In recent years, with the increase in the growing speed of industries and population, water pollution and environmental pollution is a major challenge for the scientific community, which needs a serious and real solution in the world. Because the discharge of wastewater containing toxic substances, solid waste or flue gases from factories is known as a serious problem for the sustainable development of human society. Therefore, in this paper, which is a review of recent studies on this subject, first, an introduction to the catalytic degradation of pollutants is provided, and then the researcher's studies are reviewed, and finally, a conclusion is provided. In conclusion, it is found that in photocatalytic processes, the catalyst dosage is very effective on the rate of pollutant degradation. As the catalyst dosage increases, the number of active sites absorbing the pollutant at the catalyst surface also increases. The increasing trend of dye removal with catalyst dosage can be attributed to the increase in surface area and the availability of more absorption sites. This process continues until it increases light absorption and the production of hydroxyl radicals. However, it is also noteworthy that at values above the optimum, the reaction rate decreases. In other words, if the catalyst dosage is too high, not only it is not effective on the dye removal process, but also causes more turbidity of the solution, which in turn prevents the penetration of light and the effectiveness of the photocatalytic process. Manuscript profile