Novel self-driven directed alkalization capacitive deionization for effective removal of amphoteric boron

Conventional capacitive deionization (CDI) usually suffers from low removal efficiency for amphoteric contaminants (e.g., boron) in wastewater due to the gradual electrolyte acidification and pH-dependent reversible speciation. To address these challenges, we herein propose for the first time a novel self-driven directed alkalization CDI (SDA-CDI) system, featuring an anion exchange membrane (AEM) modified anode and a Pt NPs/C-coated cathode, which enables efficient conversion of H₃BO₃ and subsequent electrosorption of B(OH)₄^-. In comparison with conventional CDI (28.7 μmol g^-1, 0.19), SDA-CDI exhibits remarkably higher boron adsorption capacity (59.6 μmol g^-1) and boron/chloride selectivity (0.47). Local pH detection, H₂O₂ measurement, and electrochemical analysis reveal that cathode-derived OH^- generation through 4e^- oxygen reduction reaction (ORR) raises local pH, while AEM suppresses anode-derived H⁺ generation and migration, collectively creating an alkaline electrolyte environment (pH increased from 6.5 to 10.3). Lattice Boltzmann method (LBM) simulation and Density Functional Theory (DFT) calculation distinguish the joint contribution of Pt NPs/C catalyst and carbon matrix to oxygen transport regulation via spatial distribution and 4e^- ORR kinetics promotion on key intermediates. Long-term cycling experiments demonstrate the operational stability of SDA-CDI, with highly reproducible pH (ΔpH>+3.0) and conductivity (Δconductivity∼102.4 μS cm^-1) variations. Its application potential is further verified via the actual wastewater treatment, with boron adsorption capacity of 52.1 μmol g^-1 and anti-interference capability of Cl^-, F^-, SO₄^2-. These findings highlight the synergistic effects of AEM and Pt NPs/C catalyst in self-driven pH directed regulation, and the newly-developed SDA-CDI offers valuable insights into efficient removal of amphoteric contaminants.