Influência do campo magnético na adsorção e degradação de agroquímicos na presença de ferroxita e hematita

Abstract

This work evaluated the adsorption and degradation of agrochemicals, such as organophosphates, carbamates, and pyrethroids, by ferroxite and hematite using their magnetic properties. The following laboratory tests were performed: synthesis and determination of the zero charge potential of ferroxite, adsorption analysis of agrochemicals in the presence and absence of a magnetic field at pH 5 and pH 10, and degradation at pH 5. The best adsorption result was obtained in the presence of the magnetic field with ferroxite, with 78.18% for diazon at pH 5 and 71.52% for bifenthrin at pH 10. The best degradation result occurred with malathion in the presence of the magnetic field with ferroxite 50.70% at a volume of 0.1 mL of hydrogen peroxide. The tricloforne obtained no result. The variables investigated in the factorial planning were the adsorbent, adsorbent mass, and magnetic field for adsorption. The volume of hydrogen peroxide was included in determining degradation. The analysis showed that the type of adsorbent and the presence of the magnetic field were the most important effects for diazon and carbaryl, whereas the adsorbent mass was the most important for bifenthrin. An optimization model used in other experiments for adsorption and degradation was performed to evaluate the mass, using a univariate method, showing the best mass of 20 mg. The degradation analysis indicated an increase in the influence of the adsorbent and adsorbent mass, while a contrary effect occurred for the volume of hydrogen peroxide for propoxur. The interaction between adsorbent and its mass is significant only for malathion and bifenthrin. The contrary occurs for propoxur. The interaction between adsorbent and hydrogen peroxide volume is not significant for malathion and propoxur, presenting a negative effect for bifenthrin. The interaction between adsorbent change and the presence of a magnetic field issignificant for all agrochemicals tested. Thus, the inclusion of a magnetic field in the presence of ferroxite increases the degradation of agrochemicals.