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481.
Longli BO Jianbo LIAO Yucai ZHANG Xiaohui WANG Quan YANG 《Frontiers of Environmental Science & Engineering》2013,7(3):395-402
The development of a combined process of catalytic oxidation and microwave heating for treatment of toluene waste gas was described in this work. Toluene, a typical toxic volatile organic compound, was oxidized through a fixed bed reaction chamber containing zeolite-supported copper oxide (CuO/zeolite) catalyst mixed with silicon carbide (SiC), an excellent microwave-absorbing material. The target compound was efficiently degraded on the surface of the catalyst at high reaction temperature achieved by microwave-heated SiC. A set of experimental parameters, such as microwave power, air flow and the loading size of CuO etc., were investigated, respectively. The study demonstrated these parameters had critical impact on toluene degradation. Under optimal condition, 92% toluene was removed by this combined process, corresponding to an 80%–90% TOC removal rate. Furthermore, the catalyst was highly stable even after eight consecutive 6-h runs. At last, a hypothetical degradation pathway of toluene was proposed based on the experimental data obtained from gas chromatography-mass spectrum and Fourier transform infrared spectroscopy analyses. 相似文献
482.
Sarika Pritam 《毒物与环境化学》2013,95(1):13-19
The article presents the reduced use of toxicologically critical solvents for the extraction and clean-up of a neo-nicotinoid pesticide, acetamiprid from vegetables. Acetamiprid was extracted from spiked vegetable samples of cabbage by the use of different techniques like microwave-assisted extraction (MWAE), sonication and by the conventional method of homogenization. The study revealed that though higher percent recoveries of 78–92 were obtained in the blending method, solvent use was high as compared to MWAE. In MWAE, the percent recoveries recorded were in the range of 46–89 depending upon the solvent used and power employed. A mixture of methanol–water and methanol–acetone at 400 W power levels gave percent recoveries of 72 and 82, respectively, as compared to solvent mixtures, namely, acetone–hexane and acetone–hexane–water, which recorded recoveries of 49 and 67%. The study indicates that the choice of solvent and power employed plays a significant role in MWAE for enhanced recoveries. 相似文献
483.
484.
Deming ZHAO Jie CHENG Michael R. HOFFMANN 《Frontiers of Environmental Science & Engineering》2011,5(1):57-64
Aqueous solutions of phenol were oxidized by hydrogen peroxide assisted by microwave (MW) irradiation. A simple kinetic model for the overall degradation of phenol in the presence of excess H2O2 is proposed in which the degradation rate of phenol is expressed as a linear function of the concentrations of phenol and H2O2. A detailed parametric study showed that the degradation rate of phenol increased with increasing [H2O2] until saturation was observed. Phenol degradation followed apparent zero-order kinetics under MW radiation or H2O2 oxidation. However, after 90 min of irradiation, the observed kinetics shifted to pseudo first order. The overall reaction rates were significantly enhanced in the combined MW/H2O2 system, mainly because microwave could accelerate H2O2 to generate hydroxyl radical (·OH) and other reactive oxygen intermediates. The observed synergetic effects of the MW/H2O2 process resulted in an increased in the net reaction rate by a factor of 5.75. When hydrogen peroxide is present in a large stoichiometric excess, the time required to achieve complete mineralization is reduced significantly. 相似文献
485.
建立了固相萃取—微波衍生化—气相色谱-质谱联用法快速同时测定水中雌酮(E1)、17α-雌二醇(α-E2)、17β-雌二醇(β-E2)、雌三醇(E3)、17α-乙炔基雌二醇(EE2)、双酚A(BPA)等6种雌激素物质的分析方法,对色谱柱升温程序、固相萃取及衍生化条件进行了优化。色谱柱最佳升温程序为:初始温度50 ℃,保持2 min;以20 ℃/min速率升至260 ℃,保持5 min;最后以10 ℃/min速率升至280 ℃,保持5 min。实验结果表明,在选取 HC-C18萃取小柱、添加双(三甲基硅烷基)三氟乙酰胺(BSTFA)+1%三甲基氯硅烷(TMCS)+吡啶作为衍生化试剂、微波315 W衍生化加热4 min的条件下,6种目标物标准曲线的相关系数均大于0.999,BPA、E1、EE2及E3的线性范围为3~300 ng/L,17α-E2及17β-E2的线性范围为5~300 ng/L,方法检出限为2.0~5.0 ng/L,加标回收率为76.45%~96.24%。 相似文献
486.
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488.
The Effect of Starch Composition on Structure of Foams Prepared by Microwave Treatment 总被引:2,自引:0,他引:2
A microwave technique was used to prepare foams from different potato starches in granular form, with varying amounts of amylose content, and water. In addition to native potato starch (PN), high amylose potato starch (HAP) and potato amylopectin (PAP) were used, as well as mixtures thereof. In all cases the native crystallinity of starch granules was lost upon microwave treatment and an amorphous material was created. An increased concentration of starch in the initial water dispersion resulted in a less dense foam structure. The potato amylopectin formed open cell foams, whereas increased amylose content, as in native potato starch, yielded a more compact structure with irregular pore shapes. The high amylose potato starch yielded a structure with hardly any porosity. Foaming experiments were done to compare pre-gelatinized and granular starches dispersed in water. The pre-gelatinisation did not affect the pore formation process. These experiments indicated that the molecular architecture of starch polymers is more important for foam formation than starch polymer organization in the granules. Studies of temperature profile and dry matter content during microwave treatment showed that water evaporates more rapidly from a high amylose starch solution than native potato starch and potato amylopectin solutions. Rheological measurements showed that the amylose solution had much lower viscosity than starch and amylopectin. This confirms that polymer – water interaction, such as in amylopectin solution, favours stabilization of bubbles formed upon boiling and evaporation of water, which yields high porosity materials. 相似文献
489.
Jie Fu Zhen Xu Qing-Shan Li Song Chen Shu-Qing An Qing-Fu Zeng Hai-Liang Zhu 《环境科学学报(英文版)》2010,22(4):512-518
A comparative study of treatment of simulated wastewater containing Reactive Red 195 using zero-valent iron/activated
carbon (ZVI/AC), microwave discharge electrodeless lamp/sodium hypochlorite (MDEL/NaClO) and the combination of ZVI/ACMDEL/
NaClO was conducted. The preliminary results showed the two steps method of ZVI/AC-MDEL/NaClO had much higher
degradation e ciency than both single steps. The final color removal percentage was nearly up to 100% and the chemical oxygen
demand reduction percentage was up to approximately 82%. The e ects of operational parameters, including initial pH value of
simulated wastewater, ZVI/AC ratio and particle size of ZVI were also investigated. In addition, from the discussion of synergistic
e ect between ZVI/AC and MEDL/NaClO, we found that in the ZVI/AC-MEDL/NaClO process, ZVI/AC could break the azo bond
firstly and then MEDL/NaClO degraded the aromatic amine products e ectively. Reversing the order would reduce the degradation
e ciency. 相似文献
490.