共查询到19条相似文献，搜索用时 171 毫秒
1.
An efficient reflux extraction of polyethylene wax （PEW） in soil is presented, followed by molecular structure characterization methods to explore its degradation mechanism. To more realistically simulate the actual degradation of PE film powders in soil, low density PE （M=5 000） powders, being used as simulated PEW residue sample, were uniformly mixed with soil and then recovered by reflux extraction with decahydronaphthalen （decalin） at 90 ℃ for 60 min. The average recovery of PEW from fortified soils was 96.5% with the developed reflux extraction procedure. The recovered PEW residue samples were characterized by infrared spectroscopy （IR）, element analysis （EA）, X-ray fluorescence （XFR）, and high-temperature gel permeation chromatography （GPC）. The results from spectra analysis show that there were no significant changes in molecular structures and molecular mass distribution of PEW samples after the reflux extraction, which demonslrate the reliability of this method. These results also indicate that the reflux extraction procedure and analytical methods of characterization could serve as a novel measurement technique to evaluate the degradation of low-density PE powders in soil over time. 相似文献
2.
The iron-loaded organic phase of naphthenic acid-isooctyl alcohol-kerosene was prepared, and the process kinetics of hydrothermal stripping of iron from the phase was studied. Several factors affecting hydrothermal stripping, such as the polymer of naphthenic acid, initial concentrations of iron and naphthenic acid, temperature and agitation time, were investigated, and based on experimental results and theoretical analysis, two kinetic models were established.The stripping rate equation suggests that the hydrothermal stripping process activation energy is 96.4 kJ·mol-1 and the stripping is controlled by hydrolysis of naphthenic complex of iron. The values calculated by the stripping fraction equation comparatively accord with the experimental data. 相似文献
3.
Two isomers ofnitrochlorobenzene （o- andp-NCB） were treated by a Pd/Fe catalyst in aqueous solutions through catalytic amination and dechlorination. Nitrochlorobenzenes are rapidly converted to form chloroanilines （CAN） first through an amination process, and then rapidly dechlorinated to become aniline （AN） and CI^-, without the involvement of any other intermediate reaction products. The amination and dechlorination reaction are believed to take place predominantly on the surface site of the Pd/Fe catalysts. The dechlorination rate of the reductive degradation of the two isomers of nitrochlorobenzene （o-, and p-NCB） in the presence of Pd/Fe as a catalyst was measured experimentally. In all cases, the reaction rate constants were found to increase with the decrease in the Gibbs free energy （correlation with the activation energy） of NCBs formation; the activation energy of each dechlorination reaction was measured to be 95.83 and 77.05 kJ/mol, respectively for o- and p-NCB. The results demonstrated that p-NCBs were reduced more easily than o-NCBs. 相似文献
4.
Supercritical carbon dioxide fluid extraction (SFE) was studied as a rapid method for extraction of volatile and semivolatile compounds of Chinese commercial cigarettes. The method was compared with simultaneous distillation and extraction (SDE). Temperature and pressure for the SFE were optimized. The extracts obtained by the two methods showed different characters in composition and represented differently the flavor characteristics of tobacco; compared to SDE, SFE can extract compounds within a shorter time and avoid the thermal degradation and solvent contamination of samples. The extracts by the two extraction methods are complementary for investigating the flavor characteristic of tobacco products. 相似文献
5.
Imprinted polymers were prepared for selective removal of Cu（Ⅱ） ions from metal solutions. Three ion-imprinted polymers were synthesized with methacrylic acid （MAA）, acrylamide （AA） and N,N＇-methylenebisacrylamide （MBAA） respectively as the functional monomers, ethleneglycoldimethacrylate （EGDMA） as the cross-linking agent, 2,2＇- azobisisobutyronitrile （AIBN） as the initiator and Cu （Ⅱ） ion as the imprint ion. The template Cu （Ⅱ） ion was removed from the polymer by leaching with a liquid of a 1：1 volumetric ratio of HCl to ethylenediaminetetraacetic acid （EDTA）. The capacity and selectivity of Cu（Ⅱ） ion adsorption were investigated with the three imprinted polymers and their non-imprinted counterparts. The polymers have a maximum adsorption capacity at pH 7.0. The isotherm of their batch adsorption of Cu（Ⅱ） ions shows a Langmuir adsorption pattern. Imprinted polymers all have a much higher capacity and higher selectivity of Cu（Ⅱ） adsorption than nonimprinted ones. MAA polymer benefits the most from imprinting. Imprinted MAA polymer has the highest selectivity when used to rebind Cu （Ⅱ） ion from an aqueous solution in the presence of other metal ions. Ion imprinting can be a promising technique of preparing selective adsorbents to separate and preconcentrate metal in a medium of multiple competitive metal ions through solid phase extraction （SPE）. 相似文献
6.
苏州河底泥重金属形态分析 总被引：2，自引：0，他引：2
Nine elements （As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn） in sediment samples at 7 sites （Site 1-7） from Suzhou Creek in Shanghai were analyzed with the Community Bareau of Reference （BCR） （sequential extraction （SE）） protocol and simultaneously extracted metals （SEM）/acid volatile sulfide （AVS） procedure to assess the metal bioavailability and toxicology in this area. The results showed that the BCR extraction can be utilized as an additional tool with the AVS method for assessing the potential bioavailability and toxicity of metals in sediments. Pollution from S5 （Site 5） was more severe than from other sites, especially Pb, Cu and Zn. Among all the sites, more than 80% of the total concentration of Fe existed in the residual fraction, As, Cr, Mn also dominated in the residual fraction （more than 50%）. While Cd, Ni and Zn （more than 35%） were mainly in the non-stable phase. Cu had a strong affinity with oxidizable phase and Pb varied from site to site. The SEM/AVS ratio was less than one in these sediments and results implied that the majority of Zn and Ni （〉 40%） were bound to AVS. In contrast, Pb, Cu and Cd were little bound to AVS due to their low ration of SEM-Pb, Cu, Cd to corresponding total concentration and relatively high Dorewater concentration. 相似文献
7.
Vacuum pyrolysis was employed to dispose scrap brominated epoxy printed circuit boards (PCBs). Pyrolysis characteristics of waste PCBs under normal pressure and vacuum were investigated in this paper. A detailed study on the analysis of the elemental composition of PCBs and the pyrolysis products was performed. The thermal decomposition kinetics was measured by a thermogravimetric (TG) analyzer. The activation energy of pyrolysis under nitrogen atmosphere and vacuum were 193 kJ/mol to 206 kJ/mol and 145 kJ/mol to 165 kJ/mol, respectively. The composition of materials was analyzed by elemental analyzer. The pyrolysis products were analyzed by GC (gas chromatograph), GC-MS (chromatography and mass spectrometry) and FT-IR (Fourier transform infrared spectroscopy). Vacuum helped to increase the yield of pyrolysis oil. The liquid yield of PCBs pyrolysis at 15 kPa and normal pressure were 31.3? and 23.5?, respectively. The main components in pyrolysis oils were phenol, isopropyl-phenol, and their brominated substitution. 相似文献
8.
The purpose of this study was to evaluate the potential of electron beam to decompose chloramphenicol （CAP） in aqueous solutions. At the absorbed dose of 15 kGy, the decomposition rate of CAP was 95.24%. The degradation of CAP under electron beam irradiation followed pseudo-first-order kinetics. Redox reactions of CAP aqueous solutions with hydroxyl radicals （.OH）, hydrated electrons （eaq） and hydrated atoms （·H） were studied. The increase of the additives would result in the decrease of the degradation efficiency. The concentration of Cl- and NO3- in aqueous solution increased after electron beam irradiation. On the basis of the experimental results, a photocatalytic mechanism was discussed. The rate constant for reactions of .OH and CAP was 9.36×10^7 L/（mol.s） and for reaction of eaq and CAP was 7.33×10^7 L/（mol.s）..OH was supposed to play the key role in the radiation system of aqueous solution. Other free radicals like eaq and .H could also initiate the degradation. 相似文献
9.
Edgar Scavino Dzuraidah Abdul Wahab Aini Hussain Hassan Basri Mohd Marzuki Mustafa 《浙江大学学报(A卷英文版)》2009,10(6):794-799
An experimental machine vision apparatus was used to identify and extract recyclable plastic bottles out of a conveyor belt. Color images were taken with a commercially available Webcam, and the recognition was performed by our homemade software, based on the shape and dimensions of object images. The software was able to manage multiple bottles in a single image and was additionally extended to cases involving touching bottles. The identification was fulfilled by comparing the set of measured features with an existing database and meanwhile integrating various recognition techniques such as minimum distance in the feature space, self-organized maps, and neural networks. The recognition system was tested on a set of 50 different bottles and provided so far an accuracy of about 97% on bottle identification. The extraction of the bottles was performed by means of a pneumatic arm, which was activated according to the plastic type; polyethylene-terephthalate （PET） bottles were left on the conveyor belt, while non-PET bottles were extracted. The software was designed to provide the best compromise between reliability and speed for real-time applications in view of the commercialization of the system at existing recycling plants. 相似文献
10.
Emissions of volatile organic compounds and carbonyl compounds from residential coal combustion in China 总被引：1，自引：0，他引：1
Emissions of volatile organic compounds （VOCs） and carbonyls from residential coal combustion of five coals with different maturities were studied in a simulated room.The coals were burned in form of honeycomb briquettes in a domestic coal stove,one of the most common fuel/stove combinations in China.Through a dilution system,VOCs and carbonyls samples were collected by canisters and silica-gel cartridges and analyzed by gas chromatography and mass spectrum （GC/MS） and high performance liquid chromatography/ultraviolet （HPLC/UV）,respectively.The results show that the bituminous coals with medium volatile matter content produce the highest emissions while the anthracite yields the lowest.Among the identified carbonyls from the coal smoke,the aromatic compounds （benzaldehyde,2,5-dimethylbenzaldehyde and p-tolualdehyde,m/o-tolualdehyde,benzene,m,p-xylene and trimethyl-benzene） were relatively abundant,which might be due to the molecular structure of the coal.For formaldehyde,aromatic carbonyls and aliphatic alkanes,their concentrations increase up to the maximum values and then decrease with increasing coal maturity.The total carbonyls and VOCs have the same tendency,which was observed for the emission factors of organic carbon （OC）,elemental carbon （EC）,particulate matter （PM） and polycyclic aromatic hydrocarbons （PAHs） detected in the series study. 相似文献
11.
采用Benson基团贡献法估算了三醋酸甘油酯的合成反应热．计算结果表明：该反应的焓变分别为ΔHf1＝－41．1 kJ/mol、ΔHf2＝－12．3 kJ/mol、ΔHf3＝－12．3 kJ/mol ,所得的计算结果与实验测定数据基本相符合．考察了在采水条件下温度对三醋酸甘油酯合成的影响,建立了拟一级反应动力学模型,结果表明,该模型能较好的拟合实验数据． 相似文献
12.
由于Nation的强离子交换能力和多壁碳纳米管(MWCNTs)卓越的性能,一种高灵敏度、无汞的基于MWCNT-Nafion复合修饰玻碳电极测定痕量Zn2+的新方法被建立.在0.01 mol/dm3 KCl(pH=7)溶液中,采用阳极溶出伏安法(ASV)在MWCNT-Nafion复合修饰电极上检测Zn2+.实验结果表明伏安图上能出现一灵敏的氧化峰,峰电位为-1.05 V,利用该峰可以进行痕量Zn2+的检测.峰电流与Zn2+浓度在2.0×10-12～1.0×10-10 mol/dm3的范围内呈良好线性关系,相关系数为0.998,检出限为0.2×10-13mol/dm3.这种方法为痕量Zn2+的检测提供了新手段. 相似文献
13.
提出用丁二酮肟修饰碳糊电极的制备及对Cu（Ⅱ）的测定.以铂丝电极为对电极,Ag/AgCl电极为参比电极,在pH=3.2的邻苯二甲酸氢钾—盐酸缓冲溶液中通过在-1.0V电位下富集后,在-1.0V～＋0.6V电位范围内作线性扫描溶出伏安法测定,峰电流与Cu（Ⅱ）浓度在4.0×10^-6～5.0×10^-5mol/L范围内呈良好线性关系,当富集300s时检测限为1.0×10^-9mol/L,且大多数阳离子不干扰测试结果. 相似文献
14.
We deformed AZ31 magnesium alloys by cold forging and cold compression process, and investigated their static recrystallization kinetics during the annealing process. The results demonstrate that the relationship between the annealing time and the fraction of recrystal grains can be described by the Johnson-Mehl-Avrami-Kolmogorov （JMAK） equation. Based on the kinetics analysis, we calculated that the activation energy of recrystallization by cold forging and cold compression were about 53.5 kJ/mol and 85.0 kJ/mol, respectively. The activation energy of cold compression process was higher than that of the cold forging process because the latter had high-rate deformation, which caused more energy storage during deformation. 相似文献
15.
刘小英 《泉州师范学院学报》2005,23(4):51-54
用非等温热重法研究了腰果酚甲醛铁聚合物的热分解反应动力学,结果表明：腰果酚甲醛铁聚合物的热分解过程是一级反应，用Ozawa法和Reich法求得的平均活化能分别为191．1kJ／mol和191．0kJ／mol。 相似文献
16.
研究了Bi^3＋在碳糊电极上的阳极溶出伏安特性,结果表明：在1．0mol·L^-1的HCl溶液中,于-0．055V处出现一灵敏的溶出峰,电极反应过程是受吸附控制的电极过程。并考察了测定Bi^3＋的最优化条件,在1．0mol·L^-1的HCl溶液中,于0．4V富集80s后,以120mV／s扫描速度进行测定,结果表明：在1．0×10^-7-1．0×10^-4mol·L^-1浓度范围内,Bi^3＋的溶出峰电流Ip与其呈良好的线性关系,检出限为6．0×10^-8mol·L^-1（信噪比RSN=3）。将该法应用于药物中铋含量的测定,回收率在99—102％,结果令人满意。 相似文献
17.
使用粉煤灰作为催化剂,对聚丙烯进行热解处理,并用程序升温的热重法(TG)和恒温法两种模型方法对热解反应进行研究。结果表明,这两种方法都适用于聚丙烯的催化降解,且粉煤灰含量为2%时,恒温模型计算得到的反应活化能为196kJ/mol,TG模型计算的结果是233kJ/mol(反应级数为1)。从两种模型计算的计算结果与实验结果的拟合情况来看,恒温法得到的结果与实验结果更加吻合。 相似文献
18.
Quantum chemical simulation was used to investigate the catalytic mechanism of Na/K on NO-char heterogeneous reactions during the coal reburning process. Both NO-char and NO-Na/K reactions were considered as three-step processes in this calculation. Based on geometry optimizations made using the UB3LYP/6-31G（d） method, the activation energies of NO-char and NO-Na/K reactions were calculated using the QCISD（T）/6-311G（d, p） method; Results showed that the activation energy of the NO-Na/K reaction （107.9/82.0 kJ/mol） was much lower than that of the NO-char reaction （245.1 kJ/mol）. The reactions of NaO/KO and Na2O/K2O reduced by char were also studied, and their thermodynamics were calculated using the UB3LYP/6-31G（d） method; Results showed that both Na and K can be refreshed easily and rapidly by char at high temperature during the coal reburning process. Based on the calculations and analyses, the catalytic mechanism of Na/K on NO-char heterogeneous reactions during the coal reburning process was clarified. 相似文献
19.
采用荧光光谱和紫外可见吸收光谱法研究了地美硝唑与牛血清蛋白的结合反应,发现地美硝唑对牛血清白蛋白有较强的荧光猝灭作用,该猝灭过程主要为静态猝灭过程。从荧光光谱数据,由Stern—Volmer方程和Lineweaver—Burk方程分析并处理实验数据得到了23℃时结合反应的结合常数K=1．03×10^4L／mol,结合位点数为0．70,结合反应的标准焓变、标准熵变、和标准吉布斯自由能变分别为～63．48kJ／mol,-96．22J／K,-35．00kJ／mol。 相似文献