Degradation of methylene blue in aqueous solution by ozone-based processes

The aim of this study was to compare the efficiency of conventional ozonation and catalytic ozonation (ozone/activated carbon (O₃/AC) and ozone/TiO₂/activated carbon (O₃/TiO₂/AC)) in the degradation of methylene blue (MB) component from MB aqueous solution. The removal rates of color and chemical oxygen demand (COD_Cr) were assessed to screen the most appropriate oxidative process of MB treatment. In this experiment conditions, the color was completely disappeared in the presence of TiO₂/AC catalyst, after 40 min of reaction time. However, only ozone system still existed 11.8% MB in aqueous solution, while in case of O₃/AC system MB of 4.6% was not removed. In the COD removal experiment, the catalytic ozonation process showed a superior performance, compared to that of the conventional ozonation. COD removal efficiency was significantly promoted in the presence of catalysts such as AC and TiO₂. O₃/TiO₂/AC was found to be the most effective approach to eliminating the color and enhancing COD removal efficiency. The catalyst of TiO₂/AC was characterized by using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS).     

可见光响应的壳-核结构Ag/AgCl光催化剂性能

利用光化学还原法制备了Ag/AgCl壳-核结构的复合纳米粒子,以亚甲基蓝为模型降解物,研究了其可见光催化性能。结果表明,壳-核结构的Ag/AgCl纳米材料具有表面等离子效应,提高了其对可见光吸收和光催化活性。在可见光照射下,亚甲基蓝溶液浓度为10 mg·L^-1,催化剂用量10 mg·L^-1,光照60 min,亚甲基蓝降解率达95%,COD去除率为92%。     

Electro-catalytic degradation of methylene blue wastewater assisted by Fe2O3-modified kaolin

The electrochemical oxidation of methylene blue (MB) wastewater assisted by Fe₂O₃-modified kaolin in a 200 mL electrolytic batch reactor with graphite plate as electrodes was investigated. The catalyst was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of pH, current density and introduction of NaCl on the efficiency of the electrochemical degradation process were also studied. It was found that Fe₂O₃-modified kaolin has higher catalytic activity in the electrochemical degradation of MB wastewater. 96.47% chemical oxygen demand (COD) removal was obtained in 40 min of electrochemical treatment of MB wastewater at pH 3, current density was equal to 69.23 mA cm⁻².     

花生壳吸附耦合Fenton氧化技术处理次甲基蓝废水研究

利用花生壳耦合Fenton氧化技术对次甲基蓝废水处理工艺进行了研究。结果显示:花生壳吸附法对次甲基蓝的脱色效果比去除效果好。而耦合工艺对次甲基蓝的去除效果比脱色效果好。最佳耦合工艺条件为:对于250 mL 100 mg/L的废水,当花生壳投加量为3 g时,pH=5,FeSO4.7H2O浓度为1.0 g/L,H2O2=3 mL时去除效果较好。随着反应时间的增加,去除率几乎不变,但是脱色效率降低。当FeSO4.7H2O和H2O2过量的时候,对色度的去除有较强的抑制作用。     

Degradation of azo dye from aqueous solutions using nano-SnO2/Ti electrode prepared by electrophoretic deposition method: Experimental Design

In this work, degradation of C.I. Acid Red 33 (AR33) in aqueous solutions was investigated. The combined electrolysis–ozone (ECO) process optimized based on SnO₂ nanoparticles electrode (nano-SnO₂/Ti) as anode using response surface methodology (RSM) involving a five-level central composite design (CCD). The nano-SnO₂/Ti electrode was prepared using electrophoretic deposition (EPD) method. The electrode was characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and cyclic voltammetry (CV). The initial pH, current density, reaction time and electrolyte concentration were selected as independent variables in central composite design while color removal efficiency was considered as the response function. Based on analysis of variance (ANOVA), the coefficient of determination value (R² = 0.981) was high. In optimum conditions, maximum color removal efficiency (93.2%) was obtained after 16 min; and the removal of chemical oxygen demand (COD) was reduced to 57.1% after 60 min.     

TiO2-HNTs催化剂协同介质阻挡放电等离子体降解亚甲基蓝废水

为进一步提高介质阻挡放电等离子体（DBD）降解亚甲基蓝（MB）的效率,研究了采用介质阻挡放电等离子体和光催化剂协同技术。实验采用溶胶-凝胶法制备TiO₂-HNTs复合光催化材料,并利用XRD、FTIR、TGA方法对催化剂进行表征分析。考察了该材料的光催化性能,以及它与介质阻挡放电的联合降解过程中操作因素的影响,并对反应进行动力学研究。研究结果表明,TiO₂-HNTs复合光催化材料与介质阻挡放电产生协同作用,并能有效地提高MB的去除率,处理60min后,协同体系对MB的降解率为85.37%,MB的降解过程符合表观一级反应动力学方程。MB的去除率与MB的初始浓度,TiO₂-HNTs的投加量、煅烧温度、放电功率和通气量有关。当MB的初始浓度为100mg/L、TiO₂-HNTs的投加量为70mg/L、煅烧温度为300℃、放电功率为200W、通气量为200mL/min时,MB的去除效果较好。     

平行磁场对介质阻挡放电降解亚甲基蓝废水影响

以亚甲基蓝溶液作为模拟印染废水,通过改变放电电压、充气速率、处理时间等初始条件,考察了亚甲基蓝溶液的pH、电导率、COD等参数的变化,并借助高效液相色谱仪分析亚甲基蓝部分降解产物的浓度变化,研究了介质阻挡放电条件下,平行磁场的加入对亚甲基蓝降解效果的影响。实验结果表明:外加磁场所产生的洛伦兹力会影响等离子体中电子的行为,限制放电空间中电子的横向运动,增加高能电子与其他粒子的碰撞概率,从而使等离子体的化学活性增强,从而可以提高亚甲基蓝降解率5%~10%。     

Synthesis of AgBiS2/gC3N4 and its application in the photocatalytic reduction of Pb(II) in the matrix of methyl orange,crystal violet,and methylene blue dyes

The removal of lead ions in contaminated water by the reduction of Pb(II) ions to the useful metallic Pb is challenging, especially in water polluted by other contaminants such as dye molecules. Most investigations focussed on the removal of Pb(II) in a single system. In reality, contaminated water contains a mixture of organic pollutants and heavy metals. Herein, we synthesized graphitic carbon nitride functionalized with ternary silver bismuth sulphide (AgBiS₂/gC₃N₄) for the photocatalytic removal of Pb(II) from dye-containing water. The as-synthesized gC₃N₄, AgBiS₂, and AgBiS₂/gC₃N₄ composite were characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and transmission electron microscopy (TEM). The composite was used for the photocatalytic reduction of Pb(II) in the matrix of methyl orange, crystal violet, and methylene blue. The effect of the presence of easily-oxidizable organics and persulphate on the photocatalytic reduction of Pb(II) was also investigated. The results revealed that the presence of easily-oxidizable organics has synergistic effects on the photocatalytic reduction of Pb(II), while persulphate displayed inhibitive effect on Pb(II) reduction. The removal of Pb(II) in the dyes matrix was influenced by the type of dyes that were present in the water. The rate of Pb(II) reduction was reduced in the presence of methylene blue and methyl orange, but crystal violet displayed synergistic effects. Finally, the rate of degradation of dyes in the presence of Pb(II) was investigated. The rate of photocatalytic reduction of Pb(II) decreased from 0.0045 min^?1 to 0.0036 min^?1 and 0.0016 min^?1 in the matrix of methyl orange and methylene blue respectively. On the contrary, there was an increase in the rate of photocatalytic reduction of Pb(II) from 0.0045 to 0.0096 min^?1 in the matrix of crystal violet.     

High Performance Removal of Anionic and Cationic Dye Pollutants with Co<Subscript>3</Subscript>O<Subscript>4</Subscript> Modified Nanoclinoptilolite: Kinetics and Adsorption Equilibrium Studies

In this paper Co₃O₄ doped nanoclinoptilolite was synthesized and characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM) and energy-dispersive X-ray spectroscopy (EDX) techniques. The adsorption efficiency for removing of methylene blue was about 95% in 10 min. The effect of some factors such as adsorbent dose, concentration of analyte and pH was investigated for enhancing the removing efficiency. Moreover Freundlich and Langmuir patterns were plotted for this new nanocomposite. Maximum of adsorption capacity was obtained from slope of Langmuir and was about 25 mg/g. The kinetic study for methylene blue shows a second order kinetic with rate constant about 0.02 g/mg/min. The prepared nanocomposite was successfully applied for removing some color compounds such as methylene blue, methyl green, and methyl red and also binary dye mixtures.     

Removal of a Toxic Anthraquinone Dye by Combination of Red Mud Coagulation and Ozonation

Removal of a toxic anthraquinone dye—Disperse Blue 56 (DB56) by single red mud (RM) coagulation, single ozonation and combined RM coagulation/ozonation (RM/O₃) was carried out in laboratory-scale experiments. RM/O₃ treatment exhibited more effective in toxicity removal, color removal and chemical oxygen demand (COD) reduction than the other two methods. The effect of several operational parameters, including initial dye concentration, pH value, RM coagulant dose and O₃ dose, on color removal and COD reduction was also investigated. Among these factors, pH value had the most important effect.     

超声波-Fenton法协同降解含表面活性剂SDS弱酸艳红染料废水的研究

采用Fenton氧化、超声辐射和超声-Fenton氧化三种方法处理含阴离子表面活性剂SDS的弱酸艳红B染料废水,考察溶液初始pH、H2O2投加量、FeSO4投加量、反应时间和超声功率对废水色度和COD的影响。结果表明:单独超声对废水色度和COD的去除没有效果,超声-Fenton氧化法对废水COD的去除效果明显优于Fenton氧化法。在pH 2.5,温度50℃,H2O2投加量4 mL/L,FeSO4投加量300 mg/L,反应时间90 min及超声功率400 W的条件下,废水色度去除率为98%,COD去除率为72%,比单独Fenton氧化法COD去除率提高25%。     

Application of in situ electrochemically generated ozone for degradation of anthraquninone dye Reactive Blue 19

Degradation of anthraquninone dye C.I. Reactive Blue 19 (RB19) via generated ozone by electrochemical oxidation process was investigated in this research. Ti/Sn–Sb–Ni electrode was used as an anode for ozone generation. The anode electrode was characterized electrochemically by cyclic voltammetry and characterized morphologically by scanning electron microscopy and X-ray diffraction. The amount of ozone concentration and RB19 degradation increased with increasing of applied voltage, electrolysis time, and in 1 M HClO₄ at room temperature. The results of UV/Vis spectroscopy showed that the anthraquinone structure was degraded by dissolved generated ozone and also intermediate compounds were detected by integrated gas chromatography–mass spectrometry (GC/MS). Removal of color and COD were 100 % after 3 min and 48.2 % after 15 min reaction time, respectively.     

An electrochemical impedance spectroscopy and scanning electron microscopy study of the influence of positive plate compression on the electrochemical behaviour of lead-acid batteries

This study has developed an electrochemical impedance spectroscopy (EIS) method for the in situ investigation of the influence of positive plate compression on the electrochemical behaviour of lead-acid batteries during charge/discharge cycling. The EIS data for a fully charged and fully discharged battery are internally consistent with the expected kinetics of a battery in the opposite states of charge, and demonstrate that EIS measurements may be recorded with a high level of reproducibility. Furthermore, this study has necessitated the development of a special cell incorporating horizontally orientated battery plates that can be subjected to elevated pressure through the stacking of lead bricks on top of the cell, as well as a physically robust reference electrode system that can withstand the application of pressure. For this purpose, a platinum-wire pseudo-reference electrode has been developed, and has been shown to exhibit sufficient electrode stability over the period of an EIS recording, enabling the measurement of reproducible and meaningful EIS data. Additionally, the influence of positive plate compression on the behaviour of the lead-acid battery has been investigated by using scanning electron microscopy (SEM). Clearly, the experimental data show that plate compression enhances significantly the kinetics and concomitant performance of the lead-acid battery, and this is related to the enhanced reactivity of the active material, as rationalized by using the agglomeration-of-spheres (AOS) model.     

可溶铅酸液流电池模拟与仿真

可溶铅酸液流电池是一种使用单个容器存储电解液并且不需要微孔隔膜的氧化还原液流电池,这使得电池设计简单并降低了成本。建立二维暂态可溶铅酸液流电池模型,模型基于对质量、电荷以及能量的转移与守恒以及包含铅离子反应的宏观动力学模型为基础,研究了电极间隔、电极形状、电流密度、实验温度、入口电解液流速和电解质初始浓度对电池性能的影响。研究表明：与平板电极相比,弧形电极明显提高了充电时的电池电压。在影响铅酸液流电池性能的诸多条件中,电池温度和电流密度可能是优化电池性能的重要因素。     

Comparative Study of Electrocoagulation and Electrooxidation Processes for the Degradation of Ellagic Acid From Aqueous Solution

A comparative study of electrocoagulation and electrooxidation processes for the degradation of ellagic acid from aqueous solution was carried out. For the electrocoagulation process, metallic iron was used as electrodes whereas graphite and RuO₂/IrO₂/TaO₂ coated titanium electrodes were used for the electrooxidation processes. The effect of the process variables such as initial pH, concentration of the supporting electrolyte, applied current density, electrolysis time, and anode materials on COD removal were systematically examined and discussed. Maximum COD removal of 93% was obtained at optimum conditions by electrocoagultion using an iron electrode. The ellagic acid was degraded completely by electrooxidation using graphite electrodes under the optimum conditions. During electrooxidation, the chloride ion concentration was estimated and the effect of the Cl^? ion was discussed. The finding of this study shows that an increase in the applied current density, NaCl concentration, and electrolysis time enhanced the COD removal efficiency. The UV–Vis spectra analysis confirms the degradation of ellagic acid from aqueous solution.     

Electrochemical removal of the insecticide imidacloprid from water on a boron-doped diamond and Ta/PbO<Subscript>2</Subscript> anodes using anodic oxidation process

The removal of pesticides from water is a major environmental concern. This study investigates the electrochemical removal of the insecticide imidacloprid (IMD) from aqueous solutions on a boron-doped diamond (BDD) and Ta/PbO₂ anodes under galvanostatic electrolysis. The influence of operating parameters, such as applied current density (50–100 mA cm^?2), initial chemical oxygen demand COD (0) (281–953 mg L^?1), temperature (25–65 °C) and pH (3.0–10.0) on COD and instantaneous current efficiency (ICE), was studied using the BDD electrode. The degradation efficiency of IMD increased by increasing current density and temperature, but noticeably decreased by the increase of initial pH value and initial concentration of IMD. The COD decay follows a pseudo-first-order kinetic, and the process was under mass transport control. COD removal reaches 90% when using an apparent current density of 100 mA cm^?2, initial COD of 953 mg L^?1, pH of 3.0 and at 25 °C after 4.5 h electrolysis time. Compared with Ta/PbO₂, BDD anode has shown better performance and rapidity in the COD removal using the same electrolysis device.     

Adsorption Studies of Methylene Blue and Malachite Green From Aqueous Solutions by Pretreated Lignocellulosic Materials

Lignocellullosic materials have been used as low-cost adsorbents for the removal of methylene blue (MB) and malachite green (MG) dyes from aqueous solutions. The organic compounds in the adsorbents that contribute to chemical oxygen demand (COD) have been removed through pretreatment of the adsorbents. The percentage of color removal and COD reduction of both MB and MG dyes were found relatively close in values. The adsorption process followed the Langmuir isotherm as well as the Freundlich isotherm and pseudo-second order kinetic model. The process was found to be endothermic in nature.     

TiO2-coated glass hollow fiber membranes: preparation and application for photocatalytic methylene blue removal

A glass hollow fiber membrane coated with TiO₂ was successfully synthesized by dip-coating and calcination. In addition, the effects of the calcination temperature, number of coating layers, and treatment method on the photocatalytic removal of methylene blue from wastewater by the membrane were investigated. The results showed that the TiO₂-coated membrane calcined at 550 °C was uniform. It showed good photocatalytic and anti-fouling properties. As compared to the basement membrane, the TiO₂-coated membrane showed significantly improved photocatalytic removal of methylene blue. It showed a methylene blue removal degree as high as 97.2% and could be recycled multiple times by a simple treatment. The methylene blue removal degree of the membrane remained 92.3-93.6% after five recycling operations. Therefore, the membrane prepared via the simple method proposed in this study could be used as an efficient photocatalyst to remove methylene blue from wastewater.     

一种平面Pd(Ⅱ)配合物的合成结构以及光催化性质的研究

配合物[Pd(dmphen)CO3]·H2O(dmphen是2,9-二甲基-1,10-菲咯啉)已合成和表征。钯配合物是采用水热合成法制备的,利用X射线单晶衍射法、元素分析、红外等方法对其进行表征。本文以亚甲基蓝(MB)为探针进行了光催化反应对其进行降解,测评了[Pd(dmphen)CO3]·H2O配合物的光催化降解活性。结果表明,在300 W氙灯光源照射下,该配合物对亚甲基蓝光的催化降解有一定效果,亚甲基蓝(MB)的光催化降解率由时间和Pd配合物的参与共同决定。     

Post-Treatment of Composting Leachate by Ozonation

The post-treatment of composting leachate via an ozonation process in laboratory scale was studied in batch mode. According to the experiments, the COD removal was 47% after 30 min of ozonation via 0.4 g/h ozone (equivalent to 2.8 mg O₃/mg COD removed) at pH 9. In this circumstance, the removal of color and turbidity was also 86% and 89%, respectively. Increasing the ozone mass flow rate higher than 0.4 g/h had no considerable effect on the process variables. However, increasing the reaction time had a significant effect on both the removal of color and on COD of the leachate. Experimental data indicated that complete removal of color and 51% removal of COD were achieved after about 40 min of ozonation via 0.4 g/h ozone (equivalent to 3.3 mg O₃/mg COD removed). The ozone consumption rate increased as the reaction progressed and reached 4.1 mg O₃/mg COD removed after 60 min.