Advanced Oxidation Advanced Treatment Technology

(1) chemical oxidation technology.

In the advanced treatment of printing and dyeing wastewater, O3 and Fenton reagents are commonly used oxidants.

O3 has a strong decolorization effect, although it has little effect on the removal of COD, but it can change the B/C of wastewater, thereby improving the biodegradability of wastewater.

Lu Ningchuan et al. [5] used O3 oxidation to treat printing and dyeing wastewater. The results showed that the removal rate of COD was 72%, while the chromaticity was 94%.

Guo Zhaohai, et al. [6] studied the effect of O3 on chroma removal and B/C, and found that the removal rate of chromaticity could reach 70% and B/C more than doubled when the dosage of ozone was 15 mg/L.

The main advantage of O3 oxidation is that the equipment is simple and compact, with a small footprint and easy to realize automatic control. The main disadvantage is that the treatment cost is high and is not suitable for the treatment of large flow wastewater.

Fenton reagent is an oxidant composed of H2O2 and Fe2+. The OH OH, which is produced under acidic conditions, is highly oxidizing. It is especially suitable for treating complex dye wastewater.

Jiang Xinghua et al. [7] used Fenton reagent to carry out advanced treatment of printing and dyeing wastewater. The results showed that the dosage of pH 2~3 and H2O2 was 3.2 mL/L, and the volume ratio of iron carbon to 1: 1. When the reaction time was 90 min, the effluent COD COD was removed more than 90%, the chroma was reduced by 99%, the salinity was reduced by 64%, and the water quality indexes of reclaimed water all met the requirements of reuse.

Shi Hongxiang et al. [8] also studied the treatment of printing and dyeing wastewater by Fenton reagent. Similar results were obtained.

Fenton oxidation has a strong ability to remove COD and chromaticity, but the presence of iron ions may affect the color of water, and the pH of the reaction is relatively low, which may affect other processes.

(2) photocatalytic oxidation technology.

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OH, which has strong oxidation capacity under UV radiation, is used to treat wastewater. It has the advantages of low energy consumption, no two pollution and thorough oxidation. Most commonly used are UV/Fenton, UV/O3 and UV/H2O2.

More photocatalytic research is carried out with photosensitized semiconductor as catalyst. TiO2 photocatalyst is the most widely used and has the best treatment effect.

TiO2 rays will produce electron hole (h+) on the valence band under the light radiation. The organic adsorbed on TiO2 TiO2 surface will be degraded by activation and oxidation of strongly oxidized h+.

Feng Lina et al. [9] adopted the TiO2/ activated carbon loading system to treat the two stage effluent from a printing and dyeing mill. The influent COD was about 300 mg/L. Under the optimum reaction conditions, the effluent COD dropped to 50 mg/L and the chroma decreased to 2 times. The research shows that the adsorption performance of activated carbon can help solve the problem of the loss, separation and recovery of TiO2, and improve the treatment effect of the photocatalyst.

However, the light pmittance and light utilization efficiency of wastewater restrict the application of photocatalysis technology in wastewater treatment industry.

(3) electrochemical oxidation technology.

Under the action of an external electric field, a large number of free radicals can be produced in a specific reactor through a certain chemical reaction, electrochemical process or physical process.

Electrochemical technology is easy to control, pollution-free or less polluting and highly flexible.

M. Kennedy [10] points out that the electrochemical method is correct.

The decolorization is very effective. When the concentration of Fe2+ in the main stream of the electrochemical reactor is 200~500 mg/L, the removal rate of chroma is 90%~98%, and the removal rate of COD and BOD is 50% and 70% respectively.

However, the electrode consumption of this soluble electrode oxidation method is too large, so the development of new electrode has become one of the research hotspots.

Jia Jinping et al. [11] deactivated many kinds of simulated printing and dyeing wastewater by using activated carbon fiber and iron composite electrode, and achieved good results.

Lei Yangming, et al. [12] PbO2/Ti

The removal rate of chromaticity and COD can reach 99.5% and 78.6% respectively.