Effect of montmorillonite nanosheets on the adsorption performance of hydrogel beads and the study of column adsorption

In this work, hydrogel beads with 3D network structure were successfully prepared using montmorillonite nanosheets (MMTNS) combined with macromolecule polymers. Batch adsorption tests revealed that the increase in exfoliation degree of MMTNS was beneficial to improve the methylene blue (MB) adsorption on hydrogel beads (HB). In addition, the HB with 25 % MMTNS-3 dosage achieved high mechanical strength and reached the maximum adsorption capacity of 543.1 mg/g. Effects of MB concentration (40–120 mg/L), adsorbent dosage (1–1.5 g) and flow rate (5–15 mL/min) on fixed-bed column adsorption indicated that the HB column exhibited an excellent dynamic adsorption performance and recycling performance, much better than the D113 resin. The good fits of Pseudo-first-order model and Pseudo-second-order model and a better Langmuir model fitting result implied a monolayer chemical adsorption and physical adsorption nature of MB on HB. Moreover, scanning electron microscope combined with the energy dispersive spectrometer, fourier transform infrared spectroscope and X-ray photoelectron spectroscopy measurements indicated that the adsorption mechanism was mainly attributed to Ca ion-exchange and chemical bonding of –COOH and –OH groups with MB. Such hydrogel beads showed a good potential in the application of practical wastewater treatment.