With the continuous rapid growth of China's economy in the past two decades, the huge amount of atmospheric pollutants emitted by coal-based energy structures has made China's urban outdoor air pollution index high, and the widespread use of interior decoration materials has also led to excessively high indoor harmful gases. Has seriously endangered human health. As a kind of advanced oxidation technology, photocatalytic oxidation has been widely studied in the treatment of refractory pollutants in recent years. Scientists have found that TiO2 semiconductor photocatalysis can degrade almost all organic matter, produce CO2 or small molecules that are easily biodegraded, and the photocatalyst has high stability. How to apply photocatalytic technology to daily life, how to choose the best photocatalytic effect products, and to protect human health from harm, has become a practical problem that we urgently need to solve.
I. Air pollution seriously endangers human health
The outdoor air pollution situation is severe, mainly including industrial enterprises' exhaust emissions, automobile exhaust emissions, and soil dust. According to data from relevant departments, due to China's coal-based energy structure (60-70%), coal combustion produces 90% of SO2, 85% of CO2, 67% of NOX and soot and other atmospheric pollutants, reducing atmospheric visibility. It also causes severe acid deposition, causing respiratory diseases such as bronchitis and asthma, which seriously endanger human health.
Indoor air pollution is a serious hazard to human health. People spend more than 90% of their lives indoors. In the indoor air environment where we live and work every day, dust, smoke, harmful gases, pathogenic viruses, odors, etc. are common. Contaminants, because the indoor space is relatively closed, the air does not circulate, and the pollutants float in it. Indoor air pollutants are mainly classified into three categories: inhalable particulate matter, biologically active particulate pollutants and gaseous chemical pollutants.
One of the indoor air pollutants, the harmful gas VOCs, mainly including formaldehyde (from indoor decorative materials and furniture in the board, such as wood-based panels, sandwich panels, etc.); benzene, toluene, xylene (from paint, glue, paint, etc.) ); ammonia (such as antifreeze added by construction contains ammonia); æ°¡ (from cement, stone, floor tiles, etc.).
The US Environmental Protection Agency (EPA) defines VOC as a volatile carbonaceous compound that participates in atmospheric photochemical reactions in addition to carbon dioxide, carbonic acid, metal carbides, carbonates, and ammonium carbonate. The main source of VOC is outdoor, mainly from fuel combustion and transportation: indoors are mainly from combustion products such as coal and natural gas, smoke from smoking, heating and cooking, construction and decoration materials, furniture, household appliances, detergents. And the body's own emissions and so on. There are nearly a thousand. In the interior decoration process, VOC is mainly from paints, coatings and adhesives.
The indoor VOC concentration is usually between 0.2 and 2 mg/m3. When the indoor VOC concentration is between 0.16 and 0.3 mg/m3, it is basically harmless to human health, and even in the improper decoration construction, it can be dozens of times higher. Because VOC itself is extremely harmful, it has been hailed by society as the "invisible killer" of human beings.
Common degradation methods for VOCs: adsorption, thermal catalytic combustion (250-500 °C), UV degradation (UV/O3).
Photocatalysis and Thermal Catalytic Oxidation of Vinyl Chloride on 0.1wt% Pt/TiO2 Catalyst: Photocatalytic Oxidation Is Different from General
The effect of trichloroethylene (500 ppm) was compared; the results indicate a lower photolysis reaction. Under the action of the catalyst, photocatalysis showed significant catalytic oxidation activity at 120 °C. The activity is much higher than the latter.
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