Abstract:

Rubidium is a rare alkali metal with high economic value and promising applications， and it is of great importance to effectively extract rubidium from brines. A novel rubidium （Rb⁺） adsorbent （KCuFC-PCG） is prepared by synthesizing a hydrogel matrix （polyacrylamide/carboxymethylcellulose/graphene oxide hydrogel， PCG） immobilized with copper ferrocyanide （KCuFC） by thermal initiation polymerization. The structure and properties of KCuFC-PCG are characterized by physicochemical methods. The effects of pH， contact time， initial mass concentration of Rb⁺， temperature and competing ions on the adsorption are investigated by batch adsorption experiments. The results show that the KCuFC-PCG adsorbent exhibits good adsorption capacity in the pH range （5～9）， with the best performance at pH=8. The adsorption equilibrium can be reached at 6 h under the conditions of 5 mg/L Rb⁺ and pH=8， and the adsorption capacity of KCuFC-PCG is 89.12 mg/g. The kinetic behavior can be described by a quasi-secondary kinetic model， indicating that the adsorption process is dominated by chemisorption. The adsorption process is in accordance with the Langmuir isothermal adsorption model， and it is a single molecular layer adsorption with a maximum adsorption capacity of 258.4 mg/g. The desorption rate is 77% at 3 h with 0.2 mol/L NH₄Cl as desorbent.

Key words: Carboxymethyl cellulose, Copper ferrocyanide, Hydrogel, Adsorption, Rubidium ion