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.     

Eco-friendly synthesis of nanostructured mesoporous materials from natural source rice husk silica for environmental applications

Environmental Science and Pollution Research - Nanostructured mesoporous materials of MCM-41 type were synthesized using a natural, non-toxic, and cheap source of silica from rice husk. Then, this...     

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.     

Adsorption properties of regenerative materials for removal of low concentration of toluene

A specific type of material, activated carbon fiber (ACF), was modified by SiO₂, and the final products ACF-x were obtained as ACF-12.5, ACF-20, ACF-40, and ACF-80 according to different dosages of tetraethoxysilane (TEOS). The modified material on the ACF surface had a significant and smooth cover layer with low content of silica from scanning electron microscope (SEM) image. The modified ACF-x showed the stronger hydrophobicity, thermal stability, and adsorption capacity, which had almost no effect in the presence of water vapor and no destruction in multiple cycles. ACF-20 was proven as the most efficient adsorbent in humid conditions. The dual-function system composed of the regenerative adsorbents and the combustion catalyst would be efficient in consecutive toluene adsorption/oxidation cycles, in which the combustion catalyst was prepared by the displacement reaction of H₂PtCl₆ with foam Ni. Therefore, the adsorption/catalytic oxidation could be a promising technique in the indoor air purification, especially in the case of very low volatile organic compound (VOC; toluene) concentration levels.

Implications: Exploring highly effective adsorptive materials with less expensive costs becomes an urgent issue in the indoor air protection. ACF-20 modified by SiO₂ with Pt/Ni catalysts shows stronger hydrophobicity, thermal stability, and adsorption capacity. This dual-function system composed of the regenerative materials and the combustion catalyst would be a promising technique in the indoor air purification, especially in the case of removal of very low concentration of toluene.     

中孔硅胶负载过氧乙酸深度脱除柴油硫化物

采用滴定吸附法将过氧乙酸组装于中孔硅胶中,通过红外光谱分析和N2吸附法对组装体进行了表征,研究了常温常压下,该组装体氧化、吸附、脱除柴油硫化物的活性.结果表明,该组装体具有优良的脱硫性能.柴油中硫化物与过氧乙酸在硅胶孔中发生氧化反应,氧化产物被吸附在硅胶上,使柴油的含硫量从1697μg/g降到14μg/g,符合美国环境保护署标准.     

Removal of basic dye from waste-water using silica as adsorbent

The kinetics of removal of Basic Blue 3 from a textile effluent was studied using silica as an adsorbent. The adsorption was found to follow a first-order process. The influences on the rate of adsorption of various factors, such as temperature, concentration of dye solution, pH of the system and the amount of adsorbent have been investigated. On the basis of the isotherm studies, the various thermodynamical parameters have been calculated. The effect of electrolytes and surfactants has also been seen on the removal of the dye from the waste-water.     

介孔TiO2的制备及光催化降解有机染料的研究

以十六烷基三甲基溴化胺为模板剂,用溶胶-凝胶法制备了介孔TiO2,用x射线衍射、透射电子显微镜、热重/差热分析及氮气吸附等方法对其进行了分析表征,并用偶氮染料阳离子红X-GRL为目标污染物分析了它的光催化活性.实验结果表明,450℃热处理后的介孔TiO2是锐钛矿型的,平均孔径为18 nm.氮气吸附曲线呈典型的介孔材料Ⅳ型吸附等温线特征.由于介孔TiO2具有较大的比表面积,因此表现出比非介孔TiO2高的光催化活性.     

稻壳制备介孔状二氧化硅的光催化性

以利用农业废弃物稻壳制备光催化性的SiO2为目的,用NaOH消解稻壳得到了含有硅资源的溶液。以CTAB为模板,利用稻壳消解液合成了含硅固体样品。通过红外光谱分析法和X射线衍射法分别表征了合成样品是介孔状SiO2。并通过紫外可见分光光度法研究了合成的SiO2对染料代表的亚甲基蓝的光催化降解性,发现亚甲基蓝溶液的吸光度随时间变小,证明了所制备的SiO2具有光催化性。运用单因子变量法,得知在SiO2投加量为300 mg,pH为6时,对浓度为40 mg/L的50 m L亚甲基蓝溶液的光催化降解率可达62.3%。     

镧改性介孔材料对砷、磷的吸附

为探究在复合污染条件下介孔吸附材料对砷、磷的去除效果,通过水热合成法制备镧金属改性介孔吸附材料(La-MCM-41),采用X-射线衍射(XRD)、比表面积测定(BET)、扫描电镜(SEM)等分析方法对改性前后的介孔吸附剂进行了表征;研究了介孔吸附剂在不同吸附体系中对砷、磷的降解效果、等温线及动力学。结果表明：La-MCM-41仍具有长程有序的六方相介孔结构,BET比表面积、总孔容均减小,平均孔径有所增加;介孔吸附剂在单独吸附体系下对砷、磷的吸附量大于同步吸附体系,且均符合二级反应动力学。通过分析可知,在2种体系下,改性后的介孔吸附剂极大地提高了对砷、磷的吸附量,是一种经济高效的吸附材料。     

Fast and reversible adsorption for dibenzothiophene in fuel oils with metallic nano-copper supported on mesoporous silica

Environmental Science and Pollution Research - Dibenzothiophene (DBT) in fuel oils causes the release of toxic sulfur oxide gases, and it is necessary to remove DBT in fuels. Herein, metallic...     

Visible light-driven photocatalytic degradation of methylene blue dye over bismuth-doped cerium oxide mesoporous nanoparticles

Environmental Science and Pollution Research - A series of Bi3+-doped ceria nanoparticles (0 to 20 wt% of Bi3+) were synthesized by sol-gel assisted hydrothermal method at a lower temperature of...     

Effects of ammonia on methane oxidation in landfill cover materials

The effects of ammonia (NH₃) on CH₄ attenuation in landfill cover materials consisting of landfill cover soil (LCS) and aged municipal solid waste (AMSW), at different CH₄ concentrations, were investigated. The CH₄ oxidation capacities of LCS and AMSW were found to be significantly affected by the CH₄ concentration. The maximum oxidation rates for LCS and AMSW were obtained at CH₄ concentrations of 5 % and 20 %(v/v), respectively, within 20 days. CH₄ biological oxidation in AMSW was significantly inhibited by NH₃ at low CH₄ concentrations (5 %, v/v) but highly stimulated at high levels (20 % and 50 %, v/v). Oxidation in LCS was stimulated by NH₃ at all CH₄ concentrations due to the higher conversion of the nitrogen in NH₃ in AMSW than in LCS. NH₃ increases CH₄ oxidation in landfill cover materials.     

Production of copper-based rare earth composite metal materials by coprecipitation and applications for gaseous ammonia removal

This study addresses the oxidation of ammonia (NH3) at temperatures between 423 and 673 K by selective catalytic oxidation (SCO) over a copper-based, rare earth composite metal material that was prepared by coprecipitating copper nitrate, lanthanum nitrate, and cerium nitrate at various molar ratios. The catalysts were characterized using Brunner, Emmett, and Teller spectroscopy, Fourier-transform infrared spectroscopy, Xray diffraction, ultraviolet-visible spectroscopy, cyclic voltammetric spectroscopy, and scanning electron microscopy. At a temperature of 673 K and an oxygen content of 4%, approximately 99.5% of the NH3 was reduced by catalytic oxidation over the 6:1:3 copper-lanthanum-cerium (molar ratio) catalyst. Nitrogen (N2) was the main product of this NH3-SCO process. Results from the activity and selectivity tests revealed that the optimal catalyst for catalytic performance had the highest possible cerium content and specific surface area (43 m2/g).     

Cu-SBA-15催化湿式过氧化氢氧化水溶液中罗丹明B

采用水热晶化法合成了不同含铜量的Cu—SBA-15介孔分子筛,并且用XRD、N2吸附、TEM以及uV—vis对所合成的样品进行表征。以Cu—SBA-15为催化剂,H2O2为氧化剂,催化湿式过氧化水溶液中的罗丹明B,主要考察H2O2浓度、催化剂用量、处理温度、初始pH等因素对罗丹明B氧化效果的影响。结果表明,在同样的处理条件下罗丹明的脱色率明显高于TOC去除率,处理温度、初始pH对罗丹明B的脱色与氧化有重要影响。在罗丹明B初始浓度100mg／L,H2O2初始浓度1．8g／L,催化剂量0．3g／L,温度60℃,pH为7．0,处理时间100min时,罗丹明B的脱色率为98．6％,TOC去除率为62．8％。     

The excretion of pesticides in saliva and its value in assessing exposure

The possibility that pesticides are secreted in the saliva and that this secretion can be used to assess exposure to pesticides is discussed. Both Kepone and carbaryl were tested through a series of in vitro studies and in vivo experiments including both acute and subchronic studies. In the in vivo studies, both Kepone and carbaryl were detected in the saliva in the first twenty-four hours, but seldom thereafter. Analysis of urinary samples indicated a rapid clearance of the substances from the animals. In vitro uptake and efflux studies suggested that movement of both substances was by passive diffusion and reached a plateau after 60 minutes of incubation. Efflux rates were unaffected by experimental conditions, but were ten times faster for carbaryl.     

蓄热式氧化炉在无机材料煅烧尾气处理中的应用

分子筛煅烧尾气中含有三乙胺、正丁胺等挥发性有机化合物（VOCs）,严重影响厂区及周边环境。为彻底治理有机废气污染,采用三床式蓄热式氧化炉（RTO）处理有机废气,通过优化调整控制工艺,以排烟温度控制法替代原有的排烟时间控制法。结果表明：排烟温度控制法可确保排烟温度保持在设计范围内,有效降低了排烟热损失;蓄热式氧化炉通过吸热-燃烧-放热周期性稳定运行,在天然气平均耗量4.5 m3·h-1的情况下,获得99%以上的VOCs去除效率,达到预期目标。蓄热式氧化法是一种经济、高效、稳定和安全的有机废气处理技术。     

Cu-SBA-15催化湿式过氧化氢氧化水溶液中罗丹明B

采用水热晶化法合成了不同含铜量的Cu-SBA-15介孔分子筛,并且用XRD、N2吸附、TEM以及UV-vis对所合成的样品进行表征。以Cu-SBA-15为催化剂,H2O2为氧化剂,催化湿式过氧化水溶液中的罗丹明B,主要考察H2O2浓度、催化剂用量、处理温度、初始pH等因素对罗丹明B氧化效果的影响。结果表明,在同样的处理条件下罗丹明的脱色率明显高于TOC去除率,处理温度、初始pH对罗丹明B的脱色与氧化有重要影响。在罗丹明B初始浓度100 mg/L,H2O2初始浓度1.8 g/L,催化剂量0.3 g/L,温度60℃,pH为7.0,处理时间100 min时,罗丹明B的脱色率为98.6%,TOC去除率为62.8%。     

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 an individual exposure model for application to the Southern California children's health study

The Southern California Children's Health Study (CHS) investigated the relationship between air pollution and children's chronic respiratory health outcomes. Ambient air pollutant measurements from a single CHS monitoring station in each community were used as surrogates for personal exposures of all children in that community. To improve exposure estimates for the CHS children, we developed an Individual Exposure Model (IEM) to retrospectively estimate the long-term average exposure of the individual CHS children to CO, NO₂, PM₁₀, PM_2.5, and elemental carbon (EC) of ambient origin. In the IEM, pollutant concentrations due to both local mobile source emissions (LMSE) and meteorologically transported pollutants were taken into account by combining a line source model (CALINE4) with a regional air quality model (SMOG). To avoid double counting, local mobile sources were removed from SMOG and added back by CALINE4. Limited information from the CHS survey was used to group each child into a specific time-activity category, for which corresponding Consolidated Human Activity Database (CHAD) time-activity profiles were sampled. We found local traffic significantly increased within-community variability of exposure to vehicle-related pollutants. PM-associated exposures were influenced more by meteorologically transported pollutants and local non-mobile source emissions than by LMSE. The overall within-community variability of personal exposures was highest for NO₂ (±20–40%), followed by EC (±17–27%), PM₁₀ (±15–25%), PM_2.5 (±15–20%), and CO (±9–14%). Between-community exposure differences were affected by community location, traffic density, and locations of residences and schools in each community. Proper siting of air monitoring stations relative to emission sources is important to capture community mean exposures.     

Deposition of atmospheric ammonia to moorlands

Micrometeorological methods were applied to measure fluxes of atmospheric ammonia (NH3) to moorlands. Measurements were made in a wide variety of surface conditions and included both Calluna vulgaris (L.) Hull and Eriophorum vaginatum L. dominated sites. NH3 was found to deposit rapidly to all the sites investigated, providing large deposition velocities (Vd, typically 10-40 mm s(-1)) and usually minimal surface resistances (rc). A small number of measurements were made in frozen conditions and suggest a possible exception to this pattern with mean rc of 50-200 s m(-1). The effect of vegetation drying was also investigated and a possible increase in rc observed, though this was small (< 10 s m(-1)). The results are interpreted in terms of the processes controlling exchange; it is shown that NH3 deposition is predominantly to the leaf surfaces and that the net NH3 compensation point approaches zero. Annual estimates show that dry deposition of NH3 is a major source of atmospheric nitrogen to moorland ecosystems. For two typical UK sites subject to background air concentrations, NH3 dry deposition is of similar magnitude to equivalent NH4+ inputs in wet deposition. In the vicinity of emission sources, NH3 dry deposition is expected to dominate inputs of atmospheric nitrogen.