Electrostatically assembled graphene oxide-wrapped Fe-pillared bentonite electrodes for capacitive deionization

GO is electrostatically assembled on Fe-pillared bentonite at mild conditions. • The optimized GO/PB electrode delivers a desalination capacity of 41.11 mg g −1 in 10 mM NaCl. • A balanced GO loading improves conductivity without blocking ion-accessible pores. • The electrode retains 91.12% capacity after 100 CDI cycles. • Real groundwater desalination achieves >85% removal for major ions. Bentonite is an abundant layered clay mineral with intrinsic negative charge and ion-exchange capability, but its direct use as a capacitive deionization (CDI) electrode is restricted by poor electrical conductivity. In this work, graphene oxide-encapsulated Fe-pillared bentonite (GO/PB) composites were prepared through a mild electrostatic self-assembly strategy. Fe pillaring enlarged the interlayer space and exposed ion-accessible surfaces, while cationic surfactant-assisted assembly enabled negatively charged GO sheets to uniformly anchor onto the pillared bentonite surface. The resulting composite integrated the structural stability and cation-affinity of pillared bentonite with a uniformly assembled GO-PB interface, providing more efficient charge transfer and desalination than the physically mixed counterpart. The optimized GO/PB-0.2 with 14.6% GO delivered a salt adsorption capacity of 41.11 mg g −1 in 10 mmol L −1 NaCl and achieved 59.77 mg g −1 in 50 mmol L −1 NaCl. The capacity still maintained 91.12% after 100 continuous cycles, with no obvious change in the crystalline structure. Desalination tests using actual groundwater further showed simultaneous removal of multiple ions with removal efficiencies above 85%. This work demonstrates that charge-directed interfacial assembly provides an effective strategy for improving the electrical accessibility and utilization of pillared-clay ion-storage domains, offering a mild route for developing low-cost and stable CDI electrodes for brackish-water treatment. Download: Download high-res image (146KB) Download: Download full-size image