A Study on the Correlation Between Adsorption and Swelling for Poly(Hydroxamic Acid) Hydrogels-Triarylmethane Dyes Systems

Abstract

The influence of crosslinker and dye type on the swelling and adsorption characteristics of poly(hydroxamic acid) (PHA) hydrogels have been investigated. PHA hydrogels with crosslinker such as N,N′-methylenebisacrylamide or ethylene glycol dimethacrylate were used in experiments on swelling, diffusion and adsorption of the triarylmethane dye such as Malachite Green, Methyl Violet 6B and Crystal Violet. The equilibrium swelling (Se) values of PHA hydrogels in the dye solutions were calculated as 2.26–21.57 g g−1. Some swelling, swelling kinetics, diffusional behavior and diffusional kinetics parameters were found. Diffusional behavior of the triarylmethane dye solutions was investigated. Diffusion behavior analyses determined that dye solution diffusion into hydrogels followed the anomalous Fickian behavior. It was observed that swelling characteristics of hydrogels are highly affected by the by the crosslinker type. Sorption of the triarylmethane dyes onto PHA hydrogels were studied by batch sorption technique at 25 °C. PHA hydrogels in the triarylmethane dye solutions showed the dark coloration. In the experiments of the adsorption, S type adsorption in the Giles classification system were found with an adsorption mechanism well represented by the Freundlich model. It has been found that there is an increasing linear correlation between swelling and adsorption values. The adsorbed amounts of the dyes by PHA–EGM hydrogels were very high (95% of the total concentration of the dyes), whereas the dyes were adsorbed in smaller (77%) amounts by PHA–NBis hydrogels. At the end of this study, it can be said that PHA hydrogels may be used a sorbent for removal of some agents (such as organic molecules) and dye molecules.