abstract
ETS-4 was prepared by hydrothermal synthesis and characterized by powder X-ray diffraction in order to assess its ion exchange capacity towards the removal of Cs+ from aqueous solutions in both batch and fixed-bed operation modes. Several assays were carried out to measure isotherm (8 experiments) and breakthrough curves (5 experiments); a set of loading-regeneration-loading experiments was also performed highlighting the ability of ETS-4 to be used in cyclic ion exchange. Powder X-ray diffraction showed that parent and Cs+-exchanged ETS-4 are isostructural. The Langmuir equation achieved good correlation results (average deviation of 6.58%), while the Nernst-Planck based model proposed for the fixed-bed assays fitted one breakthrough curve with 18.66% error, and was able to predict the remaining four experiments with 9.55% error. The Nernst-Planck parameters are the self-diffusion coefficients of Cs+ and Na+ in ETS-4, whose values (DCs+ = 3.193 x 10(-16) m(2) s(-1) and DNa+ = 6.088 x 10(-15) m(2) s(-1)) are consistent with the microporosity of ETS-4 framework and with the size of the counter ions. (C) 2016 Elsevier B.V. All rights reserved.
keywords
ION-EXCHANGE PROPERTIES; TITANOSILICATE ETS-4; LANTHANIDE SILICATE; HG2+ IONS; CESIUM; STRONTIUM; WASTE; WATER; PURIFICATION; ADSORPTION
subject category
Engineering
authors
Figueiredo, BR; Portugal, I; Rocha, J; Silva, CM
our authors
Bruno Reis Figueiredo
PhD Student
Carlos Manuel Silva
Associate Professor
Inês Portugal
Assistant Professor
João Rocha
Full Professoracknowledgements
B.R. Figueiredo acknowledges a Ph.D. grant from Fundacao para a Ciencia e a Tecnologia (SFRH/BD/75457/2010). 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.