Adsorption of rare earths ( III ) by calcium alginate–poly glutamic acid hybrid gels

BACKGROUND Adsorption is believed to be an effective and green technology for the removal and recovery of rare earths ( III ) from dilute solution . RESULTS A novel hybrid gel, abbreviated as ALG‐PGA , has been prepared through crosslinking calcium alginate ( ALG ) and γ‐poly glutamic acid ( PGA ), and its adsorption behavior towards whole rare earths ( III ) has been examined. Taking Nd( III ) as a representative element, the adsorption capacity, kinetics, reusability, selectivity and mechanism have been investigated. Cation exchange is proposed as a possible adsorption mechanism. Doping PGA molecules into calcium alginate beads can significantly enhance the adsorption capacity and the selectivity of rare earths from non‐rare earths. The maximum adsorption capacity obtained for Nd( III ) was 1.65 mmol g −1 . Reutilization of ALG‐PGA gel was confirmed for up to eight consecutive sorption–desorption cycles with no damage to the gel . CONCLUSION The prepared biosorbent, ALG‐PGA , was biocompatible and cost effective with a good adsorption ability for Nd( III ), and provides a new approach to the recovery of rare earths ( III ) from rare earths‐containing wastewater.