Metal sorption behavior of poly(N-vinyl-2-pyrrolidone)/(acrylic acid-co-styrene) hydrogels synthesized by gamma radiation

Abstract

pH-sensitive hydrogels based on Poly (N-vinyl-2-pyrrolidon) (PVP), acrylic acid (AAc) and styrene (Sty) were prepared by gamma irradiation. PVP/(AAc-co-Sty) hydrogels were modified to use as adsorbent materials for removal of heavy metal ions from aqueous solution. Effect of functionalization of hydrogels by sulfonation (Sf), partial hydrolysis with alkaline solution (NaOH) and treated with the two processes (NaOH/Sf) on metal ion uptake has been studied, and it results in appreciable uptake of Co2+, Cu2+ and Fe3+ ions from aqueous solution. The degree of swelling and gel content increase with increasing AAc ratio in the initial feed solutions. The structure of hydrogels was characterized by FT-IR and 1H NMR spectral data and the results were consistent with the expected structures. It was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The capacity of the hydrogels to bind various metal ions was tested under a range of uptake conditions, with varying uptake time, pH, temperature and initial feed concentration. The metal ion uptake efficiency of PVP/(AAc-co-Sty) hydrogel is in the order: hydrogel treated with NaOH/Sf>hydrogel treated with NaOH>hydrogel treated with Sf>untreated hydrogel. The highest metal ion uptake was observed for Fe3+ and the lowest was observed for Cu2+. It was observed that the specific interaction between metal ions and ionic moieties on the polymeric chains can affect the metal binding capacity of the hydrogel. These results are of interest for the development of hydrogel-based technologies for water purification and metal ions separation and enrichment.