Degradação simultânea de quatro pesticidas utilizando tecnologias não térmicas com foco no tratamento de água

Abstract

The increasing use of pesticides in agriculture has caused serious environmental impacts, contaminating soils and water, and consequently, also poses risks to human health. The conventional processes currently used for water treatment are ineffective in removing pesticides, which drives the search for new alternatives to minimize these impacts. As a result, non-thermal technologies have stood out as promising alternatives for treating contaminated water, mainly because they operate without the addition of chemicals and possess many highly oxidizing reactive species capable of degrading pesticides. In this context, the present work aimed to simultaneously degrade four pesticides (aldrin, dieldrin, chlorpyrifos, and deltamethrin) in aqueous solution using ultrasound, dielectric barrier discharge (DBD) plasma, glow discharge plasma, and corona discharge plasma. Different operational conditions were investigated for each technique: power (3125, 4687,5 and 6250 W/L) and time (3, 6.5, and 10 minutes) for ultrasound; flow rate (10, 20, and 30 mL/min) and time (5, 10, and 15 minutes) for glow discharge; and frequency (50, 500, and 1000 Hz; 5, 10, and 15 kHz) and time (5, 10, and 15 minutes) for the dielectric barrier and corona discharges, respectively. The experiments were conducted in batch mode, and degradation rates were quantified by gas chromatography coupled with mass spectrometry (GC-MS). Overall, the degradation efficiencies were satisfactory, with results ranging from 60.33 to 99.98%. Ultrasound, even at short times and the lowest power, already achieved degradation results above 98% for all studied pesticides and technologies, which generates even more interest in economic terms. In the processing using DBD, aldrin achieved degradation above 99% in all operational conditions tested, despite this pesticide being a persistent organic pollutant. Glow discharge yielded very similar results, with degradation efficiency above 95% for the four pesticides. Corona discharge showed the highest efficiency in aldrin degradation and achieved the best results at the longest time studied (15 minutes). Despite the high degradation efficiency of the pesticides, the identification of the formed byproducts was inconclusive using the analytical technique employed. However, based on the zebrafish toxicity assays, it was concluded that no toxic byproducts were formed during any of the studied treatments.