Catalytic activity of cerium-doped Ru/Al2O3 during ozonation of dimethyl phthalate

In this paper, factors influencing the mineralization of dimethyl phthalate (DMP) during catalytic ozonation with a cerium-doped Ru/Al₂O₃ catalyst were studied. The catalytic contribution was calculated through the results of a comparison experiment. It showed that doping cerium significantly enhanced catalytic activity. The total organic carbon (TOC) removal over the doped catalyst at 100 min reached 75.1%, 61.3% using Ru/Al₂O₃ catalyst and only 14.0% using ozone alone. Catalytic activity reached the maximum when 0.2% of ruthenium and 1.0% of cerium were simultaneously loaded onto Al₂O₃ support. Results of experiments on oxidation by ozone alone, adsorption of the catalyst, Ce ion’s and heterogeneous catalytic ozonation confirmed that the contribution of heterogeneous catalytic ozonation was about 50%, which showed the obvious effect of Ru-Ce/Al₂O₃ on catalytic activity.     

Ce-MCM-41分子筛用于臭氧氧化对氯苯甲酸的活性评价

通过水热法合成了铈掺杂MCM-41(Ce-MCM-41)介孔分子筛,并将其用于臭氧氧化水中对氯苯甲酸(p-CBA).小角X射线衍射(XRD)、氮气吸附-脱附(BET)、紫外可见漫反射光谱(UV-Vis DRS)、透射电镜(TEM)表征结果表明,铈成功进入MCM-41分子筛骨架,以正四面体形式存在,且Ce-MCM-41保持了纯硅MCM-41有序的介孔结构,具有较高的比表面积;铈的掺杂显著提高MCM-41催化臭氧氧化对氯苯甲酸的活性,反应60 min后,TOC去除率由MCM-41的63%提高到86%(Si/Ce=60),而单独臭氧氧化仅为52%;铈的溶出仅为0.085 mg.L-1,较同样负载量的铈负载Ce/MCM-41的溶出(0.44 mg.L-1)有较大减少.催化剂重复使用3次后仍保持较高的活性,这表明Ce-MCM-41具有较好的活性和稳定性,是一种有前景的臭氧氧化催化剂.     

TiO2/浮石光催化降解水中邻苯二甲酸二甲酯

采用溶胶.凝胶法制备,TiO2/浮石催化剂,光催化氧化水中内分泌干扰物邻苯二甲酸二甲酯(DMP).考察催化剂用量、pH值对降解率的影响;同时分析降解动力学和有机物矿化程度.结果表明,催化剂最佳投放量为40 g·L-1,最佳pH为6.5.在最佳条件下,DMP初始质量浓度20.0 mg·L-1,5 h DMP降解率达90%以上.降解速率符合准一级动力学方程,动力学方程为:Ln(p0/p)=0.470t-0.050,速率常数=0.470h-1.考察降解过程水样的矿化程度,前4 h矿化率没有明显变化,4 h后矿化率逐渐加快,7 h矿化率达到70%.TiO2/浮石具有成本低、易回收利用、能充分与被降解物接触等优势,用于治理水体中DMP具有一定的实际可行性.     

Catalytic ozonation of organic compounds in water over the catalyst of RuO2/ZrO2-CeO2

This research investigates the performances of RuO₂/ZrO₂-CeO₂ in catalytic ozonation for water treatment. The results show that RuO₂/ZrO₂-CeO₂ was active for the catalytic ozonation of oxalic acid and possessed higher stability than RuO₂/Al₂O₃ and Ru/AC. In the catalytic ozonation of dimethyl phthalate (DMP), RuO₂/ZrO₂-CeO₂ did not enhance the DMP degradation rate but significantly improved the total organic carbon (TOC) removal rate. The TOC removal in catalytic ozonation was 56% more than that in noncatalytic ozonation. However this does not mean the catalyst was very active because the contribution of catalysis to the overall TOC removal was only 30%. The adsorption of the intermediates on RuO₂/ZrO₂-CeO₂ played an important role on the overall TOC removal while the adsorption of DMP on it was negligible. This adsorption difference was due to their different ozonation rates. In the catalytic ozonation of disinfection byproduct precursors with RuO₂/ZrO₂-CeO₂, the reductions of the haloacetic acid and trihalomethane formation potentials (HAAFPs and THMFPs) for the natural water samples were 38%–57% and 50%–64%, respectively. The catalyst significantly promoted the reduction of HAAFPs but insignificantly improved the reduction of THMFPs as ozone reacts fast with the THMs precursors. These results illustrate the good promise of RuO₂/ZrO₂-CeO₂ in catalytic ozonation for water treatment.     

Catalytic ozonation performance and surface property of supported Fe3O4 catalysts dispersions

Fe₃O₄ was supported on mesoporous Al₂O₃ or SiO₂ (50 wt.%) using an incipient wetness impregnation method, and Fe₃O₄/Al₂O₃ exhibited higher catalytic efficiency for the degradation of 2,4-dichlorophenoxyacetic acid and para-chlorobenzoic acid aqueous solution with ozone. The effect and morphology of supported Fe₃O₄ on catalytic ozonation performance were investigated based on the characterization results of X-ray diffraction, X-ray photoelectron spectroscopy, BET analysis and Fourier transform infrared spectroscopy. The results indicated that the physical and chemical properties of the catalyst supports especially their Lewis acid sites had a significant influence on the catalytic activity. In comparison with SiO₂, more Lewis acid sites existed on the surface of Al₂O₃, resulting in higher catalytic ozonation activity. During the reaction process, no significant Fe ions release was observed. Moreover, Fe₃O₄/Al₂O₃ exhibited stable structure and activity after successive cyclic experiments. The results indicated that the catalyst is a promising ozonation catalyst with magnetic separation in drinking water treatment.     

钴负载MCM-41分子筛催化臭氧氧化水中氯代苯甲酸

通过水热法合成介孔分子筛MCM-41,采用等体积浸渍法制备了Co负载MCM-41分子筛催化剂(Co/MCM-41).小角X-射线粉末衍射(XRD)、紫外-可见漫反射光谱(UV-vis DRS)、N2吸附-脱附等温线及透射电镜(TEM)等对催化剂的成分、结构的表征结果显示,Co/MCM-41保持了纯硅MCM-41有序的介孔结构,钴元素以钴氧化物形式存在,比表面达到772 m.2g-1.将Co/MCM-41分子筛用于催化臭氧氧化水中对氯苯甲酸(p-CBA)的研究,结果表明,在优化条件下(2%负载量和25℃反应温度),催化剂的加入显著改善了TOC去除率,达到84.6%,是单独臭氧氧化的1.6倍.     

不同活性物种对光催化降解水中邻苯二甲酸二甲酯动力学的贡献研究

采用光催化氧化技术对邻苯二甲酸二甲酯（DMP）进行降解研究,并在基础上考察了催化剂量,溶液pH和溶液初始浓度对降解速率的影响。且采用Langmuir-Hinshelwood动力学模型来描述DMP的光催化降解,研究表明DMP的光催化降解符合假一级动力学。系统研究了光催化降解DMP过程中不同活性物种对光催化反应速率的贡献,实验结果表明：在TiO2光催化降解DMP的过程中,？OH为主要的活性物种,其对DMP的降解速率贡献高于94%,而其它活性物种（ecb-,hvb＋,O2？-和H2O2）对光催化贡献较小。     

Catalytic activity of NiW electrodeposits

NiW systems are known as one of the best catalysts for various desulfurization processes. In this study, we examined catalytic properties of NiW electrodeposits, produced from two different electrolytes, towards sulfide ion oxidation in alkaline solution. Despite the big difference in morphology and structure of both materials, they exhibit almost the same catalytic activity for the examined reaction. A possible explanation of this experimental fact is that the overall reaction is controlled by the transport of oxygen through the catalyst samples.     

Inhibition of bromate formation by reduced graphene oxide supported cerium dioxide during ozonation of bromide-containing water

GO or RGO promotes bromate formation during ozonation of bromide-containing water. CeO₂/RGO significantly inhibits bromate formation compared to RGO during ozonation. CeO₂/RGO shows an enhancement on DEET degradation efficiency during ozonation. Ozone (O₃) is widely used in drinking water disinfection and wastewater treatment. However, when applied to bromide-containing water, ozone induces the formation of bromate, which is carcinogenic. Our previous study found that graphene oxide (GO) can enhance the degradation efficiency of micropollutants during ozonation. However, in this study, GO was found to promote bromate formation during ozonation of bromide-containing waters, with bromate yields from the O₃/GO process more than twice those obtained using ozone alone. The promoted bromate formation was attributed to increased hydroxyl radical production, as confirmed by the significant reduction (almost 75%) in bromate yield after adding t-butanol (TBA). Cerium oxide (less than 5 mg/L) supported on reduced GO (xCeO₂/RGO) significantly inhibited bromate formation during ozonation compared with reduced GO alone, and the optimal Ce atomic percentage (x) was determined to be 0.36%, achieving an inhibition rate of approximately 73%. Fourier transform infrared (FT-IR) spectra indicated the transformation of GO into RGO after hydrothermal treatment, and transmission electron microscope (TEM) results showed that CeO₂ nanoparticles were well dispersed on the RGO surface. The X-ray photoelectron spectroscopy (XPS) spectra results demonstrated that the Ce³⁺/Ce⁴⁺ ratio in xCeO₂/RGO was almost 3‒4 times higher than that in pure CeO₂, which might be attributed to the charge transfer effect from GO to CeO₂. Furthermore, Ce³⁺ on the xCeO₂/RGO surface could quench Br⋅ and BrO⋅ to further inhibit bromate formation. Meanwhile, 0.36CeO₂/RGO could also enhance the degradation efficiency of N,N-diethyl-m-toluamide (DEET) in synthetic and reclaimed water during ozonation.     

Removal of elemental mercury with Mn/Mo/Ru/Al2O3 membrane catalytic system

In this work, a catalytic membrane using Mn/Mo/Ru/Al₂O₃ as the catalyst was employed to remove elemental mercury (Hg⁰) from flue gas at low temperature. Compared with traditional catalytic oxidation (TCO) mode, Mn/Al₂O₃ membrane catalytic system had much higher removal efficiency of Hg⁰. After the incorporation of Mo and Ru, the production of Cl₂ from the Deacon reaction and the retainability for oxidants over Mn/Al₂O₃ membrane were greatly enhanced. As a result, the oxidization of Hg⁰ over Mn/Al₂O₃ membrane was obviously promoted due to incorporation of Mo and Ru. In the presence of 8 ppmv HCl, the removal efficiency of Hg⁰ by Mn/Mo/Ru/Al₂O₃ membrane reached 95% at 423 K. The influence of NO and SO₂ on Hg⁰ removal were insignificant even if 200 ppmv NO and 1000 ppmv SO₂ were used. Moreover, compared with the TCO mode, the Mn/Mo/Ru/Al₂O₃ membrane catalytic system could remarkably reduce the demanded amount of oxidants for Hg⁰ removal. Therefore, the Mn/Mo/Ru/Al₂O₃ membrane catalytic system may be a promising technology for the control of Hg⁰ emission.     

High mineral adsorption of glyphosate versus diethyl phthalate and tetracycline,during visible light photodegradation with goethite and oxalate

Environmental Chemistry Letters - The increasing presence of pesticides, pharmaceuticals and plasticizers in environmental media is threatening public health and ecosystems. Remediation of...     

六铝酸盐负载CuO催化还原NO性能

采用共沉淀法制备了LaAl12O19六铝酸盐载体,采用等体积浸渍法制备了不同负载量的CuO/LaAl12O19催化剂,并对其进行了XRD、H2-TPR和BET表征,考察了催化剂对CH4选择催化还原NO的性能.结果表明,CuO的负载并未改变六铝酸盐载体的结构,Cu在载体上以Cu2+的形式存在,活性组分CuO与载体LaAl12O19之间存在协同作用;CuO/LaAl12O19催化剂对CH4选择催化还原NO表现出良好活性,所制备的催化剂均能使NO的转化率达到99%;其中负载量为1.0 wt%的CuO/LaAl12O19催化剂的活性最好,完全反应温度T99%为560℃,且在80 h稳定性试验中表现出了良好的高温活性和热稳定性.     

Fe-Mn/AC催化湿式过氧化氢氧化间甲酚

采用等体积浸渍法制备了一种新型Fe-Mn/AC催化剂,应用于催化湿式过氧化氢氧化(CWPO)间甲酚废水.通过SEM和XRF表征了其表面形态结构和元素组成,通过穆斯堡尔谱分析了催化剂中铁离子的存在形态,结果表明,新型Fe-Mn/AC催化剂中的铁以二价铁、三价铁以及四氧化三铁的形式存在.通过正交实验考察了CWPO降解间甲酚的影响因素,结果表明,各因素对间甲酚转化率影响的大小顺序依次为:底物初始p H值反应温度反应时间催化剂投加量.通过正交实验得到CWPO降解间甲酚的最佳反应条件.当间甲酚浓度为100 mg·L-1、反应温度为40℃、反应时间为40 min、催化剂投加量为0.6 g·L-1及底物初始p H值为3时,间甲酚转化率为99.8%,TOC去除率为28.3%.气相色谱/质谱联用没有检测到中间产物,气相色谱检测到CWPO降解间甲酚中间产物主要为乙酸和丙酸.     

木薯皮堆肥过程中酶活性的变化

以木薯皮为原料进行高温堆肥发酵,研究了堆肥化过程中理化性质和酶活性的变化情况.结果表明:在堆肥发酵过程中.温度变化呈先上升后下降趋势,到后期已趋近于初始温度;而含水率在堆肥处理过程中变化不大.各处理的pH值在发酵结束时为7.3～7.5.过氧化氢酶活性初期较高,随后迅速降低,并维持在较低水平.纤维素酶和脲酶活性在堆肥初期增加,之后逐渐降低.由于堆肥原料不同,不同处理的酶活性变化趋势表现出一定的差异.考虑到堆肥腐熟度受多方面因素的影响,判断堆肥腐熟度时应根据多种指标(包括生物学、化学、物理学指标)综合判断.     

Catalytic activity of noble metal nanoparticles toward hydrodechlorination: influence of catalyst electronic structure and nature of adsorption

In this study, stabilized Pd, Pt and Au nanoparticles were successfully prepared in aqueous phase using sodium carboxymethyl cellulose (CMC) as a capping agent. These metal nanoparticles were then tested for catalytic hydrodechlorination toward two classes of organochlorinated compounds (vinyl polychlorides including trichloroethylene (TCE), tetrachloroethylene (PCE), and alkyl polychlorides including 1,1,1-trichloroethane (1,1,1-TCA), and 1,1,1,2-tetrachloroethane (1,1,1,2-TeCA)) to determine the rate-limiting steps and to explore the reaction mechanisms. The surface area normalized reaction rate constant, k_SA, showed a systematic dependence on the electronic structure (the density of states at the Fermi level) of the metals, suggesting that adsorption of organochlorinated reactants on the metal catalyst surfaces is the rate-limiting step for catalytic hydrodechlorination. Hydrodechlorination rates of 1,1,1-TCA and 1,1,1,2-TeCA agreed with the bond strength of the first (weakest) dissociated C-Cl bond, suggesting that C-Cl bond cleavage, which is the first step for dissociative adsorption of the alkyl polychlorides, controlled the catalytic hydrodechlorination rate. However, hydrodechlorination rates of TCE and PCE correlated with the adsorption energies of their molecular (non-dissociative) adsorption on the noble metals rather than with the first C-Cl bond strength, suggesting that molecular adsorption governs the reaction rate for hydrodechlorination of the vinyl polychlorides.     

Utilization of energy substrates during calling activity in tropical frogs

Calling activity in frogs is energetically demanding to males because they usually perform at or near their physiological capacities. Metabolic fuel for muscle contractions during bouts of aerobic calling activity comes from carbohydrates and lipids that are stored in the trunk muscles. I monitored nightly calling performance in males of seven tropical frog species from two families, Hylidae and Leptodactylidae, and compared levels of glycogen and lipid in the trunk muscles from males collected before and after a three-hour period of calling activity. Trunk muscles from late-evening males in five species had up to 63% less glycogen than the trunk muscles from early-evening males; relatively little depletion was observed in two other species. Overall, glycogen reserves and rates of depletion were highest in species with very high calling rates. It was not possible to measure changes in the relatively large stores of lipid in the trunk muscles after only 3 h of calling. Nevertheless, intramuscular lipid stores probably provide a greater percentage of the energy needed for sound production than glycogen stores, and are largest in species with high calling rates. Received: 7 January 1997 / Accepted after revision: 20 July 1997     

Photocatalytic degradation of chlorophenols using Ru(bpy) 3 2+ /S2O 8 2−

Advanced oxidation processes, such as photocatalysed oxidation, provide an important route for degradation of wastes. In this study, the lowest excited state (³MLCT) of Ru(bpy)₃²⁺ is used to break down chlorophenol pollutant molecules to harmless products. This has the advantage of using visible light and a short-lived catalytically active species. Photolysis of deaerated aqueous solutions of a variety of mono- and poly-substituted chlorophenols has been followed in the presence of Ru(bpy)₃²⁺/S₂O₈²⁻ with near visible light (λ > 350 nm) by UV/visible absorption spectroscopy, luminescence, potentiometry, NMR and HPLC techniques. Upon irradiation, a decrease is observed in the chlorophenol concentration, accompanied by the formation of Cl⁻, H⁺ and SO₄²⁻ ions as the main inorganic products. Benzoquinone, phenol, dihydroxybenzenes and chlorinated compounds were the dominant organic products. As the ruthenium(II) complex is regenerated in the reaction, the scheme corresponds to an overall catalytic process. The kinetics of the rapid chlorophenol photodechlorination has been studied, and are described quite well by pseudo-first order behaviour. Further studies on this were made by following Cl⁻ release with respect to the initial Ru(bpy)₃²⁺ and S₂O₈²⁻ concentrations. A comparison is presented of the photodechlorination reactivity of the mono and polychlorophenols studied at acidic and alkaline pH.     

退化喀斯特植被恢复过程中土壤酶活性特征研究

采用空间代替时间的方法,在贵州西南部花江典型喀斯特峡谷区选择裸地、草本、灌木、乔林四个植被恢复阶段作为退化植被恢复过程中不同恢复阶段。然后在一年中四个季节的每一季节分别对四个阶段样地进行取土,带回实验室风干磨细。分别用比色法测定脲酶活性,用比色法测定淀粉酶活性,用碘量滴定法测定多酚氧化酶活性。通过一年的实验结果表明,土壤酶活性随植被恢复过程逐渐提高,即裸地阶段〈草本群落阶段〈灌木群落阶段〈乔林阶段。土壤酶在土壤中分布是根际土大于非根际土,垂直剖面上,A层总是大于B层。脲酶、淀粉酶、多酚氧化酶活性在一年中总体表现为春夏季高,冬季低的特点,具体的酶表现不尽相同。各层次酶活性季节性变化趋势相同。     

Catalytic oxidation of CO over Pt/Fe3O4 catalysts: Tuning O2 activation and CO adsorption

• Strong metal-support interaction exists on Pt/Fe₃O₄ catalysts. • Pt metal particles facilitate the formation of oxygen vacancies on Fe₃O₄. • Fe₃O₄ supports enhance the strength of CO adsorption on Pt metal particles. The self-inhibition behavior due to CO poisoning on Pt metal particles strongly impairs the performance of CO oxidation. It is an effective method to use reducible metal oxides for supporting Pt metal particles to avoid self-inhibition and to improve catalytic performance. In this work, we used in situ reductions of chloroplatinic acid on commercial Fe₃O₄ powder to prepare heterogeneous-structured Pt/Fe₃O₄ catalysts in the solution of ethylene glycol. The heterogeneous Pt/Fe₃O₄ catalysts achieved a better catalytic performance of CO oxidation compared with the Fe₃O₄ powder. The temperatures of 50% and 90% CO conversion were achieved above 260°C and 290°C at Pt/Fe₃O₄, respectively. However, they are accomplished on Fe₃O₄ at temperatures higher than 310°C. XRD, XPS, and H₂-TPR results confirmed that the metallic Pt atoms have a strong synergistic interaction with the Fe₃O₄ supports. TGA results and transient DRIFTS results proved that the Pt metal particles facilitate the release of lattice oxygen and the formation of oxygen vacancies on Fe₃O₄. The combined results of O₂-TPD and DRIFTS indicated that the activation step of oxygen molecules at surface oxygen vacancies could potentially be the rate-determining step of the catalytic CO oxidation at Pt/Fe₃O₄ catalysts. The reaction pathway involves a Pt-assisted Mars-van Krevelen (MvK) mechanism.     

Catalytic hydrolysis of gaseous HCN over Cu–Ni/γ-Al2O3 catalyst: parameters and conditions

? The Cu–Ni/γ-Al₂O₃ catalyst was prepared to study HCN hydrolysis ? On catalyst calcined at 400°C, the HCN removal efficiency reaches a maximum. ? HCN removal is the highest at 480 min at a H ₂ O/HCN volume ratio of 150 ? The presence of CO facilitates HCN hydrolysis and increases NH ₃ production. ? O ₂ increases the HCN removal and NO_x production but decreases NH ₃ production GRAPHIC ABSTRACT To decompose efficiently hydrogen cyanide (HCN) in exhaust gas, g-Al₂O₃-supported bimetallic-based Cu–Ni catalyst was prepared by incipient-wetness impregnation method. The effects of the calcination temperature, H₂O/HCN volume ratio, reaction temperature, and the presence of CO or O₂ on the HCN removal efficiency on the Cu–Ni/g-Al₂O₃ catalyst were investigated. To examine further the efficiency of HCN hydrolysis, degradation products were analyzed. The results indicate that the HCN removal efficiency increases and then decreases with increasing calcination temperature and H₂O/HCN volume ratio. On catalyst calcined at 400°C, the efficiency reaches a maximum close to 99% at 480 min at a H₂O/HCN volume ratio of 150. The HCN removal efficiency increases with increasing reaction temperature within the range of 100°C–500°C and reaches a maximum at 500°C. This trend may be attributed to the endothermicity of HCN hydrolysis; increasing the temperature favors HCN hydrolysis. However, the removal efficiencies increases very few at 500°C compared with that at 400°C. To conserve energy in industrial operations, 400°C is deemed as the optimal reaction temperature. The presence of CO facilitates HCN hydrolysis andincreases NH₃ production. O₂ substantially increases the HCN removal efficiency and NO_x production but decreases NH₃ production.