Microesferas do biossorvente quitosana: obtenção e aplicabilidade na remoção de 17­β­estradiol em meio aquoso

Abstract

The presence of emerging pollutants in water resources represents a serious threat to the environment and human health. In recent years, the increase in drug consumption has made the substances that constitute them the main contaminants of wastewater. Among these substances, 17-β-­estradiol has been studied because it is an emerging pollutant that in small concentrations, on the scale of micro and nanograms per liter, can cause physiological changes in both humans and animals, especially those that live in an environment aquatic. The present work aimed to study the obtainment and applicability of chitosan biosorbent microspheres in the removal of 17-­β­-estradiol in aqueous medium. Chitosan microspheres were obtained using the alkaline coagulation method and modified with glutaraldehyde. The biosorbents were characterized by Optical Microscopy (OM), Fourier Transform Infrared Spectroscopy (FTIR) and adsorption kinetics and equilibrium studies were performed. In this sense, for the kinetics, the pseudo­first order and pseudo­second order models were adjusted, while for equilibrium, the Langmuir and Freundlich isotherms were adjusted. From the OM images, it was possible to observe the presence of microspheres, without the formation of aggregates, with a mean diameter of 894.8 ± 65.4 μm for the dehydrated chitosan microspheres. The FTIR results indicated the existence of functional groups C=O (amide) and the imine bond (C=N), confirming the modification of chitosan with glutaraldehyde. As for adsorption, dehydrated chitosan microspheres were able to remove 98% of 17-­β­estradiol, for equilibrium the Langmuir model was adjusted (R²adj= 0.946; qmax= 242.0 mg g­1), suggesting that the adsorption can be reversible and confirming the possibility of regeneration of the adsorbent. Chitosan microspheres, as a system for removing pollutants present in the aqueousmedium, proved to be a good adsorbent in relation to the hormone 17-­β-­estradiol. However, from the point of view of basic science, we conclude that other parameters must be analyzed in order to better understand the system, as well as its mechanism of action. From the point of view of applied science, the results presented here indicate that the studied system has potential for use in real situations, in which hormone­like pollutants, with structure similar to estradiol, are contaminants of water resources. Both perspectives point to possibilities for the continuation of this work.