Magnetite nanoparticle embedded Pectin-graft-poly(N-hydroxyethylacrylamide) hydrogel: Evaluation as adsorbent for dyes and heavy metal ions from waste water.

A pectin (Pec) based gel has been made by grafting N-hydroxyethylacrylamide (HEAA) on pectin using potassium peroxodisulphate as initiator and N,N-methylenebisacrylamide as crosslinker under microwave irradiation. The magnetite (FeO) nanoparticles were incorporated within this gel via in situ diffusion of Fe and Fe followed by reaction with ammonia solution. The synthesized gel, pectin-graft-poly(N-hydroxyethylacrylamide) (Pec-g-PHEAA); and the magnetite containing composite (Pec-g-PHEAA/FeO) were characterized by FTIR, TGA, XRD, BET and SEM techniques. The magnetic property measurement indicated ferromagnetic nature of the nanocomposite. The Pec-g-PHEAA and Pec-g-PHEAA/FeO systems were evaluated for removal of dye and metal ions from aqueous solution using Rhodamine 6G (R6G), a cationic dye; Cu(II) and Hg(II) ions. Both adsorbents showed significant adsorption capacity towards these species, with greater adsorption capacity in case of Pec-g-PHEAA/FeO. Adsorption process is observed to follow both Langmuir and Freundlich isotherm models for R6G dye and Freundlich isotherm model for Cu(II) and Hg(II) ions. The adsorption was found to be a pseudo first order process for R6G and pseudo second order process for Cu(II) and Hg(II) ions. The positive values of ∆H and the negative values of ∆G indicated the adsorption process to be endothermic and spontaneous.