电渗析技术进展

电渗析技术进展
学院：轻化与环境工程学院
班级：环科11-2
姓名：张超
学号：201105011079
Progress electrodialysis
Abstract: electrodialysis membrane separation technology are widely used in food, chemical, waste water treatment and other industries of the separation and purification of the production process, high efficiency, clean and economical energy saving. This paper describes the types of electrodialysis technology, focuses on the principle of electrodialysis technology, introduces electrodialysis technology in the food industry as well as applied research in wastewater treatment, and the prospects of its development prospects. Keywords: electrodialysis; film; Application
Electrodialysis is under the effect of external electric field, the use of ion-exchange selective membrane permeability, so that ion migration from one part of water to another part of the physical and chemical processes in water. Electrodialysis, is the use of multi-compartment electrodialysis desalination process to achieve the purpose. Main components electrodialysis membrane, electrodes, clamps or the like by a partition, ion-exchange composition. Ion exchange membranes for ions with different charge through sexual selection. Yang membrane allows only cations, anions stop by, overcast membrane only allows anions, cations stop by. Under the influence of an external DC electric field, ions in water as directed migration.Because electrodialysis is composed by multi-compartment, so light ions migrate to the chamber adjacent to concentrate cells, allowing saline water desalination. In
the food and pharmaceutical industry, electrodialysis can be used to remove organic ions from the electrolyte solution, whey desalination, desalination sugars and amino acids are more refined application was successful [1]. As a new electrodialysis membrane separation technology, in natural water desalination, seawater concentrated salt, waste water treatment, etc. [2] plays an important role, has become a more sophisticated water treatment methods.
1. Type electrodialysis technology
1.1 inverted pole electrodialysis (EDR)
Inverted pole electrodialysis ED principle is based, at regular intervals (typically 15 ~20 min), the positive and negative electrode polarity switching each other, dirt can automatically clean the ion-exchange membrane and the electrode formed on the surface, in order to ensure the efficiency of the ion exchange membrane the long-term stability and the quality and quantity of fresh water.
1.2 Liquid electrodialysis (EDLM)
Electrodialysis film with the same function instead of solid liquid membrane ion exchange membrane [3], the experimental model is to use a semi-permeable cellophane bag made of thin liquid film solution like partitions, and then into electrodialyser run. Liquid extraction agent for use electrodialysis membrane film may find efficient separation method for enrichment and extraction of precious metals, heavy metals, rare metals, etc., because the film looking for some form of special selective ion extraction
efficiency and improve electrodialysis related. Improve the separation efficiency of electrodialysis, combined direct and film it is promising.
1.3 packed bed electrodialysis (EDI)
Packed bed electrodialysis (EDI) is a new treatment method that combines electrodialysis and ion exchange, its biggest feature is the use of water dissociation of H + and OH- generated automatically filled in renewable freshwater compartment electrodialysis mixed bed ion exchange resin, in order to achieve a sustained deep desalination. Which focused on the advantages of electrodialysis and ion exchange method, to improve the limiting current density and current efficiency.
1.4 bipolar membrane electrodialysis (EDMB)
Bipolar ion-exchange membrane is a novel composite membrane, it is generally laminated together by a cation exchange membrane, the water molecules through the membrane instantly decomposed into H + and OH-, may be used as a supply of H + and OH- in. Bipolar membrane electrodialysis prominent advantage is the process simple, high energy efficiency, less waste emissions.
1.5 The Promise water electrodialysis
Promise is a modified form of water electrodialysis electrodialysis tradition, its main feature is the removal of the traditional electrodialysis pole and electrode. E.g., electrode means in one or more layers close to the ion exchange membrane, which are electrically coupled to each other, so that both
can prevent the metal ions into the ion-exchange membrane, while preventing the plate fouling and prolong the service life of the electrode . With the removal of the electrode compartments, stepless water discharge, greatly improving the utilization of raw water [4].
2.The electro-osmosis technology in the food industry
2.1 Application of inulin production
Inulin is a polysaccharide having health functions, system owners by β- (2, 1) fructan molecules glycosidic linkage, also linked at the end of a glucose residue. Its degree of polymerization of from 2-60, spanning classic definition of oligosaccharides, so it was put in a range of inulin oligosaccharides called oligofructose inulin. Inulin is widely distributed in the middle of a variety of plants, of which the largest amount of chicory inulin, Jerusalem artichoke and dahlia containing (about 20% dry basis), with the value of the commercial production of inulin.Yang Lian and other crude inulin using electrodialysis in the purification process applied research carried out in the course of electrodialysis, pH, chrysanthemum sugar solution at a constant decline for some time, the time constant of the operating voltage and electrodialysis negative related decline in the operating voltage of the positive correlation between pH. Ju sugar solution and an ash content of crude protein can be removed by electrodialysis, the greater the operating voltage, the faster the rate of decline of charged impurities, in an initial stage of electrodialysis these charged impurities removed faster.Free amino acids as a result of smaller
molecules more easily removed than short peptides. Inulin at 10V operating voltage conditions, hydrolysis of inulin no obvious single, double sugar content increased only slightly. Ju sugar solution in electrodialysis process continuously diluted, but inulin molecules can not pass through the ion exchange membrane electrodialysis so purified inulin have higher recovery. At a voltage of 10V, the use of flow 10L / h, and after electrodialysis 1h, crude
inulin 70% ash and 47% crude protein is removed, the total loss of
the original sugar only 4%.In short, can be effectively used as a crude inulin electrodialysis desalination and deproteinized and economic means, with the follow-up actions, such as ultrafiltration good convergence, can greatly reduce the pressure downstream purification operation is technically feasible [5].
2.2 Application in the production of bamboo shoots
Along with the traditional bamboo processing to produce a lot of waste Bamboo Shoots, for example, about 30% of edible part, while about 30% bamboo shell, shoot first 40%, in addition, will produce large amounts of waste processed bamboo shoots boiled water[6] .Shoots dope (shoots boiled water) is rich in sterols, polysaccharides, amino acids, vitamins, flavonoids, Dai soap and salt and other natural active ingredients, the presence of these salts on the one hand is not conducive to the classification and purification of amino acids and other ingredients from the stock solution, the impact the nutritional value of bamboo shoots dope [7], on the other hand, if treated on direct emissions will cause soil compaction, plant burns, pollute the water. In addition, bamboo
extract also contains cadmium, lead (<0. 5mg / kg), arsenic (<0. 3mg / L) and other heavy metal ions, directly processed into products in the food field, the body will have a negative impact [8], through desalination can effectively remove heavy metal ions, so as to achieve the standards prescribed by the state.Therefore, bamboo shoots dope desalination research has social and economic benefits, to achieve deep conversion and utilization of bamboo processing waste, and the development of high value-added products, improve enterprise management level economic and industry, upgrading of traditional industries. Michael, etc[9]. On the basis of experiments to explore the feasibility and process optimization shoots dope desalination by ion exchange membrane electrodialysis.After 90m in desalination, shoots dope ash fell 49.10%, the main element contents: potassium decreased 53.76%, 75.27% decrease sodium, calcium decreased 69.80%, 57.86% decrease magnesium, iron decline 66.67%, 76.98% decline in copper, cadmium fell 42.51%[10], while the number of heavy metal ion content is generally low, are within the scope of the national standards, such as mercury and arsenic were not detected, so the electrodialysis of bamboo shoots dope desalination better[11]. Amino acid content before and after the desalting shoots dope flat:Before the amino acid content of 8.22 percent desalination (dry basis), the amino acid content of desalinated 8.37% (dry basis), and according to the amino acid test report to know: before and after shoots dope desalination and various types of amino acids approximately the same percentage of the class, so the electrodialysis
desalination technology shoots dope on which functional components - the smaller the impact of amino acids [12].
2.3 Application in the production of soy sauce
Soy sauce is one of people's daily lives the most popular condiment, usually soy sauce salt content of 16% to 18%,[13] which is due to soy sauce koji is made in an open state, in order to avoid microbial contamination, need high lower salt concentrations, and the unique flavor of soy sauce only at this salt concentration can lead. Modern medicine has shown that high sodium diet easily lead to high blood pressure,[14] kidney disease and other diseases, because of the high salt content of ordinary soy sauce, to meet the demand for low-sodium diet can be an ordinary soy sauce in a low salt removal salt soy sauce [15]. Soy sauce flavor virtually unchanged, soy sauce proved electrodialysis desalination is feasible separation method [16].
3.Electro-osmosis technology in wastewater treatment
3.1 electro-osmosis technology research ammonium nitrate condensate
wastewater treatment[17]
Ammonium nitrate is the basic chemical raw materials and agricultural chemical fertilizer, widely used in agriculture, defense, chemical, pharmaceutical, textile, light industry and other fields. Due to historical reasons, China's traditional ammonium nitrate production facilities are mostly obsolete technology and equipment,[18] backward technology, low level of environmental protection, a large amount of nitrogen-containing industrial
waste in the production process. In particular, since the production process of ammonium nitrate is determined by the dilute nitric acid into the water in the neutralization, evaporation and crystallization process in the form of secondary steam discharge, process condensate formed contains ammonia and ammonium nitrate, ammonium nitrate production has become a major water source.Limited use of 24 units Chuanhuagufen electrodialysis unit has a special dedicated film electrodialysis device consisting of a maximum amount of condensate wastewater treatment for 36 t / h,[19] ammonium nitrate condensing water circulating through electrodialysis device concentrate, after desalination treatment, concentrated ammonium nitrate content in water volume percentage is 20%,[20] more than 96% recovery rate, qualified freshwater discharge water mass fraction of ammonia content! 40mg / L.Not only to achieve the reduction of nitrate wastewater emissions, pollution abatement purposes, but also improve the comprehensive utilization of resources, reduce production costs, and achieved significant environmental and economic benefits [21].
3.2 Research ammonia wastewater treatment electro-osmosis technology
With the rapid development of China's economy[22], emissions of various pollutants increased dramatically, especially on the environment caused serious water pollution, data show, ammonia nitrogen[23], phosphorus and other pollutants in surface water main. Excessive emissions of ammonia wastewater is one of the main reasons eutrophication. Deaminase methods
currently used in industry mainly biological nitrogen removal method, air stripping, breakpoint chlorination, ion exchange method [24]. Biological nitrogen removal method is suitable for the treatment of low concentration of ammonia nitrogen waste water containing organic matter, the law technically reliable, good effect, mainly used in chemical wastewater containing ammonia and sewage treatment[25]. Breakpoint chlorination and ion exchange method is suitable for wastewater treatment free of organics of low concentrations of ammonia[26].For high concentrations of inorganic ammonia wastewater, such as nitrogen fertilizer plant wastewater, many industrial applications currently using air stripping, but deaminase rate was 70%, can not meet the national emission standards, and large investments, secondary pollution [27]. Tang Yan, such as the use of electrodialysis ammonia wastewater treatment, process conditions were optimized to obtain process parameters under laboratory conditions[28]. Electrodialysis voltage of 55V, the water flow is 24L / h, ammonia wastewater influent conductivity of 2920 s / cm, ammonia concentration was 534. 59mg / L. Concentrated water and fresh water chambers each 19% and 81%, the concentration of water and fresh water conductivity was 14000 s / cm and 11. 8 s / cm, ammonia content was 2700mg / L and 13mg / L[29]. Ammonia wastewater processed after the electrodialysis device to meet emission standards, to meet the reuse requirements [30].
4.Prospects:
With the deepening of the scientific concept of development,
sustainability needs of China's economic development, energy conservation, clean industrial development, among other factors, membrane separation technologies are penetrating into all areas of industry and research, development and scale applications in the field has also been accelerated.,, Especially in the food industry, biological products, pharmaceuticals, chemical separation and other areas, has made tremendous progress. With the continuous development of science and technology, continuous improvement of membrane technology, continue to lower the cost of film, the new electrodialysis equipment manufacturing level will be greatly improved, the manufacturing cost of the equipment will be greatly reduced, and it will meet more modern industry high separation requirements, electrodialysis technology will be rapid development. In short, electrodialysis technology for industrial wastewater treatment and separation technology, will accelerate the modernization of industrial application prospect is very considerable. References:
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