Enhanced Adsorption of Ammonium Using Hydrogel Composites Based on Chitosan and Halloysite

Abstract

In this work, chitosan was used as the backbone to graft poly(acrylic acid) to form granular hydrogel composite with halloysite (HT) particles being embedded within the polymeric networks. This hydrogel composite was characterized by means of Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). Then, this hydrogel composite was selected as the adsorbent to remove ammonium from synthetic wastewater. The results indicate that by introducing HT particles into the polymeric networks, the resulting composite shows comparable adsorption capacity to that of pure polymer hydrogel for NH₄ ⁺ removal. The adsorption equilibrium can be achieved within 5 min with the equilibrium adsorption capacity of 27.7 mg N/g and monolayer adsorption capacity of 40.9 mg N/g (30 wt% HT). The adsorption process is pH-independent within 4.0–7.0, and the adsorption capacity of as-prepared adsorbent is not affected over the cycles of adsorption studied (5 cycles).

Keywords:

• Adsorption
• ammonium
• chitosan
• halloysite
• hydrogel composite

Acknowledgements

The authors thank the National Natural Science Foundation of China (No. 20877077) and Taihu Project of Jiangsu Provincial Science and Technology Office (No. BS2007118). for joint support.