Study on the photodegradation of emerging pollutants in aqueous solution under simulated sunlight: Effect of natural photosensitizers

LUCIANO CARLOS; DANIEL O. MARTIRE; JUAN GOMIS; ANTONIO BERNABEU; ANTONIO ARQUES

Mendoza

Simposio; 21st Inter-American Phot.ochemistry Society, conference; 2011

The presence of pharmaceutical and personal care products in surfaces waters is an emerging environmental issue. Sunlight mediated photodegradation may occur via direct or indirect reactions and may play an important role in the fate of these compounds in natural waters. In this work, the effects of the presences of natural photosensitizers such as humic substances (HS), nitrate and Fe3+ on the photodegradation of a mixture of six emerging pollutants (EPs) were studied. The EPs employed in the mixture were acetominophene (analgesic), caffeine (stimulating agent), acetemiprid (pesticide), clofibric acid (fungicide), carbamazepine (psychiatric drug) and amoxycilin (antibiotic). The experiments were performed under simulated sunlight at 30-35°C and the pH was adjusted to 7. In all the experiments, 5 mg/L of each EPs was used. The concentration profiles of the EPs were followed by HPLC. Direct photolysis of the EPs mixture showed that after 5 h of irradiation clofíbrico acid, acetamiprid and amoxicillin were completely removed of the solution while acetaminophen, caffeine and carbamazepine reached almost 30% of consume. The presence of SH showed that Aldrich humic acid (AHA; 5-100 mg/L) act mainly as inner filter, decreasing the rate of photodegradation of all studied EPs, instead of as photosensitizers. This effect was higher with increasing the AHA concentration on clofibric acid, amoxicillin and acetamiprid. In additional experiments, with different sources of SH (humic and fulvic acid from different brands), the same inner filter effect was observed. Experiments carried out at different pH (5, 7 and 9) with 20 mg/L of AHA, showed that only for acetaminophen and amoxicillin a significant enhanced in their photodegradation rates at pH 9. On the other hand, the presence of Fe3+ and AHA in the EPs mixture showed a complex effect. 1mg/L of Fe3+ results in an increase of photodegradation rates of acetaminophen, caffeine, carbamazepina and clofíbrico acid, while 5 mg/L of Fe3+ caused a reduction of the photodegradation rates of all EPs. Finally, for almost all studied compounds, except acetamiprid and amoxicillin the presence of nitrate ions in aqueous solutions (50 mg/L) results in a reduction of their consumption time.