Electrodialysis recovery of boric acid from simulated boron-containing radioactive wastewater: influence of salt species

Abstract

During the electrodialysis treatment of boron-containing radioactive waste liquid in nuclear power plants, the effective separation and recovery of boric acid is crucial. However, the influence mechanisms of coexisting salt species on the migration behavior of boric acid as an electrically neutral molecule remain unclear. This study systematically investigated the effects of different cations and anions on boric acid migration behavior during electrodialysis by establishing migration equations. The results demonstrate that salt species affected both the diffusion and electroosmotic migration of boric acid to varying degrees: divalent cations (Ca²⁺, Mg²⁺) with strong hydration capacity mainly reduced boric acid's diffusion and electroosmotic migration coefficients by decreasing membrane chain spacing and increasing solution viscosity; while anions (Cl⁻, NO₃⁻, SO₄²⁻) had minimal impact on boric acid diffusion behavior, but SO₄²⁻ could form hydrogen bonds with boric acid molecules, significantly enhancing its electroosmotic migration coefficient. Separation performance evaluation showed that the boron separation factor remained stable above 0.9 across different salt systems, confirming that electrodialysis maintains excellent separation performance for boric acid under slightly acidic conditions at pH = 6, effectively achieving boric acid retention in the dilute compartment and concentrating ionic pollutants in the concentrate compartment.