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 (Fe3O4) nanoparticles were incorporated within this gel via in situ diffusion of Fe2+ and Fe3+ 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/Fe3O4) 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/Fe3O4 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/Fe3O4. 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 ∆H0 and the negative values of ∆G0 indicated the adsorption process to be endothermic and spontaneous.