Degradation of amicarbazone herbicide by direct photolysis and H2O2/UV in an annular coaxial photochemical reactor.

Author(s)

André Luís de Castro Peixoto

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Escola Politécnica (EP/BC)
• Defense date: 2013-08-26

Examining board members

Antonio Carlos Silva Costa Teixeira; Roberto Guardani; Hélcio José Izário Filho; Raquel Fernandes Pupo Nogueira; Carla Sirtori

• Advisor: Antonio Carlos Silva Costa Teixeira

Abstract

Amicarbazone is a triazolinone herbicide developed to substitute atrazine in the world market. Several technologies have been studied aiming at the removal of pesticides from wastewater, seeking to study the degradation mechanisms involved and the degree of toxicity of the photoproducts formed. In this context, the main goal of this work is to study the degradation of amicarbazone in aqueous solution by direct photolysis, suggesting possible chemical structures for the transformation products according to a theoretical and fundamental approach. Parameters such as herbicide concentration, pH, dissolved oxygen concentration, nitrate concentration, and propan-2-ol as a free radical scavenger were considered. Among the parameters studied in the photolysis process, the pH showed influence on the photochemical mechanism of amicarbazone degradation, favoring or not the formation of particular intermediates. It was found that the photolysis generates amicarbazole as the primary degradation product in acidic medium as a result of the deamination mechanism. The use of UV/H2O2 process enabled the complete degradation of amicarbazone in a reaction time of 60 minutes at most. However, even with the use of the auxiliary oxidant reactant, the complete mineralization of amicarbazone was not achieved, with 58% reduction of dissolved organic carbon in the best experimental condition studied. (AU)