Construction of alkalized MXene-supported CoFe2O4/CS composites with super-strong adsorption capacity to remove toxic dyes from aqueous solution

Owing to the unique surface microstructure, plentiful active sites and rich functional groups, two-dimensional transition metal carbide/nitride (MXene) is getting more and more attention in the field of pollutant removal. Now, we design a new magnetic adsorbent with CoFe2O4/chitosan (CS) composite supported onto alkalized MXene (alk-MXene) sheet using a facile hydrothermal and self-assembly technique. The structure and surface properties of the as-synthesized alk-MXene/CoFe2O4/CS composites are characterized by XRD, SEM, FTIR, TGA, BET and XPS. Batch experiments on adsorbing Congo Red (CR), Rhodamine B (RhB) and Malachite Green (MG) dyes are carried out, where the introduction of CoFe2O4/CS into alk-MXene can greatly enhance the adsorption capacity for cationic and anionic dyes. Notably, it is concluded that 24 h is a more suitable etching time to improve the adsorption performance of the composite during the synthesis process. An ultra-high adsorption capacity of S1 achieves up to 2095.9, 1333.9 and 537.6 mg g-1 for CR, RhB and MG dyes, respectively. The influence factors (etching time, pH values, contact time, initiate concentration and temperature) on the adsorption behaviors are discussed, where spontaneous and endothermic adsorption nature is confirmed. Analyses of the adsorption mechanism indicate that the synergistic effects of electrostatic interaction, 7C-7C interaction and hydrogen bonding lead to superior adsorption abilities of the alk-MXene/CoFe2O4/CS composites. In a word, with the specific consideration on the advantages of MXene, CoFe2O4 and CS, this study offers a new track to obtain the MXene-based magnetic adsorbents with the simultaneous and high-efficiency removal of cationic and anionic dyes from the aqueous solutions.