The desalination of seawater/wastewater utilizing flow-electrode capacitive deionization (FCDI) has received significant interest. However, challenges like the low electrical conductivity of flow electrode and excessive energy consumption have prevented the scaling up of desalination operations. To overcome these issues, this study introduces a new FCDI system termed the two-stage FCDI (TS-FCDI) system, in which desalination modules are equipped with freestanding and flow electrode. The TS-FCDI system offers a graded desalination module design that produces an average salt removal rate (ASRR) of 113 µg cm·min. However, the TS-FCDI system requires substantially reduced infrastructure investment, device size, and energy expenses. Notably, the design allows for the simultaneous operation of freestanding and flow electrode and enables the transport of ions and charges in the electrode region. Experimental evidence from multiple device configurations (CDI, FCDI, and TS-FCDI) supports this claim. Notably, the TS-FCDI system shows about twice the desalination performance over FCDI, with approximately 50 h of single-cycle (SC) operation. This enhancement links the freestanding electrode with the flow electrode, enabling the device to be well-suited for practical applications. The continuous flow of electrode particles in contact with the freestanding electrode initiates secondary ion transport, merging two different types of electrodes to enhance the active space of the electrode, effectively improving ion adsorption performance. In summary, the results of this study indicate the potential of the TS-FCDI system as a suitable desalination technology for scaling up applications.

中文翻译：

---

一种新型两级连续电容去离子系统，具有连接流电极和独立电极


利用流电极电容去离子（FCDI）对海水/废水进行淡化已经引起了人们的极大兴趣。然而，流电极电导率低和能耗过高等挑战阻碍了海水淡化业务的扩大规模。为了克服这些问题，本研究引入了一种新的 FCDI 系统，称为两级 FCDI (TS-FCDI) 系统，其中海水淡化模块配备了独立式流动电极。 TS-FCDI 系统提供分级脱盐模块设计，平均除盐率 (ASRR) 为 113 µg cm·min。然而，TS-FCDI系统需要大幅减少基础设施投资、设备尺寸和能源费用。值得注意的是，该设计允许独立式电极和流动电极同时运行，并能够在电极区域传输离子和电荷。来自多种设备配置（CDI、FCDI 和 TS-FCDI）的实验证据支持这一说法。值得注意的是，TS-FCDI 系统的海水淡化性能约为 FCDI 的两倍，单周期 (SC) 运行时间约为 50 小时。这一增强功能将独立电极与流动电极连接起来，使该设备非常适合实际应用。电极颗粒与独立式电极接触的连续流动引发二次离子传输，融合两种不同类型的电极，增强电极的活性空间，有效提高离子吸附性能。总之，本研究的结果表明 TS-FCDI 系统作为适合扩大应用规模的海水淡化技术的潜力。