Highly efficient capacitive deionization of copper(Ⅱ) ions from wastewater in symmetric Ti3C2Tx MXene-based electrode: Performance, optimization and deionization mechanism

Due to the use of Cu(II) ions as catalysts, the production of polyacrylamide generates Cu-containing wastewater, constituting an environmental safety hazard and a waste of resources. This study proposes symmetric Ti3C2Tx MXene-based electrodes for capacitive deionization to remove Cu(II) ions from chemical wastewater as a clean, low-energy, and resource-recyclable method and investigates their performances and mechanisms. Results showed that the adsorption capacity and removal efficiency of Cu(II) ions could reach 49.4 mg·g−1 and 98.6% under the optimal experimental conditions (the initial Cu(II) ions concentration was 100.0 mg·L−1, imposed voltage of 1.0 V, circulation velocity of 25.0 mL·min−1, and the initial pH of 4.0). At the same time, the adsorption capacity and removal efficiency of Cu(II) ions in real copper-containing wastewater were 47.4 mg·g−1 and 97.7%. In addition, by analyzing the changes of the electrode, the mechanism of electroadsorption was determined to include capacitive electroadsorption (double layer with pseudo-capacitance synergy) and cathodic electrodeposition. Ultimately, by applying a reverse voltage, Ti3C2Tx MXene-based electrodes can be rapidly regenerated and recycled for continued use as catalysts. This simple operation has the advantage of potential economic benefits. Therefore, the Ti3C2Tx MXene-based electrodes can be used potentially to remove Cu(II) ions in practical applications for environmental remediation.