The adsorption behaviors of the multiple stimulus-responsive poly(ethylene glycol)-based hydrogels for removal of RhB dye

Abstract

In this article, the multiple stimulus-responsive organic/inorganic hybrid hydrogels by combining poly(2-(2-methoxyethoxy) ethyl methacrylate-co-oligo (ethylene glycol) methacrylate-co-acrylic acid) (PMOA) hydrogel with magnetic attapulgite/Fe3O4 (AT-Fe3O4) nanoparticles were applied to the removal of Rhodamine B (RhB) dye from wastewater. The adsorption of RhB by the hydrogels was carried out under different external environmental, such as pH, temperature and magnetic-field. The results showed that the hydrogels still possessed temperature, pH and magnetic-field sensitivity during the adsorption process, which indicated that the adsorption could be controlled by the hydrogels responsive. The dye adsorption had a significant increment at 30°C and the removal of RhB could reach to over 95%. Besides, the low pH values were also favorable for the RhB adsorption, the removal was over 90% at pH=4.56. Kinetic studies showed that the pseudo-second order kinetic model well fitted the experimental data. The rate constant of adsorption was 0.0379 g/mg min. Langmuir and Freundlich isotherm models were applied to the equilibrium adsorption for describing the interaction between sorbent and adsorbate. The maximum KL and KF were 2.23 (L/g) and 0.87 (mg/g) at 30°C, respectively. Under the external magnetic-field, the adsorption rate significantly increased within 250 min and the hydrogels could be separated easily from wastewater.