Since my country's reform and opening up, the industrial industry has achieved rapid development and played an irreplaceable and important role in the development of my country's national economy. However, at the same time, it also exposed the problem of increasing environmental pollution due to the problem of industrial wastewater discharge, especially the serious pollution and damage to my country's water resources environment. As for industrial wastewater, it not only has complex components, but also has poor biodegradability. The content of COD, salt and toxic substances is relatively high, and it also shows different forms of pollutants. In recent years, while countries around the world have paid more attention to environmental protection issues, my country has also strengthened research on industrial wastewater treatment technology. Among them, for the difficult-to-degrade and difficult-to-decompose pollutants such as ammonia nitrogen, total phosphorus, total nitrogen, aniline and heavy metals in industrial wastewater, the more effective way is micro-electrolysis technology, and it also shows the advantages of less investment and simpler operation in application, and has a wide range of applications in current industrial wastewater treatment.
1. Principle of micro-electrolysis technology
Take iron-carbon micro-electrolysis as an example. Its main principle is that the primary cell is composed of inert carbon such as iron filings, activated carbon, coke, etc., and this primary cell can play the role of oxidation-reduction, electrical enrichment, physical adsorption, and flocculation sedimentation. This kind of micro-electrolysis technology can not only remove some substances that are difficult to degrade in industrial wastewater, but also change the morphology and structure of some organic matter in it. Specifically, the principle adopted is the principle of metal corrosion. In the process of treating industrial wastewater through the above-mentioned primary cell, it is not necessary to energize. After the wastewater fills the micro-electrolysis material, a potential difference will be formed, and then the wastewater can be electrolyzed and the organic pollutants can be degraded. As mentioned above, in a neutral or slightly acidic environment, the micro-electrolyte will undergo oxidation-reduction reactions with the above-mentioned generated ][H and other components, so that the color-producing and color-auxochrome groups of the colored substances in the industrial wastewater can be destroyed and the chain can be broken. In this way, it can play a role in decolorization and reduce the COD in it, improving biodegradability. It can also oxidize metal ions and control toxicity. The activated carbon plays the role of cathode in the above-mentioned primary battery, and can also play the role of reduction and adsorption. This is mainly due to the electric field effect generated around the electrode of the primary battery. Under the influence of this effect, the charged particles in the solution will be promoted to move in a directional manner and deposit on the electrode, so that the pollutants in industrial wastewater can be removed.
2. Analysis of the application of micro-electrolysis technology in industrial wastewater treatment
2.1 Treatment of printing and dyeing wastewater
For the printing and dyeing wastewater generated by the textile industry, it contains dyes, various products in the intermediate production industry, crystallization mother liquor, and materials during production. Not only does it have a more complex composition, but it also has a larger pH range, higher COD and solid suspended matter concentration. In the process of applying micro-electrolysis technology to this kind of wastewater, its main principle is that after the divalent and trivalent iron ions are hydrolyzed, chromium ions will be formed, which will coagulate the reducing substances in the industrial wastewater, and precipitate and reduce the sulphur dyes. Moreover, because the activated carbon used in it has a strong adsorption capacity, it can adsorb pollutants dissolved in industrial wastewater, and regulate the pH of wastewater through the hydrogen ions and oxygen ions of the cathode. After the redox reaction with some components in the industrial wastewater, it can remove the water color and improve the biodegradability.
2.2 Treatment of chemical wastewater
In view of the characteristics of high COD, color and salinity in chemical wastewater, and the number of difficult-to-degrade compounds in it is also large, and there is a large toxicity. Therefore, when applying micro-electrolysis technology, its precipitation, flotation, adsorption, filtration, concrete and oxidation effects are used to treat nitrobenzene, phenols and chlorobenzene compounds.
2.3 Treatment of heavy metal ion wastewater
In a weakly alkaline environment with heavy metal ions, the characteristics of micro-carbon particles and iron filings with high activity in micro-electrolysis technology can be used to adsorb and remove heavy metal ions in industrial wastewater. Moreover, because iron ions are relatively active, they can replace less active metals and exist in the form of precipitation on the surface of iron metals. Other compounds and ions with strong oxidizing properties in industrial wastewater will also be reduced to less toxic substances under the action of divalent and trivalent iron ions in this technology. In addition, iron ions will react with the complex products of heavy metal ions to produce a precipitation treatment effect.
3. Experimental analysis of chromium ions in industrial wastewater treated with micro-electrolysis technology
3.1 Materials and devices
For chromium ions in industrial wastewater, the main materials used are iron filings, inert carbon and acid in micro-electrolysis technology, and no special equipment is required, only filters and wastewater collection tanks are needed. The treatment process is shown in Figure 4.1. Analysis of water quality of industrial wastewater Since the water quality of chromium-containing industrial wastewater needs to be determined in the process of treatment by micro-electrolysis technology in industrial wastewater containing chromium ions, it is necessary to determine its contamination, that is, to determine the content of pollutants therein. However, the chromium content in industrial wastewater will increase during the above-mentioned electroplating process. Moreover, since wastewater will be generated during the cleaning process, in order to avoid contaminating the next solution during the electroplating process, or causing the appearance of impurities that are difficult to remove, it is necessary to do a good job of cleaning. In addition, when the solution is replaced during the electroplating process, wastewater will also be generated, and it contains chromium ions and other heavy metal ions. Therefore, if it is discharged directly, it will not only affect the normal growth of crops, but also harm fish and livestock, and endanger people's health. Therefore, it is necessary to focus on controlling the chromium content in industrial wastewater.
3.2 Determination of the content of each metal ion
Industrial wastewater that mainly contains chromium ions usually contains other types of metal ion impurities, which requires the determination of the metal ion content. In the process of applying micro-electrolysis technology to treat industrial wastewater, heavy metal ions can be removed through the oxidation and reduction of heavy metal ions, adsorption of colloidal flocs, ferrite complex precipitation, etc., and it has been known through experiments that when the pH value and water environment are relatively good, this technology can be used to treat heavy metals such as chromium and nickel and meet the treatment requirements. In addition, the mixed solution of divalent copper ions, zinc ions, nickel ions and chromium ions can also be treated, and the content can be determined based on the actual properties of different metals.
3.3 Results and Discussion
In this test, 100 kg of industrial wastewater was taken, and the concentration of hexavalent chromium ions was 100 mg/L. The above treatment was carried out in the wastewater pool by this technology, and then the hexavalent chromium ion concentration was measured until its concentration was lower than 0.2 mg/L before it could be discharged. The test results were analyzed, first of all, the treatment results of Cr. It is mainly manifested in that after this technology, the concentration of chromium ions in industrial wastewater can be reduced from 100 mg/L to below the standard 0.2 mg/L, and there will be no secondary pollution during the treatment process. After treatment, the remaining harmful substances can be filtered by precipitation. Secondly, the treatment results of other metal ions. It is mainly to treat zinc ions, nickel ions and copper ions. After treatment, the industrial wastewater with a zinc ion content of 2.9 mg/L and a lead ion content of 1.5 mg/L was treated to achieve a removal rate of more than 99%. Finally, the treatment results of the total iron content in the inlet and outlet water are presented. This method is mainly used to react and precipitate the high iron ions in the inlet and outlet water with other substances, thereby reducing the iron ion content in the outlet water.
4. Conclusion
While the industrialization process in my country is accelerating, the blind pursuit of economic benefits and development has caused serious problems of industrial wastewater discharge and environmental pollution. In view of this industrial wastewater problem and the characteristics of industrial wastewater with high pollution and toxicity, this paper proposes a method to remove ammonia nitrogen and heavy metals through micro-electrolysis technology. This method shows good wastewater treatment effect in printing and dyeing wastewater, chemical wastewater and heavy metal ion wastewater. However, it is still necessary to strengthen the research, application and technical level of this technology, and combine it with other sewage treatment technologies to achieve the improvement of the overall industrial wastewater treatment effect.
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