Removal of Oil Products from Water Using a Combined Process of Sorption and Plasma Exposure to DBD

The paper presents the results of studies of a combined process involving the sorption of engine oil on a sorbent (diatomite) followed by regeneration of the sorbent by plasma-oxidative destruction of oil in DBD of atmospheric pressure in oxygen. The process parameters (gas flow rate, sorbent mass, power, treatment time), which provide the possibility of fivefold regeneration of the sorbent and 100% degree of oil decomposition, are revealed. It was found that the kinetics of oil degradation obeys the pseudo-first kinetic order equation with a rate constant of 0.017 s^?1. The energy efficiency of the decomposition was 0.169 molecules of oil per 100 eV of input energy. It is shown that treatment of the sorbent for 5 min leads to the complete decomposition of oil. The products of oil decomposition are carboxylic acids, aldehydes and CO₂. Complete removal of acids and aldehydes requires the time of about 40 min. The possible participation of ozone in the oxidative degradation of oil is discussed.     

Decomposition of Benzene Using a Pulse-Modulated DBD Plasma

To improve the energy yield (EY) of plasma volatile organic compound decomposition, a dielectric barrier discharge plasma driven by pulse-modulated AC power was used to experimentally study the abatement of benzene in atmospheric pressure air and at room temperature. The effects of the duty cycle on decomposition efficiency, EY, CO₂ selectivity and the formation of ozone and NO₂ were investigated. The results show that applying pulse modulation improves the EY and the CO₂ selectivity and greatly reduces the wall temperature of the reaction chamber.     

Investigation of CO2 Splitting Process Under Atmospheric Pressure Using Multi-electrode Cylindrical DBD Plasma Reactor

Plasma Chemistry and Plasma Processing - In this paper, the CO2 splitting process was performed under atmospheric pressure in a multi-electrode cylindrical dielectric barrier discharge (DBD) plasma...     

纳米级Pd/Fe双金属体系对水中2,4-二氯苯酚脱氯的催化作用

 利用化学沉淀法制备了纳米级Fe和纳米级Pd/Fe双金属催化剂,研究了它们对2,4-二氯苯酚(2,4-DCP)还原脱氯的催化性能. 结果表明,纳米级颗粒具有较高的比表面积和表面反应活性,其BET比表面积可达12.4 m2/g,当Pd/Fe用量为6 g/L时,2,4-DCP脱氯率达到90%以上. 脱氯效率与pH值、温度、钯含量和Pd/Fe投加量等因素有关. 2,4-DCP在脱氯过程中先生成2-氯苯酚和4-氯苯酚,最终生成苯酚,而少量的2,4-DCP可直接降解成苯酚.     

Destruction of Freon HFC-134a Using a Nozzleless Microwave Plasma Source

In this paper, results of the pyrolysis of Freon HFC-134a (tetrafluoroethane C₂H₂F₄) in an atmospheric pressure microwave plasma are presented. A waveguide-based nozzleless cylinder-type microwave plasma source (MPS) was used to produce plasma for the destruction of Freon HFC-134a. The processed gaseous Freon HFC-134a at a flow rate of 50–212 l min⁻¹ was introduced to the plasma by four gas ducts which formed a swirl flow in the plasma reactor (a quartz cylinder). The absorbed microwave power was 0.6–3 kW. The experimental results showed that the Freon was converted into carbon black, hydrogen and fluorine. The total conversion degree of HFC-134a was up to 84% with selectivity of 100% towards H₂, F₂ and C₂, which means that there was no conversion of HFC-134a into other hydrocarbons. The Freon destruction mass rate and corresponding energetic mass yield were up to 34.5 kg h⁻¹ and 34.4 kg per kWh of microwave energy absorbed by the plasma, respectively.     

Photocatalytic Decomposition of 2,4-Dichlorophenol Using Platelike SnO2/ZnO Composites Prepared by a Facile Route

Russian Journal of Physical Chemistry A - Well dispersed SnO2/ZnO composites with platelike shape were synthesized via a facile method. X-ray diffraction (XRD), field emission scanning electron...     

分散液液微萃取-高效液相色谱法测定环境水样中2,4-二氯酚

建立了简便、快速、有效的分散液液微萃取-高效液相色谱法测定环境水样中2,4-二氯酚的分析方法。对萃取剂、分散剂的种类和体积、萃取时间、离心时间、盐浓度等影响萃取效率的因素进行了优化。方法的线性范围为1～500μg/L(r=0.9997),相对标准偏差(RSD)为3.8%(n=6),检出限为0.19μg/L。该法适用于环境水样中的痕量2,4-二氯酚的检测。     

Competitive Sorption of Copper and Nickel Ions from Aqueous Solution Using Peat

Bicomponent aqueous solutions of copper and nickel ions have been used to investigate the sorption of metal ions onto peat. Peat, a low cost sorbent, has shown a high capacity for the sorption of single component metal ions attributed to extensive carboxylic acids within its structure. Copper and nickel ions were selected as typical metals in the effluents of electroplating industries. The effects of competitive sorption in batch systems were studied at various metal ion concentrations. In this study the Butler and Ockrent model was modified using a coefficient, . Two models were developed based on the interaction coefficient . The first model incorporates a constant fixed factor for each metal ion into the Butler-Ockrent equation. The second model incorporates a variable factor into the Butler-Ockrent equation; this interaction factor varies as a function of sorbent surface coverage. Predicted equilibrium data are found to be in excellent agreement with experimental values using both modified models for various mole ratios of copper and nickel ions in competitive sorption.     

Sorption of Arsenic Oxyanions from Aqueous Solution on Goethite: a Study of Process Modelling

In the course of researching methods of sampling and monitoring toxic metals (as arsenic ions) in water and wastewaters, we selected the use of sorption for in-depth examination. Among other things, sorption modelling was investigated by the mechanism of surface complexation in order to describe the process or even predict the outcome for the expected rate, and in general, to develop this detection technique for pollutants. This investigation will include the application of goethite mineral as the suitable metal ion sorbent and the use of appropriate computer software. The relative thermodynamic aqueous speciation of the solution, in similar experimental conditions, was also studied.     

Separation of Gold from Sulfide Using a Plasma Arc Fuming Process

Transferred-arc plasma treatment of iron sulfides containing gold is examined from both thermodynamic and experimental points of view. Three cases are analyzed: argon plasma with sulfide, argon plasma with a carbon–sulfide mixture, and argon–methane plasma with sulfide. The carboreduction of the materials appears to be well adapted for gold separation by fuming, but experimentally the process is limited by the poor mixing of graphite with molten material. The reduction with a CH₄ (10%) plasma is a proved alternative to the aforementioned process. A gold extraction efficiency of 90% is achieved for batch smelting operations.     

Sorption of Water Vapor by Gelatin-Based Polymers: Estimation of Rate and Degree of Sorption Using the Spin-Probe Method

Moscow University Chemistry Bulletin - The spin-probe method is applied to estimate the rate and degree of sorption of water vapor by gelatin-based polymers. The rate and the sorption degree of...     

Generation Characteristics of Long-Lived Active Species in a Water Falling Film DBD Reactor

Plasma Chemistry and Plasma Processing - Water falling film dielectric barrier discharge (WFFDBD) has been widely studied for water treatment, due to its good performance on production of active...     

固相萃取-高效液相色谱串联质谱法同时检测地表水中的2,4-二氯酚、2,4,6-三氯酚和五氯酚

建立了简便、快速、同时测定地表水中2,4-二氯酚、2,4,6-三氯酚和五氯酚的固相萃取-高效液相串联质谱方法。HLB固相萃取小柱富集水样中待测物质,经二氯甲烷-丙酮(1∶1,V/V)混合溶液洗脱后,氮吹浓缩,溶剂转换为甲醇,采用高效液相色谱串联质谱检测,选择反应监测模式(SRM),进行特征母离子-子离子采集信号。本方法对2,4-二氯酚、2,4,6-三氯酚和五氯酚检测的线性方程分别为Y=2524 X-6029、Y=1809 X-11341、Y=2296 X-2894,相关系数分别为0.9993、0.9996和0.998;检出限(LOD)分别为2.0,3.0和0.1ng/L;定量限(LOQ)分别为6.7,10.1和0.3ng/L;7次加标回收相对标准偏差在2.2%～14.7%之间;回收率为70.5%～102.3%,能很好地满足水源地监测的需求。     

DBD Plasma Treatment of Titanium in O2, N2 and Air

Dielectric Barrier Discharge plasma treatment of a titanium metal foil in oxygen, nitrogen and air under atmospheric conditions is investigated employing X-Ray Photoelectron Spectroscopy (XPS). We investigated three different reference samples and compare the results with a large number of studies on the XPS analysis of titanium compounds containing oxygen and nitrogen. The plasma treatment in all three different process gases leads to the formation of titanium dioxide films, while rather small nitrogen fractions are found after nitrogen and air plasma treatments. This finding is explained basing on plasma chemistry insight from the literature.     

Destruction of Organic Compounds in a High-Frequency Discharge Plasma at Reduced Pressure

Plasma Chemistry and Plasma Processing - Conditions of the destruction of organic compounds in a hf discharge plasma at reduced pressure and parameters of this plasma type are determined. The...     

Effect of Water Vapor on Benzene Decomposition Using a Nonthermal-Discharge Plasma Reactor

The effect of water vapor on benzene decomposition in air was investigatedusing a nonthermal-discharge plasma reactor packed with ferroelectricmaterials. The conversion of benzene was found to decrease with an increaseof water concentration. On the other hand, the selectivity to CO₂ in thedecomposition products increased with an increase of water concentration. Acomparison between the benzene conversion to CO and CO₂ suggested that COformation was suppressed by water to a greater extent than was CO₂formation. N₂O formation also decreased with an increase of waterconcentration. These results suggest that the activity of oxygen speciesresponsible for the formation of CO and N₂O is reduced by water.     

Effect of Water Vapor on NO Removal in a DBD Reactor at Different Temperatures

The present work investigates experimentally the effect of H₂O vapor on the removal of NO at elevated temperatures. Breakdown voltage, discharge characteristics and NO removal efficiency were studied under various conditions of water vapor content. The experimental results indicate H₂O can greatly enhance the NO removal efficiency from a NO/O₂/N₂/C₂H₄/H₂O system, but the breakdown voltage increases as the relative humidity of the gas increases. Moreover, the effect of temperature on NO removal at a relative gas humidity of 30 % was analyzed. With an increase in temperature, E/N increased, producing more active species and energetic electrons; electron detachment also became significant at high temperature and the rates of major reactions were promoted, intensifying the conversion of NO.     

电-Fenton及类电-Fenton技术处理水中有机污染物

传统Fenton技术是一种广泛用于水体里有机污染物降解的高级氧化技术(advanced oxidation technologies, AOTs)。它利用Fenton试剂Fe²⁺与H₂O₂反应生成具有强氧化性的羟基自由基(^·OH),从而降解有机污染物。基于相似的机理,过渡金属离子(Fe²⁺、Co²⁺和Ag⁺等)也可与过硫酸盐反应生成氧化能力较强的硫酸根自由基(SO₄^·-),而被称之为类Fenton技术。传统Fenton技术存在Fe²⁺投加量多,产生的铁污泥多等缺点,因此,有学者将Fenton技术与电化学技术结合,使Fe²⁺在阴极得以持续再生,这就是广为关注的电-Fenton技术。同样地,类Fenton技术也遇到与传统Fenton技术相似的问题。借鉴电-Fenton技术的成功应用,基于硫酸根自由基的类电-Fenton技术应运而生。本文在介绍电-Fenton和类电-Fenton技术原理的基础上,概括了电-Fenton和类电-Fenton技术的主要类型及其改进方法,并就值得深入研究的问题和热点趋势进行了展望。     

Non-Steady-State Combined Process of Etching and Imidization of Polyamidoacid Film in Nonequilibrium Oxygen Plasma

The non-steady-state process of etching of a polyamidoacid film in an nonequilibrium oxygen low-pressure inductively coupled radiofrequency-discharge plasma was studied. It was shown that an unsteady imidization process develops in the bulk of the film simultaneously with occurrence of an unsteady film etching process. The time dependence of film etching rate at varying film thickness and incident ion energy was determined. The mechanism of the unsteady etching–imidization process of the polyamidoacid film in an oxygen plasma and the role of oxygen atoms and molecules in the process are discussed.     

Chemical Effects of Air Plasma Species on Aqueous Solutes in Direct and Delayed Exposure Modes: Discharge,Post-discharge and Plasma Activated Water

The chemical interaction between non-thermal plasma species and aqueous solutions is considered in the case of discharges in humid air burning over aqueous solutions with emphasis on the oxidizing and acidic effects resulting from formed peroxynitrite ONOO^? and derived species, such as transient nitrite and stable HNO₃. The oxidizing properties are mainly attributed to the systems ONOO^?/ONOOH [E°(ONOOH/NO₂) = 2.05 V/SHE], ^·OH/H₂O [E°(^·OH/H₂O) = 2.38 V/SHE] and to the matching dimer system H₂O₂/H₂O [E°(H₂O₂/H₂O) = 1.68 V/SHE]. ONOOH tentatively splits into reactive species, e.g., nitronium NO⁺ and nitrosonium NO ₂ ⁺ cations. NO⁺ which also results from both ionization of ^·NO and the presence of HNO₂ in acidic medium, is involved in the amine diazotation/nitrosation degradation processes. NO ₂ ⁺ requires a sensibly higher energy than NO⁺ to form and is considered with the nitration and the degradation of aromatic molecules. Such chemical properties are especially important for organic waste degradation and bacterial inactivation. The kinetic aspect is also considered as an immediate consequence of exposing an aqueous container to the discharge. The relevant chemical effects in the liquid result from direct and delayed exposure conditions. The so called delayed conditions involve both post-discharge (after switching off the discharge) and plasma activated water. An electrochemical model is proposed with special interest devoted to the chemical mechanism of bacterial inactivation under direct or delayed plasma conditions.