A novel MoS2/GA electrode based on hybrid capacitive deionization technology for ion removal in polypeptide solution

Hybrid capacitive deionization (HCDI), an emerging desalination technique, is employed for the first time to remove the salt ions in the polypeptide solution, with the novel graphene aerogel (GA)/MoS 2 material as the cathode and the GA material as the anode. Structural characterization and performance tests demonstrate that the dispersed nanosheet structure of MoS 2 and the conductive 3D cross-network structure of GA synergistically stimulate more accessible redox active sites in GA/MoS 2 composite for ion storage. Specifically, the specific capacitance of the GA/MoS 2 composite electrode (143F·g −1 ) is twice that of the single MoS 2 electrode (72F·g −1 ). Also, the GA/MoS 2 electrode possesses exceptional ion removal capacity (32.71 mg·g −1 ) and high mean salt adsorption rate (0.85 mg·g −1 ·min −1 ). The ion removal mechanism and ion selectivity of the Cell GA(+)‖GA/MoS 2 (−) are investigated based on the electrode pairing mode, valence state and radius of ions, and Lewis acid-base theory. More importantly, the application of the Cell GA(+)‖GA/MoS 2 (−) in the polypeptide purification was confirmed by removing salt ions from the Ricinus communis biomarkers (RCB-2) polypeptide solution. The results display that the salt ions (92.1 %) were rapidly removed and the absolute recovery of the RCB-2 sample (62.4 %) was effectively obtained by mass spectrometry analysis. Therefore, this work provides a forward-looking strategy for the fast removal of salt ions from the polypeptide solution.