Kinetics And Mechanism Of Photodegradation Of Selected UV Filters In Simulated Natural Water

Ultraviolet filters (UV filters) are compounds that reflected, scattered and absorbed solar UV radiation and widely used in personal care products, such as sunscreens, lipsticks, shampoos, and hair sprays, which protect the human body from the deleterious effects of sunlight. They have been found in surface waters (e. g., lakes and rivers), wastewater, sludge, fish, blood and urine. Their growing use may increase environmental contamination and expose, UV filters currently represent a new pollutant.To date, there is a scarcity of data on the fate and behavior of UV filters in the environment. The aqueous photolysis of a UV filter p-aminobenzoic acid (PABA) using Xe lamp as simulated solar irradiation source was investigated. Hydroxyl radicals determined by using the molecular probe method played a very importnant role in the photolysis process of PABA. Photoproducts upon irradiation of PABA in nitrate solution were isolated by means of solid-phase extraction (SPE) and identified by LC/MS techniques. The probable photoinduced degradation pathways were proposed.The primary results of the study were as follows:1) The study was conducted to compare the photostability of Benzophenone-3, Ethylhexyl methoxycinnamate, Homosalate, Octocrylene and p-aminobenzoic acid. Benzophenone-3 and Octocrylene have high photostability after irradiation. Homosalate and p-aminobenzoic acid were easily photodegradation in irradiation. The study showed that tras isomer of Ethylhexyl methoxycinnamate when exposed irradiation yield the cis form which has high photostability.2) The degradation rate of p-aminobenzoic acid was promoted in the presence of nitrate ion. The same phenomenon was found in the condition of high pH value. However, both of SRHA and SRFA retarded the photodegradation of p-aminobenzoic acid. In all cases the photolysis process of p-aminobenzoic acid followed the first order kinetics, it was noteworthy that OH-radicals were determined using the molecular probe method and four photoproducts formatted in the presence of nitrate ion were characterized by using LC-MS.3) The photosensitizatin degradation of p-aminobenzoic acid was inhibited in the presence of SRHA and SRFA under simulated solar irradiation and followed pseudo-first-order reaction. The Fe (â…¢)-EDTA complexes promoted photodegradation of p-aminobenzoic acid. With the increase of Fe (â…¢)-EDTA complexes concentration, the photodegrdation of p-aminobenzoic acid greatly increased.