Synergistic interfacial engineering in organic-inorganic hybrid electrode for enhanced phosphate capture via local microenvironment modulation

The deep removal of phosphate plays a vital role in controlling eutrophication and improving aquatic environmental quality. Nevertheless, traditional adsorbents demonstrate poor performance in treating low-concentration phosphate-contaminated water. Herein, we developed an electro-assisted adsorption system using an organic-inorganic hybrid electrode, which integrates hierarchical carbon framework, polyaniline coating, and Mg[sbnd]Al layered double hydroxide (ZPMA3) for advanced phosphate removal. The unique organic-inorganic architecture creates a positively charged microenvironment through PANI's amine/imine groups, which pre-concentrates phosphate ions at the electrode-electrolyte interface. This local microenvironment modulation significantly enhances the phosphate ion concentration gradient around the electrode surface, markedly improving the mass transfer driving force. Molecular dynamics simulations quantitatively verify that the PANI-induced interfacial phosphate concentration (18.2 mg/cm3) is 2.8-fold higher than that of pristine MgAl-LDH (6.6 mg/cm3), overcoming diffusion limitations in low-concentration systems. As expected, the ZPMA3 electrode demonstrated outstanding advanced removal performance in low-concentration phosphate pollution scenarios, with the effluent total phosphorus concentration below 0.24 mg/L and a removal efficiency exceeding 91 %. Moreover, it exhibited remarkable adaptability and cycling stability under a wide range of operational conditions and practical water sample. After 9 consecutive adsorption–desorption cycles, the desorption efficiency remains 68.6 % with accumulated phosphate in the regenerant up to 17.9 mg/L, evidencing the material's reusability. This study not only proposes a novel strategy for advanced phosphate treatment but also advances the development of electrode materials for deep dephosphorization. © 2024 Published by Elsevier B.V.