Composite hydrogel particles encapsulated ammonium molybdophosphate for efficiently cesium selective removal and enrichment from wastewater

Highlights: • A biocompatible, robust, low-cost and easily recycled APS hydrogel was prepared for both Cs⁺ removal and enrichment. • APS has high permeability, and a maximum adsorption capacity of 71.28 mg/g can be achieved within a short time. • The concentration of Cs⁺ could be enriched for approximately double that of wastewater after each desorption step. • Adsorption thermodynamic, kinetic and isotherm have been investigated. -- Abstract: A novel ammonium molybdophosphate (AMP)/ polyvinyl alcohol (PVA)/ sodium alginate (SA) composite hydrogel (APS) was prepared for Cs⁺ removal and enrichment from radioactive wastewater. Batch experiments with the subject of AMP concentration, pH value, initial Cs⁺ concentration, contact time, temperature, competing ions were investigated. The results showed this APS hydrogel with high permeability and stability could effectively adsorb Cs⁺ at widely broad pH value range and low Cs⁺ concentration within a short time. Adsorption thermodynamic parameters indicated the endothermic and spontaneous nature of the adsorption process, and the Lagergren pseudo-second order model was found to exhibit the best correlation with the adsorption results. Equilibrium data was better described by the Langmuir isotherm equation, and the maximum adsorption capacity of APS hydrogel calculated was in consistent with the experimental results. Furthermore, the APS hydrogel could be easily reused at least five times without obvious decrease in absorption activity and selectivity using ammonia nitrate as the eluent, and what's more, the Cs⁺ concentration in eluent was approximately concentrated for 2 times after single cycle. All the results suggest that the environmental friendly and low-cost APS hydrogel could be used as effective and selective material for Cs⁺ removal and enrichment from wastewater.