Preparation of Thermo-Sensitive Magnetic Cationic Hydrogel for the Adsorption of Reactive Red Dye

In this study, thermo-sensitive magnetic cationic hydrogel (TSMCH) based on (3-acrylamidopropyl) trimethyl ammonium chloride (APTMACl) and N-isopropylacrylamide (NIPAm) was synthesized by free radical copolymerization. The TSMCH was characterized with Fourier transform infrared spectroscopy, thermal gravimetric analysis, x-ray diffraction, scanning electron microscope with energy dispersive x-ray, vibrating sample magnetometer, and zeta potential, and employed as adsorbent for adsorbing reactive red (RR) dye. Effects of molar ratios of APTMACl to NIPAm on the adsorption capacity of TSMCH were studied, and the results showed that a maximum adsorption capacity (1428.57 mg RR g−1 TSMCH) had been achieved when the molar ratio of APTMACl to NIPAm was 1:1. The adsorption isotherm of RR was well fitted by the Langmuir isotherm equation. TSMCH had good selectivity for adsorbing RR. Solution pH hardly affected the adsorption of RR on the TSMCH. The adsorption amount of RR increased with the increase of temperature. The adsorption–desorption of TSMCH was evaluated in three circles and a high regeneration rate was demonstrated.