Degradation of glyphosate in water using the UV/H2O2 advanced oxidation process

CRISTINA ZALAZAR, AGUSTINA MANASSERO, MELISA MARIANI, ANTONIO NEGRO, RODOLFO BRANDI,ALBERTO CASSANO

Santa Fe

Workshop; 2° Workshop latinoamericano sobre residuos de plaguicidas; 2009

Universidad Nacional del Litoral- Facultad de Ingeniería Química- Laboratorio Central

Glyphosate (N-phosphonometyl glycine) is a non- selective, post-emergence, broad spectrum organophosphate herbicide, wich is the one most used in the world. Argentina is the second largest world producer of glyphosate- resistant (GR) soy. This production has been accompanied by an increase in the use of the herbicide (over 160 million L between 2004 and 2005). The United Nations estimates that all of pesticides used in agriculture, less than 1% actually reaches the crops. The other part ends up contaminating the soil, the air and, mainly, the water. Advanced Oxidation Processes (AOPs) seem to be a suitable option to decrease glyphosate concentration in water within acceptable limits. AOPs are based on the generation of very reactive non- selective oxidizing species, paricularly the hydroxil radical (OH). The combination of H2O2 and UV radiation could be a convenient process for the treatment of this type of pollutants. In this work the effects of H2O2 initial concentration, initial pH and irradiation rates in the glyphosate degradation were studied. In addition to this the main reaction intermediates were identified with the intention of proposing a plausible reaction pathway.The best conditions of glyphosate degradation for an initial concentration of 50 mg/L are pH 7 and hydrogen peroxide concentrations from 75 to 200 mg/L.