Adsorção de contaminante herbicida atrazina por meio de hidróxido duplo lamelar e carvão ativado em coluna de leito fixo

Abstract

In order to meet the needs for food resources of the world population, the use of pesticides has grown quite sharply and consequently several environmental problems have appeared. Atrazine, for example, is a highly toxic herbicide used in sugarcane and corn plantations due to its low cost. This makes it increasingly feasible to search for alternatives that have the ability to remove contaminants from natural resources. In this context, fixed-bed column adsorption is a continuous, non-stationary process that utilizes adsorbents inside it, such as Activated Carbon (A.C.), so that it retains the contaminant species of the solution, also called as adsorbate. In addition to A.C., another known adsorbent is Layered double hydroxides (LDH), which is a class of anionic clay that has promising adsorbent application for most experimental conditions such as pH variations, concentration, solid charges and ionic strength. From that, this work investigated the efficacy of atrazine adsorption by [Co-Al-Cl] LDH synthesized by the constant-pH coprecipitation method, associated with A.C. in a laboratory scale fixed-bed column. From the X-ray Diffractometer (XRD), it was observed defined diffraction peaks and with unit cell parameters similar to those of hydrotalcite. In the image obtained by scanning electron microscopy (SEM), it was possible to visualize a heterogeneous morphology with LDH irregular sizes. In the adsorption tests, the breaking points, which are the time that starts the fixed-bed column’s saturation, for the atrazine 1 mg L-1 on a "C.A." column were 80 minutes and 110 minutes for the C.A. + HDL column. For 2 mg L-1, the times were 60 and 80 minutes, "for only C.A." and C.A. + HDL, respectively. Regarding the atrazine removal percentage for C.A. + HDL column was of 96.35% for atrazine 1 mg L1, and for 2 mg.L-1 the result was 97.54%. For "C.A. column" was 93.71% removal percentage for 1 mg.L-1 and 95.30% for 2 mg.L-1.