Adsorption behaviour and mechanism of Gd(Ⅲ) over EDTA functionalized MIL-101-graphene oxide

Recovery of REEs from secondary source is in line with both resource utilization and environmental cleanup. Herein, EDTA functionalized MIL-101-graphene oxide (MIL-101-GO-EDTA) was prepared, characterized and exploited for adsorptive recovery of Gd(Ⅲ). Adsorption mechanism was meticulously scrutinized via statistical mechanics calculation, isothermic and kinetic fittings, as well as spectroscopic inspection. Under pH = 9, adsorption of Gd(Ⅲ) onto MIL-101-GO-EDTA equilibrates in 40 min, reaching recovery percent 99.50 %. The maximum adsorption capacity is 307.69 mg·g^-1, given by Langmuir fitting. Statistical mechanics calculation proposes spontaneous, exothermic and randomness increasing adsorption. Isothermic and kinetic fittings suggest favorable and heterogeneous chemical adsorption, with surface chemical reaction as the rate controlling step. Finally, atomic scale adsorption mechanism was illuminated by spectroscopic analysis. Particularly, CO, C = O and N participate in adsorption via electron donation towards Gd(Ⅲ). This work deciphers the adsorption behaviour and mechanism of Gd(Ⅲ) over MIL-101-GO-EDTA, as to furnish reference for recovery of REEs using MOFs based adsorbents.