Adsorptive features of polyacrylamide--aluminosilicate composites for methylene blue

Authors : DEMET BAYBAŞ, ULVİ ULUSOY

Pages : 147-162

View : 17 | Download : 7

Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :Polyacrylamide--montmorillonite insert ignore into journalissuearticles values(PAAm-Mt); and polyacrylamide--clinoptilolite insert ignore into journalissuearticles values(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 insert ignore into journalissuearticles values(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 insert ignore into journalissuearticles values($\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 insert ignore into journalissuearticles values($\Delta $G$_{PAAm-Mt}$ = --9.0, $\Delta $G$_{PAAm-Z}$ = --14.4 kJ mol$^{-1});$. The adsorption kinetics obeyed a pseudo-second order model insert ignore into journalissuearticles values(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 insert ignore into journalissuearticles values(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 insert ignore into journalissuearticles values(E$_{a}$ = 9.4 kJ mol$^{-1});$. The composites had amphoteric features buffering the pH of the studied adsorption environment to approximately neutral levels.
Keywords : Adsorption, methylene blue, aluminosilicate, composite, polyacrylamide