Research and development of iron-carbon microelectrolysis in wastewater treatment

In recent years, micro-electrolysis has been widely used in wastewater treatment in many industries, and the process has become increasingly mature. The factors affecting the effect of micro-electrolysis treatment mainly include pH value of wastewater, residence time, treatment load, iron particle size, iron-carbon ratio, aeration, micro-electrolytic material selection and combination, and some may affect the reaction mechanism. Generally speaking:
1) The pH value of the incoming water should be selected to be acidic, and can be controlled to 3-6.5. Although the acidity is too strong, it can promote the effect of micro-electrolysis, but the subsequent floccules are destroyed, and the consumption of iron is large, and the subsequent processing load is heavy. More iron mud. As the microelectrolysis proceeds, the H+ in the wastewater is gradually consumed to cause an increase in the pH value, so that the microelectrolysis reaction tends to be moderated.
2) Residence time is also an important factor affecting the effect of micro-electrolysis treatment, and its length is directly related to the progress of micro-electrolysis reaction. The general treatment effect increases with the extension of the residence time, but when the reaction reaches a certain time, the reaction basically stops, and the excessive residence time of the amount will bring about a large iron consumption, adverse factors such as reverse color, and the reaction time is insufficient to complete the reaction. Different wastewaters have different pollutants, and the reaction time required varies greatly. . Therefore, for a specific wastewater, the hydraulic retention time should be determined by experiment.
3) Aeration of the filler is beneficial to the oxidation of certain substances, and also increases the movement of iron filings, reduces agglomeration, and removes the passivation film deposited on the surface of the iron filings in time, and also increases the flocculation effect of the water. However, excessive aeration also affects the contact time between wastewater and iron filings, which reduces the removal rate of organic matter. Under neutral conditions, aeration supplies oxygen on the one hand, promotes the anode reaction, and on the other hand acts as a stirring and oscillating, weakens the concentration polarization, and accelerates the electrode reaction. [8]
4) Adding catalysts (such as metal oxides CuO, MnO2, A120, etc.) to the system can improve the electrode performance of the cathode and improve its electrochemical activity, and the effect is remarkable. The presence of salts (sodium chloride, ammonium chloride) also contributes to the progress of the electrolysis reaction by increasing the electrical conductivity of the wastewater.
5) The proportion of suitable filler iron and carbon can maximize the number of micro-cells formed in the wastewater to achieve the best treatment effect. Generally, the mass ratio of iron and carbon can be controlled within a certain range. Between 0.5-30:1, for different production wastewater, the appropriate iron-to-carbon mass ratio can achieve different treatment effects.
6) The smaller the particle size of the filler, the larger the specific surface area, and the more micro-cells formed in the wastewater, the faster the micro-electrolysis reaction. The better the treatment of wastewater is. However, in practical engineering, the use of small filler particle size will lead to more serious problem of filler compaction. For comprehensive consideration, it is best to use iron powder with a particle size of 10-20. Due to the difficulty of the general iron powder source, the waste cast iron chips of the factory are widely used.
7) The post-treatment of the micro-electrolysis effluent and the pH of the sedimentation. Generally, micro-electrolysis effluent will inevitably contain a certain concentration of ferrous ions, which not only interferes with the determination of CODcr, but also brings adverse effects such as reverse color, so it should be removed. The widely used alkali-added coagulation method is to remove the ferrous ions by adding an alkali solution to precipitate ferrous ions into dark green Fe(OH)2. It is reported that the suitable pH value for neutralization sedimentation is 8-8 5 . The theoretical calculation of the complete precipitation of ferrous ions has a pH of 8.95, and the pH should generally be adjusted to above 9.
8) Material selection, different components, different impurity materials have different reaction activities, so the corresponding treatment effects vary greatly. Generally, the anode material is cast iron scrap, small broken iron, cast aluminum scrap, pot gold, etc., and the cathode material is made of coke, activated carbon, graphite, coal powder, etc., so many combinations can be performed.

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