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 1.65mmolg^-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.