Can 3D-printed flow electrode gaskets replace CNC-milled graphite current collectors in flow capacitive deionization?

As billions of people suffer from water scarcity, finding sustainable water resources is imperative. Flow capacitive deionization (FCDI) is a highly promising desalination process that can produce clean water from saline streams such as brackish and seawater. Conventional FCDI systems employ Computerised Numerical Control (CNC)-milled graphite plates that serve as current collectors and flow electrode channels. However, they have drawbacks such as high manufacturing costs, waste generation, and the difficulty of producing complex geometries required for efficient flow electrode mixing. Here, we successfully demonstrate that 3D-printed flow electrode gaskets, made of non-conductive polyethylene terephthalate glycol (PET-G) or a carbon black-infused conductive polylactic acid (PLA), are viable alternatives to traditional graphite plates. In specific cases, the desalination and energy efficiency in FCDI cells with 3D-printed conductive gaskets were even 25 % and 10 % higher, respectively, compared to traditional CNC-milled current collectors. The transition to 3D printing offers notable benefits, such as the competence to fabricate complex designs that enhance internal mixing and charge percolation. This innovation represents a change of paradigm in the way FCDI cells should be designed and manufactured, using additive manufacturing, which represents an efficient, scalable, and cost-effective substitute for the conventional approach, contributing therefore for the advancement of FCDI desalination technology.