RESUMEN

A novel CoFe2O4/chitosan magnetic composite, where CoFe2O4 is known as cobalt ferrite, was synthetized, characterized and applied to adsorb indigotine blue dye (IBD). According to the central composite design (CCD), adsorption of IBD onto CoFe2O4/chitosan composite was favored when initial pH and adsorbent dosage were 3.0 and 0.75 g L-1, respectively. Adsorption was a fast process, well represented by pseudo-first order model, being the equilibrium reached at 15 min. Concerning the equilibrium behavior, the adsorption was satisfactorily modeled by the Langmuir model, reaching maximum adsorption capacity of 380.88 mg g-1 at 328 K. The thermodynamic parameters indicated a spontaneous, favorable and endothermic adsorption process. CoFe2O4/chitosan magnetic composite is an efficient adsorbent to remove dyes from aqueous media, presenting advantages like fast kinetic, high adsorption capacity and interesting magnetic properties that allows the easy separation after the adsorption operation.

RESUMEN

This research was conducted to evaluate the methylene blue dye adsorption by piaçava fibers. The effects of adsorbent amount, pH, kinetics, equilibrium, and thermodynamics were analyzed, as well as the adsorbent performance in the treatment of synthetic textile effluents. The adsorbent characterization was also performed. Experimental kinetic data were fitted with pseudo-first-order, pseudo-second-order, and Elovich models. The equilibrium tests were done at 298, 308, and 318 K, and the models of Freundlich, Langmuir, Redlich-Peterson, and Sips were used. The adsorption was favored using 0.025 g of adsorbent, pH 10, and 318 K. The Elovich model provided better fit to kinetic data. The equilibrium experimental points were well represented by the Sips model. The maximum experimental adsorption capacity of methylene blue dye was 427.3 mg g-1. It was verified a spontaneous, favorable, and endothermic adsorption. Piaçava fiber was a promising low-cost material to be used for color removal in effluents containing methylene blue.

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RESUMEN

Adsorption of copper ions onto chitosan films was studied, and the matrix effect was evaluated using a synthetic solution and a real effluent from closed copper mine. Chitosan films were prepared by casting technique and characterized. The adsorption study was carried out by equilibrium isotherms, thermodynamics, and kinetics. The thermodynamic parameters indicated that the copper adsorption onto chitosan film was favorable, spontaneous, and exothermic, suggesting an increased randomness at the solid/solution interface. The matrix effect was evaluated in kinetic assays, where a synthetic solution and a real system were carried out at different stirring rates. The highest values of adsorption capacity reached in all stirring rates were about 20% lower in the real effluent, and this reduction in the competitiveness was due to the presence of other ions in the matrix of the real effluent. The maximum adsorption capacity of copper ions onto chitosan films for the synthetic solution was of 450 mg g-1, and the removal percentage was in the range from 78 to 96%, and these values for the real effluent were of 360 mg g-1 and removal ranging from 62 to 76%. The mapping done of ions present in the water adsorbed of the mine in the films showed that the same was homogeneously distributed in the films' surfaces.

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