Development of adsorbent from Teflon waste by radiation induced grafting: Equilibrium and kinetic adsorption of dyes

Abstract

Mutual radiation grafting technique was employed to graft polyacrylic acid (PAA) onto Polytetrafluoroethylene (Teflon) scrap using high energy gamma radiation. Polyacrylic acid- g-Teflon (PAA- g-Teflon) adsorbent was characterized by grafting extent measurement, FTIR spectroscopy, SEM and wet ability & surface energy analysis. The PAA- g-Teflon adsorbent was studied for dye adsorption from aqueous solution of basic dyes, namely, Basic red 29 (BR29) and Basic yellow 11 (BY11). The equilibrium adsorption data were analyzed by Langmuir and Freundlich adsorption isotherm models, whereas, adsorption kinetics was analyzed using pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models. Equilibrium adsorption of BR29 was better explained by Langmuir adsorption model, while that of BY11 by Freundlich adsorption model. The adsorption capacity for BY11 was more than for BR29. Separation factor ( R L) was found to be in the range 0 < R L < 1, indicating favorable adsorption of dyes. Higher coefficient of determination ( r 2 > 0.99) and better agreement between the q e,cal and q e,exp values suggested that pseudo-second order kinetic model better represents the kinetic adsorption data. The non-linearity obtained for intra-particle diffusion plot indicated, more than one process is involved in the adsorption of basic dyes. The desorption studies showed that ∼95% of the adsorbed dye could be eluted in suitable eluent.