Adsorção de corante diazo secundário por ZnAl / hidróxido duplo lamelar

Abstract

Every day, several emerging pollutants, such as dyes, pesticides, drugs and hormones are commonly detected in aqueous matrices around the world and, as they are found in low concentrations, they require specific treatments so that they can be removed from the water in the water stations. treatment. When there is a need for a higher quality treatment, adsorbents are becoming a key alternative. Lamellar Double Hydroxides (LDHs), also known as anionic clays, have bidimensionally organized structures and flexible pores like clay minerals. Furthermore, they are capable of incorporating negative species in the interlamellar region in order to neutralize the positive charges of the lamellae. Due to unique characteristics such as: ion exchange capacity, high surface area, porosity and thermal stability, HDLs have a wide variety of applications, and can be used as adsorbents, anion exchangers and catalysts. In this work, the synthesis of ZnAl/HDL was carried out through the coprecipitation method containing zinc and aluminum cations in a molar ratio of 3:1 (Zn:Al) by the coprecipitation method at increasing pH in order to analyze the potential of the material as adsorbent in the removal of Congo red dye. The obtained material was characterized by three techniques: Energy Dispersive X-ray Fluorescence Spectrometer (EDX), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (DRX), confirming the presence of cations on the surface of HDL and subsequently used in adsorption tests. The adsorption studies proved that ZnAl/HDL had affinity with the Congo red dye, obtaining a removal in the range of 84% for a mass of 0.1 g of adsorbent material. For an increase in the dosage of HDL in the order of 0.3 g, it was possible to verify that the adsorption process became more favorable, presenting a removal capacity of approximately 95%. The pseudo-first and pseudo-second order models were evaluated for the kinetic study, which stated that the system enters equilibrium in the first 240 minutes and the experimental data are better described by the pseudo-second order model. The isotherms are best represented by the Freundlich model.