A novel hybrid half-membrane membrane capacitive deionization(MCDI)device was constructed for the removal of anionic dyes using MCDI for the first time,based on the characteristic that dyes do not pass through the membrane.The composite electrodes were prepared by doping iron oxides in carbon felt(CF)with different iron-to-carbon mass ratios.The morphology,structure and chemical composition of the electrode materials were characterized by multiple means such as scanning electron microscopy(SEM),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS),indicating the successful doping of iron oxides.It was also demonstrated that the modified material CF-Fe(25％)with 25％Fe oxide doping has the best electrochemical performance based on cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS).The effect of CFs on the removal of the anionic dye congo red(CR)was compared and the effect of parameters such as voltage,dye concentration and pH on the removal performance of CR was investigated to verify the removal of other anionic dyes under optimal conditions.The mechanism of degradation of anionic dyes by MCDI was investigated in conjunction with free radical capture experiments.The removal rates of CR,new carmine(NC)and sundown yellow FCF(SY FCF)at 100 mg·L-1 were 66.3％,61.6％and 60.7％,respectively,within 15 min at 1.2 V,a flow rate of 3 mL·min-1 and pH 7 in the feed water,and the acidic environment was favorable to the removal of dyes.The new hybrid half-membrane MCDI device can directly enrich ionic dyes,which are later degraded and removed by the oxidation of highly reactive radicals(OH)generated by the anode.The doping of iron oxides increases the active site of the electrode reaction,which facilitates the adsorption of dyes and promotes the production of·OH.OH is the main force for the degradation of dyes.The method is highly efficient in removal,while avoiding membrane contamination,and provides a scientific basis for MCDI in the removal of anionic dyes.
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