CuO（-CeO2）/SBA-15对萘氧化的催化活性及CO2选择性研究

通过浸渍法制备CuO/SBA-15和CuO-CeO2/SBA-15两种介孔材料催化剂,采用BET、XRD、TPR和XPS等对催化剂进行表征,重点考察催化剂对萘氧化反应的催化活性及对产物CO2的选择性。BET、XRD和XPS等实验结果表明CuO高度分散于介孔分子筛SBA-15中,CeO2可促进CuO在载体上的分散,同时能降低催化剂的TPR还原温度。活性测试结果表明CuO/SBA-15对萘氧化反应的催化活性较高,但是催化氧化的CO2选择性较低,温度在380℃时CO2的生成率仅为60%左右;CeO2的添加不仅提高了CO2的生成率,15%CuO-15%CeO2/SBA-15在325℃使CO2生成率达到99%,而且CeO2增强了催化剂的稳定性。     

等离子体协同MnOx/SBA-15催化降解正己醛的研究

采用浸渍法制备了MnOx/SBA-15催化剂,利用BET、XRD和SEM等对催化剂进行表征。考察了介质阻挡放电等离子体协同MnOx/SBA-15催化剂对正己醛的降解性能。结果显示,负载MnOx后的SBA-15仍然保持介孔结构,且MnOx均匀地分散在SBA-15中;等离子体与催化剂表现出较好的协同作用,干燥条件下7.5 kV的放电电压结合10%MnOx/SBA-15时降解效果最佳,正己醛去除率达99%;相比干燥条件,相对湿度低于20%时正己醛去除率变化不明显,但高于20%时催化效果明显下降;该催化剂具有很强的O3分解能力,O3在催化剂表面的分解不仅促进了正己醛的氧化,同时也提高了CO2的选择性。     

CuO(-CeO_2)/SBA-15对萘氧化的催化活性及CO_2选择性研究

通过浸渍法制备CuO/SBA-15和CuO-CeO2/SBA-15两种介孔材料催化剂,采用BET、XRD、TPR和XPS等对催化剂进行表征,重点考察催化剂对萘氧化反应的催化活性及对产物CO2的选择性。BET、XRD和XPS等实验结果表明CuO高度分散于介孔分子筛SBA-15中,CeO2可促进CuO在载体上的分散,同时能降低催化剂的TPR还原温度。活性测试结果表明CuO/SBA-15对萘氧化反应的催化活性较高,但是催化氧化的CO2选择性较低,温度在380℃时CO2的生成率仅为60%左右;CeO2的添加不仅提高了CO2的生成率,15%CuO-15%CeO2/SBA-15在325℃使CO2生成率达到99%,而且CeO2增强了催化剂的稳定性。     

TiO₂ supported over SBA-15: an efficient photocatalyst for the pesticide degradation using solar light

Photocatalytic degradation and mineralization of pesticides are studied over TiO(2) supported mesoporous SBA-15 composite system using solar light. TiO(2) is immobilized over SBA-15 by solid sate dispersion method. The catalysts are characterized by XRD, surface area, UV-Vis diffused reflectance spectra, SEM and TEM. The detailed photocatalytic degradation studies are carried out over TiO(2), SBA-15 and different TiO(2) wt% supported SBA-15. The activity evaluation parameters such as catalyst amount, pH, and pollutant initial concentration are studied taking isoproturon as a model compound and established conditions for pesticide degradation. The optimum degradation is achieved over 10 wt% TiO(2)/SBA-15 within 30 min and the reaction is following pseudo-first order kinetics. The isoproturon mineralization is monitored with TOC reduction and it takes around 9h for disappearance. The commercial pesticide solutions containing imidacloprid and phosphamidon are also successfully degraded over these composites with the established conditions. The data indicates that 10 wt% TiO(2)/SBA-15 composite is an effective and highly active system for the pesticide degradations.     

Modified SBA-15 mesoporous silica for heavy metal ions remediation

N-Propylsalicylaldimino-functionalized SBA-15 mesoporous silica was prepared, characterized and used as an adsorbent for heavy metal ions. The organic-inorganic hybrid material was obtained using successive grafting procedures of SBA-15 silica with 3-aminopropyl-triethoxysilane and salicylaldehyde, respectively. For comparison an amorphous silica gel was functionalized using the same procedure. The structure and physicochemical properties of the materials were characterized by means of elemental analysis, X-ray diffraction (XRD), nitrogen adsorption-desorption, thermogravimetric analysis and FTIR spectroscopy. The organic functional groups were successfully grafted on the SBA-15 surfaces and the ordering of the support was not affected by the chemical modification. The behavior of the grafted solids for the adsorption of heavy metals ions from aqueous solutions was investigated. The hybrid materials showed high adsorption capacity and high selectivity for copper ions. Other ions, such as nickel, zinc, and cobalt were adsorbed by the modified SBA-15 material. The adsorbent can be regenerated by acid treatment without altering its properties.     

The effects of manganese precursors on Mn-based/TiO2 catalysts for catalytic reduction of NO with NH3

Manganese acetate (MnAc) and manganese nitrate (MnN) were employed as precursors for the preparation of MnAc)/TiO2, Mn (N)/TiO2, Mn(Ac)-Ce/TiO2, and Mn(N)-Ce/TiO2 by impregnation. These complexes were used as catalysts in the low-temperature selective catalytic reduction of NO with NH3. The influence of manganese precursors on catalyst characteristics, the reduction activity, and the stability of the catalysts to poisoning by H2O and SO2 were studied. Experiments showed that Mn(N) produced MnO2 with large grain sizes in Mn(N)/TiO2 catalyst. On the contrary, Mn(Ac) led to highly dispersed and amorphous Mn2O3 in Mn (Ac)/TiO2 catalyst, which had better catalytic activity and stability to SO2 at low temperatures. The doping of cerium reduced the differences in catalytic performance between the catalysts derived from different Mn precursors.     

改性锰砂对废水中锰的吸附特性研究

通过正交实验,研究pH值、反应时间、锰砂投加量和锰砂改性时间等因素对Mn2+吸附效果的影响。结果表明,在25℃,吸附反应体系pH=9,锰砂投加量为15 g/L,吸附时间为30 min,锰砂的高锰酸钾改性时间为36 h时,改性锰砂对锰的吸附去除率最高,达到了99.99%。四因素的影响顺序为:pH>反应时间>锰砂投加量>锰砂改性时间。在单因素实验中,当pH=7,吸附剂投加量为25 g/L时,经60 min可达吸附平衡,锰的去除率为60.04%,其等温吸附符合Freundlich和Langmuir模型,并且与Langmuir模型的拟合程度更高。本研究还对改性锰砂吸附除锰的机理做了初步探讨。     

氧化锰矿渣改性制备SCR脱硝催化剂

以锰酸钾生产过程中产生的氧化锰矿渣为原料,制备了一系列Mn基SCR脱硝催化剂。研究了活性炭、二氧化钛、以及含锰量的变化对催化剂的脱硝活性的影响。结果表明,直接由矿渣制备的催化剂和添加活性炭、二氧化钛制备的催化剂,其最大脱硝率分别为40%和78%。XPS表征发现催化剂中的锰元素存在多种氧化价态,活性炭的加入在一定程度上改变了不同价态之间的相对含量;在矿渣中加入硫酸锰后,发现总锰含量达到10%时,催化剂的最大脱硝率从78%降低至57%,XRD测试发现硫酸锰的加入导致S2O27-物种的生成,可能是引起催化剂活性下降的原因之一;而加入醋酸锰至总锰含量达到10%时,增大了催化剂的活性温度窗口,当总锰含量达到20%时,在空速10 000 h-1条件下,催化剂的最大脱硝率达到86.7%。     

Co3O4/介孔分子筛催化剂对苯催化完全氧化的研究

分别以介孔分子筛MCM-41、MCM-48、SBA-15为载体，采用等体积浸渍法制备了氧化钴/介孔分子筛催化剂，利用N₂吸附、X射线衍射、程序升温还原等技术对催化剂进行了表征，考察了Co₃O₄的负载量及载体的孔结构对催化剂完全催化氧化苯的性能的影响。结果表明，Co₃O₄的负载量为20%时，催化剂的催化活性最好；载体的孔径和催化剂的可还原性能是影响催化活性的主要因素，催化剂活性顺序为Co₃O₄ /SBA-15> Co₃O₄ /MCM41> Co₃O₄ /MCM-48。     

Characterization and reactivity of natural manganese ore catalysts in the selective catalytic oxidation of ammonia to nitrogen

Natural manganese ore (NMO) catalysts were characterized and tested in the selective catalytic oxidation of ammonia to nitrogen oxides under dilute conditions. Also, the oxidation of ammonia (NH(3)) was carried out using pure MnO(2), Mn(2)O(3) for comparing with the activity. It is found that the activity of NMO was similar to that of MnO(2) at low temperature below 150 degrees C but above this temperature, the activity of these catalysts showed the difference. In the course of NH(3) oxidation, N(2), NO, N(2)O and H(2)O were produced. But the quantity of NO(2) produced in this experiment was negligible. At temperature below 250 degrees C, selectivity into N(2) from NH(3) oxidation was in the order, NMO > MnO(2) > Mn(2)O(3). This is the reverse of activity of these manganese oxides. Also the characterization of NH(3) oxidation was proposed and supported by the effect of space velocity, inlet O(2) and NH(3) concentration. The increase of space velocity remarkably influenced not only the conversion but also selectivity into N(2). The higher the reaction temperature was, the higher the effect of inlet O(2) and NH(3) concentration on the reaction rate was. By introducing NO during NH(3) oxidation reaction, the possibility of NMO as selective catalytic reduction catalyst at low temperature was studied and showed positive results.     

Adsorption of nitrosamines in acidic solution by zeolites

Adsorption of N-nitrosopyrrolidine (NPYR) by zeolite NaZSM-5, Hbeta and NaZSM-11 in acidic solution with pH of 1 was investigated. The NPYR uptake process obeyed the first-rate Lagegren kinetic equation describing adsorption, and the equilibrium data were fitted to the Langmuir or Freundlich adsorption equation. Zeolite ZSM-5, Hbeta and NaZSM-11 possessed a higher adsorption capacity than amorphous silica or ordered mesoporous siliceous SBA-15, implying their potential application for adsorption of nitrosamines in gastric juice to anti-cancer.     

Adsorption of CO2 from flue gas streams by a highly efficient and stable aminosilica adsorbent

Three ordered mesoporous silicas (OMSs) with different pore sizes and pore architectures were prepared and modified with amine functional groups by a postgrafting method. The carbon dioxide (CO2) adsorption on these amine-modified OMSs was measured by using microbalances at 348 K, and their adsorption capacities were found to be 0.2-1.4 mmol g(-1) under ambient pressure using dry 15% CO2. It was found experimentally that the CO2 adsorption capacity and adsorption rate were attributed to the density of amine groups and pore volume, respectively. A simple method is described for the production of densely anchored amine groups on a solid adsorbent invoking direct incorporation of tetraethylenepentamine onto the as-synthesized OMSs. Unlike conventional amine-modified OMSs, which typically show CO2 adsorption capacity less than 2 mmol g(-1), such organic template occluded amine-OMS composites possessed remarkably high CO2 uptake of approximately 4.6 mmol g(-1) at 348 K and 1 atm for a dry 15% CO2/nitrogen feed mixture. The enhancement of 8% in CO2 adsorption capacity was also observed in the presence of 10.6% water vapor. Durability tests done by cyclic adsorption-desorption revealed that these adsorbents also possess excellent stability.     

Importance of the polarity on nanostructured silica materials to optimize the hydrolytic condensation with molecules related to CO2 adsorption

Environmental Science and Pollution Research - The present work reports the changes for the mesoporous materials SBA-15 and KIT-6 associated with the structural, textural, and chemical properties...     

Development of regenerative dye impregnated mesoporous silica materials for assessing exposure to ammonia

The mesostructured materials MCM-41 and SBA-15 were studied as possible supports of bromocresol green (BG) dye impregnation for the ammonia gas detection because of their large surface area, high regenerative property, and high thermal stability. X-ray diffraction, transmission electron microscopy, scanning electron microscope, and N₂ adsorption analysis were used to characterize the prepared materials. These materials could sense ammonia via visible color change from yellowish-orange to blue color. The color change process of the nanostructured materials was fully reversible during 10 cyclic tests. The results indicated that the ammonia absorption responses of the two nanostructured materials were both very sensitive, and high linear correlation and high precision were achieved. As the gaseous ammonia concentrations were 50 and 5 ppmv, the response times for the SBA-15/BG were only 1 and 5 min, respectively. Moreover, the BG dye-impregnated SBA-15 was less affected by the variation in the relative humidity. It also had faster response for the detection of NH₃, as well as lower manufacturing price as compared to that of the dye-impregnated MCM-41. Such feature enables SBA-15/BG to be a very promising material for the detection of ammonia gas.

Implications: The detector tube is a convenient ambient ammonia detection device. However, almost all the commercial detector tubes can be used once only, which not only increases the purchase cost but also produces lots of waste. In this study, we developed two sensing materials that are sensitive for repeated usage. The two mesoporous silica-based materials, MCM-41 and SBA-15, are impregnated by an organic dye of bromocresol green to induce color change behavior that can be easily observed by the naked eye, and it is concluded that dye-impregnated SBA-15/BG is a very promising material for the detection of ammonia gas.     

Degradation of CL-20 by white-rot fungi

In previous studies, we found that the emerging energetic chemical, CL-20 (C6H6N12O12, 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane), can be degraded following its initial denitration using both aerobic and anaerobic bacteria. The C and N mass balances were not determined due to the absence of labeled starting compounds. The present study describes the degradation of the emerging contaminant by Phanerochaete chrysosporium using ring-labeled [15N]-CL-20 and [14C]-CL-20. Ligninolytic cultures degraded CL-20 with the release of nitrous oxide (N2O) in amounts corresponding to 45% of the nitrogen content of CL-20. When ring-labeled [15N]-CL-20 was used, both 14N14NO and 15N14NO were observed, likely produced from -NO2 and N-NO2, respectively. The incubation of uniformly labeled [14C]-CL-20 with fungi led to the production of 14CO2 (> 80%). Another ligninolytic fungus, Irpex lacteus, was also able to degrade CL-20, but as for P. chrysosporium, no early intermediates were observed. When CL-20 was incubated with manganese peroxidase (MnP), we detected an intermediate with a [M-H]- mass ion at 345 Da (or 351 and 349 Da when using ring-labeled and nitro-labeled [15N]-CL-20, respectively) matching a molecular formula of C6H6N10O8. The intermediate was thus tentatively identified as a doubly denitrated CL-20 product. The concomitant release of nitrite ions (NO2-) with CL-20 degradation by MnP also supported the occurrence of an initial denitration prior to cleavage and decomposition.     

Elimination of Cs+ from aquatic systems by an adsorbent prepared by immobilization of potassium copper hexacyanoferrate on the SBA-15 surface: kinetic,thermodynamic, and isotherm studies

Environmental Science and Pollution Research - For elimination of cesium from aqueous solutions, mesoporous SBA-15 was synthesized and employed as the support for immobilization of potassium copper...     

Effect of carbon dioxide concentration on biomass production and partitioning in Betula pubescens Ehrh. seedlings at different ozone and temperature regimes

Seedlings of Betula pubescens were grown at two CO(2) concentrations, in combination with either two O(3) concentrations or two air temperatures, during 34-35 days at 24 h day(-1) photoperiod in growth chambers placed in a greenhouse. Increasing the CO(2) concentration from 350 to 560 micromol mol(-1) at 17 degrees C air temperature increased the dry weight of the main leaves, main stem, branches and root. The mean relative growth rate (RGR) was increased 10% by CO(2) enrichment, while increasing the O(3) concentration from 7 to 62 nmol mol(-1) decreased the RGR by 9%. The relative biomass distribution between the different plant components was not significantly affected by the CO(2) concentration irrespective of the O(3) concentration. No significant interactions between CO(2) and O(3) concentration were found except on leaf size, which was stimulated more by elevated CO(2) concentration at high, compared to low, O(3) levels. In another experiment, elevated CO(2) (700 micromol mol(-1)) significantly increased the dry weight of the different plant components, and more at 20 degrees C than at 15 degrees C. Raising the CO(2) concentration increased the RGR by 5 and 10% at 15 and 20 degrees C, respectively. CO(2) enrichment increased the branch dry weight relatively more than the dry weight of the other plant parts. Increasing the CO(2) concentration or temperature increased the plant height and stem diameter, however, no interactions between CO(2) and temperature were found.     

Comparison of photosynthetic responses to manganese toxicity of deciduous broad-leaved trees in northern Japan

The effects of manganese (Mn) toxicity on photosynthesis of four tree species in northern Japan representing different successional traits were examined. The four species are: Betula ermanii (Be) and Alnus hirsuta (Ah) representing two early successional species, Ulmus davidiana var. japonica (Ud) as the mid-successional species, and Acer mono (Am) as the late successional species. Seedlings were grown hydroponically in a solution containing nutrients and Mn of four concentrations (1, 10, 50, 100 mg litre(-1)) for 50 days. Gas exchange measurements indicate that in all species, Mn accumulation in leaves resulted in the decline of light-saturated net photosynthetic rate ai ambient CO(2) pressure (35 Pa, Pn(amb)) and at saturating (5%) CO(2) pressure (Pn(sat)), and of carboxylation efficiency but has little effect on the maximum efficiency of photochemistry. Sensitivity to elevated levels of Mn differed among species where the decline of Pn(amb) was much more modest in the two early successional species of Be and Ah than the mid- and late successional species of Ud and Am. The same trends were observed in both Pn(sat) and carboxylation efficiency. Based on these results, we suggest that early successional species (Betula ermanii and Alnus hirsuta) have greater tolerance for excess Mn in leaves than mid- and late successional species.     

Manganese-modified biochar for highly efficient sorption of cadmium

Environmental Science and Pollution Research - In this study, corn stalk was modified by manganese (Mn) before (MBC1) and after (MBC2) pyrolysis at different temperatures (400~600 °C)...     

大洋锰结核在环境污染治理方面的应用

大洋锰结核能够有效分解转化气体污染物(如CO、CH、VOC、NOx、SO2);能够吸附水体中的Cu、CO、Ni、Mn、Zn、Cr、Hg、Pb、As等重金属阳离子和PO4^3-、SeO3^2-等阴离子;可做生物固定化载体除去水体中的有机污染物。大洋锰结核具有良好的环境矿物学属性,是一种理想的环境矿物材料,为环境治理提供了新的方向。