abstract
Microporous stannosilicate AV-6 was investigated for cadmium(II) removal from aqueous solutions in batch experiments. Ion exchange equilibrium of the Cd2+/K+/AV-6 system was modeled using the mass action law combined with activity coefficient models for the solution (ideal, Debye-Htickel and Pitzer equations) and for the solid (Wilson equation) with absolute average relative deviations (AARDs) between 6.56% and 6.75%. It was concluded that the system embodies strong intraparticle non-idealities, namely solid activity coefficients between 0.2602 and 0.7180 for Cd2+. The kinetics of cadmium(II) sorption was analyzed measuring removal curves and modeling the data with pseudo-first and pseudo-second order expressions, commonly adopted in the literature, and with Maxwell-Stefan (MS) and Nernst-Plank (NP) based models. The best results were achieved by MS and NP approaches, for which AARD was 3.74% and 3.71%, respectively. The kinetic performance of the ion exchange was also discussed taking into account structural aspects of the AV-6 material. (C) 2016 Elsevier B.V. All rights reserved.
keywords
LANTHANIDE SILICATE EU-AV-20; MAXWELL-STEFAN APPROACH; EXCESS GIBBS ENERGY; TITANOSILICATE ETS-4; AQUEOUS-SOLUTION; STRUCTURAL-CHARACTERIZATION; MASS-TRANSFER; METAL-IONS; REMOVAL; SYSTEMS
subject category
Engineering
authors
Cardoso, SP; Azenha, IS; Lin, Z; Portugal, I; Rodrigues, AE; Silva, CM
our authors
Carlos Manuel Silva
Associate Professor
Inês Portugal
Assistant Professor
Ivo Samuel Caniceiro Azenha
PhD Student
Simão Pedro Pereira Cardoso
Post-Doc Fellowship
Zhi Lin
Principal Researcheracknowledgements
This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT Ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate co-financed by FEDER under the PT2020 Partnership Agreement. S.P. Cardoso acknowledges a Ph.D. grant from Fundacao para a Ciencia e a Tecnologia (Portugal) (SFRH/BD/75164/2010).