Size and morphology control over MOF-74 crystals.

Precise control of the size and morphology of metal-organic framework (MOF) crystals is challenging yet critical for the expansion of the application potential of MOF materials. This work presents a detailed investigation of the impact of various synthetic conditions such as reactant ratio, acidity, capping agent, reaction solution (H2O, ethanol and DMF) etc. on the size and morphology of Mg-MOF-74, a classical MOF with record high CO2 uptake capacity. By varying these fabrication parameters and modulators, the morphology and size of crystals can be precisely tuned in the nanometer to micrometer range. Particularly, the nanosized flaky Mg-MOF-74 crystals with an aspect ratio of ∼0.5 were synthesized for the first time by varying the amount of water. The MOF-74 crystals with different size and morphologies are good candidates for more advanced applications favored by crystal size and morphology control.

Enhanced Adsorption and Separation of Xenon over Krypton via an Unsaturated Calcium Center in a Metal-Organic Framework.

Krypton (Kr) and xenon (Xe) are nowadays widely applied in technical and industrial fields. Separating and collecting highly pure Xe from nuclear facilities are necessary and urgent. However, the technology is limited due to the inert nature of Xe and other interferential factors. In this work, a calcium-based metal-organic framework, Ca-SINAP-1, which comprises a three-dimensional microporous framework with a suitable pore width, was researched for xenon and krypton separation through both experimental and theoretical methods. Ca-SINAP-1, synthesized in solvothermal and gamma ray conditions, features accessible open-metal sites, exhibits a high Xe/Kr selectivity of 10.32, and owns a Xe adsorption capacity of 2.87 mmol/g at room temperature (1.0 bar). Particularly, its excellent chemical stability (from pH 2 to 13) and thermal stability (up to 550 °C), as well as radiation-resistance (up to 400 kGy ß irradiations), render this material a promising candidate for radioactive inert gases treatment.

An improved combustion apparatus for the determination of organically bound tritium in environmental samples.

This paper reports an improved combustion apparatus for the determination of organically bound tritium in environmental samples. The performance of this apparatus including the recovery rate and reproducibility was investigated by combusting lettuce and pork samples. To determine the factors for the different recovery rates of lettuce and pork and investigate whether the samples were completely oxidized, the ashes and exhaust gases produced by the combustion were analyzed. The results indicate that the apparatus showed an excellent performance in the combustion of environmental samples. Thus, the improvements conducted in this study were effective.

[Size distribution of carbonaceous particulate matter in atmosphere of Shanghai, China].

Using STAPLEX pumping system with a six-stage cascade impactor (size range: <0.49 microm, 0.49-0.95 microm, 0.95-1.5 microm, 1.5-3.0 microm, 3.0-7.2 microm, > 7.2 microm), the atmospheric particulate samples at suburb (Jiading District) and urban (Xuhui District) sites in Shanghai, China were collected from May 2010 to May 2011. The organic carbon (OC) and the element carbon (EC) of those samples were analyzed by a DRI Model 2001 thermal/optical carbon analyzer with the reflectance (TOR) method. The size distributions of OC and EC in atmospheric particles both showed bimodal distributions at Jiading and Xuhui, with the peaks at size range of < 0.49 microm. Meanwhile, the average annual concentrations of OC and EC in PM3.0 were 16.35 microg x m(-3) and 2.22 microg x m(-3) at Jiading, 11.85 microg x m(-3) and 1.91 microg x m(-3) at Xuhui, respectively. The higher concentrations of particulate matters together with their carbonaceous species at the suburb site indicated that the particulate and carbonaceous aerosol pollution was more serious at suburb than at urban in Shanghai. Compared with Xuhui, the OC shared a higher homology with EC at < 1.5 microm sizes at Jiading, which suggested that OC was mostly derived from combustion sources at urban site in Shanghai. Furthermore, the OC/EC mass ratios at various particulate sizes and those ratios of different sources were discussed. The result suggested that more vehicle emission and more road dust were present at Xuhui District. Moreover, the second organic carbon (SOC) were estimated using EC as a tracer of primary organic carbon, the SOC mass concentration in PM3.0 was 6.76 microg x m(-3) and had a proportion of 69% of OC in Shanghai, which also showed a bimodal distribution with peaks at size of 0. 49-0.95 microm and 3.0-7.2 microm, respectively.

[Quantitative estimation source of urban atmospheric CO2 by carbon isotope composition].

To effectively reduce urban carbon emissions and verify the effectiveness of currently project for urban carbon emission reduction, quantitative estimation sources of urban atmospheric CO2 correctly is necessary. Since little fractionation of carbon isotope exists in the transportation from pollution sources to the receptor, the carbon isotope composition can be used for source apportionment. In the present study, a method was established to quantitatively estimate the source of urban atmospheric CO2 by the carbon isotope composition. Both diurnal and height variations of concentrations of CO2 derived from biomass, vehicle exhaust and coal burning were further determined for atmospheric CO2 in Jiading district of Shanghai. Biomass-derived CO2 accounts for the largest portion of atmospheric CO2. The concentrations of CO2 derived from the coal burning are larger in the night-time (00:00, 04:00 and 20:00) than in the daytime (08:00, 12:00 and 16:00), and increase with the increase of height. Those derived from the vehicle exhaust decrease with the height increase. The diurnal and height variations of sources reflect the emission and transport characteristics of atmospheric CO2 in Jiading district of Shanghai.

[Photo-chemical decomposition of perfluorooctanoic acids in aqueous periodate].

The influence of reaction atmosphere and TiO2 on photochemical decomposition of perfluorooctanoic acid (PFOA) in aqueous periodate was investigated using a type of low-pressure mercury lamps emitted at 254 nm. PFOA photolysis was slight with 254 nm light irradiation under nitrogen, whereas significant decomposition PFOA obtained with the addition of IO4-. In addition, oxygen restrained photochemical decomposition of PFOA. In UV/TiO2/IO4- system, PFOA degradation ratio was 54%, 15% lower than that for UV/IO4- system. *OH radicals generated from UV/TiO2 system exhausted a lot of IO4-, resulting in lower degree of IO3* production. IO3* was high reactive radical which great excitated PFOA decomposition. The accumulation of short-chain perfluorocarbonxylic acids (PFCAs) as products were identified with HPLC/MS. PFCAs bearing shorter perfluoroalkyl groups were formed in a stepwise way from PFCAs that bear longer perfluoroalkyl groups.