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分光光度法测定降水中微量过氧化氢 总被引:3,自引:0,他引:3
研究了一种测定降水中微量过氧化氢的方法。在0.4~1.5mol/L磷酸介质中,过氧化氢与钒(V)及2-(3,5-二溴-2-吡啶偶氮)-5-二乙氨基苯酚(3,5-diBr-PADAP)反应形成一种组成比为1:1:1的蓝色三元配合物,其最大吸收波长为598nm,表现摩尔吸光系数为5.6×104L·mol-1·cm-1。过氧化氮量在2×10-7~1.3×10-5mol/L时服从比耳定律。方法简便,选择性较高,用于降水中微量过氧化氢的直接测定,结果令人满意。 相似文献
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As part of a broader study of the environmental geochemistry behavior of vanadium(V), the release kinetics of V from the dissolution of natural vanadium titano-magnetite under environmentally relevant conditions was investigated. In both the acidic and basic domains, the V release rate was found to be proportional to fractional powers of hydrogen ion and dissolved oxygen activities. The dependence of the rate on dissolved oxygen can also be described in terms of the Langmuir adsorption model. The empirical rate equation is given by: r= k′α(H~+)~α(Kα(O_2))/(1+Kα(O_2)) where, α = 0.099–0.265, k′ = 3.2 × 10~(-6)–1.7 × 10~(-5), K =2.7 × 10~4–3.9 × 10~4 mol/L in acid solution(pH 4.1), and α =-0.494-(-0.527), k′ = 2.0 × 10~4–2.5 × 10~(-11), and K = 4.1 × 10~3–6.5 × 10~3 mol/L in basic solution(pH 8.8) at 20°C. Based on the effect of temperature on the release rate of V, the activation energies of minerals at p H 8.8 were determined to be 148–235 k J/mol, suggesting that the dissolution of vanadium titano-magnetite is a surface-controlled process. The presence of Na~+, Ca~(2+), Mg~(2+), K~+, NO_3~-, Cl~-, SO_4~(2-)and CO_3~(2-)was found to accelerate the V release rates. This study improves the understanding of both the V pollution risk in some mine areas and the fate of V in the environment. 相似文献
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Experiments were conducted in a fixed-bed reactor that contained a commercial catalyst, V2O5–WO3/TiO2, to investigate mercury oxidation in the presence of NO and O2. Mercury oxidation was improved by NO, and the efficiency was increased by simultaneously adding NO and O2. With NO and O2 pretreatment at 350°C, the catalyst exhibited higher catalytic activity for Hg0 oxidation, whereas NO pretreatment did not exert a noticeable effect. Decreasing the reaction temperature boosted the performance of the catalyst treated with NO and O2. Although NO promoted Hg0 oxidation at the very beginning, excessive NO counteracted this effect. The results show that NO plays different roles in Hg0 oxidation; NO in the gaseous phase may directly react with the adsorbed Hg0, but excessive NO hinders Hg0 adsorption. The adsorbed NO was converted into active nitrogen species (e.g., NO2) with oxygen, which facilitated the adsorption and oxidation of Hg0. Hg0 was oxidized by NO mainly by the Eley–Rideal mechanism. The Hg0 temperature-programmed desorption experiment showed that weakly adsorbed mercury species were converted to strongly bound ones in the presence of NO and O2. 相似文献
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Vanadium (V) is widely used industrially, and plays an important role in the biosphere. Sensitive and reliable analytical methods to determine V in various kinds of samples are of extensive interest. Mainly two spectrophotometric methods developed in the last decade are discussed, namely complex formation methods and catalytic methods. The former is based on either oxidation or reduction of V leading to coloured complexes with proper reagents; they are applicable to determination of V at the mg L?1 level. Catalytic methods are based on the ability of V to catalyse the oxidation of various organic dyes and are applicable to determination at the μg L?1 level. Both methods are used for determination of V in environmental and biological samples. 相似文献