resumo
Cadmium is one of the most toxic contaminants of superficial waters, whose effects are particularly harmful to human health. In 20 years the European Union will impose total elimination of cadmium from industrial discharges. Such facts induce researchers to develop fine separation processes for cadmium removal, especially at the tertiary treatment level. In this work, we studied the applicability of the microporous titanosilicate ETS-4 (Engelhard Titanium Silicates No. 4) to uptake Cd(2+) from aqueous solution, in order to evaluate its potential as ion exchanger material. The effect of pH was investigated by performing batch stirred tank experiments. The results obtained shown that Cd(2+) removal increases up till pH 6, which is a very important conclusion since this value is commonly found in effluents and other wastewaters. The equilibrium data at pH 6 were accurately represented by the Langmuir-Freundlich isotherm under the experimental conditions studied (average absolute deviation, AAD=1.67%). The amount of Cd(2+) removed by ETS-4 at pH 6 clearly surmount results found in literature for the same titanosilicate at pH 4 and for different materials. The kinetic of Cd(2+) uptake by ETS-4 was analyzed using a Nernst-Planck based model. The absolute average deviation found point out the reasonable data representation accomplished by Nernst-Planck: AAD=17.2%. (C) 2009 Elsevier B. V. All rights reserved.
palavras-chave
HEAVY-METAL IONS; LENGTH-COLUMN METHOD; ZEOLITE-A; DIFFUSION-COEFFICIENTS; EXCHANGE PROCESSES; MASS-TRANSFER; SODIUM-IONS; WASTE-WATER; CLINOPTILOLITE; ADSORPTION
categoria
Engineering
autores
Barreira, LD; Lito, PF; Antunes, BM; Otero, M; Lin, Z; Rocha, J; Pereira, E; Duarte, AC; Silva, CM
nossos autores
Carlos Manuel Silva
Professor associado
João Rocha
Prof. Catedrático
Patrícia Ferreira Lito
Bolseiro de pós-Doutoramento
Zhi Lin
Investigador Principalagradecimentos
Patricia F.Lito wishes to thank PhD grant provided by Fundacao para a Ciencia e Tecnologia (Portugal) (SFRH/BD/25580/2005). Authors acknowledge FEDER for financial support.