Efficient Degradation of Nitrobenzene Induced by Glow Discharge Plasma in Aqueous Solution

The oxidative degradation of nitrobenzene (NB) induced by gaseous glow discharge plasma in contact with aqueous solution was investigated. The experimental results indicated that NB removal obeyed first-order kinetics under certain applied currents. The major degradation byproducts such as nitrophenols, phenol, 1,3-dinitrobenzene and carboxylic acids have been detected. The distribution of nitrophenols follows the order o- > p- > m- and oxalic, formic and acetic acids are major carboxylic intermediates. The eventual products were nitrate ion and carbon dioxide. During the treatment, a large amount of hydrogen peroxide was produced. Addition of ferrous or ferric ions into the solution greatly enhanced the degradation rate due to Fenton’s reaction. The energy efficiencies of NB removal and hydrogen peroxide formation were compared with those of other discharges. Hydroxyl radicals were shown to be the most likely species responsible for NB degradation     

Kinetics and Mechanism of the Organic Degradation in Aqueous Solution Irradiated with Gaseous Plasma

The degradation of organic compounds in an aqueous solution induced by a gaseous plasma, which was sustained locally on the surface of solution by means of contact glow discharge electrolysis, was mechanistically studied. The oxidation of phenol was extensively examined and it was revealed that the rate of disappearance followed the first-order rate law when the initial concentration of phenol was lower than 100 mM. As the initial concentration increased, the rate equation gradually deviated from the first-order and eventually shifted to zero-order above 250 mM. Such a kinetical behavior could be rationalized by assuming the reaction scheme where hydroxyl radical would act as the most responsible key-species for the organic degradation in competition with the coupling to hydrogen peroxide. In addition, the catalytic effects of Fe ions in the solution on the rate of organic degradation were closely investigated and could be consistently explained on the above concept.     

Sonochemical Degradation of Polychlorinated Biphenyls in Aqueous Solution

Ultrasonic waves in a liquid induce the formation of cavitation bubbles. Submitted to an oscillating pressure field, cavities filled with vapor and dissolved gas pulsate, grow and implode violently when they reach a critical resonant size. According to the 慼ot spot?theory, extremely high temperature and pressure are produced during the collapse of cavitation bubbles1. Under these extreme conditions, the molecules vaporized in the bubbles as well as in the surrounding condensed layer could …     

Heterogeneous Photocatalytic Mineralization of Chlorobenzene by Paratungstate-loaded Titania Catalysts in an Aqueous Medium

Paratungstate-loaded titania catalysts were prepared via the addition of a series of aqueous solutions of paratungstate( denoted as W7 ) into an isopropanol solution of Ti[ OCH( CH3 )2 ]4 by means of the sol-gel method. The catalysts were characterized by EDX, BET, FTIR, UV-Vis DRS, XRD and the results indicate that such paratungstateloaded catalysts maintained their heptatungstate structure in the anatase titania matrix up to 400℃. The catalysts were tested for the heterogeneous photodegradation of chlorobenzene in aqueous media and showed a better catalytic activity than P-25 TiO2 because paratungstate can prevent the recombination of the holes and electrons produced during irradiation. Moreover, the paratungstate-loaded titania catalysts can resist the disaggregation during the photoirradiation and can be easily recycled from the aqueous suspensions after reactions.     

环境激素邻苯二甲酸二丁酯的光催化降解机理探讨

环境激素邻苯二甲酸二丁酯的光催化降解机理探讨;邻苯二甲酸二丁酯;光催化降解;降解机理;二氧化钛     

活性炭和H2O2存在下辉光放电等离子体降解邻苯二胺

活性炭和H2O2存在下辉光放电等离子体降解邻苯二胺;辉光放电等离子体;降解;邻苯二胺;废水处理     

Corona Above Water Reactor for Systematic Study of Aqueous Phenol Degradation

A small batch reactor is developed to study the removal of phenol from a thin layer of water by creating pulsed corona discharges above the water. Pulses of up to 40 kV are applied with a duration of ~50 ns and an energy of ~60 mJ. In this CAW (Corona Above Water) reactor an ozone yield of upto 90 g/kWh is obtained in ambient air. The phenol degradation is 48 g/kWh, using a 1 mM initial concentration in demineralized water. The degradation yield increases to almost 100 g/kWh by adding to the water either H₂O₂ or Fe₂SO₄ or NaOH. The first two additions are considered to increase to amount of OH radicals. In the case of NaOH addition it is observed that much more ozone dissolves in the water. The addition of the OH scavenger t-butanol shows that in most cases the main oxidation route of phenol in the CAW reactor is direct ozone attack.     

One-Step Hydroxylation of Benzene to Phenol Induced by Glow Discharge Plasma in an Aqueous Solution

Direct phenol synthesis from benzene in aqueous solution where water was used as the oxidant through glow discharge plasma (GDP) process was described for the first time. The effect of pH, ferrous and cupric ions on the phenol yield and selectivity was examined. Phenol yield of 8.3% and selectivity of 81% has been achieved.     

一种水处理的新方法:金属卟啉和空气存在下光催化降解亚甲基蓝水溶液

在450W高压汞灯照射及聚对苯二磺酰氧基苯基卟啉钴存在下,考察了亚甲基蓝降解过程中紫外-可见吸收光谱的变化,研究了空气光催化降解亚甲基蓝水溶液反应的动力学.实验结果表明,亚甲基蓝可迅速降解,并且符合一级动力学过程,其表观动力学常数K=0.35435 h-1,半衰期t1/2=1.96 h.经光催化降解后,亚甲基蓝水溶液脱色率可达57.4%;其COD浓度降低43.1%.太阳光具有与高压汞灯相似的作用,这为以金属卟啉作光敏剂进行太阳能转化、贮能提供很大的应用潜能.光催化剂具有较好的光稳定性,可回收利用,而且反应结束后可自动沉降,避免二次污染.初步实验结果表明,该方法是一种具有应用前景的水处理方法.     

偶氮染料刚果红在水中的光催化降解过程

 通过研究在间歇悬浮体系中直接偶氮染料刚果红在水中的光催化降解过程,确定了最佳降解条件. 同时测定了染料溶液的脱色率、COD去除率和矿化率以考察降解过程中脱色与矿化的关系. 另外,对降解过程中溶液pH值的变化及反应的可能中间体进行分析,结果表明: 刚果红染料分子的光催化降解过程分为脱色和矿化两个阶段. 矿化主要发生在脱色结束以后, 并且伴随着脱色溶液的酸化现象. 脱色过程进行较快,完全脱色后形成的中间产物需要较长时间才能被逐步矿化.     

Plasma-induced deposition of thin films of aluminum oxide

Plasma-induced deposition of wear-protecting A1₂O₃ films has been investigated for two different gas mixtures, one of which is ususally used in thermal CVD. It is shown that, contrary to thermal CVO, the properties of thin films deposited from an AlCl₃/O₂/Ar mixture are superior to those prepared from AICl₃/CO₂/H₂. High Vickers hardness of 1800-2500 and a low chlorine content of 0.7 at. % have been obtained in films deposited from an AICl₃/O₂/Ar mixture at a substrate temperature of 500°C.     

Direct Detection of FeVI Water Oxidation Intermediates in an Aqueous Solution

In situ detection of highly-oxidized metal intermediates is the key to identifying the active center of an oxygen evolution reaction (OER) catalyst, but it remains challenging for NiFe-based catalysts in an aqueous solution under working conditions. Here, by utilizing the dynamic stability of the Fe^VIO₄²⁻ intermediates in a self-healing water oxidation cycle of NiFe-based catalyst, the highly-oxidized Fe^VI intermediates leached into the electrolyte are directly detected by simple spectroelectrochemistry. Our results provide direct evidence that Fe is the active center in NiFe-based OER catalysts. Furthermore, it is revealed that the incorporation of Co into NiFe-based catalyst facilitates the formation of Fe^VI active species, thus enhancing the OER activity of NiCoFe-based catalyst. The insights into the mechanisms for the sustainable generation of Fe^VI active species in these NiFe-based catalysts lay the foundation for the design of more efficient and stable OER catalysts.     

光催化甲胺磷降解效率和降解机理的研究

本文以自制的纳米TiO2为光催化剂,研究了光催化条件(溶液pH值、催化剂浓度及甲胺磷浓度)对甲胺磷在水中降解率的影响。结果表明:通过优化催化条件,可以大大提高甲胺磷的降解率。在甲胺磷浓度为20 mg/L,反应液起始pH为10.00,催化剂用量为0.5 g/L,光照时间为3 h的条件下,甲胺磷的降解效率可达到71.8%。通过化学计算模拟了甲胺磷的分子构型,并结合离子色谱的检测结果初步探讨了甲胺磷光催化降解的反应机理。     

Photocatalytic Degradation of Styrene in Aqueous Solution: Central Composite Design Optimization

In this study, the response surface methodology was first applied to optimize the photocatalytic degradation of styrene in aqueous phase under UV/TiO₂ system. Twenty experiments were done by adjusting three parameters (styrene concentration, TiO₂ dose, and pH) at five levels. Optimal experimental conditions for arbitrary aqueous styrene concentration (115 mg L^?1) were found: initial pH 7 and TiO₂ loading 2 g L^?1 with photocatalytic degradation efficiency of 79.2%. Furthermore, the main degradation intermediate produced was identified by GC/MS. The total organic carbon results revealed that the photocatalysis process could be effectively mineralized. Kinetics of the photocatalytic reaction followed a pseudo-first-order model.     

Oxidative Degradation of Aqueous Cresols Induced by Gaseous Plasma with Contact Glow Discharge Electrolysis

The oxidative degradation of cresols smoothly proceeded toward inorganic end products when a gaseous plasma generated by means of dc glow discharge was sustained in contact with the surface of aqueous solution containing organic compounds. In order to get mechanistic insight, the monohydroxylation products from each isomeric cresol were closely examined as primary intermediates to reveal that the aromatic hydroxylation preferentially occurred at the position para to the hydroxyl group of each starting material. It was also established that the degradation of cresols strictly followed the first-order rate law. On the basis of the orientational analysis and the kinetical consideration including the effects of Fe ions added on the reaction rate, it was concluded that hydroxyl radical, which might result from the homolytic cleavage of water molecules by the action of plasma, was the most likely reagent responsible for the mineralization of cresols.     

Degradation of Poly(2-hydroxyethyl methacrylate) Obtained by Radiation in Aqueous Solution

The degradation of poly(hydroxyethyl methacrylate), PHEMA obtained by γ -radiation induced polymerization of HEMA in aqueous solution, was studied. The polymer was a gel type and insoluble in common organic solvents. The DSC thermogram of the polymer gave a Tg value at 88.2°C and an endothermic peak showed further polymerization or crosslinking at 110–160°C. The degradation observed in TGA was a depolymerization type. However, the FT-IR of TGA fragments showed no monomer, which was degraded further. The degradation of monomer was studied by the GC-MS method. Similar results were also observed.     

液相辉光放电原子发射光谱法测定溶液中Cd的方法研究

通过改进放电装置,建立了一种新的液相辉光放电原子发射光谱(LGD-AES)测量溶液中Cd元素的方法。探索了放电电压和Cd浓度对放电稳定性、光谱信号强度、测定灵敏度和检出限的影响,并将测试结果与电解液阴极放电-原子发射光谱(ELCAD-AES)的分析结果进行比较。结果表明,当放电电压从600V升至720 V时,电子温度从2 000 K升至3 300 K,电子密度从2.47×10~(16)cm~(-3)降至1.77×10~(16)cm~(-3),Cd的发射光谱强度增强,灵敏度升高,检出限为1.22~2.95 mg/L。LGD-AES技术检测水中金属离子具有放电设备小型、能量消耗低、放电稳定性高、背景光谱干扰小和灵敏度高等优点。     

AlMn复合柱撑粘土负载CrCe催化剂用于氯苯催化降解性能初探

利用高温高压一步法合成系列Al Mn-复合柱化剂,该方法的步骤、物料消耗等较传统制备方法均大大减少,可大大降低生产成本及减少对环境的污染。通过离子交换合成系列Al Mn复合柱撑粘土(Al Mn-PILC)。改变Al/Mn摩尔比、老化温度、老化时间,可调控Al Mn-复合柱化剂的结构,从而影响Al Mn-PILC的结构性能(包括比表面积、孔体积、孔径、层间距等)。通过XRD,N2吸附,高分辨电镜及程序升温还原等实验对材料的结构及性能进行了表征。结果表明:经550℃焙烧4 h后,Al Mn-PILC的比表面积和孔体积可达174.2~246.7 m2·g-1和0.126~0.158 cm3·g-1,层间距可达1.85 nm。经柱撑改性合成的Al Mn-PILC,其负载Cr Ce催化剂对氯苯的催化降解性能远高于原土(Nammt)和单核Al-PILC的,尤其以Cr Ce(9∶1)/Al Mn-PILC的催化活性最佳,在250℃时可完全降解低浓度的氯苯,是一类性能优异的用于有机物催化降解的多孔材料。     

Degradation of Phenol in Aqueous Solutions by Gas–Liquid Gliding Arc Discharges

The efficiency of a gliding arc reactor designed with the aim to degrade aqueous phenol solutions is studied as a function of supply voltage, electrode gap distance, and gas–liquid flow properties. This efficiency, which steeply increases when increasing the supply voltage, can reach 96% when the minimum electrode distance is fixed at 3 mm. Experiments show that phenol degradation efficiency also depends on solution pH, Fe²⁺ addition, gas nature and gas flow rate. Furthermore, degradation pathways of phenol in aqueous solutions are proposed.     

A New Property of Conjugated Polymer PFP： Catalytic Degradation of Methylene Blue Aqueous Solution

A new property of conjugated polymer poly（furancarbinol-co-phenol）（PFP） was studied. The target copolymer was used as a catalyst after proper heating treatment. And dye methylene blue （MB） could be fully degraded and largely mineralized on PFP, under natural light or even in dark, in a few minutes. Furthermore, the catalytic activity could be preserved after several runs and the catalyst was readily separated. The effect of calcination temperature was also observed.