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排序方式: 共有596条查询结果,搜索用时 203 毫秒
341.
硫氰酸汞分光光度法测定空气中氯化氢,方法试剂空白值不稳定,曲线线性不好。现就在大气中氯化氢的测定(硫氰酸汞分光光度法)过程中遇到的若干问题作了分析和探讨,并且通过实验,证明提高硫氰酸汞的浓度,可以提高该测量方法灵敏度。 相似文献
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本研究以南方某含溴水源为原水,利用饮用水常规工艺及臭氧-活性炭深度处理中试连续实验,评价臭氧氧化过程中溴酸盐生成情况,并考察了氨氮、过氧化氢(H_2O_2)对溴酸盐控制效果及对三卤甲烷生成势(THMFP)的去除影响.结果表明,在不同水质条件下,臭氧消耗量为1.0 mg·L~(-1)以上时,溴酸盐的生成量超过标准(10.00μg·L~(-1)).利用氨氮和H_2O_2投加均能有效控制溴酸盐生成量,且随投加量增大,溴酸盐生成量逐渐降低,氨氮投加0.10~0.30 mg·L~(-1)或m(H_2O_2)/m(O3)(质量比)为0.2~1.0时,能够将溴酸盐控制在标准以内.当氨氮-H_2O_2联合控制溴酸盐时,溴酸盐生成量随m(H_2O_2)/m(O3)先升高后降低.在利用氨氮和H_2O_2投加进行溴酸盐控制过程中,氨氮对THMFP的去除效率影响并不显著,而投加H_2O_2使得THMFP去除效能有所降低. 相似文献
344.
Kalyani Mer Baharak Sajjadi Nosa.O. Egiebor Wei-Yin Chen Daniell.L. Mattern Wendong Tao 《环境科学学报(英文版)》2021,33(1):267-273
Generation of hydroxyl radicals (?OH) is the basis of advanced oxidation process (AOP). This study investigates the catalytic activity of microporous carbonaceous structure for in-situ generation of ?OH radicals. Biochar (BC) was selected as a representative of carbon materials with a graphitic structure. The work aims at assessing the impact of BC structure on the activation of H2O2, the reinforcement of the persistent free radicals (PFRs) in BC using heavy metal complexes, and the subsequent AOP. Accordingly, three different biochars (raw, chemically- and physiochemically-activated BCs) were used for adsorption of two metal ions (nickel and lead) and the degradation of phenol (100 mg/L) through AOP. The results demonstrated four outcomes: (1) The structure of carbon material, the identity and the quantity of the metal complexes in the structure play the key roles in the AOP process. (2) the quantity of PFRs on BC significantly increased (by 200%) with structural activation and metal loading. (3) Though the Pb-loaded BC contained a larger quantity of PFRs, Ni-loaded BC exhibited a higher catalytic activity. (4) The degradation efficiency values for phenol by modified biochar in the presence of H2O2 was 80.3%, while the removal efficiency was found to be 17% and 22% in the two control tests, with H2O2 (no BC) and with BC (no H2O2), respectively. Overall, the work proposes a new approach for dual applications of carbonaceous structures; adsorption of metal ions and treatment of organic contaminants through in-situ chemical oxidation (ISCO). 相似文献
345.
臭氧氧化水中2,4,6-三氯酚的反应机理研究 总被引:16,自引:3,他引:16
研究了臭氧氧化对2,4,6-三氯酚的去除效果,以及氧化过程中过氧化氢、氯离子、甲酸和乙二酸的变化情况,探讨了臭氧氧化2,4,6-三氯酚的反应机理和反应途径.实验结果表明,如果溶液中没有自由基清除剂,在臭氧投加量为24mg·L~(-1)时,0·1mmol·L~(-1)的2,4,6-三氯酚在6min内,去除率可达99%.臭氧分子氧化2,4,6-三氯酚的过程中产生过氧化氢,检测到的过氧化氢的最大摩尔浓度为初始2,4,6-三氯酚摩尔浓度的22·5%.中间产物过氧化氢随后和臭氧反应生成大量的羟基自由基,此时2,4,6-三氯酚是被臭氧和羟基自由基联合氧化,生成甲酸和乙二酸.当溶液中含有大量的自由基清除剂时,2,4,6-三氯酚首先被臭氧分子氧化成黄色的氯代对苯醌,然后氧化成甲酸和乙二酸.臭氧氧化2,4,6-三氯酚存在臭氧分子氧化以及O3/OH·联合氧化两种反应途径. 相似文献
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348.
Thomas H. Christensen Poul L. Bjerg Steven A. Banwart Rasmus Jakobsen Gorm Heron Hans-Jrgen Albrechtsen 《Journal of contaminant hydrology》2000,45(3-4)
Evaluation of redox conditions in groundwater pollution plumes is often a prerequisite for understanding the behaviour of the pollutants in the plume and for selecting remediation approaches. Measuring of redox conditions in pollution plumes is, however, a fairly recent issue and yet relative few cases have been reported. No standardised or generally accepted approach exists. Slow electrode kinetics and the common lack of internal equilibrium of redox processes in pollution plumes make, with a few exceptions, direct electrochemical measurement and rigorous interpretation of redox potentials dubious, if not erroneous. Several other approaches have been used in addressing redox conditions in pollution plumes: redox-sensitive compounds in groundwater samples, hydrogen concentrations in groundwater, concentrations of volatile fatty acids in groundwater, sediment characteristics and microbial tools, such as MPN counts, PLFA biomarkers and redox bioassays. This paper reviews the principles behind the different approaches, summarizes methods used and evaluates the approaches based on the experience from the reported applications. 相似文献
349.
The thermal hazards of dicumyl peroxide (DCP) and benzoyl peroxide (BPO), self-reactive chemicals are identified and characterized using high-pressuredifferential scanning calorimeter, and simultaneous thermogravimetric analyzer, a C80 micro-calorimeter is used. The apparent exothermic onset temperature of DCP is found to be between the range of 112–122 °C for different heating rates in DSC tests. There are two coupled peaks of BPO around 105 °C at both the heating rates of 4.0 and 8.0 °C/min while no endothermic peak showed at lower heating rates. Furthermore, another endothermic peak appears immediately after the exothermic peak at about 211 °C of DCP under high-pressure conditions. For BPO, the endothermic peak before the exothermic peak disappears as the pressure increases to 1.0 and 1.5 MPa. The average values of apparent activation energy calculated by Flynn-Wall-Ozawa and Kissinger-Akahira-Sunose methods during the conversion rate between 15 and 75% of DCP are 80.69 and 74.05 kJ/mol, and that of BPO are 119.96 and 112.93 kJ/mol, respectively. According to the isothermal tests, the thermal decomposition of DCP behaviors is an n-th order reaction while BPO conforms to the laws of autocatalytic reaction. 相似文献
350.
为解决水源水中孳生的水蚤类浮游动物难以被常规的水处理工艺有效地去除,困扰水厂正常生产运行的问题,进行了O3氧化、H2O2氧化和O3/H2O2高级氧化对水体中剑水蚤类浮游动物灭活效果的试验研究.发现3种方法中,O3/H2O2联合时除蚤效果最佳,在蒸馏水中投量为O31.0mg/L、H2O24mg/L时,接触30min达到100%的灭蚤率;单独O3氧化效果也较好,投加1.0mg/L的灭蚤率为80%;H2O2氧化效果不理想,投加4mg/L几乎无灭蚤效果.进而考察确定了O3/H2O2灭活剑水蚤的最佳工艺条件为:先加O3后加H2O2,投加间隔时间30~60s为宜;并探讨了H2O2投量、水体pH值以及有机物含量对O3/H2O2系统灭活剑水蚤效果的影响.试验中发现H2O2投量在4~10mg/L之间效果无较大变化,有机物含量对灭蚤影响较大,pH值的影响则较小.最后对O3/H2O2预氧化与水处理混凝沉淀工艺的协同除蚤效能进行了考察.结果表明,O3/H2O2预氧化与水处理混凝沉淀工艺的协同作用将会进一步提高除蚤的效果. 相似文献