Enhancement of Phenol Degradation by Electron Acceptors in Anodic Contact Glow Discharge Electrolysis

Effects of several electron acceptors (Fe³⁺, Cu²⁺, Cr(VI), and H₂O₂) on phenol degradation in anodic contact glow discharge electrolysis have been investigated. Results show that the electron acceptors have positive effects on phenol removal, with the sequence of Fe³⁺?>?Cr(VI)?>?H₂O₂?>?Cu²⁺. Under conditions of voltage 500?V and current 100?mA, 100?mg/L phenol can be removed with 10?min of discharge treatment in the presence of 1.0?mmol/L Fe³⁺, while without any additive only 35?% of phenol is removed in 30?min. The mechanism of the degradation enhancement was discussed based on the reactions taking place in the presence of the different additives.     

Phenol Degradation Features in Aqueous Solutions upon Dielectric-Barrier Discharge Treatment

The formation kinetics and mechanism were studied for the intermediate and final products of degradation of aqueous phenol solutions in air and oxygen low-temperature dielectric-barrier discharge plasmas in a reactor with different geometric arrangements of electrodes. It was shown that the plasma-enhanced oxidation of phenol could be described in the general form by the well-known mechanism of enzymatic oxidation of toxic pollutants (-mechanism). The estimated effective rate constant of phenol degradation in an aqueous solution in an ₂ plasma in reactors with the parallel-plate and coaxial arrangement of electrodes was 2.2 × 10^–3 s^–1 and 5.8 × 10^–2 s^–1, respectively. It was found that the potential toxicity of solutions after treatment was 7.5 times lower than that of the untreated solutions.     

Degradation of Phenol in Water by Photocatalytic Reactors

Environmental applications of heterogeneous photocatalysis are one of the rapidly growing areas of research. Photocatalytic oxidation had die advantage of complete mineralisation of pollutants into environmentally harmless confounds. In recent years, interest has focused on the use of TiO₂ as a photocatalyst for the destruction of polluting materials^[1,2].     

电化学氧化法去除苯酚研究

利用氯碱厂报废的DSA电极电解苯酚,结果显示:此电极对一定浓度的苯酚溶液有较好的去除效果.按影响电解效果各主要因素进行筛选,最佳实验条件为:电流密度30mA/cm2,pH10,支持电解质浓度10mg/L,苯酚浓度10mg/L.电解2h后,CODcr的去除率为66.7%,吸光度去除率为90%.     

Degradation Mechanism of Phenol in C/PTFE O2-Fed Cathode by Determining the Product of Oxygen Electroreduction

A terylene membrane which kept pH〉12 in cathode compartment was used to construct a divided cell with a carbon/polytetrafluoroethylene（C/PTFE） O2-fed cathode. The concentrations of hydrogen peroxide （H2O2） and hydroxyl radical （HO^-）in the catholyte were 8.3 mg/L and 2.15 μmol/L, respectivel.y, which were determined by permanganate titration, electron spin resonance （ESR） spectrum and the fluorescence spectra. ;The efficiency of the removal of phenol achieved 100% as a result of these two kinds of stronger oxidizer.     

Regulating Degradation Pathways of Polymers by Radical-Triggered Luminescence

Understanding the radical behaviours during polymer degradation is beneficial to unveil and regulate the degradation pathways of polymers to achieve a sustainable polymer development. However, it is a long-standing challenge to study radical behaviours owing to the ultra-short lifetime of the transient radicals generated during the polymer degradation. In this contribution, we have proposed the radical-triggered luminescence to monitor the radical behaviours during polymer degradation without/with the addition of inorganic additives. It was disclosed that the pure polymers showed a single sigmoidal dynamic curve from peroxy radicals (ROO⋅) emissions, leading to the exponential proliferation for the degradation evolution. Alternatively, the degradation pathways with the addition of additives, layered double hydroxides (LDHs) with positively charged Al centers, could be modulated into a double sigmoidal dynamics, involving the main product of alkoxy radicals (RO⋅) with the activation energy of 40.2 kJ/mol and a small amount of ROO⋅ with 76.3 kJ/mol, respectively. Accordingly, the polymers with the additive-regulated pathways could exhibit prominently anti-degradation behaviours. This work is beneficial for the deep understanding of the radical mechanisms during polymer degradation, and for the rational design of anti-degradation polymers.     

Silane-Based Coatings on Polypropylene,Deposited by Atmospheric Pressure Glow Discharge Plasmas

The aim of this paper is to show the possibility to synthesize silicon-based deposits on a polypropylene substrate, using a glow dielectric barrier discharge at atmospheric pressure, and to correlate the gas phase behavior with the properties of the thin film deposits. The discharge is generated in a mixture of nitrous oxide and silane, diluted in nitrogen. The influence of the [N₂O]/[SiH₄] ratio on the layer characteristics is mainly studied. Deposits are analyzed by XPS, SSIMS, AFM and wetting angle measurements. The discharges are also characterized by their optical emission spectra. Measurements are made as a function of the distance from the gas inlet, and they allow one to correlate these spectra with the film thickness and its chemical composition. Finally, chemical kinetics of the reactive gas decomposition reactions are proposed.     

苯酚及其光催化降解中间产物的HPLC法同时测定

研究了苯酚光催化降解过程中苯酚及３种中间体（对苯二酚、对苯二醌、邻苯二酚）含量的高效液相色谱测定方法,获得了同时测定４种物质的较佳液相色谱条件：流动相Ｖ（甲醇）：Ｖ（水）＝３０：７０,流速为０．８ｍｌ／ｍｉｎ,进样体积为２０ｕＬ,检测波长为２８０ｎｍ。用外标法进行了定量,相对标准偏差和回收率分别为０．３１％～１．１３％和９７．２％～１０１．７％,该法快速、简便、准确,适合于苯酚光催化降解过程中样品     

表面改性活性炭活化过硫酸盐降解苯酚

采用硝酸氧化联合高温处理法对活性炭(AC)进行表面改性(样品记为ACNH),并将其用于活化过硫酸盐(PS)降解苯酚.通过氮气等温吸附、元素分析、X射线光电子能谱和扫描电子显微镜等手段对改性前后活性炭的表面性质进行了表征分析.考察了活性炭投加量、PS/苯酚摩尔比、苯酚初始浓度和初始p H等条件对苯酚降解率的影响.结果表明,改性后活性炭活化PS能力显著提高,在ACNH/PS体系中苯酚的降解速率是AC0/PS体系中的5倍;ACNH的pH值适用范围宽;活性炭表面醌基、吡喃酮结构和碳原子平面层上的离域π电子(Cπ)在活化PS过程中起主要作用,而羧基起抑制作用.     

Joint QSAR Analysis Using the Free-Wilson Approach and Quantum Chemical Parameters

Abstract

A new quantitative structure-activity relationship (QSAR) technique combining the Free-Wilson method and constructed quantum chemical parameters was used to simulate the aqueous solubility (S _w), 1-octanol/water partition coefficient (K _ow) of 14 new synthesized benzanilide derivatives and their 96 h acute toxicity (EC₅₀) to Daphnia magna. The mode of action of the 14 selected compounds to Daphnia magna was shown to be a complex process involving a physical partition stage and a biochemical reaction stage. The results also indicated that the joint (QSAR) analysis was much effective than the original Free-Wilson method and Hansch method not only in predicting properties/toxicity, but also in investigating the mode of action of chemicals.     

Chemical and Physical Characteristics of Pulsed Electrical Discharge Within Gas Bubbles in Aqueous Solutions

The chemical and physical characteristics of pulsed electrical discharge within gas bubbles immersed in an aqueous solution were investigated using a reactor with long protrusion length high voltage needle electrodes. Argon gas was introduced at the base of the needle electrode causing gas bubbles to flow upwards in contact with the needle. The effects of needle protrusion length were evaluated by using 2, 4, and 6 cm length needles under a wide range of power input (3–78 W). No significant differences in chemical or electrical characteristics were found among the different protrusion lengths. H₂ and H₂O₂ generation rates were proportional to input power and the energy yield efficiency for these species was not affected dramatically by input power. The results of discharge within bubbles in aqueous solution were also compared with those for direct liquid phase discharge and gas phase discharge above the liquid surface.     

An Atomistic Modeling and Quantum Mechanical Approach to the Hydrolytic Degradation of Aliphatic Polyesters

This paper reports computational simulations at two different scales employed to investigate the hydrolytic degradation of two homopolyesters: polyglycolide, PGA and poly(L-lactide), PLLA. Atomistic bulk models were used to investigate the dry and various hydrated states of the two systems. In addition, the first moments of contact between the polymers and water were studied employing atomistic interface models. A higher affinity of water to polyglycolide in comparison with poly(L-lactide) was observed, while diffusion of water was found to be lower in the first polymer. Quantum chemical calculations for the first step of the water-assisted hydrolysis revealed a higher resistance to hydrolytical scission of the L-lactyl units in comparison to glycolyl units.     

Degradation of Organic Contaminants in Water by Pulsed Corona Discharge

Degradation of organic contaminants in water by high-voltage pulse discharges was investigated. The effects of gas flow rate and liquid conductivity on the degradation of 4-chlorophenol were studied. With the increase of time, the liquid conductivity increases, which have an important effect on discharge. Meanwhile, with the increase of time, the concentration of H₂O₂ increases. Addition of 200 mg/L H₂O₂, the conversion of 4-chlorophenol was greatly enhanced. This may be due to the synergistic effect of high-voltage pulsed discharge and H₂O₂. Also, it was found that the influence of quantity of TiO₂or CuO on degradation of acetophenone is not apparent, maybe the presence of metal oxides hinders the formation of plasma channel due to increase of collusions between metal oxides and oxygen.     

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.     

Degradation of Phenol by Hydroxyl Radicals on Different Coating Lead Dioxide Electrodes

Lead dioxide electrodes on Ti substrates were prepared by thermal-deposition or electro-deposition. The amount of hydroxyl radicals generated at the electrodes prepared by the above-mentioned two methods was compared with that at the electrodes mingled with Bi or La prepared by electro-deposition. The experimental results indicate that the highest concentration of hydroxyl radicals generated by thermal-deposition, electro-deposition mingled with nothing, electro-deposition mingled with Bi or La was 0.781, 1.048, 1.838 or 2.044 μmol/L, respectively. When phenol was electrolyzed on the four electrodes at a current density of 30 mA/cm2, the removal efficiency of phenol after electrolysis for 1.5 h was 87.30%, 93.55%, 97.95% or 98.70%, TOC removal efficiency after electrolysis for 5 h was 86.76%, 94.26%, 98.53% or 99.60%, respectively. Through the degradation experiments of phenol, the amount of hydroxyl radicals was responsible for the removal efficiency of phenol. The electro-catalytic characteristics were investigated by SEM, the generation amount of hydroxyl radicals, the degradation degree of phenol and the stability and conductivity of the electrodes were also investigated. The experimental results indicate that the four electrodes all show good electro-catalytic characteristics; the electro-catalytic characteristics of the electrode mingled with La were superior to those of the other three ones, and the electrochemical degradation of phenol followed one-step reaction dynamics.     

铁钛双金属共柱撑膨润土光催化-Fenton降解苯酚

 通过简单的离子交换方法成功合成了铁钛双金属共柱撑膨润土催化剂, 并利用 N2 吸附、X 射线衍射和等离子体发射光谱对所合成的样品进行了表征. 以苯酚为目标污染物, 考察了 pH 值、催化剂的投加量以及双氧水的加入量等对苯酚降解性能的影响. 结果表明, 在中性条件和紫外光照射下, 铁钛双金属柱撑膨润土上苯酚降解率和矿化率都高达 95%, 且铁离子的溶出率始终低于 2 mg/L, 均优于单一铁柱撑膨润土催化剂. 经过五次循环测试, 催化剂均表现出较高的活性. 即使在碱性 (pH = 9.0) 条件下, 反应 180 min 苯酚降解率也高达 70.3%, 表现出较好的酸碱适应性. 并讨论了双金属柱撑土所具有较大的比表面积和较强的表面酸性与活性之间的关系.     

不同电催化工艺下苯酚的降解特性

比较了苯酚在电催化阳极氧化(AE)、阴阳两极协同降解(ACE)及亚铁离子存在下阴阳两极协同催化降解(FeACE)₃种工艺下的降解及产物变化.在电流0.25A下处理2h,废水中COD的去除率在AE下仅30％,在ACE下为60％,而在FeACE下高达90％.苯酚降解的中间产物主要为对苯二酚、邻苯二酚、间苯二酚、对苯醌、顺丁烯二酸、反丁烯二酸和草酸等.在FeACE工艺下,中间产物还有甲酸.最终产物为CO₂.FeACE不仅提高了COD的去除速率,而且还有助于有毒中间产物的迅速消除,并使有机物彻底氧化,因而在环境保护中更具有应用前景.采用水杨酸作捕获剂证实了3种电催化工艺降解有机物的羟基自由基作用机理,其进攻苯环的活性顺序为:对位>邻位>间位,根据产物变化提出了苯酚降解路径.     

Kinetics of Phenol Oxidation under Flash Corona Electric Discharge

A study was made of the kinetics of phenol oxidation in a 3.5-l (liquid) tank at the initial chemical oxygen demand of the solution of 200-6000 mg O l^-1. The total current of flash corona electric discharge from 50 electrodes was 3 mA.     

Surface Treatment of Cotton Yarn by Underwater Capillary Electrical Discharge

An alternating current (50 Hz) capillary underwater discharge in aqueous solution of NaH₂PO₄·2H₂O is used for surface treatment of cotton yarn. The capillary discharge emits of ultraviolet radiation in the wavelength range 280–340 nm (OH band). The process of bubble generation and expansion inside the capillary results in the formation of weak shock waves. The effect on cotton yarn exposed to the discharge is quantified by a liquid wicking rate test. The treatment effect strongly depends both on the distance between plasma and cotton yarn and on the voltage. The maximum effect is observed at an applied voltage of 5.8 kV and at 1.5 mm distance to the plasma zone. Analysis of the experimental data shows that the changes in cotton yarn hydrophilicity cannot be explained solely by the locally overheated water. The nonlinear dependence of the treatment effect on the applied voltage is delivered to be due to the generation of weak shock waves in the capillary discharge.