CuO impregnated activated carbon for catalytic wet peroxide oxidation of phenol

This paper presents an original approach to the removal of phenol in synthetic wastewater by catalytic wet peroxide oxidation with copper binding activated carbon (CuAC) catalysts. The characteristics and oxidation performance of CuAC in the wet hydrogen peroxide catalytic oxidation of phenol were studied in a batch reactor at 80 °C. Complete conversion of the oxidant, hydrogen peroxide, was observed with CuAC catalyst in 20 min oxidation, and a highly efficient phenol removal and chemical oxygen demand (COD) abatement were achieved in the first 30 min. The good oxidation performance of CuAC catalyst was contributed to the activity enhancement of copper oxide, which was binding in the carbon matrix. It can be concluded that the efficiency of oxidation dominated by the residual H₂O₂ in this study. An over 90% COD removal was achieved by using the multiple-step addition in this catalytic oxidation.     

Heterogeneous catalytic degradation of phenolic substrates: catalysts activity

This review article explored the catalytic degradation of phenol and some phenols derivates by means of advanced oxidation processes (AOPs). Among them, only the heterogeneous catalyzed processes based on catalytic wet peroxide oxidation, catalytic ozonation and catalytic wet oxidation were reviewed. Also selected recent examples about heterogeneous photocatalytic AOPs will be presented. In details, the present review contains: (i) data concerning catalytic wet peroxide oxidation of phenolic compounds over metal-exchanged zeolites, hydrotalcites, metal-exchanged clays and resins. (ii) Use of cobalt-based catalysts, hydrotalcite-like compounds, active carbons in the catalytic ozonation process. (iii) Activity of transition metal oxides, active carbons and supported noble metals catalysts in the catalytic wet oxidation of phenol and acetic acid. The most relevant results in terms of catalytic activity for each class of catalysts were reported.     

Enabling Specific Benzene Oxidation by Tuning the Adsorption Behavior on Au Loaded MgAl Layered Double Hydroxides

Direct and selective oxidation of benzene to phenol is a long-term goal in industry. Although great efforts have been made in homogenous catalysis, it still remains a huge challenge to drive this reaction via heterogeneous catalysts under mild conditions. Herein, a single-atom Au loaded MgAl-layered double hydroxide (Au₁-MgAl-LDH) with a well-defined structure, in which the Au single atoms are located on the top of Al³⁺ with Au-O₄ coordination as revealed by extended x–ray–absorption fine–structure (EXAFS)and density–functional theory (DFT)calculation is reported. The photocatalytic results prove the Au₁-MgAl-LDH is capable of driving benzene oxidation reaction with O₂ in water, and exhibits a high selectivity of 99% for phenol. While contrast experiment shows a ≈99% selectivity for aliphatic acid with Au nanoparticle loaded MgAl-LDH (Au-NP-MgAl-LDH). Detailed characterizations confirm that the origin of the selectivity difference can be attributed to the profound adsorption behavior of substrate benzene with Au single atoms and nanoparticles. For Au₁-MgAl-LDH, single Au-C bond is formed in benzene activation and result in the production of phenol. While for Au-NP-MgAl-LDH, multiple Au C bonds are generated in benzene activation, leading to the crack of C C bond.     

膨胀石墨基炭/炭复合电极的制备及含酚废水的降解

以压缩膨胀石墨为基体、蔗糖为炭源、磷酸为活化剂,经碳化、活化压片制得膨胀石墨基炭/炭复合电极(EGC电极)。采用低温液氮吸附法和扫描电镜(SEM)进行表征,研究了蔗糖浓度对电极表面结构和孔道特征的影响规律,并以苯酚为处理目标物,考察了不同的电解条件。结果表明,EGC电极以膨胀石墨为骨架,包覆炭膜,孔径主要分布在0.5～2.5nm之间,蔗糖浓度为50%制备的EGC电极比表面积最高,电化学氧化苯酚效果最优。电解苯酚试验中,降低苯酚初始浓度、增加电流密度和电解质浓度有利于提高苯酚的降解效率。     

Shape-controlled synthesis of bare ZnO nanomaterials with improved photoactivity and photostability

ABSTRACT

Understanding the growth mechanisms of nanomaterials usually leads to the successful preparation of targeted micro-structures with excellent properties. In this paper, flower-like and roughly spherical ZnO nanocrystals have been successfully synthesised through facile wet chemical methods, i.e. hydrothermal pathways and homogeneous precipitation method. The photocatalytic activities of the prepared photocatalysts were evaluated by degradation of rhodamine B (RhB) and phenol under ultraviolet (UV) irradiation. Remarkably, the ZnO powder via homogeneous precipitation (urea/Zn²⁺?=?2.0) exhibited better photocatalytic performance and photostability than those of flower-like ZnO substrate. The enhanced photocatalytic properties could be attributed to more active catalytic sites and effective separation of carriers, which were confirmed by low-temperature nitrogen adsorption, photocurrent responses, and photoluminescence spectral analysis. A possible mechanism for the excellent photocatalytic activity of ZnO substrates was proposed.     

Sn~(4+)-TiO_2的制备及其光催化降解苯酚的研究

采用硬脂酸法制备出Sn4+-TiO2复合光催化剂,用透射电子显微镜和X光衍射仪对粉体的粒径、物相、形貌和热稳定性进行了表征。样品经500℃焙烧2h后,5%Sn4+-TiO2纳米粉末颗粒细小均匀,形状完整,粉末的平均晶粒度约为14nm。通过粉体对苯酚的降解情况对其光催化活性进行了测试,结果表明,与纯TiO2相比,Sn4+-TiO2的光催化活性有较大提高,当SnO2的掺入量为摩尔比5.0%时催化活性最高。以高压汞灯为光源,苯酚的初始浓度为80mg.L-1、催化剂5%Sn4+-TiO2投加量为1.0g.L-1时,溶液的pH为4,苯酚的光催化降解效果最好。     

Catalytic properties of carbon materials for wet oxidation of aniline

A mesoporous carbon xerogel with a significant amount of oxygen functional groups and a commercial activated carbon, were tested in the catalytic wet air oxidation of aniline at 200 degrees C and 6.9 bar of oxygen partial pressure. Both carbon materials showed high activity in aniline and total organic carbon removal, a clear increase in the removal efficiency relatively to non-catalytic wet air oxidation being observed. The best results in terms of aniline removal were obtained with carbon xerogel, an almost complete aniline conversion after 1h oxidation with high selectivity to non-organic compounds being achieved. The materials were characterized by thermogravimetric analysis, temperature programmed desorption, N(2) adsorption and scanning electron microscopy, in order to relate their performances to the chemical and textural characteristics. It was concluded that the removal efficiency, attributed to both adsorption and catalytic activity, is related to the mesoporous character of the materials and to the presence of specific oxygen containing functional groups at their surface. The effect of catalytic activity was found to be more important in the removal of aniline than the effect of adsorption at the materials surface. The results obtained indicate that mesoporous carbon xerogels are promising catalysts for CWAO processes.     

基于纳米光催化的旅客机座舱新型空气净化系统

旅客机座舱空气质量关系到机组成员和乘客的安全、健康和舒适；座舱内空间狭小，人员密集，空气质量与地面建筑环境不同。针对旅客机的座舱环境，提出了基于纳米光催化的新型座舱空气净化系统；与传统的高效过滤器/活性炭复合净化装置相比，纳米光催化装置全寿命期费用非常低，不仅能控制座舱内挥发性有机污染物，还能净化座舱内的微生物，有助于旅客机环境控制系统减小新风量，节省能耗，降低飞机成本。     

The effect of the methods of recovering diamond nanopowders on their physicochemical properties

The effect has been considered of the methods of recovering (liquid oxidation of nondiamond carbon with a mixture of sulphuric and chromic acids, selective gas oxidation of nondiamond carbon in the presence of copper salts as a catalyst, and oxidation of nondiamond carbon with a mixture of concentrated sulfuric and nitric acids) diamond nanopowders from detonation-synthesized diamond-carbon products on physicochemical properties of diamond, for which the structural state of the diamond surface is responsible. It has been found that diamond nanopowders recovered using different technologies exhibit a decrease of the volume fraction of aggregates among particles. Nanodiamonds recovered by a catalytic gas-phase oxidation in the presence of copper have been found to be characterized by the highest adsorption activity, thermostability, and electroconductivity due to the carbon-containing cover of a complex composition. The recommendations have been given on the use of diamond nanopowders recovered by different technologies.     

甲醛湿式氧化催化剂的制备及性能研究

用FTIR和N2吸附法对活性炭进行表面分析,通过原子吸收光谱考察了铜在活性炭表面的吸附行为,制备了几种甲醛湿式氧化的催化剂,对比研究了它们在常温常压下对甲醛氧化的催化性能。结果表明,活性炭氧化改性后表面含氧基团增加,对铜和甲醛的吸附性能提高。活性炭表面负载的铜、银、铁对甲醛湿式氧化都有一定的催化能力,其中栽铜活性炭的催化效果最好,载铁活性炭的催化性能优于载银活性炭,催化动力学曲线表明,氧化改性后,载铜活性炭的催化性能进一步提高。     

活性炭纤维电极法处理含酚废水的研究

以活性炭纤维作为阳极,不锈钢板为阴极,采用电化学氧化法对模拟的含酚废水进行了处理.结果表明,该方法可以有效分解除去水中的苯酚,苯酚和COD的去除率均能达到95%以上,其最佳的操作条件为:pH值为3、进水苯酚浓度为500mg/L、电流密度为26mA/cm2、Na2SO4浓度为15g/L.同时,通过对比不同电极材料的降解效果,证明了具高比表面积的活性炭纤维作为电极材料,能充分将其导电、吸附、催化及稳定性能有效地结合起来,实现高效净化,具有良好的应用前景.     

Adsorption of phenol by MMT-CTAB and WPT-CTAB: Equilibrium,kinetic, and thermodynamic study

In this study, the phenol adsorption capacity of cetyltrimethylammonium bromide modified clays (MMT-CTAB) and cetyltrimethylammonium bromide modified pulp tea (WPT-CTAB) were studied. In batch adsorption experiments performed with MMT-CTAB, the effects of parameters such contact time, phenol concentration, pH of solution and adsorbent dosage were investigated. The effect of temperature on phenol adsorption onto MMT-CTAB and WPT-CTAB was examined; equilibrium and thermodynamic studies were completed. The highest phenol removal was found at pH 4.0 for MMT-CTAB and WPT-CTAB. To analyze the kinetics of phenol adsorption onto MMT-CTAB, the pseudo first-order and pseudo second-order kinetic models were applied. The kinetic data fitted better to the pseudo second-order model than the pseudo first-order kinetic model for MMT-CTAB. The characterization of adsorbents in phenol adsorption was clarified with the FTIR technique. Thermodynamic parameters such as ΔH°, ΔS° and ΔG° were calculated for each adsorption process. The adsorption process was found to be exothermic and spontaneous for phenol adsorption by MMT-CTAB and WPT-CTAB. The results were analyzed with the Langmuir, Freundlich, Temkin and Harkins–Jura equations using linearized correlation coefficients at different temperatures. The Langmuir equation was found to best represent the equilibrium data for phenol adsorption onto MMT-CTAB and WPT-CTAB.     

Oxidative degradations of reactive blue 4 dye by different advanced oxidation methods

The degradations of an anthraquinone dye, the reactive blue 4 (RB4), were studied by wet air oxidation (WAO), wet peroxide oxidation (WPO), photocatalytic oxidation, and electro-Fenton (EF) advanced oxidation. The RB4 oxidation was evaluated by the decrease in total organic carbon (TOC) content and concentration. The most efficient method for mineralization of RB4 was WPO, but in all methods TOC removal efficiency was above 75% after 60 min of treatment.     

Catalytic wet air oxidation of chlorophenols over supported ruthenium catalysts

A series of noble metal (Pt, Pd, Ru) loaded zirconia catalysts were evaluated in the catalytic wet air oxidation (CWAO) of mono-chlorophenols (2-CP, 3-CP, 4-CP) under relatively mild reaction conditions. Among the investigated noble metals, Ru appeared to be the best to promote the CWAO of CPs as far as incipient-wetness impregnation was used to prepare all the catalysts. The position of the chlorine substitution on the aromatic ring was also shown to have a significant effect on the CP reactivity in the CWAO over 3wt.% Ru/ZrO(2). 2-CP was relatively easier to degradate compared to 3-CP and 4-CP. One reason could be the higher adsorption of 2-CP on the catalyst surface. Further investigations suggested that 3wt.% Ru/ZrO(2) is a very efficient catalyst in the CWAO of 2-CP as far as high 2-CP conversion and TOC abatement could still be reached at even lower temperature (393K) and lower total pressure (3MPa). Additionally, the conversion of 2-CP was demonstrated to increase with the initial pH of the 2-CP solution. The dechlorination reaction is promoted at higher pH. In all cases, the adsorption of the reactants and the reaction intermediates was shown to play a major role. All parameters that would control the molecule speciation in solution or the catalyst surface properties would have a key effect.     

Structure and oxidation resistance of plasma sprayed Ni–Si coatings on carbon steel

Ni–Si coatings consisting of mainly NiSi₂ and NiSi were deposited on a carbon steel by air plasma spraying. Isothermal oxidation tests of the carbon steel substrates with the Ni–Si coatings at 500–800 °C have been carried out. The result indicated that a protective SiO₂-based oxide scale was formed on the surface of the coatings after oxidation. On the other hand, during oxidation, phase transformation occurred among the NiSi₂, NiSi and Ni₂Si phases constructing the Ni–Si coatings. This was caused by the extraction of silicon from the silicides and the reformation of silicides at the silcide/Si-blocks interface. Above 700 °C, the outward diffusion of iron and carbon became very fast and consequently decarburization happened at the coating/substrates interface, which induced the formation of pores in the substrates near the interface. In addition, grain boundary oxidation of Cr in the steel substrate was observed above 700 °C.     

Amplification of amperometric biosensor responses by electrochemical substrate recycling. 3. Theoretical and experimental study of the phenol-polyphenol oxidase system immobilized in Laponite hydrogels and layer-by-layer self-assembled structures

The amperometric response toward phenol of PPO-based rotating disk bioelectrodes is analyzed on the basis of a kinetic model taking into account internal and external mass transport effects and a CEC' electroenzymatic mechanism. Monophenolase activity of PPO catalyses the oxidation of phenol to o-quinone (step C). o-Quinone can then enter an amplification recycling process involving electrochemical reduction (step E) and enzymatic reoxidation (step C': catecholase activity). The rate-limiting steps such as monophenolase activity, catecholase recycling, permeability of the membrane, and activity and accessibility of the catalytic enzyme sites are theoretically considered and experimentally demonstrated for different electrode configurations including PPO immobilized in Laponite hydrogels and layer-by-layer self-assembled multilayers of PPO and poly(diallyldimethylammonium).     

Pt/Fe_2O_3/TiO_2的制备、表征及其光催化活性研究

报道了担载不同贵金属或过渡金属氧化物的TiO2 催化剂对空气中微量甲醛的光催化氧化的研究结果。实验发现 ,TiO2 上担载Fe2 O3 或Pt时对甲醛均有较高的光催化氧化活性。同时担载双组分的光催化剂Pt Fe2 O3 TiO2 ,由于 2种组分的协同作用 ,具有更高的光催化活性。研究了催化剂制备因素、催化剂的结构及表面特性对催化活性的影响     

苯酚在竹炭上的吸附平衡和动力学研究

研究了20℃下苯酚在3种竹炭上的吸附平衡和动力学。采用低温下氮气吸附法测定了3种竹炭的BET比表面积和孔径分布,并用SEM观察了其微观形貌。根据Langmuir吸附等温线模型和Freundli ch模型分别对吸附数据进行拟合,结果表明Freundli ch吸附等温线模型能较好的用来描述苯酚在竹炭上的吸附平衡,并确立了20℃下苯酚在竹炭上吸附的Freundlich模型表达式;竹炭的BET比表面积和中孔容积越大,饱和吸附量也越大;对同一种竹炭,随竹炭用量的增加,溶液中苯酚残余浓度就越低,而竹炭用量与达到饱和吸附的时间无关。     

Effects of operational conditions on sludge degradation and organic acids formation in low-critical wet air oxidation

Wet air oxidation processes are to treat highly concentrated organic compounds including refractory materials, sludge, and night soil, and usually operated at supercritical water conditions of high temperature and pressure. In this study, the effects of operational conditions including temperature, pressure, and oxidant dose on sludge degradation and conversion into subsequent intermediates such as organic acids were investigated at low critical wet oxidation conditions. The reaction time and temperature in the wet air oxidation process was shown an important factor affecting the liquefaction of volatile solids, with more significant effect on the thermal hydrolysis reaction rather than the oxidation reaction. The degradation efficiency of sludge and the formation of organic acids were improved with longer reaction time and higher reaction temperature. For the sludge reduction and the organic acids formation under the wet air oxidation, the optimal conditions for reaction temperature, time, pressure, and oxidant dose were shown approximately 240 degrees C, 30min, 60atm, and 2.0L/min, respectively.     

Characterization of platinum–iron catalysts supported on MCM-41 synthesized with rice husk silica and their performance for phenol hydroxylation

Mesoporous material RH-MCM-41 was synthesized with rice husk silica by a hydrothermal method. It was used as a support for bimetallic platinum−iron catalysts Pt–Fe/RH-MCM-41 for phenol hydroxylation. The catalysts were prepared by co-impregnation with Pt and Fe at amounts of 0.5 and 5.0 wt.%, respectively. The RH-MCM-41 structure in the catalysts was studied with x-ray diffraction, and their surface areas were determined by nitrogen adsorption. The oxidation number of Fe supported on RH-MCM-41 was + 3, as determined by x-ray absorption near edge structure (XANES) analysis. Transmission electron microscopy (TEM) images of all the catalysts displayed well-ordered structures, and metal nanoparticles were observed in some catalysts. All the catalysts were active for phenol hydroxylation using H₂O₂ as the oxidant at phenol : H₂O₂ mole ratios of 2 : 1, 2 : 2, 2 : 3 and 2 : 4. The first three ratios produced only catechol and hydroquinone, whereas the 2 : 4 ratio also produced benzoquinone. The 2 : 3 ratio gave the highest phenol conversion of 47% at 70 °C. The catalyst prepared by co-impregnation with Pt and Fe was more active than that prepared using a physical mixture of Pt/RH-MCM-41 and Fe/RH-MCM-41.