Carbon-covered Fe-pillared bentonite electrode boosting capacitive deionization.

Capacitive deionization (CDI), as an energy-efficient desalination technique, has attracted worldwide attention. Bentonite, a natural clay with 2-dimensional structure, is much popular for water treatment because of its high adsorption capacity, low cost and environmental benign properties. However, the poor conductivity and narrow interlamellar spacing limit its electrochemical application. In this work, a carbon-covered Fe-pillared bentonite (PILB@C) was fabricated as a new type of electrode materials for CDI. Through Fe-pillaring in bentonite, the interlayer spacing enlarged, accompanied with enhanced specific surface areas and abundant mesopores. The further carbon coating endowed the bentonite with good conductivity and facilitating ion-transportation. The dual-regulated composites possessed the negatively charged surface feature, favorable for inverted capacitive deionization (i-CDI) with improved deionization performance. Under the optimal carbon loading, the PILB@C electrode delivered a superior desalination capacity (16.23 mg g−1, in 10 mM NaCl). Because of the intrinsic structural stability of bentonite, the desalination system exhibited the excellent cycling stability (90 % capacity retention over 50 cycles). When applied for industrial and domestic water purification, the PILB@C electrode realized salinity reduction and de-mineralization. This natural bentonite is nontoxic and cheap, rendering it highly promising as an electrode material candidate for future water treatment. [Display omitted] • Pillared bentonite (PILB) is synthesized by introducing iron proppant. • Carbon-coated PILB (PILB@C) is obtained by chitosan adsorption and carbonization. • PILB@C retains lamellar structure and its conductivity significantly increases. • PILB@C delivers Na+ adsorption capacity of 16.23 mg g−1 in 10 mM NaCl (10 mA g−1). • PILB@C is cheap and safe, applicable for cooling water and tap water desalination. [ABSTRACT FROM AUTHOR]