Optimization of the adsorption process of epoxiconazole, penconazole and cyproconazole with chitosan

WILLIMAN, CELIA; MEDINA, MARÍA BELÉN; ALBERINI, IVANA; BARRAGÁN, RODRIGO; MUNITZ, MARTÍN

Workshop; 8º Edición de Latin American Pesticide Residue Workshop (LAPRW); 2021

Traditional agricultural techniques involve treatments with different pesticides aimed at maintaining the production quality. Fungal diseases can cause considerable losses when they are not timely controlled. Triazoles such as epoxiconazole, penconazole and cyproconazole, are one of the most frequently used fungicides, and are applied to various crops in the Salto Grande region, Argentina.Environmental pollution and water quality deterioration are the biggest problems associated with the pesticide usage. To minimize the pesticides levels in water, mainly for human consumption, it is necessary to apply various technological processes to remove these compounds, such as adsorption with powdered activated carbon or other adsorbents.Activated carbon is commonly used in water purification treatments. However, there are other types of adsorbents with different characteristics. Chitosan is a copolymer obtained by partial deacetylation of chitin from seafood processing industry waste. It has a great adsorptive capacity. The use of this biopolymer emerges as a technological alternative for pesticide?s removal. It has been used by various authors for metallic pollutants adsorption. However, there are few studies in the literature about its use for pesticides adsorption.The objective of this work is to apply a Response Surface Methodology (RSM) for the optimization of pesticides removal from water using chitosan. Type 1 grade water fortified at 20 μg / l with the analytes was prepared. RSM and a factorial design were used with 2 variables: amount of chitosan (400-1800 mg / l) and contact time (20-60 minutes). Water samples with chitosan were stirred in a thermostatized bath at 25 °C, with a frequency of approximately 60 movements per minute. Then, samples were filtered, and fungicides residues were extracted by solid phase microextraction, using a 100 μm polydimethylsiloxane fiber. Finally, a gas chromatography with a micro-electron capture detector determination, and a mass spectrometry confirmation were performed.The statistical analysis of the results indicated that the optimal combination was obtained with 1800 mg / l of chitosan and 60 minutes of contact time, for all pesticides. The % reduction optimized were: 83.0%; 70.7% and 90.1% for penconazole, cyproconazole, and epoxiconazole, respectively. The optimized values were corroborated, and the % reduction obtained were 85.0%; 73.2% and 92.1% for the three compounds, respectively.We can conclude that the maximization of the removal percentages of these analytes occurs with the highest contact time and adsorbent concentration used.