Fig. 5: Effect of pore size of microporous membranes on the separation performance for differentiating monovalent and divalent anions.

a Free volume pore sizes of the TB and QA-TB membranes obtained via PALS. b Schematic illustration of the separation mechanisms for monovalent (Cl-) and divalent (CO3²⁻, SO4²⁻) anions, considering the influence of hydration energy.