Study and comparison of several methods to remove Ni(II) ions in aqueous solutions using poly(acrylamide-co-itaconic acid) hydrogels

In this paper we present the results of the recovery of Ni(II) ions in aqueous media using poly(acrylamide-co-itaconic acid) hydrogels. The copolymer was synthetized via free radical polymerization at 30 °C using the potassium persulfate and N,N,N′,N′-tetramethylethylenediamine redox pair. Several methodologies were studied and compared by varying the following parameters: temperature, pH of the media, Ni(II) ion concentration and aqueous solution / xerogel weight ratio. Finally, the removal efficiency of the applications of the hydrogel and the influence of the parameters was measured. Our main result was found by swelling the hydrogel in an aqueous media with pH 13, then placed at the Ni(II) solution. With this methodology, the ion recovery performance was up to 94%, this because the polymeric matrix is saturated with a NaOH solution and the nickel ions cannot penetrate the hydrogel considerably. Thus instead of absorbing the Ni(II) ion, it reacts with the OH− ions delivered at the surface of the hydrogel, forming Ni(OH)2 layer at the surface, which is partially absorbed.