电化学杀菌技术在水处理中的研究进展

电化学杀菌是一种对环境友好的杀菌技术,现对该技术近30 a在杀菌机理和电极材料方面的研究进展进行了总结.电化学杀菌的机理包括活性氯、H2O2、O3、活性中间体、铜或银离子的化学作用以及电场的物理作用;采用的电极材料分别为钛阳极、炭阴极、PbO2阳极等;根据应用对象和目标选择适宜的电极材料,是提高杀菌效果的有效途径;目前电化学杀菌技术存在的主要问题是电流效率较低,阴极结垢以及杀菌剂浓度难以控制等.     

The electrocatalytic hydrogenation of soybean oil

Soybean oil has been hydrogenated electrocatalytically at a moderate temperature, without an external supply of pressurized H₂ gas. In the electrocatalytic reaction scheme, atomic hydrogen is produced on an active Raney nickel powder cathode surface by the electrochemical reduction of water molecules from the electrolytic solution. Adsorbed hydrogen then reacts with an oil’s triglycerides to form a hydrogenated product. Experiments were carried out at 70°C with a flow-through electrochemical reactor operating in a batch recycle mode. The reaction medium was a two-phase mixture of soybean oil in a water/t-butanol solvent containing tetraethylammoniump-toluenesulfonate as the supporting electrolyte. In all experiments the reaction was allowed to continue for sufficient time to synthesize a brush hydrogenation product. The effects of oil content, applied current, solvent composition, and supporting electrolyte concentration on the efficiency of hydrogen addition to the oil and on the chemical properties of the hydrogenated oil product were determined. The electrohydrogenated oil is characterized by a high stearic acid content and a low percentage of totaltrans isomers, as compared to that produced in a traditional hydrogenation process.     

Characterization of an electrochemical reactor for the ozone production in electrolyte-free water

The filter-press electrochemical ozonizer is characterized as a function of the applied electric current, temperature, and linear velocity of the electrolyte-free water. Lead dioxide electroformed on surface of a non-platinized fine mesh stainless steel support was used as anode. Electrolysis of the electrolyte-free water was carried out using the membrane electrode assembly (MEA) adequately compressed by means of a specially designed clamping system. Electrochemical characterization studies were carried out galvanostatically as a function of temperature and linear velocity of the circulating water. It was verified that the electrochemical ozone production (EOP) taking place at the reacting zones formed at the solid polymer electrolyte (SPE)/mesh electrode interface is not considerably affected by circulating water when the linear velocity inside the distribution channels is higher than 1.20 cm s⁻¹. A current efficiency for the EOP of 13% and a specific electric energy consumption of 70 Wh g⁻¹ were obtained when an electric current of 130 A was applied at 30 °C. The reactor service life test revealed that the MEA using the lead dioxide fine mesh electrode as anode and a fine mesh stainless steel electrode as cathode, pressed against the SPE, is stable for the ozone production.     

RuO2/Ti阳极电化学氧化吸收氨废气

采用溶液吸收结合电化学氧化法处理氨废气。电化学反应器采用尺寸为φ35mm×350mm的管式玻璃反应器,内壁贴附不锈钢网作为阴极,反应器中心轴向设置有φ10mm×350mm的钌钛电极(RuO₂/Ti)棒作为阳极。电极浸没在吸收液中,含氨气体从反应器底部经气体分布器导入反应器。实验结果表明,与溶液吸收相比,溶液吸收结合电化学氧化可以更长时间保持较高的氨气去除率。由于RuO₂/Ti电极产生的有效氯的间接氧化作用,氨气在NaCl溶液比在Na₂SO₄溶液中的去除率更高。以NaCl为电解液时,酸性条件下更有利于氨气的吸收和降解,并且氨气的去除率随着电流密度的增加而增加。产物分析发现氨气在NaCl和Na₂SO₄溶液中被电化学氧化后,主要产物为氮气,也有少量氨转化为硝酸根离子。     

Electrochemical waste water treatment using high overvoltage anodes Part II: Anode performance and applications

The performance of highly doped SnO₂ anodes for the oxidative treatment of biologically refractory waste water was compared with PbO₂ and Pt. The oxidation of a wide range of organic compounds proceeds with an efficiency which is about 5 times higher than with platinum anodes. The oxidation efficiency was found to be independent of the pH of the water. In chloride containing media, SnO₂ anodes produce less chlorine gas than platinum anodes and hence show less potential to form hazardous chlorinated organic by-products. The design of a simple plate-and-frame reactor with undivided cells for waste water treatment using SnO₂ anodes was based on two experimental findings: (a) no interference of the cathode with the oxidation has been found: (b) the rate of oxidation is not limited by mass transfer, indicating the participation of homogeneous reactions in the overall oxidation. The new anode material reduces the specific energy requirement of electrochemical oxidation of organics in waste water to 30 to 50 kWh kg^–1 of COD removed. This makes the process an interesting alternative to chemical oxidation using oxidants such as ozone and hydrogen peroxide, or wet oxidation using oxygen at elevated temperature and pressure.     

Oilfield produced water treatment in internal-loop airlift reactor using electrocoagulation/flotation technique

Oilfield produced water is large quantities of salty water trapped in underground formations and subsisted under high temperatures and pressures that are brought to the surface along with oil during production. Produced water(PW) contains a lot of pollutants such as hydrocarbons and metals, this water must be treated before disposal. Therefore, different techniques are being used to treat produced water. Electrocoagulation is an efficient treatment technique involving the dissolution of anodes and formation of electro-coagulants, while the simultaneous generation of H_2 bubbles at the cathode leads to the pollutant removal by flotation. Electrocoagulation(EC)method is one of the most promising and widely used processes to treat oilfield produced water. In the present work, a conventional internal-loop(draught tube) airlift reactor was utilized as electrocoagulation/flotation cell for PW treatment by inserting two aluminum electrodes in the riser section of the airlift reactor. The EC airlift reactor was operated in a batch mode for the liquid phase. Different experimental parameters were studied on the oil and turbidity removal efficiencies such as current density, initial pH, electrocoagulation time, and air injection.The experimental results showed that mixing of the oil droplets in the PW was accomplished using only the liquid recirculation resulted by H_2 microbubbles generated by EC process which enhanced the oil removal. The experimental results further showed that the EC time required achieving ≥ 90% oil removal efficiency decreases from 46 to 15 min when operating current density increases from 6.8 to 45.5 mA·cm~(-2). This reactor type was found to be highly efficient and less energy consuming compared to conventional existing electrochemical cells which used mechanical agitation.     

Prediction and measurement of multi-metal electrodeposition rates and efficiencies in aqueous acidic chloride media

A novel process is being developed for metal recovery from waste electrical and electronic equipment (WEEE) and involving a leach reactor coupled to an electrochemical reactor. Metals such as Ag, Au, Cu, Pb, Pd, Sn, etc. are dissolved from shredded WEEE in an acidic aqueous chloride electrolyte by oxidizing them with aqueous dissolved chlorine species. In the electrochemical reactor: (i) chlorine is generated at the anode for use as the oxidant in the leach reactor, and, simultaneously, (ii) at the cathode, the dissolved metals are electrodeposited from the leach solution. The Butler-Volmer equation was used to provide predictions of the electrode potential dependences of partial current densities, and hence total current densities, current efficiencies and alloy compositions, for acidic aqueous chloride electrolytes containing Ag(I), Au(III), Cu(II), Fe(III), Pb(II), Pd(IV) and Sn(IV) species, together with dissolved chlorine. With judicious choice of kinetic parameters, the predicted total current density—electrode potential behaviour of such solutions was in good agreement with experimental data for a rotating Pt disc electrode. Reduction of dissolved chlorine at a Pt rotating disc electrode exhibited mass transport controlled behaviour, in agreement with Levich's equation over the potential range 0.3-0.9 V (SHE). This could form the basis of a linear sensor, possibly using a microelectrode for measurement and control of the dissolved chlorine concentration in the efflux of leach reactors and inlet to cathodes of the electrowinning reactors, in the envisaged process.     

Performance of an activated carbon adsorber in a water reclamation system with an electrolysis reactor

In this study, an activated carbon adsorber was designed to remove chlorine that was generated from an electrolytic reactor in a water reclamation system. Among three commercial granular activated carbons, an appropriate one, which has relatively high surface area with small headloss, was chosen to fill up the adsorber. The chlorine removal efficiencies of the adsorber were found to be 93.3% in total and 73.6% in free chlorine, showing its great effect on chlorine removal. In particular, since total chlorine was removed more than free chlorine, one would expect that as the residence time gets shorter, the chlorine removal efficiency will increase. Thus the results will be useful for continuous experiments to determine the chlorine removal efficiency in the membrane separator for the effluent from the adsorber. Beside chlorine removal, the organic matters can be additionally removed through the adsorber by 13.3% in COD_Mn whereas the removal efficiencies of T-N and T-P by the adsorber were found to be similar to those by the electrolytic reactor.     

Application of an experimental design method to study the performance of electrochlorination cells

A study of the effects of some parameters on the active chlorine production from aqueous sodium chloride solutions in the hypochlorite electrochemical production cells was undertaken. These varying parameters included the anodic surface area (S_a), the ratio of anodic and cathodic surface areas () the inter-electrode gap, and the type of the cathode used. In addition, a study of the performance of some electrochemical cells that differ in the type of anodes (platinum-coated titanium, ruthenium-coated titanium, and graphite) was made. By means of the experimental design method employing a full factorial of2² the effects ofthe most influencing parameters, the set-up of optimum conditions, and the formation of optimal concentration of active chlorine were assessed. Under the following conditions, a concentration of as high as 65.67 g/L of active chlorine was gained: ruthenium-coated titanium anode (S_a = 24 cm²); titanium cathode, ; inter-electrode gap, 0.5 cm; current density, 35 A/dm² ; temperature, 20°C; concentration of NaCl aqueous solution, 3 M; time, 2 h.     

电化学法处理水时常见离子对产生活性氯的影响

研究了电化学法处理水时常见离子对产生活性氯的影响。结果表明,水中有多种离子会对活性氯的产生有较大的影响,其中最主要的是NO2等还原性物质。     

电解法制备活性氯的研究

以石墨为阴极和 Ir Ru Ti贵金属氧化物电极为阳极 ,采用离子隔膜电解装置 ,直接电解低浓度的氯化钠溶液制备活性氯。对氯化钠浓度、表观电流密度、温度、p H值、电解时间和流速在电化学反应过程中对活性氯浓度及电流效率的影响进行了研究。由实验结果得出最佳的试验条件为 :电解温度 2 2°C,电解液浓度 2 0 .0 g/ L,电流密度 4.46m A/ cm2 ,时间 2 h,流速 1 .40 m/ s,p H值 4.2 0～ 5.0 0。另外 ,利用活性氯分别对生活污水和河水进行杀菌消毒 ,测定了杀菌消毒后的生活污水和河水中的 COD值、细菌和大肠杆菌。由于活性氯具有很强的杀菌消毒功能 ,此方法在水处理中将会得到广泛应用     

Electrochemical removal of dissolved oxygen from water

A new electrochemical method of oxygen removal has been developed in which oxygen-rich water flows through the three-dimensional cathode of an electrochemical cell. The cathode removes the dissolved oxygen from the water and the anode releases it as gas into the air. By this technique oxygen levels lower than 3 µmg oxygen per kilogram of water can be reached (starting level: oxygen-saturated water, 8000 µg kg^–1). This result is better than that obtained by physical methods and is equal to those obtained by chemical methods. Compared with conventional methods, the advantages of the electrochemical method are high effIciency, low energy consumption and avoidance of the use of toxic deoxygenation chemicals.     

Gas–liquid–solid reaction system for CO2 electroreduction to formate without using supporting electrolyte

The use of bismuth-based catalysts is promising for formate production by the electroreduction of CO₂ captured from waste streams. However, compared to the extensive research on catalysts, only a few studies have focused on electrochemical reactor performance. Hence, this work studied a continuous-mode gas–liquid–solid reaction system for investigating CO₂ electroreduction to formate using Bi-catalyst-coated membrane electrodes as cathodes. The experimental setup was designed to analyze products obtained in both liquid and gas phases. The influence of relevant variables (e.g., temperature and input water flow) was analyzed, with the thickness of the liquid film formed over the cathode surface being a key parameter affecting system performance. Promising results, including a high formate concentration of 34 g/L with faradaic efficiency for formate of 72%, were achieved.     

Comparative study of chemical and electrochemical Fenton treatment of organic pollutants in wastewater

The technological and economic aspects of using the Fenton process to treat industrial wastewater containing morpholyne and diethylethanolamine, as well as sodium salts of naphthalene sulfonic acid and of ethylenediaminetetraacetic acid based on data obtained in pilot tests are discussed. Chemical Fenton technology was tested using commercial 30–35% solutions of H₂O₂ and iron (II) salts, which was followed by the additional electrochemical destruction of organic pollutants in an undivided reactor with catalytic stable anodes (CSA) and 1 g L⁻¹ NaCl as a supporting electrolyte and a source of active chlorine. An alternative electrochemical method involving the electrogeneration of hydrogen peroxide in polluted water at the gas -diffusion cathode was studied both with the addition of ferrous salt to the electrolyte prior to electrolysis (in-cell electro-Fenton) as well as with the post-electrolysis addition of Fe²⁺ in another reactor (ex-cell electro-Fenton). The accumulation of hydrogen peroxide in concentrations sufficient for the mineralization of organic pollutants was achieved in both cases with near 100% current efficiency. In comparison with wastewater treatment processes which use a purchased hydrogen peroxide reagent, the Fenton-like processes achieved an economic savings of as much as 64.5% in running costs due to the on-site electrochemical generation of H₂O₂. Preparative electrolysis in the membrane reactor showed higher current efficiencies and lower specific energy consumptions for H₂O₂ electrogeneration in comparison with the results of tests carried out in an undivided cell.     

微流控反应器中苯酚在Ti/SnO2-Sb2O5电极上的阳极氧化分析

目前在电化学氧化处理法降解苯酚废水的研究过程中,研究者多将重心放在活性电极的探索及制备上,而对于反应器的开发鲜有报道。就这一问题,本文研究了新型微流控反应器中苯酚的电化学降解效果。电化学氧化实验在装有Ti/SnO₂-Sb₂O₅阳极的微型流通池中操作进行,实验对循环体系的体积流率Φ_V、电极间距h的影响进行了考察。结果表明,当流通电解槽中的阴阳极间距采用微米级尺寸时,苯酚的阳极氧化反应取得了较快的氧化速度。在 em= 20 mA/cm²、Φ_V= 0.54 mL/min的电解条件下,电解2~3h苯酚去除率即可达到90%以上,相同流速下电极间距h越小降解速率越快。且由数据回归得到了苯酚的一系列随h的减小而增大的准一级反应的反应速率常数。这一结论表明微流控电解槽内的苯酚降解过程主要传质控制过程。     

Electrochemical water disinfection. Part II: Hypochlorite production from potable water, chlorine consumption and the problem of calcareous deposits

The electrolytic production of hypochlorite from tap water in a flow-through reactor system is investigated using stacked platinum or iridium oxide coated titanium sheet or expanded metal electrodes. The influence of fast chlorine consumption and polarity reversal on the hypochlorite production rate was determined along with the dependence of the hypochlorite production rate on temperature, flow through velocity and current density. It was found that in most cases, the hypochlorite production rate was higher on iridium oxide compared to platinum electrodes. An increase in the flow-through velocity leads to an increased hypochlorite production rate while the hypochlorite production rate falls with increasing temperature.     

LCA tool for the environmental evaluation of potable water production

Environmental impact assessment will soon become a compulsory phase in future potable water production projects, especially when alternative treatment processes such as desalination are considered. An impact assessment tool is therefore developed for the environmental evaluation of potable water production. The evaluation method used is the life cycle assessment (LCA) method. The quick and easy assessment of energetic and environmental performances contributes to determine the weak points of potable water production processes or the best suited treatment in a specific context. Studies of some potable water supply scenarios (groundwater treatment, ultrafiltration, nanofiltration, seawater reverse osmosis and thermal distillation associated to water transfer) are presented in order to illustrate the environmental information drawn from this tool. The main source of impacts is shown to be electricity production for plant operation. Improvement levers are presented for impact reduction and for the objective comparison between alternative and conventional water treatment processes.     

含氯漂白废水的电氧化处理

以二氧化铅为阳极,不锈钢网为阴极,用电化学氧化法处理多段漂白废水中的有害物质。其中二氧化铅电极是通过在碳棒上电镀而成的。研究发现,废水的电导率和pH值对于不同的废水在电化学氧化过程中的变化是不同的;而废水的COD和色度在整个过程中一直减少;氯化木质素的分子量和分子量分布发生了变化。     

A new type of organic electrosynthesis reactor with a two-phase gas-electrolyte stream flowing through a mercury cathode,II. Limiting currents and mass-transfer studies in organotin electrosynthesis

A new electrochemical reactor involving a mercury cathode and a two-phase (gas-liquid) flow has been studied with a view to continuously manufacturing hexaphenyl and hexabutyldistannane b'y reduction of triorganotin chloride R₃SnCl. In each case the interpretation of the determining step of the process is discussed after a study of the electrochemical kinetics. In the reactor an efficient renewal of the cathodic surface is obtained by passing the electrolysis solution together with nitrogen gas through the mercury pool. Results of mass transfer rate studies with the cell working either as a plug-flow reactor or as a continuously stirred reactor are compared for different gas and electrolyte flows. The experiments show that gas and electrolyte flows through a mercury pool offer attractive possibilities of application for large-scale preparative electrolysis, by solving simultaneously the problems of mass transport and electrode surface renewal.     

Biocides electrogeneration for a zero-reagent on board disinfection of ballast water

The feasibility of a quick electrochemical process for on board zero-reagent treatment of ballast water by anodic and cathodic production of oxidants was proposed. The process has been tested in the inactivation of the marine dinoflagellates Alexandrium minutum and A. taylori, both responsible for algal blooms and toxin-producing, and against the marine bacterium Pseudomonas aeruginosa, a Gram-negative pathogenic micro-organism. A complete inactivation of both dinoflagellates was quickly achieved with electro-generated active chlorine, while higher resistance to oxidising agents was verified for P. aeruginosa. A combined sequential treatment involving anodic oxidation followed by extended exposure time in the absence of current, and a final cathodic treatment was proposed. The cathodically electro-generated hydrogen peroxide contributed to the reduction of treatment time and the removal of residual species.