Synthesis, Swelling Characteristics, and Dye Adsorption Mechanism of a New Stimuli-Responsive Cationic Hydrogel

In this study, a new multi-stimulus cationic copolymer hydrogel was developed by bulk photo-polymerization of N-acryloyl-N’-propyl piperazine (AcrNPP) and poly (ethylene glycol) methacrylate (PEGMA) with ethylene glycol dimethacrylate (EGDMA) as crosslinker. The effect multiple external stimuli, concentration monomers, equilibrium swelling the hydrogels studied in detail. gels swelled acidic solutions due to protonation tertiary amine ring, de-swelled basic solutions. presence PEGMA enhanced imparted water-responsive property, leading disintegration at high 49.85%. evaluated an adsorbent for removal anionic dye, Congo red (CR) from water. dye uptake capacity increased increase initial concentration. Interestingly, ratio decreased formation additional physical crosslinks within matrix. increasing temperature negative-temperature responsive property hydrogel. time-dependent adsorption data fitted seven kinetic models. Pseudo second-order model best described kinetics process, CR onto could be very well phase-boundary controlled multistep process surface followed intraparticle diffusion.