Theoretical Research on the Multi-channel Reaction Mechanism of CHF Radical with HNCO by Density Functional Theory

The reaction mechanism of CHF radical with HNCO was investigated by the B3LYP method of density functional theory （DFT）, while the geometries and harmonic vibration frequencies of reactants, intermediates, transition states and products were calculated at the B3LYP/6-311＋＋G＊＊ level. In the temperature range of 100-2600 K, the statistical thermody- namics and Eyring transition state theory with Winger correction were used to study the thermodynamic and kinetic characters of the channel with low energy barrier. In addition, the analysis on the combining interaction between CHF radical and HNCO was performed by atom-in-molecules theory （AIM） and natural bond orbitals （NBO） analysis. The calculation results indicated that the reaction of CHF radical with HNCO had ten channels, and the channel of NH direct extraction （CHF ＋ HNCO→IM6→TS7→IM7→CHFNH ＋ CO） in singlet state was the main channel with low potential energy and high equilibrium constant and reaction rate constant. CHFNH and CO were the main products.

Particle number size distribution and new particle formation (NPF) in Lanzhou,Western China

Particle number size distribution from 10 to 10,000 nm was measured by a wide-range particle spectrometer （WPS-1000XP） at a downwind site north of downtown Lanzhou, western China, from 25 june to 19 July 2006. We first report the pollution level, diurnal variation of particle concentration in different size ranges and then introduce the characteristics of the particle formation processes, to show that the number concentration of ultrafine particles was lower than the values measured in other urban or suburban areas in previous studies, However, the fraction of ultrafine particles in total aerosol number concentration was found to be much higher. Furthermore, sharp increase of ultrafine particle concentration was frequently observed at noon. An examination of the diurnal pattern suggests that the burst of the ultrafine particles was mainly due to nucleation process. During the 25-day observation, new particle formation （NPF） from homogeneous nucleation was observed during 33% of the study period. The average growth rate of the newly formed particles was 4.4 nm/h, varying from 1.3 to 16,9 nm/h. The needed concentration of condensable vapor was 6.1 × 10^7 cm-3, and its source rate was 1.1× 10^6 cm-3 s 1. Further calculation on the source rate of sulphuric acid vapor indicated that the average participation of sulphuric acid to particle growth rate was 68.3%.

Rapid decolorization of Acid Orange Ⅱ aqueous solution by amorphous zero-valent iron

Some problems including low treatment capacity,agglomeration and clogging phenomena,and short working life,limit the application of pre-treatment methods involving zero-valent iron （ZVI）.In this article,ZVI was frozen in an amorphous state through a melt-spinning technique,and the decolorization effect of amorphous ZVI on Acid Orange II solution was investigated under varied conditions of experimental variables such as reaction temperature,ribbon dosage,and initial pH.Batch experiments suggested that the decolorization rate was enhanced with the increase of reaction temperature and ribbon dosage,but decreased with increasing initial solution pH.Kinetic analyses indicated that the decolorization process followed a first order exponential kinetic model,and the surface-normalized decolorization rate could reach 2.09 L/（m^2 ·min） at room temperature,which was about ten times larger than any previously reported under similar conditions.Recycling experiments also proved that the ribbons could be reused at least four times without obvious decay of decolorization rate and efficiency.This study suggests a tremendous application potential for amorphous ZVI in remediation of groundwater or wastewater contaminated with azo dyes.

Assessment of Potential Nutrient Release from Phosphate Rock and Dolostone for Application in Acid Soils

Finding alternative local sources of plant nutrients is a practical, low-cost, and long-term strategy. In this study, laboratory column experiments were conducted in a completely randomized design to evaluate the feasibility of using phosphate rock and dolostone as fertilizers or acid-neutralizing agents for application in tropical acid soils. The dissolution rates of different particle-size fractions(0.063–0.25, 0.25–0.5, and 0.5–2 mm) of both rocks were studied by citric acid solution at p H 4 and 2 and water, with extraction times of 1, 3, 5, 7, 12, 24, 72, 144, 240, and 360 h. The results showed that the dissolution of both rocks depended on the particle size,leaching solution, and extraction time. The dissolution rate of rock-forming minerals increased as the specific surface area increased,corresponding to a decrease in particle size. In all cases, the release kinetics was characterized by two phases: 1) a first stage of rapid release that lasted 24 h and would ensure short-term nutrient release, and 2) a second stage of slow release after 24 h, representing the long-term nutrient release efficiency. Both rocks were suitable as slow-release fertilizers in strongly acid soils and would ensure the replenishment of P, Ca, and Mg. A combination of fine and medium particle-size fractions should be used to ensure high nutrient-release efficiency. Much work could remain to determine the overall impact of considerable amounts of fresh rocks in soils.