A renewable and functionalized chitosan gel bead for statically and dynamically capturing aquatic Hg(II) with a prominent capacity

Abstract

Porous gel beads have aroused considerable interest in the field of wastewater treatment because of their enhanced adsorption capacity and ease of separation. Herein, a facile yet efficient method to synthesize porous chitosan gel beads (PBCSB) through the amide reaction and integrated with a porogenic process was proposed and further optimized. The well-preserved honeycomb internal structure was beneficial for aquatic Hg(II) to approach the surface and diffuse into the interior of the gel beads. The as-prepared adsorbent at a diameter of 3–5 mm possessed ultra-high adsorption ability (1139.82 mg g−1) toward Hg(II), declining the concentration from 500 mg L-1 to 0.017 mg L-1. Furthermore, the PBCSB could attain a high removal Hg(II) rate (>80%) even at pH 1 and maintained excellent Hg(II) adsorption performance (94.24%-99.99%) within five regeneration cycles. In the multi-component solution, the Kd of Hg(II) was 4–5 orders of magnitude higher in comparison with that of others. The superior adsorption performance was attributed to the complexation between Hg(II) and the functional groups involving sulfur, nitrogen, and oxygen based on the XPS analysis and density functional theory (DFT) calculation. The fixed-bed column filled with PBCSB exhibited a stable and satisfactory performance under different conditions. The findings confirmed the inherent superior performance, renewability, and application potential for selective capture Hg(II) from real industrial wastewater.