Resistance and biosorption mechanism of silver ions by Bacillus cereus biomass

Biosorption of silver ions onto Bacillus cereus biomass was investigated. Overall kinetic experiments were performed for the determination of the necessary contact time for the attainment of equilibrium. It was found that the overall biosorption process was best described by pseudo second-order kinetic model. The crystals detected by scanning electron microscope and X-ray photoelectron spectroscopy suggested the precipitation was a possible mechanism of biosorption. The molecular genetics of silver resistance of B. cereus biomass was also detected and illustrated by a whole cell sensor tool.     

Visible light responsive N-F-codoped TiO2 photocatalysts for the degradation of 4-chlorophenol

Visible light responsive N-F-codoped TiO₂ photocatalysts exhibit a higher catalytic activity than N-doped TiO₂ for the degradation of 4-chlorophenol due to the synergistic effect of nonmetal elements.     

Biosorption mechanisms involved in immobilization of soil Pb by Bacillus subtilis DBM in a multimetal-contaminated soil

Mechanisms of soil Pb immobilization by Bacillus subtilis DBM, a bacterial strain isolated from a heavy-metal-contaminated soil, were investigated. Adsorption and desorption experiments with living bacterial cells as well as dead cells revealed that both extracellular adsorption and intracellular accumulation were involved in the Pb2＋removal from the liquid phase. Of the sequestered Pb（II）, 8.5% was held by physical entrapment within the cell wall, 43.3% was held by ion-exchange, 9.7% was complexed with cell surface functional groups or precipitated on the cell surface, and 38.5% was intracellularly accumulated.Complexation of Pb2＋with carboxyl, hydroxyl, carbonyl, amido, and phosphate groups was demonstrated by Fourier transform infrared spectroscopic analysis. Precipitates of Pb5（PO4）3OH, Pb5（PO4）3Cl and Pb10（PO4）6（OH）2that formed on the cell surface during the biosorption process were identified by X-ray diffraction analysis. Transmission electron microscopy–energy dispersive spectroscopic analysis confirmed the presence of the Pb（II）precipitates and that Pb（II） could be sequestered both extracellularly and intracellularly.Incubation with B. subtilis DBM significantly decreased the amount of the weak-acid-soluble Pb fraction in a heavy-metal-contaminated soil, resulting in a reduction in Pb bioavailability, but increased the amount of its organic-matter-bound fraction by 71%. The ability of B.subtilis DBM to reduce the bioavailability of soil Pb makes it potentially useful for bacteria-assisted phytostabilization of multi-heavy-metal-contaminated soil.     

Mo-modified Pd/Al2O3 catalysts for benzene catalytic combustion

Mo-modified Pd/Al2O3catalysts were prepared by an impregnation method and tested for the catalytic combustion of benzene. The catalysts were characterized by N2 isothermal adsorption, X-ray diffraction（XRD）, X-ray photoelectron spectroscopy（XPS）, temperatureprogrammed desorption of NH3（NH3-TPD）, H2temperature-programmed reduction（H2-TPR）, and high-angle annular dark-field scanning transmission electron microscopy（HAADF-STEM）. The results showed that the addition of Mo effectively improved the activity and stability of the Pd/Al2O3catalyst by increasing the dispersion of Pd active components, changing the partial oxidation state of palladium and increasing the oxygen species concentration on the surface of catalyst. In the case of the Pd-Mo/Al2O3catalyst,benzene conversion of 90% was obtained at temperatures as low as 190°C, which was 45°C lower than that for similar performance with the Pd/Al2O3catalyst. Moreover, the 1.0% Pd-5% Mo/Al2O3catalyst was more active than the 2.0% Pd/Al2O3catalyst. It was concluded that Pd and Mo have a synergistic effect in benzene catalytic combustion.     

Pd/activated carbon sorbents for mid-temperature capture of mercury from coal-derived fuel gas

Higher concentrations of Hg can be emitted from coal pyrolysis or gasification than from coal combustion, especially elemental Hg. Highly efficient Hg removal technology from coal-derived fuel gas is thus of great importance. Based on the very excellent Hg removal ability of Pd and the high adsorption abilities of activated carbon（AC） for H2 S and Hg, a series of Pd/AC sorbents was prepared by using pore volume impregnation, and their performance in capturing Hg and H2 S from coal-derived fuel gas was investigated using a laboratory-scale fixed-bed reactor. The effects of loading amount, reaction temperature and reaction atmosphere on Hg removal from coal-derived fuel gas were studied. The sorbents were characterized by N2 adsorption, X-ray diffraction（XRD） and X-ray photoelectron spectroscopy（XPS）. The results indicated that the efficiency of Hg removal increased with the increasing of Pd loading amount, but the effective utilization rate of the active component Pd decreased significantly at the same time. High temperature had a negative influence on the Hg removal. The efficiency of Hg removal in the N2-H2S-H2-CO-Hg atmosphere（simulated coal gas） was higher than that in N2-H2S-Hg and N2-Hg atmospheres, which showed that H2 and CO, with their reducing capacity, could benefit promote the removal of Hg. The XPS results suggested that there were two different ways of capturing Hg over sorbents in N2-H2S-Hg and N2-Hg atmospheres.     

Characterization of extracellular polymeric substances in the biofilms of typical bacteria by the sulfur K-edge XANES spectroscopy

A combined approach of physicochemical extraction and sulfur K-edge X-ray absorption near-edge structure（XANES） spectroscopy was applied to characterize the extracellular polymeric substances（EPS） of typical bacterial biofilms in this study. Physicochemical analysis showed variation of the contents of DNA,polysaccharide and protein in different fractions of EPS in different mediums. The sulfur K-edge XANES analysis yielded a variety of spectra.Spectral fitting of the XANES spectra utilizing a large set of model compounds showed that there was more reduced sulfur in both LB-EPS（loosely bound EPS） and TB-EPS（tightly bound EPS） of all the biofilms in LB medium than in R2 A medium. More oxidized sulfur was identified in LB-EPS than that in TB-EPS,suggesting different niches and physiological heterogeneity in the biofilms. Our results suggested that the sulfur K-edge XANES can be a useful tool to analyze the sulfur speciation in EPS of biofilms.     

水稻光合同化碳在土壤中的矿化和转化动态

作物光合碳是"大气-植物-土壤"碳循环的重要组成部分,是农田土壤有机碳的重要来源,然而其在土壤碳库中的矿化和转化动态尚不清楚.应用室内模拟培养实验,研究水稻收获后输入土壤的光合同化碳在土壤碳库中的矿化及其转化特征.结果表明,100 d的培养期内,原有有机碳的平均矿化速率在4.44~17.8μg·(g·d)-1之间,而光合碳(新碳)的矿化速率则在0.15~1.51μg·(g·d)-1之间.光合同化碳的输入对土壤活性碳库(DOC、MBC)的转化产生显著影响,在培养期内,14C-DOC的转化量为1.89~5.32 mg·kg-1,转化速率的变化幅度为0.18~0.34 mg·(kg·d)-1,原有DOC则在61.13~90.65 mg·kg-1,减少幅度为4.10~5.48 mg·(kg·d)-1;14C-MBC和原有MBC的转化量分别为10.92~44.11 mg·kg-1和463.31~1 153.46mg·kg-1,转化速率变化幅度分别为0.80~2.87 mg·(kg·d)-1和41.60~74.46 mg·(kg·d)-1,说明水稻光合碳的输入对MBC的周转要大于DOC的周转.而且,与原有有机碳相比,输入的"新碳"易被微生物矿化分解,100 d的培养期内,有13.5%~20.2%的新碳被矿化分解,而仅2.2%~3.7%的原有有机碳被矿化分解,光合同化碳的输入对维持稻田土壤的碳汇功能具有重要作用.     

纳滤—光芬顿深度处理树脂废水研究

采用纳滤-光芬顿处理高浓度树脂废水,通过单因素和正交设计研究因素的影响和最佳反应条件。实验结果表明,纳滤-光芬顿技术对该类树脂废水具有较好的降解效果,实验的最佳反应条件为:初始pH值为2.0,30%H2O2的投加量为1mL/L,Fe2+:H2O2(摩尔比)为1:2,最佳反应时间为15min,COD的去除率达到80%,光-芬顿氧化降解树脂废水反应符合三级反应动力学,相关系数R2=0.9947,降解半衰期4.2min。     

秋季施工扬尘PM10自动监测仪参比方法比对测试

施工扬尘是一类重要的污染源.适用性检测是施工扬尘PM10自动监测仪使用的前提.参照《环境空气颗粒物(PM10和PM2.5)连续自动监测技术要求及检测方法》(HJ653-2013)和美国加州《法规403扬尘》,采用国内外9种光散射法和4种β射线法施工扬尘PM10监测仪,在秋季施工工地开展了参比方法比对测试.结果表明:有3...     

能净化空气的环保砖

香港大学研制成功一种环保砖,该砖表面布满小孔,他们在砖头表面涂上5mm厚的特制涂层,配合小孔机构,只要有阳光照射,便会产生光催化作用,将汽车排放废气的主要成分,如氮氧化物、可挥发有机物以及一氧化碳转化为无毒的固体,并藏在小孔内,遇水后污染物被水冲走。