Fabrication of attapulgite-based dual responsive composite hydrogel and its efficient adsorption for methyl violet

In this work, attapulgite (ATP)-based dual sensitive poly (N-isopropylacrylamide-co-acrylic acid) composite hydrogel, P(NIPAM-co-AA)/ATP, was prepared by free radical polymerization. The prepared composite hydrogel was characterized via methods of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), zeta potential analysis and Brunauer, Emmett, and Teller (BET) etc. The composite hydrogel showed pH and temperature sensitive behaviour, with lower critical solution temperature (LCST) of 35 degrees C and highest swelling occurred at pH 8.0. The adsorption of methyl violet (MV) can be controlled by the hydrogel responsiveness, and 95.78% of MV can be removed at pH 8.0 and 35 degrees C. The addition of a small amount of ATP (3 Wt%) can improve the swelling ratio and adsorption capacity. Kinetic analysis demonstrated that the experimental data were best fitted to the pseudo-second order model. Isotherm analysis showed that the equilibrium data followed Langmuir model with the adsorption capacity of 168.35 mg g(-1). In addition, the composite hydrogel has high adsorption selectivity for cationic dyes, and MV-loaded hydrogel is easy to regenerate, which can be used for successive adsorption cycles. These results demonstrate that the composite hydrogel has potential application in dye wastewater treatment.

Automated summary

In this study, an attapulgite-based dual sensitive poly(N-isopropylacrylamide-co-acrylic acid) composite hydrogel was successfully prepared and characterized. The composite hydrogel showed pH and temperature sensitive behavior, with good adsorption capacity under specific pH and temperature conditions. The addition of a small amount of attapulgite improved the adsorption capacity of the hydrogel. The composite hydrogel has potential application in dye wastewater treatment.