Efficient removal of dyes and heavy metal ions from waste water using Gum ghatti – graft – poly(4-acryloylmorpholine) hydrogel incorporated with magnetite nanoparticles

Abstract

Abstract Microwave irradiation of the mixture of Gum ghatti (Ggh) and 4-acryloylmorpholine (AcM) in the presence of potassium peroxodisulphate as initiator and N, N-methylenebisacrylamide as crosslinker produced the copolymer hydrogel (Ggh-g-PAcM). The magnetite (Fe3O4) nanoparticles were embedded in the gel through in situ formation. The hydrogel and the magnetite incorporated nanocomposite (Ggh-g-PAcM/Fe3O4) were characterized using FTIR, TGA, XRD, SEM, BET and VSM techniques. The nanocomposite displayed super-paramagnetic behavior with saturation magnetization (Ms) value 0.0876 emu g−1. Both the adsorbents were investigated, for removal of dyes and metal ions from aqueous solution, in the concentration range of 20−1000 mgL–1 using two cationic dyes and two bivalent metal ions as model adsorbates at 30 °C. The adsorption capacities of Ggh-g-PAcM for methylene blue, rhodamine 6 G, Cu(II) and Hg(II) were 90.6, 103.6, 224.8, 213.8 mgg−1 respectively which increased significantly to 116.8, 137.8, 249.9 and 235.1 mgg−1 respectively for Ggh-g-PAcM/Fe3O4 which is thought to be due to increase in surface are from 0.11 to 0.21 m2 g−1. The kinetic studies indicated the adsorption in all cases to be a pseudo second-order process. The adsorption isotherm is in good agreement with Freundlich model signifying surface heterogeneity of the adsorbent. Further, the thermodynamic studies revealed the adsorption to be a spontaneous and endothermic process. Both the adsorbents exhibited outstanding regeneration capacity in stripping solution of pH 1.2, the desorption being higher than 97 % for the nanocomposite. Thus, the study reveals Ggh-g-PAcM/Fe3O4 to be an efficient adsorbent for removal of cationic dyes and heavy metal ions from aqueous solutions.