Ti/RuO2-SnO2-TiO2涂层电极电催化氧化苯酚废水研究

采用热分解法将SnO_2掺杂于RuO_2-TiO_2涂层中,制得性能高效的Ti/RuO_2-SnO_2-TiO_2阳极氧化电极。以该自制电极为阳极、钛板为阴极构成电催化氧化体系,对模拟苯酚废水进行电催化氧化试验。利用高效液相色谱探讨了苯酚废水溶液在该体系中的电催化氧化反应历程,并推断出氧化降解途径。采用SEM和XRD表征电极涂层结构和形貌,循环伏安法测试电极电化学性能。通过单因素试验考察反应时间、电流密度(CD)、电极间距、Na_2SO_4电解质浓度、苯酚质量浓度、pH值五个因素对电催化氧化试验的影响,结果表明:在反应时间为240 min、电流密度为102.6 mA/cm~2、电极间距为1.5 cm、电解质浓度为0.5 mol/L、苯酚质量浓度为300 mg/L、pH=5的最佳试验条件下,苯酚的降解率达到98%以上,COD的去除率达到90%以上。     

电催化氧化降解水中磺胺嘧啶的研究

为了解并优化电化学方法对水体中磺胺类药物的去除效果,以Ir O2-Ru O2/Ti为阳极,不锈钢为阴极,Na2SO4为电解质,电催化氧化降解模拟废水中的磺胺嘧啶(Sulfadiazine,SD),反应时间为240min。探讨了SD初始质量浓度、电流密度、p H值、电解质浓度及电极板间距对电催化降解SD效率的影响,并利用HPLC-MS分析降解产物。结果表明,电催化氧化可有效去除水中的SD。升高初始质量浓度、电流密度、极板间距可提高SD降解速率,初始质量浓度由15 mg/L升高到50 mg/L时,去除率降低了9.2%;电流密度从5 m A/cm2升高到15 m A/cm2,去除率增加了38.1%,电流密度大于15 m A/cm2时其对去除率的影响不明显;极板间距由2 cm增加到4 cm,去除率增加了12.2%;酸性条件降解效果最好,碱性对SD去除率略有抑制,p H值为1和13相比于p H值为7时去除率分别增加9.9%及降低4%;电解质浓度(≤0.05 mol/L)与SD降解速率呈负相关,电解质浓度大于0.05 mol/L时,对去除率影响不明显。降解主要基于·OH的氧化过程,生成4-(2-氨基嘧啶-l(2H)-基)苯胺中间产物,过程遵循一级反应动力学模型。     

电催化氧化技术处理造纸废水的实验研究

通过邻苯二甲酸氢钾(KHP)溶液的电解实验研究了德国引进的金属铌掺硼金刚石膜电极(Nb/BDD)的电化学性质,并利用该电极处理装置处理了东莞某造纸厂造纸废水。考察了电解时间、电流强度及废水的pH值、电解质的浓度、电导率等参数对电化学降解效率的影响。结果表明,Nb/BDD具有优异的污水降解性能,在pH值为3.0,电流密度为37.23 mA/cm2,电压6.9 V,NaCl充当电解质质量浓度0.4 g/L的条件下,电解200 min,装置对再生纸造纸废水的COD的去除率接近70%,BOD/COD为0.4,比能耗为27.6(kW.h/kg)。     

低强度超声波对残留H2O2的去除

化学需氧量(COD)会受到来自众多高级氧化技术中添加的过氧化氢(H_2O_2)的干扰。为了评估低强度超声波辐射结合清除剂(Na_2CO_3或Na HCO_3)分解水样中残留H_2O_2的可行性,对去离子水、葡萄糖模拟废水和印染废水二级处理出水进行超声(超声波频率为39 k Hz,功率分别为75 W、112.5 W和150 W)处理,H_2O_2质量浓度为20 mg/L,时间为60 min或80 min,清除剂用量为50 g/L。以20 min的间隔测定H_2O_2质量浓度和COD。结果表明,COD与H_2O_2质量浓度的比值取决于废水的性质,去离子水、葡萄糖模拟废水和印染废水二级处理出水的比值分别为0.262 6 mg COD/mg H_2O_2、0.209 9 mg COD/mg H_2O_2、0.401 3 mg COD/mg H_2O_2。超声辐照对去除H_2O_2有一定的影响,但在去离子水中超声功率为150 W、60 min时的去除率最高,仅为18.1%。超声辐照联合清除剂Na_2CO_3或Na HCO_3的效果更显著。对于印染废水二次处理出水,加入Na HCO_3作为羟自由基清除剂,80 min时H_2O_2去除率达到97.3%。然而,由于Na HCO_3和H_2O_2形成的高度氧化的超氧离子能降解废水中的有机物质,水样的实际COD降低。用超声辐射结合Na_2CO_3处理80 min,将COD的测定值与通过COD、H_2O_2质量浓度比值得到的计算值进行比较,以确认经超声波联合Na_2CO_3处理的印染废水二级处理出水中的有机物未降解。研究表明,超声波照射与Na_2CO_3结合去除水样中的低浓度H_2O_2是可行的。     

好氧与电絮凝组合工艺处理糖蜜酒精厌氧出水研究

采用好氧与电絮凝联合工艺处理糖蜜酒精厌氧出水,考察COD和色度的去除效果.首先,采用SBR工艺去除废水中的易降解污染物.结果表明:采用SBR法处理稀释10倍的糖蜜酒精厌氧出水,适宜的水力停留时间为10 h;COD去除率为42％,脱色效果不明显,BOD5/COD由0.54下降到0.09,好氧出水难以生化降解.进一步采用电絮凝法处理好氧出水,并考察了极板间距、初始pH值、电流密度和电解时间等因素对COD去除及脱色效果的影响.结果表明,在极板间距为3 cm、废水pH=7.83(无须调节,最佳pH=6～8)、电流密度为10 mA/cm2、电解时间为30 min的条件下进行电絮凝处理,与稀释10倍的糖蜜酒精厌氧出水相比,COD总去除率可达86％,脱色率达95％.     

超声波／H2O2对苯酚有机废水降解的研究

研究在超声波/H2O2联合作用下,超声波场中降解苯酚有机废水的过程,考察了超声功率、超声时间、pH值、氧化剂H2O2的浓度等因素对降解率的影响.实验结果表明,超声时间越长,废水降解率越大;pH值的变化对降解率影响较大,酸性条件利于苯酚的降解,而在碱性条件下苯酚几乎没有降解;超声波/H2O2工艺与单独超声作用相比,降解率提高了大约3倍.     

含油废水理化特性对NY3菌除油效率的影响

为了将NY3菌实际应用于处理高浓度含油废水,采用摇瓶试验方法,研究了含油废水的理化特性对NY3菌去除高浓度油的影响。结果表明,NY3菌能耐高浓度油,降解石油烃的最佳p H值为7.5,24 h对质量浓度为2 000 mg/L的高含油废水中烃类的去除率高达72%。适度的含盐量可提高NY3菌降解原油的能力,与未外加Na Cl相比,2 g/L Na Cl使NY3菌降解原油效率提高约20%。Sn2+、Ag+、Pb2+、Cd2+、Hg2+等均能对NY3菌降解石油烃的效率产生抑制作用,其中Ag+作用最明显,使NY3菌24 h烃降解效率降低约38.8%。硝酸铵为NY3菌降解石油烃的最佳氮源,外加3.71 g/L硝酸铵,24 h内对油的去除率高达81.75%。外加表面活性剂(SDS)使降解体系中NY3菌细胞数量减少,同时使NY3菌降解油的效率降低约43.5%。     

一株DDT降解菌的鉴定及其生物学特性

利用DDT为唯一碳源筛选、纯化得到DDT降解菌株DT1,通过形态特征、生理生化特性及系统发育分析鉴定为假单胞菌属细菌(Pseudomonas sp.)。通过单因子试验及差异显著性分析得到菌株DT1的最佳生长条件为37℃、初始p H值8.0、DDT初始质量浓度20mg/L、最适Na Cl质量浓度1 mg/L。通过正交试验优化菌株DT1的降解能力,最优方案为温度37℃、p H值9.0、DDT初始质量浓度30 mg/L,可将DDT降解率提高到60.85%。影响其降解能力的环境因素从主到次依次为温度、p H值、DDT初始质量浓度。     

一株蜡状芽孢杆菌降解毒死蜱的影响因素研究

为了明确一株蜡状芽孢杆菌(Bacillus cereus HY-2)对毒死蜱的降解特性,在基础培养基中定量添加毒死蜱和降解菌进行混合摇培,每12 h取样检测毒死蜱残留量和菌株生长量,研究了接种量、毒死蜱初始质量浓度和含盐量等因素对菌株降解毒死蜱的影响。结果表明,接种量为8%(体积分数,接种体密度为OD600=3.0)时对80mg/L毒死蜱的降解率最高,为53%。随毒死蜱初始质量浓度增加,菌株的生长受到不同程度的抑制,然而随着毒死蜱的降解,菌体的生长量迅速增加,培养液的p H值随降解菌的增殖而逐渐上升。毒死蜱初始质量浓度为40~150 mg/L时,随降解时间延长,毒死蜱的残留质量浓度逐渐下降;而毒死蜱初始质量浓度为200 mg/L时,毒死蜱质量浓度在降解过程中出现了先上升后下降、然后逐渐下降的现象。降解菌对Na Cl有较高的耐受度,当Na Cl质量浓度为20~70 g/L时,降解菌在60 h时对80 mg/L毒死蜱的降解率为27%~53%。     

生物活性炭塔中有机物沿程降解规律和降解动力学模型

上流式曝气生物活性炭塔(BAC)中的废水、空气从下往上流过生物活性炭层。为研究废水中有机物沿活性炭层的降解规律,生物活性炭塔由下至上共设有10个废水取样口,研究沿程各区间段对有机物的降解差异。试验结果表明在水力负荷为5.02~10.04 L/(m2·min),气水比为4∶1~6∶1时,COD、UV、色度的脱除主要集中在塔的中下部,占总脱除率70%以上。进水废水浓度对脱色率影响不大,对COD的脱除率有影响,进水废水浓度过大,脱除率降低。依据推流反应器模型,推导出废水净化塔中COD的降解动力学方程:Ce=Coexp(-2.406 4 H/L0.962)。     

Safe direct synthesis of H2O2 within the explosion limit of H2 enabled by low-temperature stable bcc-PdCu alloy membrane

Pd based membrane provides an inherently safer way to handle flammable mixture of hydrogen and oxygen, as it could selectively isolate hydrogen from other gases. However, due to their susceptibility to hydrogen embrittlement, pure Pd membranes are not suitable for processes at low temperature. To solve this problem, body-centered cubic (bcc)-PdCu alloy membranes were prepared by the combination of electroplating and electroless plating. The hydrogen permeation rate (J_H2), N₂ leak rate (J_N2) and H₂/N₂ selectivity (α_H2/N2) remained stable through 200 h continuous operation in H₂ at 298 K and ΔP_H2 = 100 kPa. The excellent low-temperature tolerance of bcc-PdCu membranes rendered them ideal materials for the capture and activation of hydrogen during the direct hydrogen peroxide synthesis from hydrogen and oxygen. The reaction could be performed safely within the explosive limit of hydrogen/oxygen by feeding the gases separately from the opposite sides of the membrane with no direct contact. 60 mmol m⁻² h⁻¹ formation rate, 40% H₂O₂ selectivity, and a nearly 100% hydrogen conversion was reached at 298 K, 500 kPa.     

NH3-H2O2气雾对氰化氢气体的消毒

采用NH_3-H_2O_2气雾对1 m3密闭试验舱内氰化氢气体进行消毒,采用单因素试验研究H_2O_2和NH_3质量浓度对消毒率和消毒反应速率的影响规律。结果表明,NH_3-H_2O_2气雾对HCN的消毒符合一级反应动力学特征,NH_3质量浓度对消毒反应速率有一定影响,但当NH_3质量浓度增加至20 mg/m3以上时,对反应速率几乎没有影响; H_2O_2质量浓度对消毒反应速率有显著影响,反应速率随H_2O_2质量浓度的提高明显增大。NH_3-H_2O_2气雾消毒剂的最佳配方为H_2O_2的质量浓度为120 mg/m3、NH_3的质量浓度为20 mg/m3,在此条件下对HCN进行消毒,在28 min时HCN的残余质量浓度为0. 92 mg/m3,可以达到GBZ 2. 1—2007《工作场所有害因素职业接触限值第1部分:化学有害因素》中有关HCN最高容许质量浓度MAC值(1 mg/m3)的规定。分析消毒机理为H_2O_2首先将HCN氧化为氰酸(HCNO),氰酸不稳定,在NH_3和水的作用下可以水解成碳酸铵,也可以进一步被氧化形成CO2和N2。     

Effects of N2 and CO2 on the flammability of 2,3,3,3-tetrafluoropropene at elevated temperatures

The flammability characteristics of refrigerants are affected by environmental factors, making them prone to flammability and explosion accidents in cooling systems. In this paper, the flammability characteristics of R1234yf–air mixtures with N₂ and CO₂ were investigated comparatively at temperatures between 20 and 50 °C at 80% relative humidity. The lower and upper flammability limits of R1234yf were measured. The limiting oxygen concentration (LOC), critical flammable ratio (CFR), and critical flammable concentration (CFC) of the R1234yf–air mixtures with inert gases were investigated. The paper developed a linear formula between the flammability limit of R1234yf and the temperature. The changes in CFC with different temperatures were negligible for R1234yf. Furthermore, the mixed refrigerant had both non-flammability and the lowest vapor pressure when the CFR of the R1234yf/CO₂ mixture was 2.9. The experimental results were used to propose a new prediction model to estimate the flammability limits of R1234yf. Finally, molecular simulation explained the effect of inert gases on the flammability of R1234yf from a microscopic point of view. The research aimed to provide valid evidence and data for preventing flammable and explosive refrigerant incidents.     

Reaction hazard and mechanism study of H2O2 oxidation of 2-butanol to methyl ethyl ketone using DSC,Phi-TEC II and GC-MS

Methyl ethyl ketone (MEK) oxidation via H₂O₂ with tungsten-based polyoxometalate catalysts has gained much attention with an ever-growing body of knowledge focusing on the development of environmentally benign processes in chemical industry. In this study, two calorimetry techniques, differential scanning calorimetry (DSC) and Phi-TEC II adiabatic calorimetry, were employed to analyze the thermal hazards associated with the 2-butanol oxidation reaction system. Hydrogen peroxide was the oxidant and a tungsten-based polyoxometalate as the catalyst. Gas chromatography-mass spectrometry was used for identification of the organic products. Important thermal kinetic data were obtained including “onset” temperature, heat of reaction, adiabatic temperature rise and self-heat rate. From DSC results, three exothermic peaks were detected with a total heat generation of approximately 1.26 kJ/g sufficiently to induce a thermal runaway. Possible reaction pathway for three stages were proposed based on both DSC and GC-MS results. One exotherm was detected by Phi-TEC II calorimeter and the pressure versus temperature profile together with the DSC and GC-MS data demonstrate the complexity of 2-butanol reaction system under both thermal screening and adiabatic conditions.     

2-Methylpyridine-N-oxidation runaway studies

Calorimetry has been used in order to identify the runaway behavior of 2-methylpyridine-N-oxidation (2-picoline-N-oxidation). Experiments were performed in an Automatic Pressure Tracking Adiabatic Calorimeter (APTAC), employing 2-methylpyridine-N-oxide (2-picoline-N-oxide) with or without catalyst, 2-methylpyridine-N-oxide, hydrogen peroxide, 2-methylpyridine (2-picoline) and catalyst, and 2-methylpyridine, hydrogen peroxide and catalyst. Approximately 16.5 g of aqueous solutions were used in 100 ml closed glass cells in all but one measurement. Measurements were performed isothermally or employing the Heat-Wait-Search (HWS) technique. During reaction runaway, any excess of hydrogen peroxide and the produced 2-methylpyridine-N-oxide decompose releasing non-condensable gases and raising the pressure. It was found that the reaction runaway is condition-sensitive. Catalyst, the presence of 2-picoline and/or its N-oxide, affect hydrogen peroxide and/or 2-picoline-N-oxide decomposition rates. Further research accompanied by analytical measurements of the gas and liquid phase would provide indications in regard to the decomposition mechanisms followed in those cases.     

Using thermal analysis with kinetic calculation method to assess the thermal stability of 2-cyanopropan-2-yliminourea

Azo compounds, which are commonly used as initiators and blowing agents, are also typical self-reactive materials capable of undergoing runaway reaction during storage and transportation, which can cause severe fires and accidents. To ensure the thermal safety of azo compounds in the process, transportation, and applications, this study investigated 2-cyanopropan-2-yliminourea, which can also be called V-30. First, thermal decomposition characteristics under the non-isothermal conditions were obtained using differential scanning calorimetry. Second, the collected data were combined with a mathematical model to evaluate the primary thermal hazard during the process for V-30. Then, based on a heat-transfer model, the self-accelerating decomposition temperature (SADT) was extrapolated for consideration and non-consideration of consumption of chemicals. The results showed that SADT of V-30 was less than 80 °C. Therefore, it is essential to avoid a temperature beyond SADT or the cooling system will fail. The influence of consumption was also considered for SADT in this study.     

Corrosion behavior of steels for CO2 injection

The process chain for Carbon Capture and Sequestration (CCS) includes tubing for injection of CO₂ into saline aquifers. The compressed CO₂ is likely to contain specific impurities; small concentrations of SO₂ and NO₂ in combination with oxygen and humidity are most harmful. In addition, CO₂ saturated brine is supposed to rise in the well when the injection process is interrupted. The material selection has to ensure that neither CO₂ nor brine or a combination of both will leak out of the inner tubing. In this comprehensive paper the investigated materials range from low-alloy steels and 13% Cr steels up to high-alloy materials. Electrochemical tests as well as long term exposure tests were performed in CO₂, in brine and combination of both; pressure was up to 100 bar, temperature up to 60 °C. Whereas the CO₂ stream itself can be handled using low alloy steels, combinations of CO₂ and brine require more resistant materials to control the strong tendency to pitting corrosion. The corrosion behavior of heat-treated steels depends on factors such as microstructure and carbon content. For different sections of the injection tube, appropriate materials should be used to guarantee safety and consider cost effectiveness.     

Experimental study on CO and CO2 emissions from spontaneous heating of coals at varying temperatures and O2 concentrations

Laboratory experiments were conducted to investigate carbon monoxide (CO) and carbon dioxide (CO₂) emissions from spontaneous heating of three U.S. coal samples in an isothermal oven at temperatures between 50 and 110 °C. The oxygen (O₂) concentration of an oxygen/nitrogen (N₂) mixture flowing through the coal sample was 3, 5, 10, 15, and 21%, respectively. The temperature at the center of the coal sample was continuously monitored, while the CO, CO₂, and O₂ concentrations of the exit gas were continuously measured. The results indicate that the CO and CO₂ concentrations and the CO/CO₂ ratio increased when the initial temperature was increased. As the inlet O₂ concentration increased, the CO and CO₂ concentrations increased, while the CO/CO₂ ratios tended to converge to the same value. The ratio of CO/CO₂ was found to be independent of coal properties, approaching a constant value of 0.2. The maximum CO production rate correlated well with the maximum coal temperature rise. The apparent order of reaction for coal oxidation was estimated to be between 0.52 and 0.72. The experimental results in this study could be used for early detection and evaluation of a spontaneous heating in underground coal mines.     

An experimental study for H2S and CO2 removal via caustic scrubbing system

In this study, removal of hydrogen sulfide (H₂S) and carbon dioxide (CO₂) from simulated syngas has been studied on one column scrubbing system. Gas flow rate as a measure of gas residence time and superficial gas velocity, gas composition, inlet H₂S load, flow modes (countercurrent and cocurrent) and packing geometry were the parameters in the design and/or operation of an acid gas scrubber system. Better H₂S scrubbing efficiencies have been obtained in countercurrent flow mode than that of cocurrent flow mode. When accordingly designed, static mixer with its superior performance on H₂S removal overweighed to structured packings. The coexistence of CO₂ and H₂S has been shown to increase the sodium hydroxide (NaOH) consumption along the scrubber column thereby decreasing the H₂S removal efficiency at higher H₂S loads. The gas residence time as changing with the gas velocity was found to be more dominant on acid gas removal efficiency than the effect of superficial gas velocity within the experimented range. A gas residence times of equal or above 3 s were seemed to be closer to the optimum point.     

Ti/SnO2-RuO2-Sb电极电氧化处理五氯苯酚模拟废水研究

采用刷涂-热解法制备了Sb、Ru掺杂的Ti/SnO2电极。通过SEM、EDX、XRD和循环伏安扫描(CV)表征了电极表面形态、组成、结构和电化学性质,并通过正交试验考察了电催化氧化降解五氯苯酚的影响因素。结果表明,各因素对五氯苯酚转化率影响的大小顺序依次为:底物初始质量浓度、反应温度、反应时间、电流密度、初始溶液pH值。在底物质量浓度为50mg.L-1,反应温度50℃,反应时间180min,电流密度40mA.cm-2,溶液初始pH值为8的条件下五氯苯酚的转化率达到97.6%。