Aplicação da concha de sururu (Mytella falcata) na remoção de azul de metileno em solução aquosa

Abstract

This work aims to evaluate the application of Mytella falcata shells as an adsorbent for the removal of methylene blue (MB), a model organic pollutant present in aqueous solutions. The adsorbent was obtained by thermal decomposition of Mytella falcata shells under vacuum at relatively low temperatures (ie 500°C and 600°C). The ability of the adsorbent material to remove MB was evaluated as a function of contact time, diameter, pyrolysis temperature and influence of pH on adsorption efficiency. The material was characterized by thermal analysis (TGA/DrTGA), infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). The highest adsorption capacity was 82.41%, obtained for 0.5 g of adsorbent mass, pyrolysis at 600°C, particle diameter of 0.297 - 0.149 mm and pH 12. The data obtained from the kinetic studies fit better to the pseudo-second order model, while the adsorption isotherms followed the Redlich–Peterson model. Regeneration was evaluated by applying photolysis and oxidation by H2O2. The regeneration efficiency of these methods was evaluated, and the material was characterized by SEM, FTIR, XRD and EDX. During photolysis, the saturated material was exposed to a source of UV radiation for 60 min and the results showed that a maximum of 50% regeneration was achieved. For the H2O2 oxidation tests, the results showed that a maximum of 63% regeneration was achieved with the oxidizing agent concentration of 600 mmol.L -1 . On the other hand, the efficiency in the regeneration process in which photolysis in the presence of H2O2 was evaluated, it was observed that, in general, exposure to UV radiation showed that it influences the efficiency of the process, increasing the percentage of material regeneration from 63 to 70 %, maintained at a concentration of 600 mmol.L -1 of H2O2. Furthermore, the stability of the material was evaluated through adsorptionregeneration cycles and the results showed in general that oxidation by H2O2 with exposure to UV radiation conferred greater stability.