Potencialidades de adsorção de corantes básicos em material cerâmico isolante

Abstract

Effective environmental management permeates the monitoring, treatment, control and proper disposal of waste generated in the stages of industrial production. In this work, the physicochemical phenomenon of adsorption was used as final polish in dye solutions.The adsorbent used was the aluminosilicate present in the insulating ceramic material discarded as solid residue by the Electrical Companies of Furnas and Enel Distribuição S.A., with chemical composition based on hydrated silicates of aluminum and iron. This material was used to study its adsorption potentialities in dyes solutions of methylene blue and cristal violet, usually present in effluents from textile industries, and when discarded in water bodies affect the physicochemical parameters in the environment. The absorbent`s characterization was performed by Infrared spectroscopy analysis with Fourier transform (FTIR), Chemical composition analysis by X-ray fluorescence (FRX), X-ray diffraction analysis (XRD), Scanning electron microscopy (SEM), Multimolecular adsorption theory (BET), thermogravimetric Analysis Technique (TGA), and Point of zero charge determination (pHPCZ) (1-11). In another step, pH`s effect on the system was studied (4-12); granulometry`s effect (80-150 mesh); the mass effect (200-1500mg); equilibrium time of chemical kinetics (0 to 720 minutes); the affinity between adsorbent and adsorbate (isothermics parameters - 0 to 600 minutes); thermodynamics parameters in different temperatures - 298, 308 and 318 K. The graphics of the adsorption isotherms were constructed according to the mathematical models of Langmüir, Freundlich, Temkin and Dubini-Radushevich. The thermodynamics parameters were determined to 298, 308, 318 K temperatures. The pHpcz`s value was 3.71 ± 0.03 for aluminosilicate. The most adjusted conditions for adsorption in dye solutions of methylene blue and cristal violet were: pH 8.0 - adsorbent`s mass: 1,1 g - dye solutions concentration of 10 mg L-1 - fine granulometry (115 mesh ≤ D1 < 150 mesh) - equilibrium time from 480 to 720 minutes. The experimental`s data adjusted better to the kinetic model of pseudo-second order, and the isothermics of Langmüir and Freundlich in the 298 and 308 K temperatures; and Langmüir, Freundlich and DubininRadushkevich in the 318 K temperature, suggesting the occurrence of adsorption on a heterogeneous surface of a favorable and predominantly physical nature. The temperature study indicated that the adsorption process is not spontaneous; and Gibbs energy values (∆Gº) suggest physissorption. The best index in dye removal occurred in 298K, suggesting that adsorbent has greater removal capacity at room temperature, on average 51% of removal. The results obtained in this work suggest that the material can be used in the treatment and final polishing of dyes solutions with low concentrations in effluents, considering its great availability, excellent stability, good efficiency, low cost, use at room temperature and planned application of the system in environmental management.