Removal of dye from aqueous medium with pH-sensitive poly [(2-(acryloyloxy)ethyl]trimethylammonium chloride-co-1-vinyl-2-pyrrolidone] cationic hydrogel

In this study, p([2-(acryloyloxy)ethyl]trimethylammonium chloride-co-1-vinyl-2-pyrrolidinone) (p(AETAC-co-NVP) hydrogels containing positive charge in the structure were synthesized for the removal of anionic dyes from the aqueous media. The swelling behaviors affecting the adsorption properties of hydrogels structurally characterized by FTIR, SEM and EDX/mapping analysis were investigated. The effects of pH, dye concentration, adsorbent amount, dissolved anions and temperature on the adsorption of methyl orange (MO) and alizarin red S(AR) from aqueous media using p(AETAC-co-NVP) hydrogels were investigated. Using data obtained in adsorption studies, the Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms and pseudo-first order (PFO), pseudo-second order (PSO), intra-particular diffusion, and Elovich kinetic model analyses were performed. The results showed that the p(AETAC-co-NVP) hydrogel was a good adsorbent for MO and AR anionic dyes and the adsorption process for both dyes complied with the Freundlich isotherm and PSO kinetic model. This situation indicates that the dominant mechanism for the adsorption of MO and AR dyes by the p(AETAC-co-NVP) hydrogel is strong electrostatic interactions and occurs as multilayered adsorption, not only on a planar region. Additionally, to the maximum adsorption values using p(AETAC-co-NVP) hydrogel for MO and AR dyes were reached at pH values of 7.0 and 5.0, respectively. According to all these findings, it can be said that the p (AETAC-co-NVP) hydrogel containing positivelly charged groups is a super adsorbent for adsorption of anionic dyes.