Autonomous Enrichment of Ultra-low Concentration Sb(III) by Gradient P(AA-AM-NH2-β-CD) Hydrogels Reinforced via Hofmeister Effect
Abstract
Gradient hydrogels offer significant promise for autonomous enrichment of heavy metal ions. However, the instability of the gradient hydrogel induced by high osmotic pressure limits its application, especially for the enrichment of ultra-trace levels of neutral heavy metal species. Here, we designed a gradient hydrogel for autonomous enrichment of ultra-low concentrations of Sb(III) species. The network chain density and gradient structural distribution of the hydrogel were regulated via ion-specific effects. Gradient P(AA-AM-NH2-β-CD)-Na₂SO₄ hydrogel possesses superior mechanical strength, anti-swelling resistance, and built-in electric potential. At an ultra-low concentration of 1 mg/L Sb(III), gradient P(AA-AM-NH2-β-CD) hydrogel exhibits markedly improved Sb(III) enrichment efficiency, which is pH-independent compared to the gradient hydrogel without salt treatment, resulting from the formation of multiple hydrogen bonds. This study demonstrates the potential of Hofmeister effect-reinforced the gradient hydrogels for the autonomous removal of trace heavy metals, also opening new avenues for advanced functional hydrogels.