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Current research from around the world to the industrial wastewater treatment, including electrochemical equipment cover an area of an area small, flexible operation, the amount is small, can not only deal with inorganic pollutants, can deal with organic pollutants, even some can't biodegradation of toxic organic compounds and some wastewater containing heavy metal can be processed with this method,Plus emerging power generation such as wind, nuclear power technology developing and application of electricity cost reduction, makes the electrochemical method has more advantages in terms of governance wastewater.
Application of classification
Electrochemical treatment includes electrochemical REDOX, electrocoagulation, electric floating, photoelectrochemical oxidation, electrolysis and other methods.Electrochemical application including removal of heavy metals in wastewater treatment and recycling, biological refractory organic wastewater and drinking water sterilization and the combination with other methods.
The basic principle of
1. The electrochemical REDOX process
Electrochemical oxidation-reduction method refers to the electrolyte solution in the current, under the action of reactant particles in the anode and electrolyte solution interface lose electron oxidation reaction, occur on the cathode and the electrolyte solution interface reactant particles and electronic combination of the reduction reaction of electrochemical process.Principle of electrochemical oxidation is divided into two categories: one is direct oxidation, which pollutants directly in the anode oxidizing, lose electrons and the containing cyanide, phenol, alcohol, wastewater treatment containing organic nitrogen, direct electrochemical oxidation has played a very effective role;Another is indirect oxidation, namely by anodic oxidation reaction is strong in the middle of the product or outside in the middle of the anodic reaction reaction to oxidation contaminant, ultimately achieve the goal of oxidation degradation of pollutants.This method covers an area of less, easy to operate;But the efficiency is low, factors that affect more than (pH, electrolyte and electrode materials, etc.).
2. The electrocoagulation method
In electrolytic process, using aluminum or iron after passing a dc soluble anode, occur during the process of electrolysis anode materials dissolve, formation of the metal cation Fe3 + and Al3 + and the solution of OH - Fe (OH) 3 and Al (OH) 3 with flocculation of colloid material such as, can make the colloidal impurities in the water flocculation precipitation, so as to realize the removal of pollutants.
3. Electric float
Through the electrode reaction of wastewater by electrolysis, hydrogen and oxygen precipitation on the cathode and anode, respectively, to produce small diameter (about 20 to 100 microns) a high degree of dispersion of bubbles, the micro air bubble adhesion on the flocs formed in the colloid or already, as the bubbles rise, the flocculant colloidal or rose to the surface of the water to form foam layer.With a mechanical method to remove, so as to achieve the purpose of the separation of pollutants.Can be adjusted by electric current, electrode materials, pH value and temperature change gas production rate and bubble size, meet different needs.Electric float has broad application prospects in treatment of papermaking wastewater.It can make the decolorization rate was 94%, of papermaking wastewater removal was 98%, and the removal of 75%.In addition, electric floating oil still can make the water removal rate reaches 95%, the emulsified oil removal rate was 92%, and the average removal rate of different concentration is 91.2%.
4. The photoelectric chemical oxidation method
Semiconductor materials after the absorption of energy in the visible light or ultraviolet light can be used as a catalyst, to make waste water photocatalytic reaction so as to achieve the aim of removing harmful substances.The commonly used semiconductor materials such as TiO2 and SiO2.Experimental research shows that the photocatalytic oxidation of carbon tetrachloride, 4 - chlorophenol, benzodiazepines, p - amino acid, benzene and other organic matter and CN -, S2 -, I -, Br -, Fe2 +, Cl - has good removal effect.
5.The electrolytic process
Inner electrolysis method is the use of the characteristics of some components susceptible to oxidation reduction in wastewater, when these different attributes components meet with conductive medium in a wastewater treatment method for electrochemical reaction.Inner electrolysis method treatment of dye wastewater is flocculation, adsorption, Bridges, sweep volume, electrodeposition, electrochemical reduction, and other work together, the result of comprehensive effect.Within the industry commonly used iron electrolysis method, its principle is the use of scrap iron in the iron and carbon (or join inert electrode) constitute a tiny battery of the positive and negative, by filling the waste water as the electrolyte solution, REDOX reaction, and form a galvanic cell.New ecological electrode activity product is extremely high, with organic pollutants in the wastewater to REDOX reaction, make its structure form change, so as to realize the wastewater treatment.
In electrolytic process is waste treat waste, the advantages of less energy consumption, can remove various pollution composition;Defect is reaction speed is slow, the high concentration wastewater treatment more difficult.
The influencing factors of electrochemical treatment effect of wastewater
1. The electrode materials
The electrochemical reaction takes place on the electrode surface with the moving of the charge heterogeneous catalytic reaction.As a result, the charge rate determine the reaction rate, and the movement of the charge rate is determined by the electrode potential.
The electrode substrate material decided electrode potential.In different possibilities and rate of reaction on the electrode materials of each are not identical.Although different electrode type, but they have a common requirement, namely, good electrical conductivity and corrosion resistance.Use Sb2O3 cover Ti/SnO2 electrode is a kind of good performance and is suitable for treatment of organic industrial wastewater of the electrode.
2. The residence time
Residence time of electrochemical technology in wastewater treatment is one of the main influence factors, the longer the residence time, oxidation reduction effect, the more thoroughly.But energy consumption increased residence time increases, so the time is not as long as possible.And for different wastewater, because its composition is different, time to do the specific adjustment.For example, low initial pH value of wastewater, residence time can be relatively shorter;On the contrary, stay time should be relatively longer.
3. The electrolyte solution
Electrochemical process wastewater has certain requirements, concentration of electrolyte solution because the concentration of the electrolyte solution has great effect on the rate of catalytic degradation of organic matter, mainly manifested in two aspects: (1) the electrolysis, in general, with the increase of concentration of electrolyte solution, the degradation rate increased;But with increasing of electrolyte solution inventory and the cost.(2) different electrolytes will occur in the process of electrolytic electrochemical reaction.For example, the presence of Cl -, electrolytic process will produce Cl2, ClO -, SO42 - and CO32 -, is at the anode oxidation for sulfate and carbonate, so as to increase the ability to the oxidation of organic matter degradation.So should be based on specific reaction to determine the optimal conditions to improve the reaction rate, reduce the cost.
With the continuous development of chemical industry, more and more kinds of industrial waste water of synthetic organic compounds, and these organisms are often difficult to degradation and electrochemical process at this time is a better choice treatment of industrial wastewater.Even so, in the field of electrochemical treatment of wastewater and many problems need us to explore:
(1).Due to the inadequate for the electrochemical reaction mechanism research, greatly limits the application of electrochemical technology in industrial wastewater treatment.Therefore, further study of the electrochemical reaction mechanism is very necessary and important.
(2).With the performance of electrode materials can't meet the technological requirements, electrochemical process wastewater treatment efficiency is still low.So the production efficiency of composite electrode is a key to the popularization and application of the electrochemical process.
(3).In order to fast safely handle a growing number of industrial waste water, designing and manufacturing large and efficient chemical reactor is also facing a pressing task.
(4).Promoting electrochemical method, and the research and development of electrochemical method and biological method and other joint technology will be the future development direction in the field of industrial wastewater treatment.