaluated in terms of faradaic yield and fraction of toxic intermediates removed during the electrolysis. Results showed that, although similar average faradaic yields were obtained using Ti/PbO2 or Ti/SnO2 anodes, the latter material is preferred because of its better ability to oxidise toxic compounds. An effective electrochemical treatment (F50%) may be accomplished, in which electrolysis at Ti/SnO2 can be stopped when, in spite of a relatively high COD, only a small amount of easily biodegradable oxalic acid is present in the effluent.     

A study on the characteristics of the SO2 reduction using coal gas over SnO2-ZrO2 catalysts

SO₂, which is an air pollutant causing acid rain and smog, can be converted into elemental sulfur in direct sulfur recovery process (DSRP). SO₂ reduction was performed over catalyst in DSRP. In this study, SnO₂-ZrO₂ catalysts were prepared by a co-precipitation method, and CO and coal gas, which contains H₂, CO, CO₂ and H₂O, were used as reductants. The reactivity profile of the SO₂ reduction over the catalysts was investigated at the various reaction conditions as follows: reaction temperature of 300–550 °C, space velocity of 5000–30,000 cm³/g_-cat. h, [reductant]/[SO₂] molar ratio of 1.0–4.0 and Sn/Zr molar ratio of SnO₂-ZrO₂ catalysts 0/1, 2/8, 3/5, 5/5, 2/1, 3/1, 4/1 and 1/0. SnO₂-ZrO₂ (Sn/Zr = 2/1) catalyst showed the best performance for the SO₂ reduction in DSRP on the basis of our experimental results. The optimized reaction temperature and space velocity were 325 °C and 10,000 cm³/g_-cat. h, respectively. The optimal molar ratio of [reductant]/[SO₂] varied with the reductants, that is, 2.0 for CO and 2.5 for coal gas. SO₂ conversion of 98% and sulfur yield of 78% were achieved with the coal gas.     

非均相Fe/Al_2O_3催化H_2O_2降解偶氮染料活性黑5

以活性氧化铝为载体,制备了Fe/Al2O3负载型催化剂,用于催化H2O2分解产生羟基自由基氧化降解偶氮染料活性黑5。探讨了pH、H2O2投加量、催化剂投加量等对染料脱色率的影响。结果表明,活性黑5的脱色率随催化剂投加量的增加而升高;随H2O2投加量的增加而降低;Fe/Al2O3/H2O2体系下,活性黑5在pH为2~9之间均有一定的脱色效果,活性黑5的脱色率随初始pH的增加而先增加后减少,其中在初始pH为3时,脱色效果最佳。     

Kinetic study of formic acid oxidation on Ti/IrO2 electrodes prepared using the spin coating deposition technique

In the first part of this paper, IrO₂ electrodes produced by thermal decomposition of H₂IrCl₆ precursor were manufactured using the spin coating deposition technique, where centrifugal forces spread the precursor solution with simultaneous evaporation of the solvent on the rotating Ti substrate. It was found using this technique, that it is possible to obtain thin and uniform IrO₂ coatings with controlled loadings. The influence of the concentration of iridium salt in the precursor solution (c₀) as well as the influence of the rotation speed at which the substrate spins (ω) on the IrO₂ loading have been studied using voltammetric charge measurements. From these results, a simple relation has been proposed for the estimation of the IrO₂ loading for a given c₀ and ω.In the second part of this paper and from measurements performed using different IrO₂ loadings and formic acid concentrations, the kinetic parameters of the oxidation of formic acid have been quantitatively determined using a model that involves the redox couple IrO₃/IrO₂ as mediator of this reaction. Furthermore, using the kinetic parameters obtained together with the Nernst equation and the I-V curves of the supporting electrolyte (1 M HClO₄), theoretical I-V curves could be constructed for different concentrations of formic acid and different IrO₂ loadings.     

Preparation and characterization of TiO2/Ti film electrodes by anodization at low voltage for photoelectrocatalytic application

Multiporous TiO₂/Ti film electrodes were prepared by different anodic oxidation processes at low voltage, in which the micro-structured TiO₂ thick films were prepared in H₂SO₄–H₂O₂–H₃PO₄–HF solution for 2 h and the nano-structured TiO₂ thin films were prepared in H₃PO₄–HF solution for 30 min with post-calcination. Both types of TiO₂/Ti films were characterized by scanning electron microscopy and X-ray diffraction analysis. The photocatalytic (PC) and photoelectrocatalytic (PEC) reactivity of the TiO₂/Ti electrodes were evaluated in terms of bisphenol A (BPA) degradation in aqueous solution. The experimental results demonstrated that the nano-structured TiO₂/Ti thin-film electrodes had higher reactivity in the BPA degradation reaction. The PEC degradation of BPA was further studied using different cathodes, either a reticulated vitreous carbon (RVC) electrode or a platinum (Pt) electrode. The experimental results confirmed that the efficiency of BPA degradation could be significantly enhanced in the TiO₂/Ti–RVC reaction system due to the generation of H₂O₂ on the RVC cathode. It is believed that such a H₂O₂-assisted TiO₂ PEC oxidation process may have good potential for water and wastewater treatment.     

Degradation of C.I. Basic Red 29 solution by combined ultrasound and Co-H2O2 system

Ultrasonic degradation of Basic Red 29 (BR29) textile dye in the presence of Co²⁺-H₂O₂ system was investigated in this study. The effects of presence of ultrasonic power, concentrations of cobalt (II) acetate (Co(II)Act) and H₂O₂, temperature and initial pH on the BR29 degradation were examined. Initial dye concentration of 20 mg/L BR29 was used in the study as a model solution. In sonication experiments, an ultrasonic bath at a frequency of 40 kHz was employed. Best experimental conditions were also obtained in the studies as follows: 1000 mg/L Co(II)Act, 1000 mg/L H₂O₂, 40 °C and original pH of 6.70.According to the results, after 30 min of sonication in the presence of Co²⁺-H₂O₂ dye removal efficiency of practically 100% was achieved. It was also found that US enhanced the degradation rate of BR29.     

聚苯胺中间层改性Ti/PbO2电极的制备及其降解性能

引入导电聚合物聚苯胺膜（PANI,polyaniline）对Ti/PbO₂电极进行改性,采用两步电沉积法成功制备出Ti/PANI/PbO₂电极。通过扫描电镜（SEM）、X射线衍射(XRD)、线性伏安扫描(LSV)和交流阻抗(EIS)对制备的电极进行表征,以甲基橙为目标污染物,探讨了PANI的沉积时间对电极性能的影响,并研究了Ti/PANI/PbO₂电极对罗丹明B和4-硝基苯酚的降解性能。结果表明,PANI的引入未影响活性层PbO₂的晶相结构和形貌特征,但显著提高了电极的析氧电位,Ti/PANI/PbO₂的析氧电位可达3.43V。当PANI聚合时间为30min时,电极Ti/PANI-30/PbO₂的电化学性能和电催化降解效果最佳。在电流密度为30mA/cm²、污染物初始浓度为50mg/L、Na₂SO₄浓度为0.1mol/L的实验条件下,反应120min后,Ti/PANI-30/PbO₂对甲基橙、罗丹明B和4-硝基苯酚的去除率分别为99.8%、99.9%和94.0%。     

钆掺杂二氧化钛纳米管光催化降解制药废水

采用阳极氧化法制备TiO2纳米管阵列,并在制备TiO2纳米管阵列的同时掺杂钆元素,形成钆掺杂TiO2纳米管阵列,研究其光催化降解制药废水的性能。结果表明,经过450℃煅烧的催化剂,在碱性条件下,钆掺杂浓度为0.007 5 mol/L时,催化效果最好,光催化5 h后,制药废水降解率达到97.41%,且该催化剂稳定性好,可重复使用。     

TiO_2/PbO_2复合膜光催化氧化降解染料废水

提出了一种TiO2/PbO2复合膜圆形光催化氧化反应器,研究了该反应器对经生化处理后的染料废水进行降解的过程.研究表明:光催化氧化的最佳条件是锌片镀TiO2/PbO2复合膜、pH=8.0、H2O2质量浓度为400 mg/L.并对其他氧化剂对该过程的影响进行了探讨.有机废水通过该反应器进行处理后,其COD降为48.4 mg/L.能使有机污染物全部降解为小分子无机物,废水达到国家一级排放标准.