Use of zeolite synthesized from coal ashl from Santa Catarina for removal of iron, manganese and methylene blue dye in water

Uso de zeólita sintetizada a partir de cinzas de carvão de Santa Catarina para remoção de ferro, manganês e o corante azul de metileno em água

Abstract

The fly ash of coal, generated in a thermoelectric plant, was used to synthesize zeolite by hydrothermal treatment with a sodium hydroxide solution. The zeolite synthesized was used as an adsorbent of metals (Fe and Mn) and of the methylene blue dye in water. The characterization of the zeolite showed that silicon oxide is the main compound in its composition, followed by aluminum, iron, sodium and calcium, which together correspond to more than 86% of its composition. These were used to investigate the kinetic parameters of adsorption and the isotherm of the metals and the methylene blue dye in aqueous solutions. Three kinetic models, pseudo-first order, pseudo-second order and intraparticle diffusion were used to predict adsorption rate constants. The adsorption kinetics of the dye and metals followed the pseudo-second order kinetics and reached equilibrium in 15 minutes with a 99% removal rate for metals, independently of the pH. The values ​​of the diffusion constants (K₂) for iron in pH 5, 7 and 8 were 1.3158; 1.3881 e 0.6053 mg.g^-1.min^-1 and for manganese 1.2511; 1.5239 and 1.4336 mg.g^-1.min^-1, respectively. For methylene blue, the removal rate was 90% and the constant (K₂) value was 0.5437 mg.g^-1.min^-1. The studies showed the existence of different stages in the adsorption of the metals and the methylene blue dye in zeolite.

Keywords:
coal ashes; water purification; zeolite.