novel graphene oxide semi-ipn nanocomposite hydrogel based on partially hydrolyzed polyacrylamide: preparation, swelling properties and adsorption studies of cationic methylene blue dye from water

Fabrication of novel semi-interpenetrating polymer network (ipn) nanocomposite hydrogels composed of polyvinyl alcohol/partially hydrolyzed polyacrylamide (phpam) incorporating graphene oxide (go) as a beneficial adsorbent for the removal of toxic methylene blue from aqueous solutions is described. pva/phpam/go nanocomposite hydrogels with different go contents were synthesized via the internal ionic gelation method using chromium (iii) ions as ionic cross-linker in an aqueous solution. the structure and morphology of the prepared hydrogels were characterized by various techniques such as fourier transform infrared spectroscopy (ftir), scanning electron microscope (sem), x-ray diffraction (xrd), and thermogravimetry (tg). optimization of the hydrogel synthesis reaction condition based on the equilibrium swelling ratio criteria was performed by using taguchi standard method. adsorption kinetics and equilibrium adsorption isotherm fitted pseudo-second-order kinetic model with a high correlation coefficient and langmuir isotherm model well, respectively. thus, the prepared hydrogels had good stability and reusability as they exhibited excellent removal efficiency (70%) after five consecutive adsorption-desorption cycles. the maximum adsorption capacity calculated from the langmuir isotherm model reached 714.8 mg.g-1 at 30 °c, obviously higher than the hydrogels prepared without this addition (293.8 mg.g-1). according to the calculated thermodynamic parameters δg◦, δh◦, and δs◦, mb adsorption onto the adsorbent was a spontaneous, endothermic, and physical adsorption process.