掺硼金刚石薄膜电极电化学氧化垃圾渗滤液实验研究

采用电化学氧化法去除垃圾渗滤液中的COD和NH3-N,阳极为掺硼金刚石(BDD)薄膜电极,阴极为AISI201不锈钢,考察了对垃圾渗滤液中COD、NH3-N去除率和能耗的影响因素。结果表明,电流密度、稀释比是影响电化学氧化过程的主要因素,初始pH和极板间距对污染物去除率的影响较小。在稀释体积比1:2,电流密度75mA/cm2,不调节pH,极板间距为10 mm的最优工况条件时,COD、NH3-N的质量浓度变化分别满足线性方程COD/(mg·L-1)=1 675-3.1t/min和ρ(NH3-N)/(mg·L-1)=1 296-2.5t/min,对应线性相关系数分别为0.992、0.996。电化学氧化9 h后,COD、NH3-N去除率分别为99.13%、99.95%,能耗为88.61 kWh/m3。     

废水中难降解污染物电化学处理技术研究进展

介绍了电化学氧化法、电絮凝法、电沉积法、电浮法与微电解法等五种常见的电化学污染物处理方法及其在废水处理中的研究进展,分析了电化学技术在废水处理过程中存在的一些问题,探讨了电化学技术反应机理研究、电极材料研发、新型反应器研发以及联用技术研发等未来潜在的研究方向。     

环境污染物的电化学处理技术

对电化学技术在环境污染物治理中的应用进行了综述，分析了应用中可能存在的问题，提出了相应的对策。     

掺硼金刚石电极电化学再生粉末活性炭

使用200目粉末活性炭吸附苯酚模拟废水至饱和,用BDD电极作为阳极再生饱和炭,以再生效率为评价指标,研究不同因素对活性炭再生效果的影响。在电解质为0.05 mol/L的Na_2SO_4溶液,pH为7,电流密度为50 mA/cm²,再生时间为2 h条件下,活性炭再生率达74.8%。同时不同电解质对再生效果也有不同影响,硫酸钠优于氯化钠,再生效率随着pH的增加而增加。采用正交实验方法对影响再生效果的各因素进行评价,其影响的主次顺序是:电解质浓度、pH、电解时间。     

掺硼金刚石电极电化学再生粉末活性炭

使用200目粉末活性炭吸附苯酚模拟废水至饱和,用BDD电极作为阳极再生饱和炭,以再生效率为评价指标,研究不同因素对活性炭再生效果的影响。在电解质为0.05 mol/L的Na_2SO_4溶液,pH为7,电流密度为50 mA/cm~2,再生时间为2 h条件下,活性炭再生率达74.8%。同时不同电解质对再生效果也有不同影响,硫酸钠优于氯化钠,再生效率随着pH的增加而增加。采用正交实验方法对影响再生效果的各因素进行评价,其影响的主次顺序是:电解质浓度、pH、电解时间。     

电化学氧化有机污染物的研究进展

近年来,电化学氧化广泛用于降解对水生物种和人类构成严重威胁的难降解、有毒有机污染物。本文综述了最新电化学氧化的研究现状。首先,介绍了金属氧化物和碳基电极催化剂以及它们的氧化机理;其次,介绍了传统水处理技术(膜技术、生物法、芬顿氧化、光催化等)与电化学氧化耦合的最新进展;第三,提出了未来电化学氧化的潜在方向,包括催化剂设计、实验优化、科学探索和有效耦合技术。     

电化学氧化处理废水中有机污染物技术进展

评述了近年来废水中有机污染物电化学氧化处理技术在反应器结构、供电方式和电极材料方面的进展，指出了今后这一领域的发展方向     

液相沉积类金刚石膜的沉积机理研究

根据电化学的相关理论,提出了钛合金表面液相沉积DLC膜的反应机理,给出了可能电极过程,认为膜是通过甲基阳离子的亲电取代反应而不断生长。讨论了氢原子对金刚石结构的稳定作用,并解释了实验条件对膜结构和性能的影响。     

Pb~(2+)在掺硼金刚石膜电极上的电化学行为

为了充分发挥掺硼金刚石膜(BDD)电极在分析检测工业废水中重金属离子的优势,利用BDD电极作为工作电极,采用线性扫描阳极溶出伏安法测定水溶液中的铅离子,考察了硝酸、硫酸、高氯酸、盐酸4种酸体系对铅离子分析测试的影响。结果发现,在实验室条件下检测铅离子最优的支持电解质体系是硫酸,并且与其他3种酸(硝酸、盐酸、高氯酸)相比,硫酸更加稳定,不具挥发性。     

电化学氧化技术去除废水中的持久性有机污染物

水体中存在的微量持久性有机污染物对人类及生物的正常生命活动构成了严重威胁,有效去除这些污染物已成为当务之急。一般的水处理技术很难奏效,随着新型掺杂半导体复合电极不断开发成功,通过电化学氧化技术有望在常温、常压下将之转化为无害的CO2与H2O等物质,并不对环境造成二次污染。本文对国内外电化学氧化技术在处理水体中持久性有机污染物方面的研究进行了阐述,介绍了电化学氧化原理及影响因素,对采用不同电极氧化持久性有机污染物效果进行了论述。     

硼掺杂金刚石膜电极电催化降解环己酮废水

采用循环伏安法、稳态极化法等对硼掺杂金刚石薄膜电极的电化学性能及电氧化降解含环己酮模拟废水的电极过程进行了研究,考察了电流密度、支持电解质浓度、起始环己酮浓度和pH值等因素对硼掺杂金刚石薄膜电极电氧化降解含环己酮模拟废水效果的影响。实验结果表明,硼掺杂金刚石薄膜电极能够对环己酮进行有效且稳定的降解,通过正交优化实验,得到较优工艺条件为阳极电流密度为5 mA·cm^-2,pH值为7,Na₂SO₄浓度为10 g·L^-1,起始环己酮浓度为20 mmol·L^-1,在该条件下COD去除率达92.95%,电流效率达80.81%,降解效果显著。     

Electrochemical oxidation of water on synthetic boron-doped diamond thin film anodes

Electrolysis in aqueous 1 M HClO₄ and 1 M H₂SO₄ solutions has been carried out under galvanostatic conditions using boron-doped diamond electrodes (BDD). Analyses of the oxidation products have shown that in 1 M HClO₄ the main reaction is oxygen evolution, while in H₂SO₄ the main reaction is the formation of H₂S₂O₈. In both electrolytes small amounts of O₃ and H₂O₂ are formed. Finally, a simplified mechanism involving hydroxyl radicals formed by water discharge has been proposed for water oxidation on boron-doped diamond anodes.     

Electrochemical incineration of chloromethylphenoxy herbicides in acid medium by anodic oxidation with boron-doped diamond electrode

The electrochemical degradation of saturated solutions of herbicides 4-chloro-2-methylphenoxyacetic acid, 2-(4-chlorophenoxy)-2-methylpropionic acid and 2-(4-chloro-2-methylphenoxy)propionic acid in 1 M HClO₄ on a boron-doped diamond (BDD) thin film anode has been studied by chronoamperometry, cyclic voltammetry and bulk electrolysis. At low anodic potentials polymeric products are formed causing the fouling and deactivation of BDD. This is reactivated at high potentials when water decomposes producing hydroxyl radical as strong oxidant of organics. Electrolyses in a batch recirculation system at constant current density ≥8 mA cm⁻² yielded overall decontamination of all saturated solution. The effect of current density and herbicide concentration on the degradation rate of each compound, the specific charge required for its total mineralization and instantaneous current efficiency have been investigated. Experimental results have been compared with those predicted by a theoretical model based on a fast anodic oxidation of initial herbicides, showing that at 30 mA cm⁻² their degradation processes are completely controlled by mass transfer. Kinetic analysis of the change of herbicide concentration with time during electrolysis, determined by high-performance liquid chromatography, revealed that all compounds follow a pseudo first-order reaction. Aromatic intermediates and generated carboxylic acids have been identified using this technique and a general pathway for the electrochemical incineration of all herbicides on BDD is proposed.     

掺硼金刚石阳极电催化降解新兴抗生素类污染物研究进展

抗生素类药物是目前水环境中出现的一类新兴有机污染物,具有难自然降解、环境刺激性、生物毒性及耐药性等特点,高效去除抗生素类污染物是近年来环境工作者重点探讨的内容。掺硼金刚石（boron-doped diamond,BDD）电极由于自身优异的物理和化学性质,被认作为目前电催化氧化水中有机污染物最为理想高效的阳极材料,但关于BDD阳极在新兴抗生素类污染物的研究情况尚未进行及时的总结。本文首先论述了BDD阳极在电催化氧化有机污染物的降解过程和基于强氧化性物种的电催化氧化机理,进而分析了BDD阳极在电催化降解水中新兴抗生素类污染物的研究进展,探讨了影响抗生素类污染物电催化降解过程的关键影响因素,总结了BDD阳极材料的开发情况,同时,总结了以BDD阳极电催化氧化为基础发展而来的其他水处理联合方法,最后,进一步展望了BDD阳极在未来电催化降解抗生素类污染物存在的问题及未来的重点发展方向。     

Electrochemical oxidation of aniline at boron-doped diamond electrodes

The electrochemical oxidation of aniline at boron-doped diamond (BDD) electrodes was investigated by cyclic voltammetry, steady-state polarization measurements and bulk electrolysis under potentiostatic control. It was found that acidic media is suitable for efficient electrochemical oxidation of aniline, because at low pH, the potential required for avoiding electrode fouling is lower than in neutral and alkaline media. The results of the longtime polarization measurements suggested that more anodic potentials ensure slightly higher efficiency for the conversion of aniline to CO₂, while the direct oxidation process does not play a prominent part in the overall electrochemical incineration of aniline. The current efficiencies (44%) and the efficiency of aniline conversion to CO₂ (80%) favourably compare with those reported for other electrochemical methods for aniline destruction. The results demonstrate the possibility of using BDD as an electrode material for electrochemical wastewater treatment, mainly when very high anodic potentials are required.     

Electrochemical oxidation of 1,4‐dioxane at boron‐doped diamond electrode

BACKGROUND: The electrochemical oxidation of 1,4‐dioxane at a boron doped diamond (BDD) surface on a niobium substrate anode was studied because (i) 1,4 dioxane is a resistant contaminant in waste‐waters and ground‐waters which needs to be removed/oxidized and (ii) most of the currently applied techniques for removal/oxidation require chemicals. RESULTS: Results show that in the potential region supporting electrolyte stability 1,4‐dioxane can be oxidized directly. Adhesive products, which cause electrode fouling, are also formed during oxidation in this potential region. The BDD anode can be restored to its initial activity by simple anodic treatment in the potential region of electrolyte decomposition. In this region, oxidation reactions leading to complete oxidation of 1,4‐dioxane, can take place due to electro‐generated hydroxyl radicals. Therefore, dioxane can only be effectively oxidized at these potentials. The effect of current density on the oxidation of 1,4‐dioxane has been investigated. The experimental results have also been compared with a theoretical chemical oxygen demand (COD)–instantaneous current efficiency (ICE) model. At a current density above 32 mA cm^?2, the oxidation process is completely controlled by mass transfer and no intermediates are formed. 92% of the COD can be removed with a total consumption of 7 Ah L^?1. CONCLUSIONS: Results show that dioxane can be effectively and completely oxidized at a BDD anode. Copyright © 2010 Society of Chemical Industry     

Electrochemical oxidation of phenol at boron-doped diamond electrode in pulse current mode

In this study, a pulse current supply was initially used in a BDD anode system (pulse-BDD anode system) for electrochemical oxidation of phenol. The influences of operative parameters (current density, retention time, pulse duty cycle, power frequency) on the system performances were exmamined by response surface methodology (RSM). As for COD degradation efficiency (D_COD) and specific energy consumption (E_s), the influence of retention time was more important than current density and pulse duty cycle, while power frequency hardly presented significant influence. By the comparison with constant current mode, an obvious specific energy consumption reduction was achieved in the pulse-BDD anode system, though the D_COD was slightly lower. The significant E_s decrease might be attributed to the reduction of side reactions and concentration polarization in pulse current mode. The pulse-BDD anode system demonstrated an efficient technology to simultaneously obtain high pollutant degradation efficiency and low energy consumption.     

Electrochemical treatment of Remazol Brilliant Blue on a boron-doped diamond electrode

A detailed study on the electrochemical oxidation of aqueous solutions of Remazol Brilliant Blue Reactive on a boron-doped diamond electrode is presented. Electrolyses, conducted under galvanostatic conditions, were monitored evaluating the removal of colour, chemical oxygen demand and total organic carbon.The influence of the supporting electrolyte, current density, initial dye concentration, temperature and pH is discussed.Colour removal was found to be dependent mostly on the chloride concentration suggesting the involvement of electrogenerated active chlorine in the reaction of discolouration. Rate constants calculated from colour decay versus time revealed a zero order reaction up to 150 mg L⁻¹ in dye.The degradation efficiency was directly related to the dye concentration thus indicating that oxidation and mineralisation occurred under mass transfer control.Using 0.01 M chloride, under mild operating conditions of pH, temperature and current density, the treatment proposed enabled to achieve complete discolouration and total mineralisation of Remazol Brilliant Blue solution in a range from 50 to 150 mg L⁻¹.     

Electrochemical incineration of dyes using a boron‐doped diamond anode

The electrochemical oxidation of a synthetic wastewater containing the model dyes alizarin red (an anthraquinone) and Eriochrome black T (an azoic compound) has been studied on a boron‐doped diamond electrode (BDD) by both cyclic voltammetry and bulk electrolysis. The influence of the current density and dye concentration were investigated. The results obtained show that complete chemical oxygen demand (COD) and colour removal was obtained for both wastewaters. However, the nature of the pollutant, and specially the presence of functional groups (such as the azoic group) seems to strongly influence the performance and efficiency of the electrochemical process. The electro‐oxidation of alizarin red behaves as a mass‐transfer‐controlled process. In such a system, an increase in the current density leads to a decrease in the current efficiency. This can be explained by direct or hydroxyl radical mediated oxidation. The contrary tendency has been observed in Eriochrome black T electro‐oxidation. In this case, higher efficiencies were obtained working at high current densities. This may indicate that the mediated oxidation by electrogenerated reagent (such as peroxodisulphate) is the main oxidation mechanism involved in Eriochrome black T treatment. These compounds have a longer average lifetime than hydroxyl radicals, and it allows the reaction to be extended to the whole wastewater volume. This study has shown the suitability of the electrochemical process for completely removing the COD and total organic carbon and effectively decolourising of wastewaters containing synthetic dyes. Copyright © 2007 Society of Chemical Industry     

Electrochemical destruction of chlorophenoxy herbicides by anodic oxidation and electro-Fenton using a boron-doped diamond electrode

The degradation of herbicides 4-chlorophenoxyacetic acid (4-CPA), 4-chloro-2-methylphenoxyacetic acid (MCPA), 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) in aqueous medium of pH 3.0 has been comparatively studied by anodic oxidation and electro-Fenton using a boron-doped diamond (BDD) anode. All solutions are totally mineralized by electro-Fenton, even at low current, being the process more efficient with 1 mM Fe²⁺ as catalyst. This is due to the production of large amounts of oxidant hydroxyl radical (OH) on the BDD surface by water oxidation and from Fenton’s reaction between added Fe²⁺ and H₂O₂ electrogenerated at the O₂-diffusion cathode. The herbicide solutions are also completely depolluted by anodic oxidation. Although a quicker degradation is found at the first stages of electro-Fenton, similar times are required for achieving overall mineralization in both methods. The decay kinetics of all herbicides always follows a pseudo first-order reaction. Reversed-phase chromatography allows detecting 4-chlorophenol, 4-chloro-o-cresol, 2,4-dichlorophenol and 2,4,5-trichlorophenol as primary aromatic intermediates of 4-CPA, MCPA, 2,4-D and 2,4,5-T, respectively. Dechlorination of these products gives Cl⁻, which is slowly oxidized on BDD. Ion-exclusion chromatography reveals the presence of persistent oxalic acid in electro-Fenton by formation of Fe³⁺-oxalato complexes, which are slowly destroyed by OH adsorbed on BDD. In anodic oxidation, oxalic acid is mineralized practically at the same rate as generated.