Fenton oxidation of 2, 4-and 2, 6-dinitrotoluene and acetone inhibition

The performances and kinetic parameters of Fenton oxidation of 2,4- and 2,6-dinitrotoluene (DNT) in water-acetone mixtures and explosive contaminated soil washing-out solutions were investigated at a laboratory scale. The experimental results show that acetone can be a significant hydroxyl radical scavenger and result in serious inhibition of Fenton oxidation of 2,4- and 2,6-DNT. Although no serious inhibition was found in contaminated soil washing-out solutions, longer reaction time was needed to remove 2,4- and 2,6-DNT completely, mainly due to the competition of hydroxyl radicals. Fenton oxidation of 2,4- and 2,6-DNT fit well with the first-order kinetics and the presence of acetone also reduced DNT’s degradation kinetics. Based on the comparison and matching of retention time and ultraviolet (UV) spectra between high performance liquid chromatography (HPLC) and standards, the following reaction pathway for 2,4-DNT primary degradation was proposed: 2,4-DNT → 2,4-dinitro-benzaldehyde → 2,4-dinitrobenzoic acid → 1,3-dinitrobenzene → 3-nitrophenol.     

钯/铁双金属对土壤中2,2',3,4,4',5,5'-七氯联苯的催化脱氯研究

采用Fe0还原、钯催化法对土壤中2,2',3,4,4',5,5,-七氯联苯的的还原特性进行了实验研究.结果表明, Pd/Fe双金属能有效地进行2,2',3,4,4',5,5',-七氯联苯的催化脱氯.在钯化率为0.05%、钯/铁加入量1g、初始pH为5.6、反应时间5d的条件下,钯/铁双金属对土壤中2,2',3,4,4',5,5',-七氯联苯去除率达54%.实验还考察了钯化率、初始pH、反应时间、钯/铁投加量、2,2',3,4,4',5,5',-七氯联苯初始浓度等参数对2,2',3,4,4',5,5',-七氯联苯脱氯效果的影响.研究表明,较高的钯化率、钯/铁加入量,较低的2,2',3,4,4',5,5',-七氯联苯初始浓度及弱酸性等条件更有利于Pd/Fe对2,2',3,4,4',5,5',-七氯联苯的还原脱氯.在Pd/Fe双金属表面,2,2',3,4,4',5,5',-七氯联苯的脱氯符合一级动力学反应,反应速率常数为0.0142/h,其半衰期为49h.利用实验数据,对钯/铁双金属作用下的2,2',3,4,4',5,5',-七氯联苯还原脱氯的反应机制也进行了分析.     

钯/铁双金属对土壤中2,2′,3,4,4′,5,5′-七氯联苯的催化脱氯研究

采用Fe⁰还原、钯催化法对土壤中2,2′,3,4,4′,5,5′-七氯联苯的的还原特性进行了实验研究.结果表明,Pd/Fe双金属能有效地进行2,2′,3,4,4′,5,5′-七氯联苯的催化脱氯.在钯化率为0.05%、钯/铁加入量1g、初始pH为5.6、反应时间5 d的条件下,钯/铁双金属对土壤中2,2′,3,4,4′,5,5′-七氯联苯去除率达54%.实验还考察了钯化率、初始pH、反应时间、钯/铁投加量、2,2′,3,4,4′,5,5′-七氯联苯初始浓度等参数对2,2′,3,4,4′,5,5′-七氯联苯脱氯效果的影响.研究表明,较高的钯化率、钯/铁加入量,较低的2,2′,3,4,4′,5,5′-七氯联苯初始浓度及弱酸性等条件更有利于Pd/Fe对2,2′,3,4,4′,5,5′-七氯联苯的还原脱氯.在Pd/Fe双金属表面,2,2′,3,4,4′,5,5′-七氯联苯的脱氯符合一级动力学反应,反应速率常数为0.014 2/h,其半衰期为49h.利用实验数据,对钯/铁双金属作用下的2,2′,3,4,4′,5,5′-七氯联苯还原脱氯的反应机制也进行了分析.     

机械化学法降解2,4,6-三氯苯酚

以金属氧化物为磨料,在常温常压,行星式球磨机转速500r/min条件下,通过机械化学法降解2,4,6-三氯苯酚(TCP)。用气相色谱测定产物中剩余TCP含量,电位滴定法测定各反应阶段产物中游离氯离子含量,X射线衍射仪检测各金属氧化物磨料的晶粒尺寸和形状。结果表明磨料对TCP的摩尔配比越大,TCP降解率越高,当MgO与TCP摩尔配比为80:1时,TCP降解率达98.36%;6h后游离氯离子含量占投料TCP中总氯含量的76%,有>2/3的有机氯已转化为无机氯;不同磨料中,碱土金属氧化物对TCP降解效果较好。     

Seasonal variability of ambient NH3, NO, NO2 and SO2 over Delhi

We present the diurnal and seasonal variability of ambient NH3, NO, NO2 and SO2 over Delhi, India. Ambient NH3, NO and NO2 were measured continuously during winter, summer and autumn seasons using NH3- and NOx-analyzer, which operates by chemiluminescence method with a higher estimation e ciency (> 90%) than the chemical trap method (reproducibility 4.7%). Prominent diurnal, day-to-day and seasonal variations of ambient mixing ratio of NH3, NO, NO2 and SO2 were observed during the study period. Seasonal variation with higher mixing ratio in winter was observed for all measured trace gases except NO. Day-night variation of all measured trace gases observed was higher in winter in comparison with summer. Late morning increase in NO2 mixing ratio might be attributed to conversion of NO to NO2 with the interaction of O3.     

离子对烷基化法在2,4-D和2,4,5-T残留分析中的应用

有机阴离子可以和长碳链的季胺盐阳离子结合生成可溶于高介电常数有机溶剂的离子对.在此溶剂中,它可以和某些卤代烃发生复分解反应,生成季铵盐阳离子的卤化物及有机阴离子的相应烷基化物,故称离子对烷基化反应.此反应条件温和,转化率高,被广泛地应用于酸性及其它含活泼氢的有机化合物的烷基衍生物合成中.在这类有机物的分析中也得到应用.但尚未见应用于农药及其降解物残留分析中的报道. 2,4-D,2,4,5-T是典型的酸性有机农药,广泛用作农田除草剂.在二者的残留分析中,通常用CH_2N_2、BF_3CH_3OH、(CH_3)_2SO_4将它们烷基化,然后用气相色谱加以分析.近几年也有人用多卤素取代醇的BCl_3络合物或五氟苄基溴化物同Na_2CO_3作为     

Affordable CO2 negative emission through hydrogen from biomass,ocean liming,and CO2 storage

Mitigation and Adaptation Strategies for Global Change - A new process to remove carbon dioxide (CO2) from the atmosphere, by combining commercial industrial technologies with ocean liming and CO2...     

Sulfur(IV) oxidation by hydrogen peroxide in aqueous suspensions of SiO2, Al2O3, TiO2 and zeolite

Normal and stopped-flow spectrophotometry were used to study the rate of oxidation of sulfur(IV) (SO₃²⁻/HSO₃⁻) by H₂O₂ in aqueous suspensions of finely divided SiO₂, Al₂O₃, TiO₂ and Na-A-zeolite buffered at pH 8.2 and 4.0. Within the limits of error, the rate constants obtained agree with those measured in the absence of suspended material, i.e. under the given conditions there is no surface catalytic effect to be observed.