Influência do campo magnético nos processos de adsorção e degradação da atrazina com ferroxita e hematita

Abstract

Brazil is one of the greatest consumers of agrochemicals in the world, mainly herbicides and insecticides. With the advent of several agrochemicals, many substances were released in the environment, contaminating the soil, the water and the air. Therefore, this work aimed at the use of iron oxides and magnetic fields in the adsorption e degradation processes of the agrochemical atrazine. We studied the behavior of lab-synthesized feroxyhyte using its magnetic properties to remove atrazine. Afterwards, we ran some lab tests related to hematite and analyzed some other variables such as, atrazine concentration, feroxyhyte concentration, pH, and magnetic field influence. First, we monitored the experiments to determine the action of magnetic fields on atrazine and feroxyhyte at a given concentration, under three conditions: presence of magnetic fields, absence of magnetic fields, and stirring with presence of magnetic fields. Afterwards, we used different amounts of feroxyhyte to determine the best mass to perform the study. We used the following mass values: 0.10g, 0.20g, 0.30g, 0.40g, and 0.50g. According to the results, the most appropriate amount was 0.50g. We also carried out analyses of point of zero charge (PZC) and determined that pH = 5 and 11 (PZC extremes) were the optimal pH values to be used in the study. After choosing the concentrations of atrazine, feroxyhyte, hematite, and pH, we performed tests to choose the best conditions for fenton reaction, which were the following: feroxyhyte mass: 0.50g; atrazine: 0.10mgL-1; pH: 5, at the presence of a magnetic field. For hematite, the best conditions were the same as for feroxyhyte. The magnetic field influenced the fenton reaction for feroxyhyte and hematite, at the presence of a magnetic field; adsorption was reduced and the volume of hydrogen peroxide used was smaller than in the samples at the absence of magnetic fields. n this test, the result was 0.9 mL reducing adsorption in 87.53% for feroxyhyde at the presence of magnetic field, whereas the result for the experiment without magnetic field was 64.49% and 1.1 mL of hydrogen peroxide. For hematite, the volume was 0.5 mL with a reduction of absorbance of 56.35% at the presence of a magnetic field, while, at the absence of a magnetic field, adsorbance was 28.82% and the volume of hydrogen peroxide was 0.7 mL. According to these numbers, feroxyhyde at the presence of a magnetic field has better adsorption and degradation, and may be used at the removal of organic matter.