TY - JOUR
T1 - Experimental study of zeolitic diffusion by use of a concentration-dependent surface diffusion model
AU - Inglezakis, V. J.
AU - Fyrillas, M. M.
N1 - Funding Information:
This work was supported by the HORIZON 2020 project "Nanoporous and Nanostructured Materials for Medical Applications (NanoMed)" H2020-MSCA-RISE-2016, 734641 , European Commission Marios M. Fyrillas was supported by CRoNoS - IC408 COST Action.
Publisher Copyright:
© 2019
PY - 2019/7/1
Y1 - 2019/7/1
N2 - Surface diffusivity in adsorption and ion exchange processes is probably the most important property studied expensively in the literature but some aspects, especially its dependence on solid phase concentration, is still an open subject to discussion. In this study a new concentration-dependent surface diffusion model, equipped with a flexible double selectivity equilibrium relationship is applied on the removal of Pb2+, Cr3+, Fe3+ and Cu2+ from aqueous solutions using a natural zeolite. The model incorporates the Chen-Yang surface diffusivity correlation able to deal with positive and negative dependence with surface coverage. The double selectivity equilibrium relationship successfully represents the experimental equilibrium data, which follow Langmurian isotherm type for Pb2+, sigmoidal for Cr3+ and Fe3+ and linear for Cu2+. The concentration-dependent surface diffusion model was compared with the constant diffusivity surface diffusion model and found to be moderately more accurate but considerably more useful as it provides more insights into the diffusion mechanism. The application of the model resulted in an average deviation of 8.56 ± 6.74% from the experimental data and an average solid phase diffusion coefficients between 10−9 and 10−10 cm2/s. The results showed that the diffusion of metal ions in the zeolite structure is unhindered following the surface diffusion mass transfer mechanism.
AB - Surface diffusivity in adsorption and ion exchange processes is probably the most important property studied expensively in the literature but some aspects, especially its dependence on solid phase concentration, is still an open subject to discussion. In this study a new concentration-dependent surface diffusion model, equipped with a flexible double selectivity equilibrium relationship is applied on the removal of Pb2+, Cr3+, Fe3+ and Cu2+ from aqueous solutions using a natural zeolite. The model incorporates the Chen-Yang surface diffusivity correlation able to deal with positive and negative dependence with surface coverage. The double selectivity equilibrium relationship successfully represents the experimental equilibrium data, which follow Langmurian isotherm type for Pb2+, sigmoidal for Cr3+ and Fe3+ and linear for Cu2+. The concentration-dependent surface diffusion model was compared with the constant diffusivity surface diffusion model and found to be moderately more accurate but considerably more useful as it provides more insights into the diffusion mechanism. The application of the model resulted in an average deviation of 8.56 ± 6.74% from the experimental data and an average solid phase diffusion coefficients between 10−9 and 10−10 cm2/s. The results showed that the diffusion of metal ions in the zeolite structure is unhindered following the surface diffusion mass transfer mechanism.
KW - Adsorption
KW - Chemical engineering
KW - Clinoptilolite
KW - Diffusion coefficients
KW - Heavy metals
KW - HSDM
KW - Variable diffusivity
KW - Zeolites
UR - http://www.scopus.com/inward/record.url?scp=85069807495&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85069807495&partnerID=8YFLogxK
U2 - 10.1016/j.heliyon.2019.e02143
DO - 10.1016/j.heliyon.2019.e02143
M3 - Article
AN - SCOPUS:85069807495
SN - 2405-8440
VL - 5
JO - Heliyon
JF - Heliyon
IS - 7
M1 - e02143
ER -