Adsorptive features of polyacrylamide{aluminosilicate composites for methylene blue

Content Provider	Semantic Scholar
Author	Baybaş, Demet Ulusoy, Ulvi
Copyright Year	2016
Abstract	Polyacrylamide--montmorillonite (PAAm-Mt) and polyacrylamide--clinoptilolite (PAAm-Z) composites were prepared by cross-linked polymerization of acrylamide in dispersions of Mt and Z. The composites were characterized by FT-IR, SEM, XRD, CEC, and PZC analysis. The adsorptive features of PAAm-Mt and PAAm-Z for methylene blue (MB) were investigated by their relevance to initial dye concentration, temperature, contact time, PZC, and pH. The monolayer adsorption capacities were 0.14 and 0.08 mol kg$^{-1}$ for PAAm-Z and PAAm-Mt, respectively. The changes in pH of MB solution had an insignificant influence on their adsorption capacities. The values of enthalpy and entropy changes were positive ($\Delta $H$_{PAAm-Mt}$ = 7.6 and $\Delta $H$_{PAAm-Z}$ = 17.6 kJ mol$^{-1}$, $\Delta $S$_{PAAm-Mt}$ = 55.7, and $\Delta $S$_{PAAm-Z}$ = 107.2 J mol$^{-1}$ K$^{-1})$. The negative free enthalpy change was proof of the spontaneity of adsorption ($\Delta $G$_{PAAm-Mt}$ = --9.0, $\Delta $G$_{PAAm-Z}$ = --14.4 kJ mol$^{-1})$. The adsorption kinetics obeyed a pseudo-second order model (k$_{PAAm-Mt}$ = 11.5 and k$_{PAAm-Z}$ = 1.18 mol$^{-1}$ kg min$^{-1}$, R$^{2\, }>$ 0.99). The adsorption mechanism was the combination of chemical and physical adsorption governed by Coulombic forces (liquid film diffusion) on which the contribution of intraparticle diffusion was not significant. This was consistent with a low value of the adsorption activation energy (E$_{a}$ = 9.4 kJ mol$^{-1})$. The composites had amphoteric features buffering the pH of the studied adsorption environment to approximately neutral levels.
Starting Page	147
Ending Page	162
Page Count	16
File Format	PDF HTM / HTML
DOI	10.3906/kim-1504-32
Volume Number	40
Alternate Webpage(s)	http://journals.tubitak.gov.tr/chem/issues/kim-16-40-1/kim-40-1-12-1504-32.pdf
Alternate Webpage(s)	https://doi.org/10.3906/kim-1504-32
Language	English
Access Restriction	Open
Content Type	Text
Resource Type	Article