Síntese de hidrocarvão a partir de resíduo de erva-mate aplicado a adsorção do herbicida metribuzin

Abstract

The contamination of freshwater, groundwater or not, by pesticides occurs through runoff from irrigation or rain together with the pesticide sprayed on the plantation. And the contact, exposure or consumption of pesticides even in small doses, but for a long period of time, are linked to health problems such as neurological, cancer, asthma, among others. In view of this, the present work aimed to study the synthesis of a new adsorbent for the removal of the pesticide Metribuzin from aqueous solutions, evaluating its adsorption capacity. The synthesis process took place from the yerba mate residue as raw material, by the hydrothermal carbonization technique (CHT) at temperatures of 180, 190 and 200°C. The yield from the hydrochars synthesis was 53.80%, 53.30% and 51.99% for the synthesis temperatures of 180, 190 and 200°C, respectively. The hydrochars obtained were submitted to adsorption equilibrium test and characterized by SEM and FTIR methods. The Langmuir and Dubinin-Radushkevich models showed coefficients of determination greater than 0.8, adjusting to the experimental data for the hydrochars of 180 and 190°C, resulting in maximum adsorption capacities of 1452 and 1200 mg g-1, respectively. In both adsorbents, the adsorption process is characterized as being favorable and physical. The hydrochar synthesized at 200°C presented the best fit to the Freundlich model, physical adsorption, but unfavorable and with a maximum adsorption capacity of 903700 mg g-1. At 180°C, a greater amount of small and homogeneous pores was observed. With the adsorption kinetics test, it is concluded that the adsorption equilibrium time is less than 60 min. The hydrochar synthesized at 180°C presented the best results, higher adsorption capacity, better fit to the DR model and smaller pores.