Photochemical degradation methods are effective in removing pollutants, such as pesticides and industrial chemicals, from water and air in various environmental conditions. Some of the most effective photochemical degradation methods include:1. Photocatalysis: This method involves the use of a photocatalyst, such as titanium dioxide TiO2 , which, when exposed to ultraviolet UV light, generates reactive oxygen species ROS that can break down pollutants. Photocatalysis is effective in degrading a wide range of pollutants, including organic compounds, heavy metals, and microorganisms.2. UV/H2O2 process: This method combines UV light with hydrogen peroxide H2O2 to generate hydroxyl radicals, which are highly reactive and can degrade various pollutants. The UV/H2O2 process is particularly effective in treating water contaminated with pesticides, pharmaceuticals, and other organic pollutants.3. Solar photocatalytic oxidation: This method utilizes solar energy to activate photocatalysts, such as TiO2, to degrade pollutants. Solar photocatalytic oxidation is an environmentally friendly and cost-effective method for treating water and air pollution.4. Photo-Fenton process: This method involves the use of iron salts such as Fe2+ or Fe3+ and hydrogen peroxide H2O2 under UV light to generate hydroxyl radicals, which can degrade pollutants. The photo-Fenton process is effective in treating water contaminated with pesticides, dyes, and other organic pollutants.5. Ozone-based advanced oxidation processes AOPs : Ozone O3 can be combined with UV light or H2O2 to generate hydroxyl radicals, which can degrade pollutants. Ozone-based AOPs are effective in treating water and air contaminated with volatile organic compounds VOCs , pesticides, and other pollutants.6. Photosensitized degradation: This method involves the use of photosensitizers, such as porphyrins or phthalocyanines, which can absorb light and transfer energy to pollutants, leading to their degradation. Photosensitized degradation is effective in treating water and air contaminated with organic pollutants, such as pesticides and dyes.The choice of the most effective photochemical degradation method depends on the type and concentration of pollutants, the environmental conditions, and the availability of resources such as sunlight or electricity . In some cases, a combination of methods may be necessary to achieve optimal pollutant removal.