Bismuth Tungstate Plasma and Photocatalytic Plasticizer

Phthalic acid ester (PAEs) is mainly used as a modified additive for plastics to increase plasticity and strength of plastics; it can also be used in the production and processing of pesticides, coatings, printing and dyeing, cosmetics and spices. The PAEs has estrogen effect, which can interfere with the endocrine and reproductive systems of animals and human beings and damage reproduction and development.

Dimethyl phthalate is the largest class of organic pollutants in the world. It has been listed as a blacklist of priority pollutants in China. The wastewater has high concentration and is not suitable for degradation. A large amount of discharge will cause great harm to the water body. The most effective method at present is photocatalytic technology.

How to effectively photocatalytic degradation of phthalate, some researchers have treated two methyl esters containing phthalate by plasma and bismuth tungstate photocatalysis technology, which has the advantages of high treatment efficiency, no pollution, mild reaction conditions and so on.

The wastewater containing dimethyl phthalate  is added to the needle type hollow high pressure electrode and the grounding electrode and without the ground electrode. The air is put into the needle type hollow high pressure electrode under the condition of the bismuth tungstate catalyst, and the bismuth tungstate catalyst is suspended in the waste water, and then the high pressure power supply is opened. The corona discharge is carried out by the needle type hollow high pressure electrode. The activity of the bismuth tungstate catalyst is induced by ultraviolet and visible light produced by the discharge process, and the oxidizing group is produced by the plasma produced in the process of CO discharge, which catalyzes the oxidation of the refractory two methylene two formate, which is difficult to degrade in the wastewater. The air flux is 1.2 to 6L/h, and the high pressure is high. The voltage of the power supply is 60 ~ 120V, the current is 0.35 ~ 0.5A, and the discharge frequency is 50Hz.

Bismuth tungstate is an important catalyst model material. Because of their unique physical properties, these compounds can also be used as ionic conductors, acoustooptic materials, photoconductors, gas sensors and photocatalysts. In the process of discharge, plasma will not only produce a large number of free radicals, but also produce ultraviolet and visible light, which can greatly improve the efficiency of photocatalyst treatment, and finally achieve the effect of application. The method does not need to add a large number of chemical reagents, low treatment cost, simple operation, can be carried out under normal temperature and atmospheric pressure, the reaction conditions are mild, and the reaction parameters are easy to adjust.

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