Zeolitic Polyacrylamide Hydrogel for Methylene Blue Removal

In this work, composite hydrogel based on polyacrylamide and sodium zeolite particles was prepared. Particularly, zeolite particles were obtained in the alkaline medium via crystallization of Egyptian kaolin under hydrothermal conditions. Meanwhile, the composite polyacrylamide hydrogel was prepared via in-situ polymerization approach with different zeolite ratios using acrylamide as a commercial monomer in the presence of an initiator and a crosslinker. The formed modified hydrogel was investigated compared with the pristine one by several characterization techniques such Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), and gas sorption. The results emphasized the successful preparation and the incorporation of zeolite particles in the hydrogel matrix supporting a strong interaction as well. Application of the prepared composite hydrogel on the removal of methylene blue displayed a superior performance over the pure matrix as the removal percentage reached ~ 96 % after 2 minutes of treatment thanks to the improved properties in the presence of zeolite crystals. Adsorption isotherm and kinetic models emphasized that the adsorption reaction is pseudo-second order and obeys Langmuir. Moreover, thermodynamic studies proved the exothermic reaction as well as the strong interaction between the dye molecules and gel’s surface could be established. Also, the reaction conditions were optimized. The study showed that the best parameters in terms of the contact time, the hydrogel weight, pH, the temperature, the initial dye concentrations, and even the filler ratios were 30 min., 0.4 g (dried gel), normal, room atmosphere, 50 ppm, and 10 wt. %, respectively. Finally, the obtained composite matrix could be reused up to five cycles. It could be claimed that, the developed zeolitic hydrogel can pave the way towards a new generation of adsorbents as it deems a promising candidate in the wastewater treatment applications.