紫外光谱法结合化学计量学用于环境水样中2,4,6-三硝基甲苯及其分解物的同时测定

结合紫外吸收和偏最小二乘法建立了环境水样中2,4,6-三硝基甲苯及其分解物的分析方法,在不经过任何预先分离的情况下,实现了环境水样中2,4,6-三硝基甲苯(TNT)及其分解物2,4-二硝基甲苯(2,4-DNT)和2,6-二硝基甲苯(2,6-DNT)的快速准确测定.采用正交试验设计(OAD)配制了25个训练集样本和15个独立预测集样本,采用变量种群分析(VCPA)方法挑选特征变量以提高偏最小二乘法(PLS)模型的预测效果,预测集中每个物质的相关系数R2均达到0.99.将最优的VCPA模型用于真实水样中TNT以及DNT的检测,并采用HPLC方法进行了验证.实验结果显示,VCPA模型的回收率与HPLC法相近.紫外光谱法结合化学计量学方法可作为环境体系中多成分同时测定的一种简便、快速、有效的方法.     

Decomposition of nitrotoluenes in wastewater by sonoelectrochemical and sonoelectro-Fenton oxidation

Oxidative degradation of dinitrotoluene (DNT) and 2,4,6-trinitrotoluene (TNT) in wastewater was conducted using electrochemical and electro-Fenton processes respectively, combined with ultrasonic irradiation, wherein a synergistic effect is observed. Experiments were carried out to elucidate the influence of various operating variables on the sonoelectrolytic behavior, such as electrode potential, sonoelectrolytic temperature, acidity of wastewater, oxygen dosage, and dosage of ferrous ions. It deserves to note that the nitrotoluene contaminants could be completely decomposed by sonoelectro-Fenton method, wherein hydrogen peroxide was in situ generated from cathodic reduction of oxygen, supplied partially by anodic oxidation of water. During the sonoelectrolytic process, in spite of existence of degassing phenomenon, the high yield of hydrogen peroxide was produced due to the significantly enhanced mass transfer rate of oxygen toward the cathode, caused by ultrasonic irradiation. Because higher removal efficiency of DNTs and TNT obtained at ambient conditions, it is believed that the sonoelectrolytic method is potentially applied to dispose wastewater from toluene nitration processes.     

Adsorption of 2,4-Dinitrotoluene on Dickite: The Role of H-Bonding

The adsorption of 2,4-dinitrotoluene (DNT) on the tetrahedral and octahedral surfaces of dickite (a clay mineral of the kaolinite group with a 1:1 dioctahedral structure characterized by the common chemical formula Al₂Si₂O₅(OH)₄) was studied using small representative mineral models. The calculations have been performed at the HF/3-21G level of theory. The orientation of DNT on the tetrahedral surface of dickite was found to be coplanar with the surface plane. In the case of the adsorption on the octahedral surface the DNT molecule is placed with an inclination about 30^∘ to the surface plane. This type of adsorption results in an electron density redistribution of DNT on the surface of the mineral that is more significant in the case of the adsorption on the tetrahedral surface. The interaction energies of DNT with the octahedral and tetrahedral surfaces corrected by the BSSE energy were found. The adsorption energy of a DNT-tetrahedral fragment amounts to −6.5 kcal/mol, and the interaction energy of the DNT-octahedral fragment system is −17.7 kcal/mol.     

Fe‐enriched Clay‐coated and Reduced Graphene Oxide‐modified N‐doped Polymer Nanocomposite: A Natural Recognition Element‐based Sensing Electrode for DNT

Dinitrotoluene (DNT) is a signature material of all nitro‐aromatic explosives including the lethal 2,4,6‐trinitrotoluene (TNT). A clay‐modified reduced graphene oxide (rGO)‐polymer nanocomposite was prepared as sensing electrode for the detection of (DNT) in the aquatic systems. rGO was in situ dispersed in the electro‐conductive N‐doped phenol/formaldehyde polymer and the clay ‘montmorillonite’ was coated on the nanocomposite. The clay, containing iron as one of its mineral components, served as the recognition element for DNT. Tested using electrochemical measurement techniques – cyclic voltammetry and differential pulse voltammetry, the prepared sensing electrode exhibited a low detection limit (0.0016 μM) on signal to noise ratio basis (S/N=3) and excellent linearity (R²=0.997) over 0.02–10 mg L^?1 with high sensitivity value (428 μA mM^?1 cm^?2) for DNT. The electrode showed negligible interference with the gravimetric and volumetric salts commonly present in seawater, and also, with explosive derivatives. The separate tests performed in a simulated seawater confirmed the suitability of the prepared electrode for use in field applications.     

Membrane for in situ optical detection of organic nitro compounds based on fluorescence quenching

Fluorescent membrane formulations for detecting organic nitro compounds by fluorescence quenching were evaluated. The most sensitive membrane is prepared by solvent casting from cyclohexanone to incorporate pyrenebutyric acid into cellulose triacetate plasticized with isodecyl diphenylphosphate. The response follows the Stern-Volmer law for 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT). The membrane also responds to hexahydro-1,3,5-tri- nitro-1,3,5-triazine (RDX). For a given set of conditions, the primary factor determining sensitivity is the extent to which each nitro compound partitions into the membrane. Detection limits are ca. 2 mg l^?1 for DNT and TNT and 10 mg l^?1 for RDX. Nitrogen purging prior to the measurement enhances the sensitivity and eliminates interference from oxygen. The membrane is designed to be used for remote optical in situ screening of groundwater for contamination by explosives.     

Removal of dinitrotoluenes in wastewater by sono-activated persulfate

Oxidative degradation of dinitrotoluenes (DNTs) in wastewater was performed using persulfate anions combined with ultrasonic irradiation, wherein a synergistic effect is observed. The batch-wise experiments were carried out to elucidate the influence of various operating parameters on sono-activated persulfate oxidation, including ultrasonic power intensity, persulfate anion concentration, reaction temperature and acidity of wastewater. It is noteworthy that the nitrotoluene contaminants could be almost completely eliminated by virtue of sono-activated persulfate oxidation, wherein sulfate radicals serve as principal oxidants, of which amounts are significantly enhanced via addition of sodium sulfate. Based on the results given by gas chromatograph-mass spectrometer (GC-MS), it is postulated that the methyl group of DNTs preliminarily underwent oxidation pathway into dinitrobenzoic acid, followed by decarboxylation to form 1,3-dinitrobenzene (DNB). In sum, the sono-activated persulfate oxidation is a promising method for treatment of nitrotoluenes in wastewater.     

Mo含量对Ni-Mo-B非晶态合金催化剂结构及催化二硝基甲苯加氢性能的影响

采用化学还原法制备Ni-Mo-B非晶态合金催化剂, 研究了Mo含量对二硝基甲苯加氢制备甲苯二胺催化性能的影响. 结果表明, 当Mo含量(摩尔分数)≤6%时, Mo助剂使Ni-B非晶态合金催化剂的催化活性显著提高, 选择性均达到100%. 通过XRD, TEM, DSC, XPS, ICP和H₂-TPD技术对催化剂微观结构进行了表征, 结果表明, 随着Mo助剂含量的增加, Ni-Mo-B非晶态合金催化剂中不仅非晶态结构的无序程度增大, 催化剂粒径逐渐由60 nm左右减小至15 nm左右, 而且分布更加均匀, Ni吸附中心的H₂吸附强度变弱, 使氢物种更易于在催化剂表面流动并参与反应, 同时Mo助剂还显著提高了催化剂的热稳定性和抗氧化性. 当Mo含量为6%时, Ni-Mo-B非晶态合金催化剂的催化性能最好, 在2 MPa和110℃反应条件下, 二硝基甲苯转化率达99.8%, 甲苯二胺选择性为100%.     

采用溶胶-凝胶-溶剂热路径合成H3PW12O40/TiO2和H4SiW12O40/TiO2 及其光催化降解二硝基甲苯

以非离子表面活性剂P123为结构导向剂,采用溶胶-凝胶与溶解热相结合方法,制备了两类介孔材料H₃PW₁₂O₄₀/TiO₂和H₄SiW₁₂O₄₀/TiO₂,并对其进行了表征.?X射线粉末衍射和拉曼光谱分析表明,所制催化剂为锐钛矿晶型,体系中H₃PW₁₂O₄₀和H₄SiW₁₂O₄₀的Keggin结构经400?℃焙烧后仍保持完整.?H₃PW₁₂O₄₀/TiO₂和H₄SiW₁₂O₄₀/TiO₂的平均粒径分别为15.49和7.75?nm.?N₂吸附-脱附和扫描电镜结果表明,P123的加入使催化剂的粒径减小,比表面积和孔体积明显增大,其中H₃PW₁₂O₄₀/TiO₂和H₄SiW₁₂O₄₀/TiO₂的比表面积分别高达252.2和250.0?m²/g.?紫外漫反射吸收光谱表明,与纯TiO₂相比,复合催化剂的吸收光谱发生了明显的红移,且吸收强度明显增大.?催化剂对DNT降解实验表明,在最佳操作条件下降解率可高达95%.?     

Removal of Nitrobenzene,Isophorone, 2,6-Dinitrotoluene and 2,4-Dinitrotoluene from Aqueous Solution by Solvent Sublation

Nitrobenzene, isophorone, 2,6-dinitrotoluene and 2,4-dinitrotoluene were removed from aqueous solution by solvent sublation. The separation efficiencies of three solvents (4-methyl-2-pentanone, 1-octanol and paraffin oil) as the overlaying layer were compared. The rate of separation of these organic pollutants by solvent sublation depends strongly on the size of air bubbles, which is affected by the overlaying solvent, and concentrations of sodium dodecyl sulfate (NDS), inorganic and polar organic solute.