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

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 K-d 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 func-tional 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.