Cyclohexane oxidation and carbon deposition over metal oxide catalysts

Catalytic activity of V, Mn, Ni, Cu, Zn, Mo, Zr and Ce oxides over an -alumina support was evaluated for cyclohexane oxidation under oxygen deficient conditions in order to understand the relation between carbon deposition and catalytic activity/selectivity. Carbon formation over the catalysts during the oxidation reaction was measured by means of Fourier transformed infrared spectroscopy (FTIR). Catalysts Mn/Al₂O₃ and Ce/Al₂O₃, which are selective for deep oxidation of cyclohexane, possessed relatively carbon free surfaces. The catalysts with relatively high carbon deposition (V, Ni, Cu, Zn, Mo and Zr) produced CO in addition to CO₂. Traces of formaldehyde were produced over the catalysts Mo and V.     

Ferrioxalate-mediated photodegradation and mineralization of 4-Chlorophenol

INTENTION, GOAL, SCOPE, BACKGROUND: Advanced oxidation processes are powerful methods which are capable of transforming refractory, nonbiodegradable and/or toxic organic compounds into harmless end products such as carbon dioxide and water. However, one commen problem of all advanced oxidation processes is the high demand of electrical energy for ultraviolet lamps, which causes high operational costs. Minimization of the required irradiation time, and therefore the energy consumption, by optimization of other reaction conditions such as catalyst-oxidant type and concentration, pH, temperature, pollutant/oxidant ratio etc., therefore continues to gain importance. OBJECTIVE: The main objective of this study was the minimization of the required irradiation time through optimization of the use of a newly patented catalyst, ferrioxalate, and also to compare the performance of this catalyst with the performance of other AOPs. METHODS: Oxidation of 4-chlorophenol by photo-Fenton process using potassium ferrioxalate as a mediator was studied in a lab scale photoreactor. The influence of parameters such as hydrogen peroxide and ferrioxalate concentrations, initial pH, power-output, oxalate/iron ratio and different iron sources was evaluated. An upflow photoreactor equipped with a 1000 Watt high-pressure mercury vapour lamp and operating in a recirculation mode was used during photodegradation experiments. The extent of the reduction of 4-chlorophenol, Total Organic Carbon and Chemical Oxygen Demand was used to evaluate the photodegradation reaction. RESULTS AND DISCUSSION: The optimum pH range observed was found to be 2.7-3. The efficiency of 4-chlorophenol oxidation increased with increasing concentrations of hydrogen peroxide and ferrioxalate, reaching a plateau after the addition of 10 and 0.072 mM of those reagents, respectively. Using an Oxalate/iron ratio of 12 was 18% less efficient than using a ratio of 3:1. The efficiency increased with increasing radiation power. However, this increase was not linear. The UV/ferrioxalate/H2O2 process, by which complete mineralization of 100 mg l(-1) 4-chlorophenol was achieved in 20 min of total reaction time, was the most efficient process among the alternatives applied. CONCLUSIONS: The use of ferrioxalate as the catalyst was found to be more efficient than the use of Fe(II) and Fe(III) iron species. It was possible to completely mineralize 4-chlorophenol. RECOMMENDATION AND OUTLOOK: The results of this study demonstrate that the ferrioxalate-mediated degradation of 4-chlorophenol requires less irradiation times than other advanced oxidation processes. There are mainly 19 phenol isomers and other toxic and nonbiodegradable organic compounds. We recommend that similar studies should be performed on many such compounds in order to attain a clear understanding of the performance of this catalyst. Because of its light sensitivity, this catalyst should be used immediately after its preparation. The use of low pressure mercury vapour lamps in this process should also be considered, since low power outputs may be enough for the process.     

Experimental determination of the kinetic rate law for the oxidation of perchloroethylene by potassium permanganate

Flushing soils contaminated with trichloroethylene (TCE) and perchloroethylene (PCE) with a permanganate (MnO₄⁻) solution has been shown to reduce the solvent content of the soil. Experiments were performed to quantify the rate at which KMnO₄ oxidizes aqueous solutions of PCE over a range of concentrations. In a series of homogeneous reactors, aqueous phase PCE concentrations were monitored over time in nine experimental trials with excess oxidant concentrations ranging from 5 to 30 g/l. Analysis of the data was performed to quantify the oxidation reaction order with respect to PCE and KMnO₄ and the reaction rate constant. The reaction between PCE and KMnO₄ was determined to be first-order with respect to both PCE and KMnO₄ with an overall specific reaction rate coefficient of 2.45±0.65 M⁻¹ min⁻¹.     

混凝沉淀-水解-接触氧化-气浮工艺处理印染废水

介绍了采用混凝沉淀-水解-接触氧化-气浮工艺处理印染废水的工程应用，总结并分析了工程设计及运行的经验。运行结果表明，该工艺对CODCR，BOD5，SS，色度等均有良好的效果，出水水质达到GB4287—92《纺织染整工业水污染物排放标准》中的一级标准。     

高效氧化偶合絮凝法强化处理受污染湖水的研究

为了研究高效氯化偶合絮凝剂对有机物含量较高原水的应用效果．进行了氧化偶合絮凝法强化处理受污染湖水的试验研究．并对其作用机理进行了初步探讨。结果表明．高效氧化偶合絮凝法对COD，SS，NH3^-N和TP均有良好的去除效果．在最佳条件下,去除率分别高达85％、95％、87％和96％．出水COD，SS，NH3^-N和TP的平均浓度分别为5.8、1.4、1.6和0.9mg／L。作用机理分析表明．氯化偶合絮凝剂在处理过程中充分利用氧化絮凝协同作用．对胶体性物质和溶解性物质均有较好去除效果。     

污水处理厂实现生产设备夜间无人化操作和管理的设想

对污水处理厂实现夜间无人化管理进行了探讨,并通过实例提出了实现这种管理所需条件,指出了这种管理模式的可行性.     

有机废水湿式O_3氧化降解过程的研究

采用 O3 湿式氧化降解含氯乙烯的有机废水 ,实验研究了不同 p H、不同温度以及不同初始氯乙烯浓度对反应过程的影响 ,初步探讨了在高 p H时 O3 的自分解催化产生自由基 OH·机理和污染物的氧化降解过程。通过实验研究与分析 ,获得了氯乙烯有机废水 O3 氧化过程的动力学方程     

混凝氧化法处理精研精抛清洗废液

采用混凝、氧化的方法对精研精抛清洗废液进行处理，对絮凝过程中所用的６种混凝剂的投加量ｐＨ值和氧化过程中的氧化试剂Ｈ２Ｏ２的投加量分别进行了筛选，同时简单地分析了反应机理．经混凝氧化处理后，ＣＯＤ值由１２００ｍｇ／ｍＬ降至５００ｍｇ／ｍＬ左右，ＣＯＤ去除率达９５％；最后进行活性炭吸附，ＣＯＤ值达到国家排放标准．     

水中有机污染物物理,化学处理技术的现状及发展趋势

在系统综述了水中有机污染物物化处理技术的研究与应用现状后，进行了分析与评价。认为对有机污染物具有“破坏性”的氧化法是水处理技术发展的方向，各种单一技术特别是“破坏性”技术和“非破坏性”技术之间的联用是水处理技术发展的又一趋势。     

煤氧化特性与影响因素实验研究

为分析自热临界温度和采空区漏风风速对煤自燃的影响,在常温(30℃)、中温(60℃)、不同通气量等条件下对滕东煤矿3下煤层煤样进行了煤炭自燃氧化规律实验。结果表明:煤样在60℃氧化所放出的CO量较30℃时高3.4~4.1倍,煤炭氧化速率上升梯度约1.35 ppm/℃;在恒温变通气量条件下,CO气体浓度呈现先减小后稳定的趋势,CO的释放量随通气量的增大而减小;在通气量为50 mL/min(采空区漏风为0.1 m/min)的条件下,煤氧化释放的CO量最大且煤氧化能力最强,应加强最易发生自燃漏风区域的密封防护。