Separation of Dy(III), Yb(III) and Y(III) by ultrafiltration using a rotating disk membrane based on shear-enhanced complexation to recover heavy rare earth elements in process wastewater: Laboratory studies and DFT calculations

The effective separation and recovery of heavy rare earth elements from wastewater presents a significant challenge. This work successfully achieved the separation and recovery of Dy(III), Yb(III), and Y(III) from wastewater using shear-induced dissociation-ultrafiltration technology with acidic phosphoric chitosan (aPCS) as the complexing agent. Unlike traditional methods that depend on organic solvents, this process requires no additional chemicals, enhancing environmental sustainability. The critical shear rates for de-complexation of aPCS-RE complexes were identified, and the separation coefficients β_Y/Dy, β_Y/Yb, and β_Dy/Yb were calculated as 15.8, 21.1, and 14.8, respectively. The shear effect significantly enhanced membrane flux and mitigated fouling, representing a notable advantage over conventional filtration techniques. Additionally, DFT calculations revealed that the interactions of aPCS with rare earth metal ions were mainly ionic and that charge transfer played an important role in the stability difference of aPCS-RE complexes.