Identification of intermediates, acute toxicity removal, and kinetics investigation to the Ametryn treatment by direct photolysis (UV), UV/HO, Fenton, and photo-Fenton processes.

This paper reports the degradation of 10 mg L Ametryn solution with different advanced oxidation processes and by ultraviolet (UV) irradiation alone with the main objective of reducing acute toxicity and increase biodegradability. The investigated factors included Fe and HO concentrations. The effectiveness of the UV and UV/HO processes were investigated using a low-pressure mercury UV lamp (254 nm). Photo-Fenton process was explored using a blacklight blue lamp (BLB, λ = 365 nm). The UV irradiation process achieved complete degradation of Ametryn solution after 60 min. The degradation time of Ametryn was greatly improved by the addition of HO. It is worth pointing out that a high rate of Ametryn removal was attained even at low concentrations of HO. The kinetic constant of the reaction between Ametryn and HO for UV/HO was 3.53 × 10 L mol s. The complete Ametryn degradation by the Fenton and photo-Fenton processes was observed following 10 min of reaction for various combinations of Fe and HO under investigation. Working with the highest concentration (150 mg L HO and 10 mg L Fe), around 30 and 70% of TOC removal were reached within 120 min of treatment by Fenton and photo-Fenton processes, respectively. Although it did not obtain complete mineralization, the intermediates formed in the degradation processes were hydroxylated and did not promote acute toxicity of Vibrio fischeri. Furthermore, a substantial improvement of biodegradability was obtained for all studied processes.