Facile Preparation and Adsorption Behavior Studies of Poly(acrylic acid)-Based Hydrogels Reinforced by Hydrogen Bonds for Methylene Blue Dye

To suppress the extreme swelling of poly(acrylic acid) (PAA) hydrogels, two series of PAA-based hydrogels with additional non-covalent crosslinks were successfully synthesized by incorporating allyloxypolyethyleneglycol (APEG) or polyvinylpyrrolidone (PVP) to form hydrogen bonds. The developed hydrogels were characterized by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR). The swelling and methylene blue (MB) adsorption experiments of them were performed. Both series of hydrogels exhibited moderate swelling ratios of 213-235 g g(-1) and excellent removal efficiency of MB (> 92%). Based on kinetic assessments, the MB adsorption process could be well-described by the pseudo-second-order kinetic and Langmuir isotherm models, suggesting a monolayer chemisorption mechanism. The maximum theoretical adsorption capacity (q(m)) of the PAA-based hydrogel with PVP could achieve 2483.2 mg g(-1). Regeneration experiments showed that both series of hydrogels could endure adsorption/desorption for at least 5 consecutive cycles with MB removal efficiency of higher than 80%. Therefore, it was believed that this study could provide a facile method to develop hydrogel adsorbents and a promising adsorbent material with high adsorption capacity for the removal of MB from dye-containing wastewater.