Carbon material-immobilized ionic liquids were applied on absorption of Hg²⁺ from water phase

In this study, several immobilized ionic liquid adsorbents on carbon materials were synthesized with impregnation method. The carrier materials were activated carbon and three kinds of multi-walled carbon nanotubes. And the synthetic adsorbents immobilized different kinds of ionic liquids were characterized by Boehm titration, FT-IR, XPS, TG, and BET analysis, respectively. Finally, carbon materials after [C4mim]HSO₄ immobilization were selected as adsorbent to remove Hg²⁺ from water phase. The optimum conditions of adsorption test of ionic liquid immobilized by multi-walled carbon nanotubes were as follows: the initial concentration of Hg²⁺ was 400 mg/L, the adsorbent addition amount was 40 mg, the temperature was 20 °C, the reaction time was 200 min, the removal rate of Hg²⁺ peaked at 62.95%, the adsorption capacity was reached 79.00 mg/g. The optimum conditions of adsorption test of ionic liquid immobilized by activated carbon were as follows: the initial concentration of Hg²⁺ was 300 mg/L, the adsorbent addition amount was 0.2 g, the temperature was 20 °C, pH was 2.0, the reaction time was 100 min, the removal rate of Hg²⁺ was more than 99%, the adsorption capacity was 118.65 mg/g. The adsorption isotherm fitting study found that the adsorption of adsorbent on Hg²⁺ was more in line with the Langmuir model, and the adsorption kinetics study shows that the adsorption process is consistent with the pseudo-second-order kinetic equation. The results of kinetic analysis are further verified by thermodynamic analysis.