High-Recovery Material for Mercury Ions Based on a Polyallylamine Hydrogel with Thiourea Groups at Cross-Linking Points

We have successfully synthesized a high-recovery material for mercury based on a polyallylamine (PAA) hydrogel bearing thiourea cross-linking points and pendant amino groups. Adsorption of HgII was not significantly influenced by pH, and the PAA hydrogel was also able to adsorb HgII at a wide pH range (1–9) with high adsorption efficiency (≥93%). Adsorption was fast in the first 10 min, with 84% adsorption efficiency, and equilibrium was reached within 30 min. Langmuir and Freundlich isotherm models were employed to correlate the experimental data. The adsorption of HgII by PAA hydrogel is well supported by a Langmuir isotherm model with a maximum adsorption capacity of 2.375 gHg/ggel, which is greater than those of other polymers in the literature. The PAA hydrogel was also to adsorb efficiently in a low concentration HgII aqueous solution (0.2 ppm). This polymer will be applicable as a high recovery material for mercury.