Electrochemical degradation of chlorobenzene on boron-doped diamond and platinum electrodes

In this paper the electrochemical degradation of chlorobenzene (CB) was investigated on boron-doped diamond (BDD) and platinum (Pt) anodes, and the degradation kinetics on these two electrodes was compared. Compared with the total mineralization with a total organic carbon (TOC) removal of 85.2% in 6 h on Pt electrode, the TOC removal reached 94.3% on BDD electrode under the same operate condition. Accordingly, the mineralization current efficiency (MCE) during the mineralization on BDD electrode was higher than that on the Pt electrode. Besides TOC, the conversion of CB, the productions and decay of intermediates were also monitored. Kinetic study indicated that the decay of CB on BDD and Pt electrodes were both pseudo-first-order reactions, and the reaction rate constant (k_s) on BDD electrode was higher than that on Pt electrode. The different reaction mechanisms on the two electrodes were investigated by the variation of intermediates concentrations. Two different reaction pathways for the degradation of CB on BDD electrode and Pt electrode involving all these intermediates were proposed.     

Experimental design methodology applied to electrochemical oxidation of the herbicide atrazine using Ti/IrO(2) and Ti/SnO(2) circular anode electrodes

The degradation of the herbicide atrazine in aqueous medium (initial concentration of 100 μg l(-1)) has been studied by electrooxidation process using Ti/IrO(2) and Ti/SnO(2) circular anode electrodes. The performance of the electrolytic cell resulted from its capability of reacting on the pollutants by using indirect effect of electrical current where active chlorine is electrochemically generated. A factorial experimental design was firstly used for determining the influent parameters on the herbicide atrazine degradation. The current intensity and treatment time were the main influent parameters on the degradation rate. Using a 2(4) factorial matrix, the best performance for atrazine degradation (removal of 95%) was obtained by selecting Ti/IrO(2) anode operated at a current intensity of 2.0 A during 40 min of treatment time in the presence of 1.0 g Na Cl l(-1). Then, the optimal experimental parameters for atrazine degradation have been investigated by using a Central Composite methodology. Under the optimal conditions determined by this method, electrooxidation can economically be applied to oxidise atrazine (73% of degradation for a total cost of 0.057 US$m(-3)) while using Ti/IrO(2) anode operated at a current intensity of 1.4A during 22 min of treatment time in the presence of 1.0 g NaCl l(-1).     

Electrochemical oxidation of phenol in a parallel plate reactor using ruthenium mixed metal oxide electrode

In this study, electrochemical oxidation of phenol was carried out in a parallel plate reactor using ruthenium mixed metal oxide electrode. The effects of initial pH, temperature, supporting electrolyte concentration, current density, flow rate and initial phenol concentration on the removal efficiency were investigated. Model wastewater prepared with distilled water and phenol, was recirculated to the electrochemical reactor by a peristaltic pump. Sodium sulfate was used as supporting electrolyte. The Microtox bioassay was also used to measure the toxicity of the model wastewater during the study. As a result of the study, removal efficiency of 99.7% and 88.9% were achieved for the initial phenol concentration of 200 mg/L and chemical oxygen demand (COD) of 480 mg/L, respectively. In the same study, specific energy consumption of 1.88 k Wh/g phenol removed and, mass transfer coefficient of 8.62 x 10(-6)m/s were reached at the current density of 15 mA/cm(2). Electrochemical oxygen demand (EOD), which can be defined as the amount of electrochemically formed oxygen used for the oxidation of organic pollutants, was 2.13 g O(2)/g phenol. Electrochemical oxidation of petroleum refinery wastewater was also studied at the optimum experimental conditions obtained. Phenol removal of 94.5% and COD removal of 70.1% were reached at the current density of 20 mA/cm(2) for the petroleum refinery wastewater.     

Photocatalytic degradation of phenol under visible light using electrospun Ag/TiO2 as a 2D nano-powder: Optimizing calcination temperature and promoter content

Phenol is one of the toxic materials, and releasing it into the water can be quite irritating and harmful to the health of organisms and the environment. In this study, phenol degradation was investigated using Ag/TiO₂ electrospun nanofiber photocatalyst as a 2D nano-powder. Nanofibers have 2 dimensions in the range of nanometers but their length of them are in the range of micrometers. The micrometer size is an advantage for the separation of the photocatalyst from the suspension. Though, nanometer size is suitable for increasing the available surface for the light. The effect of silver content (0.5–15%) as a promoter and the calcination temperature (300–900 °C) was studied on the degradation of phenol over the synthesized nanofiber-based photocatalyst. Photocatalysts were characterized by various techniques including N₂-physisorption, XRD, SEM, EDX, TEM, FTIR, TGA/DSC, TPO, and DRS. The results have indicated that 5% of Ag content on TiO₂ is the best promoter loading in these experiments. Furthermore, the calcination temperature of 450 °C is found to be the optimum value with an optimum rutile fraction of 23.8%. Maximum phenol degradation was 82.65% at pH = 7, catalyst dosage of 1.5 g/L, and phenol concentration of 5 ppm under a low power visible light (18 W).     

Electrochemical degradation of waters containing O-Toluidine on PbO2 and BDD anodes

Electrochemical oxidation of O-Toluidine (OT) was studied by galvanostatic electrolysis using lead dioxide (PbO₂) and boron-doped diamond (BDD) as anodes. The influence of operating parameters, such as current density, initial concentration of OT and temperature was investigated. Measurements of chemical oxygen demand were used to follow the oxidation. The experimental data indicated that on PbO₂ and BDD anodes, OT oxidation takes place by reaction with electrogenerated hydroxyl radicals and is favoured by low current density and high temperature. Furthermore, BDD anodes offer significant advantages over PbO₂ in terms of current efficiency and oxidation rate.     

Photocatalytic degradation of phenol in aqueous solutions by Pr-doped TiO2 nanoparticles

Photocatalytic degradation of phenol in water was examined using Pr-doped TiO₂ nanoparticles. These photocatalysts were synthesized by an acid-peptized sol–gel method from titanium tetra-isopropoxide with different concentrations of Pr(III) dopant and calcination temperatures. Several tools such as XRD, BET surface area, SEM, and EDX, were used to evaluate particle structure, size distribution, and composition. The optical absorption properties of the prepared particles were also measured. Photocatalytic activity of the particles was studied in a batch reactor containing phenol solution with 400 W UV irradiation. Parameters affecting photocatalytic process such as the catalyst crystallinity, light absorption efficiency, the dosage of catalyst, dopant and phenol concentrations were investigated. The Pr-doped TiO₂ showed high activity for photocatalytic degradation of phenol. The presence of Pr ions in the TiO₂ particles would cause a significant absorption shift towards the visible region. The degradation process was optimized using 1 g/L Pr-doped TiO₂ with a Pr(III) concentration of 0.072 mol% after 2 h irradiation. It was shown that photodegradation followed a pseudo-first-order kinetics and the rate constant changed with phenol concentration.     

Facile synthesis of nano-TiO2/stellerite composite with efficient photocatalytic degradation of phenol

In this paper, we report a kind of nano-TiO₂/stellerite composite with enhanced photoactivity, which was synthesized by a typical homogeneous precipitation method followed by a calcination crystallization process using natural stellerite as support. The as-prepared composites were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption-desorption, high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The results showed that TiO₂ loading amounts and calcination temperatures had significant influence on the adsorption and photocatalytic degradation properties of phenol. Moreover, it was indicated that the TiO₂ nanoparticles (NPs) with smaller grain size (around 12.0?nm) and narrower size distributions were uniformly deposited on the surface of stellerite as a layer of film. Compared with commercial P25, the received composite exhibited more superior photocatalytic degradation performance towards phenol. The enhanced photocatalytic degradation performance should result from the better dispersibility of TiO₂ NPs and higher separation efficiency of photogenerated electron-hole pairs. This work may set foundation for the practical application of this new composite photocatalyst in the field of wastewater treatment.     

Comparative study on the catalytic electrooxidative abilities of RuO(x)-PdO-TiO(2)/Ti and RuO(x)-PdO/Ti anode

Comparative study of the catalytic electrooxidative abilities of RuO(x)-PdO/Ti and RuO(x)-PdO-TiO(2)/Ti were conducted using Active Orange 5R solution as simulated wastewater. RuO(x)-PdO-TiO(2)/Ti anode possesses higher catalytic oxidation ability, as compared to RuO(x)-PdO/Ti, in both direct oxidation and indirect oxidation processes. RuO(x)-PdO-TiO(2)/Ti could provide a discoloration rate of 98.14% within 30 min, while the COD removal could reach 51.43% in 120 min. It was indicated that higher electrooxidation ability could be achieved at RuO(x)-PdO-TiO(2)/Ti anode, which exhibited lower chlorine evolution potential and higher oxygen evolution potential probably resulted from the higher oxidation states of Ru and Pd.     

Degradation of phenol in water using a gas-liquid phase pulsed discharge plasma reactor

In this paper, a gas-liquid phase pulsed discharge plasma reactor was used to dispose phenol in aqueous solutions. The effect of pulsed peak voltage and energy, solution conductivity, solution pH, and additive gas varieties on degradation efficiency of phenol was reviewed in the research. The observed results showed that degradation efficiency of phenol increased with the increase of pulsed peak voltage, discharge energy and treatment time. The degradation efficiency of phenol with the oxygen additive was higher than that with the argon additive. The degradation efficiency was higher in the basic solution.     

Preparation and characterization of Ti/SnO(2)-Sb(2)O(3)-Nb(2)O(5)/PbO(2) thin film as electrode material for the degradation of phenol

In this work, a novel electrode of titanium substrate coated with mixed metal oxides of SnO(2), Sb(2)O(3), Nb(2)O(5) and PbO(2) was successfully prepared using thermal decomposition and electrodeposition. The surface morphology and the structure of the prepared thin film were characterized by scanning electronic microscopy (SEM) and X-ray diffraction (XRD), respectively. Experimental results showed that the structure of the prepared electrode might be described as a Ti/SnO(2)-Sb(2)O(3)-Nb(2)O(5)/PbO(2) thin film and its surface was mainly comprised pyramidal-shape beta-PbO(2) crystals. The modified electrode had higher oxygen evolution potential than that of other PbO(2) modified electrodes. Electrocatalytic oxidation of phenol in aqueous solution was studied to evaluate the potential applications of this electrode in environmental science. The phenol removal efficiency in an artificial wastewater containing 0.50g/L phenol could reach 78.6% at 20 degrees C and pH 7.0 with an applied electricity density of 20mA/cm(2) and treatment time of 120min. When 21.3g/L chloride was added to this wastewater, the removal efficiency could reach to 97.2%.     

A visible light response TiO2 photocatalyst realized by cationic S-doping and its application for phenol degradation

S-doped TiO2 photocatalyst with high visible light activity was prepared by acid catalyzed hydrolysis method using thiourea (TU) as sulfur source. The catalyst was characterized by DRS, XPS, XRD, FTIR, SEM and N2 adsorption. It was found that cation S6+ was homogeneously incorporated into the bulk phase of TiO2 and substitutes for some of the lattice titanium (Ti4+). Doped S can form a new band above the valence band and narrow the band-gap of the photocatalyst, giving rise to a second absorption edge in the visible light region. The activity of the catalyst was examined by photodegradation of phenol in aqueous solution under both artificial visible light and solar light irradiation. The activity of catalyst was found to be dependent on the doping amount of S and the maximum activity was observed when the catalyst was obtained by calcinated at 600 degrees C with the mass ratio of TU/TiO2=1. Too much of new-generated band-gap structures due to higher S-doping could act as recombination centers for electron-hole pairs. Catalyst with optimum S-doping exhibited the highest activity under both artificial light and solar irradiation for phenol degradation. In addition, doped S also beneficial for the better dispersion, large S(BET) and phase transformation retardation of TiO2.     

Preparation and properties of Ti/SnO2-Sb2O5 electrodes by electrodeposition

Sb and Sn coatings were deposited on Ti substrate by the method of cathode deposition, and the Ti/SnO₂-Sb₂O₅ electrodes were obtained by annealing at different temperatures for 3 h. Ti/SnO₂-Sb₂O₅ coating was characterized using technique such as X-ray diffraction (XRD), and scanning electron microscopy (SEM). Ti/SnO₂-Sb₂O₅ electrode calcined at 550 °C exhibits the best catalytic capacity. Ti/SnO₂-Sb₂O₅ electrode obtained by electrodeposition had longer service life and faster degradation capacity compared with that obtained by dip-coating. Accelerated service life tests were carried out in 0.5 mol L^− 1 H₂SO₄ solution with the current density of 100 mA cm^− 2. Service life of Ti/SnO₂-Sb₂O₅ electrode prepared in present study was 15 h, and it was only 0.14 h for Ti/SnO₂-Sb₂O₅ electrode obtained by dip-coating.     

Optimal exponential feeding strategy for dual-substrate biostimulation of phenol degradation using Cupriavidus taiwanensis

The exponential feeding strategy (EFS) of dual substrates (i.e., phenol and glycerol) was applied to optimize the overall performance of phenol degradation by Cupriavidus taiwanensis R186. Addition of a second substrate (e.g., glycerol) could stimulate the phenol biodegradation efficiency of strain R186. Hence, a feasible EFS was developed for fed-batch phenol biodegradation using the dual-substrate biostimulation technique. The phenol degradation kinetics was well characterized with proposed model and response surface analysis. Our findings quantitatively revealed that glycerol could effectively enhance the phenol degradation performance, as the highest phenol degradation efficiency occurred with the supplementation of 0.8–1.2 g L⁻¹ of glycerol. The optimal dual-substrate EFS was identified via contour analysis and kinetic modeling. With the optimal dual-substrate EFS (i.e., a feeding rate constant (α₁ and α₂) of 0.5 and 0.3, respectively), the shortest time (ca. 13.80 h) for phenol degradation was achieved with a specific growth rate of ca. 0.281 h⁻¹.     

Electrochemical treatment in relation to pH of domestic wastewater using Ti/Pt electrodes

This paper describes an electrochemical treatment of domestic wastewater (DW) using 0.8% (w/v) sodium chloride as electrolyte. In this technique, DW was passed through an electrolytic cell using Ti/Pt as anode and Stainless Steel 304 as cathode. Due to the strong oxidizing potential of the chemicals produced (chlorine, oxygen, hydroxyl radicals and other oxidants), the organic pollutants and nutrients (organic nitrogen, phosphorous) were wet oxidized to carbon dioxide, and nitrogen as well as phosphorous was precipitated as Ca(3)(PO(4))(2). Experiments were run in a continuous, laboratory-scale, pilot plant, at 40 degrees C and the efficiency of oxidation was studied in relation to pH. It was found that in alkaline conditions the electrolysis was more efficient. At pH 9, NaCl concentration 0.8% (w/v), current density 0.075 A/cm(2) and for 1h of electrolysis, COD was reduced by 89%, volatile suspended solids (VSS) by 90%, ammonia nitrogen by 82% and total phosphorous by 98%. The efficiency of electrolysis went up to 35 g COD(r)/(hm(2)A) and the energy consumption to 12.4 kWh/kg COD(r). It is concluded that the application of electrolytic oxidation of DW is more advantageous compared to conventional biological treatment especially for small works.     

Electrochemical treatment of paper mill wastewater using three-dimensional electrodes with Ti/Co/SnO2-Sb2O5 anode

The properties of the interlayer and outer layer of Ti/Co/SnO2-Sb2O5 electrode were studied, and the electrochemical behavior was examined as well. As a result of unsatisfactory treatment using Ti/Co/SnO2-Sb2O5 electrode, electrochemical disposal of paper mill wastewater employing three-dimensional electrodes, combining active carbon granules serving as packed bed particle electrodes, with Ti/Co/SnO2-Sb2O5 anode, was performed. The outcome demonstrates that efficient degradation was achieved. The residual dimensionless chemical oxygen demand (COD) concentration reached 0.137, and color removal 75% applying 167 mA cm(-2) current density at pH 11 and 15 g l(-1) NaCl. The instant current efficiency, energy cost, electrochemical oxidation index (EOI) and kinetic constant of the reaction were calculated. At the same time, the influence of pH and current density on COD abatement and decolorization was also investigated, respectively.     

RuO2/聚吡咯复合电极的制备及性能

通过热分解法及电化学聚合法的复合工艺制备了RuO2/聚吡咯(PPy)电极材料。使用涂覆热分解法于260℃热处理3h制备得RuO2薄膜,通过电化学聚合法把PPy粒子沉积在RuO2薄膜上。XRD表明该复合物为非晶相;红外光谱测试揭示了相对应离子结合在复合物中;SEM揭示了PPy粒子的增长规律。循环伏安及恒流充放电测试了该复合电极的电化学性能。沉积时间<25min时,复合电极的电容量与沉积时间呈递增关系;沉积时间>25min时,复合电极的电容量与沉积时间呈递减关系。复合电极的比电容则随沉积时间的增加而减小。沉积时间为25min时,其比电容为471F/g。RuO2/PPy电极循环稳定性较好。     

TiO_2/蒙脱土复合材料的制备及光催化降解苯酚性能

为了利用TiO_2优越的光催化活性和蒙脱土(MMT)的结构特性,首先,以MMT为载体、TiCl_4为原料、氨水为沉淀剂,采用水解沉淀法制备了TiO_2/MMT复合材料;然后,利用FTIR、XRD和SEM对TiO_2/MMT复合材料进行成分、晶型、结构和形貌表征;最后,在紫外光照射下,考察了不同TiO_2含量的TiO_2/MMT复合材料对模拟苯酚废水的光催化降解活性,并结合紫外-可见光谱对复合材料光催化降解苯酚的过程进行了跟踪实验。结果表明:所制备的TiO_2/MMT复合材料中TiO_2为锐钛矿相,在MMT上的晶粒尺寸为7.8nm。TiO_2/MMT复合材料中层间域内成分被钛柱取代,且柱撑反应在层间域内进行。因此MMT的基本骨架不变,且TiO_2分散在MMT的表面。当苯酚的初始浓度为10mg/L、苯酚溶液的pH为6且紫外光照射时间为150min时,37.5wt%TiO_2/MMT复合材料对苯酚降解率为63%,优于MMT(4.5%)和纯TiO_2(55%),说明MMT的负载提高了TiO_2的光催化活性。     

Ag/TiO2纳米粒子的制备及其光催化降解苯酚的性能研究

采用溶胶-凝胶法制备了TiO₂和Ag/TiO₂纳米粒子,采用涂覆法制备了TiO₂和Ag/TiO₂纳米粒子光催化剂基板样品。使用XRD、SEM和拉曼光谱等手段,对TiO₂和Ag/TiO₂纳米粒子进行了晶格结构和表面形貌研究;通过UV-Vis,研究了TiO₂和Ag/TiO₂纳米粒子光催化剂基板样品在光催化反应器中对苯酚的光催化降解性能。结果表明,制备的TiO₂和Ag/TiO₂纳米粒子均为纯净的金红石相,二者表面形貌并没有明显区别,Ag单质粒子成功负载在TiO₂纳米材料上;Ag单质粒子的负载,明显增强了TiO₂纳米粒子对可见光的吸收,且Ag/TiO₂纳米粒子薄膜对苯酚的光催化降解性能明显优于TiO₂纳米粒子薄膜;在光催化降解1 h后,TiO₂纳米粒子薄膜仅催化降解了溶液中30%(质量分数)的苯酚,且光催化降解出现了饱和趋势,而Ag/TiO₂纳米粒子薄膜可催化降解溶液中50%(质量分数)的苯酚,且在光催化降解3 h后,仍未出现饱和趋势。     

Electrochemical deposition of poly(o-anisidine) and polypyrrole at octadecanethiol coated gold electrodes

The o-anisidine and pyrrole have been polymerized by the electrochemical oxidation of monomers on gold electrodes, covered with self-assembled monolayers. The obtained polymer–monolayer systems have been investigated by cyclic voltammetry in aqueous supporting electrolyte solutions containing K₄Fe(CN)₆ and Ru(NH₃)₆Cl₃. The deposition of conducting polymers strongly depends on the integrity of a monolayer. In the case of a large number of SAM defects, the polymerization of o-anisidine and pyrrole leads to the formation of nuclei of the conducting polymer in the insulating matrix of the thiol monolayer. When the polymer is in the conducting (oxidized) form, the nuclei act as an array of microelectrodes. The polarogram-shaped voltammograms obtained for K₄Fe(CN)₆ confirm the hemispherical diffusion of redox species to the polymer nuclei. When the polymer is in the non-conducting (reduced) form, the polymer–octadecanethiol layer blocks the redox processes on the electrode. The exponential-type CV curves observed for Ru(NH₃)₆Cl₃, when the polymer is in its non-conducting state, can be assigned to the tunnelling of electrons through the passivating layer. The use of monolayers with a low number of defects influences the mechanism of polymer growth. Thus, the polypyrrole grows on the layer of thiols, and the poly(o-anisidine) forms polymer nuclei.     

钛基亚氧化钛电极电化学降解性能研究

采用SEM、EDS对钛基亚氧化钛电极进行形貌和成分表征,用线性极化曲线法和循环伏安法测试电化学性能,通过降解模拟污水测试降解性能以及用荧光光谱法检测自由基。结果表明,钛基亚氧化钛电极上不能发生直接氧化反应,但是电极析氧电位可达2.18 V(vs.SCE),并且检测到生成大量·OH,是一种类似于Ti/SnO_2的惰性电极,在Na Cl和Na2SO4电解质溶液中电流效率分别达40.95%和22.52%,降解效果优于Ti/SnO_2和Ti/Ru Ir电极。