Study on decolorization by catalytic micro electrolysis technology
Since the birth of micro electrolysis for wastewater treatment, it has attracted the attention of environmental protection scholars at home and abroad, and carried out a lot of research. There are many patents and practical technical achievements.
In recent years, the treatment of industrial wastewater by micro electrolysis has developed rapidly. It has been used in the treatment of industrial wastewater such as printing and dyeing, electroplating, petrochemical, pharmaceutical, gas washing, printed circuit board production, as well as wastewater containing arsenic and fluorine, and has received good economic and environmental benefits.
The micro electrolysis process has a good effect on decolorization of wastewater, and the waste is treated by waste with low operation cost, so it will have a good industrial application prospect in China.
Decolorization principle of catalytic iron carbon micro electrolysis
Micro electrolysis has obvious effect on chroma removal. This is due to the strong reduction ability of the new ecological divalent iron ions produced by the electrode reaction, which can reduce the chromogenic groups nitro-no2 and nitroso no of some organic compounds to amino-nh2. In addition, the biodegradability of amino organic compounds is also significantly higher than that of nitro organic compounds.
The new ecological ferrous ion can also open the double bonds of some unsaturated chromogenic groups (such as carboxyl COOH, azo-n = n -), destroy the chromogenic groups and remove the chroma, and decompose some refractory cyclic and long-chain organic compounds into easily biodegradable small molecule organic compounds to improve the biodegradability.
Micro electrolysis has obvious effect on chroma removal.
This is due to the strong reduction ability of the new ecological divalent iron ions produced by the electrode reaction, which can reduce the chromogenic groups nitro-no2 and nitroso no of some organic compounds to amino-nh2. In addition, the biodegradability of amino organic compounds is also significantly higher than that of nitro organic compounds.
The new ecological ferrous ion can also open the double bonds of some unsaturated chromogenic groups (such as carboxyl COOH, azo-n = n -), destroy the chromogenic groups and remove the chroma, and decompose some refractory cyclic and long-chain organic compounds into easily biodegradable small molecule organic compounds to improve the biodegradability.
After decolorization by micro electrolysis, the color of some dyestuff wastewater gradually deepens in a short time. The reason for this phenomenon is that iron carbon filler reacts with wastewater to destroy the chromogenic or auxiliary groups of dye molecules, but the dye molecules are only transformed into colorless small molecule organic compounds, which still exist in wastewater. These small molecule organic compounds have a certain reverse reaction trend.
But through the experimental verification, it is found that for some types of dye wastewater, when the sedimentation pH value is 8-8.5, the phenomenon of “Color Reversion” is not only manifested in the gradual deepening of the color of the wastewater, but also in the gradual turbidity of the wastewater. After a long time of standing, a small amount of dark colored sediments will appear. The results show that this is Fe (OH) 3 precipitation.
This phenomenon can be easily explained: Fe2 + is oxidized to Fe3 +, and the Solubility Product Constants of their hydrolysates Fe (OH) 2 and Fe (OH) 3 differ by more than 1021 times.
Based on the above analysis, I think that the complete removal of Fe2 + will aggravate this “Color Reversion” phenomenon to a certain extent. Therefore, in order to solve the problem of “Color Reversion” of iron bed effluent, in addition to thoroughly removing the chromogenic matrix in the follow-up treatment process, the pH value should be adjusted to above 9 during neutralization and sedimentation to make Fe2 + completely precipitate or add appropriate oxidants (such as O2, H2O2 and O3) to make Fe2 + rapidly oxidized into Fe3 + and precipitate in the form of Fe (0h) 3 colloid.
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