Photocatalytic Technology: The "Nemesis" Of Organic Pollutants

In many environmental pollution problems, organic pollutants (such as pesticides and dyes) have become the focus of environmental scientists. Organic pollutants are difficult to degrade. Most of them have three effects and genotoxicity caused by carcinogenesis, mutagenicity and teratogenicity. Even low concentrations can cause damage to organisms.

In 2007, due to Organic pollution The outbreak of cyanobacteria in Taihu is still fresh in memory. Dozens of centimeters thick blue-green algae cover the surface of the water, and foul smell. The bluish green algae everywhere, the fish and shrimp die out. The water from the tap is yellow and smelly. About two million, the people of Wuxi are facing a drinking water crisis. According to incomplete statistics, most of the waters in the Yangtze River Delta are affected by cyanobacteria to varying degrees.

　　 Zhejiang Wang Sheng, a professor at the Institute of materials and textile technology of the University of science and technology, and his research team on photocatalytic nanomaterials have been working hard to find effective ways to remove organic pollutants, and finally found the "Nemesis" against organic pollutants, and successfully applied them to the governance of the Tong Wang River in Ningbo. "Avoiding the two pollution is the biggest highlight of photocatalytic technology." Wang Sheng introduced that the biggest characteristic of photocatalytic technology is to convert organic matter into carbon dioxide and water and other inorganic substances safely under the condition of sunlight. The whole process does not need other chemical AIDS, the reaction conditions are mild, and there is no two pollution.

The miraculous effect of photocatalysis

Compared with inorganic substances such as metal ions, organic matter in water is difficult to be treated with existing treatment technologies. The photocatalytic technology appeared in the 70s of last century showed unparalleled advantages. To control water, we must restore the balance of water ecology. The key is to remove the complex and refractory organic matter in water. Wang Sheng said that the traditional physical adsorption, chemical oxidation, microbial and high temperature incineration methods all have such or other defects, such as low efficiency, easy to produce two pollution, narrow scope of application and high energy consumption.

According to Wang Sheng, the photocatalyst represented by nano-TiO2, due to its strong positive oxidation and strong reduction, can be decomposed into carbon dioxide by the positive charged holes and negatively charged electrons generated by light excitation. It can decompose almost all organic pollutants into carbon dioxide. The whole process does not require other chemical adjuvants, mild reaction conditions, no two pollution and low operation cost, and it can make full use of cheap and environment-friendly sunlight as the reaction light source. This method of photocatalytic decomposition of organic compounds has been widely studied in the field of wastewater purification and exhaust purification.

　 A good horse makes a good saddle.

However, with the deepening of research, Wang Sheng has encountered a dilemma. This is also a bottleneck that has long puzzled the application of photocatalytic technology to practical application. Such a "convenient" photocatalytic technology is facing a practical application problem: no suitable container can be found to install photocatalyst.

It is understood that the strong redox of titanium dioxide excited by ultraviolet light has no selectivity for decomposed objects. If directly combined into organic matrix materials, the service life of organic matrix materials will be shortened. If the titanium dioxide is directly injected into the reaction solution, a suspension system will be formed. Even if titanium dioxide has good reaction efficiency to organic pollutants, it will cause two pollution due to the failure to recover titanium dioxide.

"Photocatalytic technology has not been widely promoted in Japan since its birth in Japan in 1972, and that is why." Wang Sheng said that scientists have never been able to find a suitable container for photocatalysts.

With constant attempts and efforts, an unusual way of thinking in Wang Sheng's mind is gradually clear: in the silicon dioxide layer and nano titanium dioxide to create a water and air can be freely permeable nano space, the space as an effective reaction place to catalyze the reaction. Through extensive experiments, Wang Sheng and his team finally succeeded in preparing hollow interfacial photocatalyst - titanium dioxide coated with core and shell structure. The hollow structure avoids the shielding of the surface active point, thereby greatly improving its catalytic activity, and achieves the purpose of protecting the organic catalytic carrier without damaging the catalytic capacity.

Wang Sheng said that they have worked with enterprises to build a pilot plant for core and shell hollow nanomaterials, and have achieved practical results in degrading cyanobacteria and degradation of landfill leachate.

　　 practice Display one's talents

With the solution of the "container" problem, the Wang Sheng team's photocatalytic sewage treatment technology was finally successfully applied to the regulation of Tong Wang River in Ningbo.

It is understood that the Wang Sheng team and Ningbo Tianhe ecological waterscape Technology Co., Ltd. are working together to regulate the Tong Wang River, and apply and verify their advanced photocatalytic sewage treatment technology.

"Photocatalytic special fibers are made in various forms, such as artificial grass blanket, artificial net bed, etc., and placed in water." Wang Sheng said, in this way, under the sunlight, the organic pollutants causing black and stink of the river will be cleaned up soon. After that, microbes and submerged plants will be treated. The two technologies are mainly for other pollutants such as nitrogen, phosphorus and heavy metal ions.

According to the relevant departments, the main technical indicators of Tong Wang River will reach the category III standard of surface water, and the transparency reaches at least 1.5 meters. At the same time, it also pioneered the first successful application of photocatalytic technology to control river water in China. It is reported that this safe and efficient photocatalytic water ecological restoration technology will play an important role in the "five water co governance" in Zhejiang province.