Construction of Biomimetic Porous Membranes Inspired by Honeycomb for Selective Adsorption and Recovery of Rare Earth Ions

Rare earth ions (REIs) possess significant strategic and economic values. Given the dual demands of national strategy and economic development, effective recovery of REIs is of great significance in alleviating the current shortage of rare earth resources. The DCGO-PES membrane (Deeply Carboxylated Graphene Oxide Composite Poly(ether sulfone) Membrane) for rare earth ion (REI) adsorption was fabricated via a bionic honeycomb-inspired strategy. In this process, deeply carboxylated GO (DCGO) served as both a three-dimensional support material and a “structure-directing agent”, while the membrane matrix was formed by doping 3% DCGO into the poly(ether sulfone) (PES) matrix. The adsorption performance of DCGO-PES membranes was investigated using rare earth ions Sm3+, Tm3+, and Tb3+ as models. The results showed that the carboxyl groups introduced via the nucleophilic substitution reaction in the membrane had good binding ability to REIs, endowing DCGO-PES membranes with good selectivity, which could effectively separate REIs even in mixed ion solutions. Further studies via adsorption kinetics, isothermal adsorption, and thermodynamic experiments confirmed that the adsorption of DCGO-PES membranes was monolayer adsorption dominated by chemical adsorption. The maximum adsorption capacities for Sm3+, Tm3+, and Tb3+ reached 41.46 mg/g, 30.28 mg/g, and 33.78 mg/g, respectively. In addition, the membrane exhibited good cyclic stability and maintained its good REI adsorption performance after five cycles. More importantly, it was easy to recover, overcoming the drawback of the high recovery cost of DCGO powder. Wheat seed germination and zebrafish toxicity experiments further intuitively verified the good adsorption effect of DCGO-PES membranes on REIs. The establishment of this method provides an economical and environmentally friendly approach for the adsorption and recovery of REIs, and also offers a theoretical basis for the application of membrane materials in the recovery of other REIs.