| Abstract | As a promising desalination technology with high efficiency, low energy consumption, and continuous desalination process, flow-electrode capacitive deionization (FCDI) has received considerable attention and rapid development in recent years. In this study, a laboratory-scale FCDI desalination system was designed and manufactured, and its desalination performance for low-concentration saltwater was optimized and evaluated from three aspects: flow-electrode material formulation, influence of operating parameters, and long-term operating potential. For the formulation optimization of the flow-electrode, carbon fiber (CF), activated carbon (AC), carbon black (CB), multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) were selected as alternative electrode materials. The desalination performance of the individual electrode material was investigated firstly, and then the alternative materials were combined. It was determined that the two optimal formulations of the combined flow-electrode were 1.9% CB + 0.1% MWCNTs and 1.7% CB + 0.3% GNPs, and the maximum salt adsorption rate reached 1.46 ± 0.09/1.59 ± 0.02 μgcm-2 s -1 . Simultaneously, the FESEM image analysis revealed that the primary mechanism of the synergistic effect between CB and MWCNTs/GNPs was the bridging effect of one- dimension/two-dimension structured carbon nanomaterials. For the exploration and optimization of the influence of operating parameters, this study determined the optimal values of five key operating parameters of FCDI under batch mode operation through orthogonal experiments. The optimal voltage, electrolyte concentration, electrode material content, feedwater flowrate, and electrode flowrate were determined to be 1.8 V, 10.0 gL -1 , 2.0 wt.%, 80 mL min -1 , and 60 mL min -1 , respectively. Subsequently, the dominant parameter with the most significant influence on the desalination performance of the FCDI system was identified by sensitivity analysis as voltage. Afterwards, a long-term operation experiment of this lab-scale FCDI desalination system was carried out utilizing a series of optimal operating parameters under single-pass mode. The results illustrated that the lab- scale FCDI desalination system was able to maintain the desalination efficiency of 1 gL -1 feedwater (NaCl) at 40 ~ 60% for 60 hours continuously, and the loss rate of electrode material after each recovery and regeneration was less than 1%, indicating that the FCDI system has strong stability and long-term operation potential. |