Abstract:

In order to more intuitively study the mechanism of the flow electrode capacitive deionization (FCDI) ammonia removal process and make efficient improvements, an electrochemical steady-state model for the removal of ammonium ions by the FCDI device was constructed, and the simulation accuracy of the experimental results reached 93.8%. The model was used to study the energy consumption and removal efficiency change trend of the FCDI ammonia removal process under the conditions of inlet water flow, current density, and active carbon mass fraction in the electrode solution. Two indicators of ion selectivity and removal rate were calculated which qualitatively explained the influence mechanism of operating parameters on the removal of ammonia to optimize working conditions. The results showed that when the FCDI ammonia removal process has an inlet water flow of 1.25mL/min, a current density of 21.26A/m², and an activated carbon mass fraction in the electrode solution of 10%, the ammonia removal efficiency is 74.5%, and the energy consumption is 29.62kWh/kg N, which has reached the comparatively ideal result. Under the optimized working conditions, the situation that the microscopic transmission of ammonium ions in the FCDI device was discussed. Considering that the excessively long flow channel length would increase the polarization of the current and reduce the ammonia removal performance of the device, suggestions for series installation were put forward. Keeping the length of the flow channel and the working conditions unchanged, the series-connected device can increase the removal efficiency by 32.9% compared with the original device, and at the same time can reduce the energy consumption per unit mass of N by 22.0%, indicating that the improvement of the device is effective. The optimized FCDI ammonia removal process with higher ammonium ions removal efficiency, lower energy consumption, and broad application prospects has more advantages than similar treatment processes.

Key words: flow electrode capacitive deionization (FCDI), electrochemistry, model, waste water, ammonia nitrogen

摘要：

为了更直观地研究流动电极电容去离子（flow electrode capacitive deionization, FCDI）除氨工艺的机理并进行高效改进，本文构建了FCDI装置去除NH{}_{\mathrm{4}}^{+}的电化学稳态模型，实验结果模拟准确率达到93.8%。利用该模型研究了FCDI除氨工艺在进水流量、电流密度、电极液中活性炭质量分数等工况条件下的能耗和去除效率变化趋势，计算离子选择性和去除速率两个指标，定性阐明操作参数对去除氨的影响机理，筛选出较优化工况。研究结果表明，FCDI除氨工艺在进水流量1.25mL/min、电流密度21.26A/m²、活性炭质量分数为10%时，除氨效率为74.5%，能耗为29.62kWh/kg N，达到较为理想的状态。在优化的工况条件下，讨论了NH{}_{\mathrm{4}}^{+}在FCDI装置内部的微观传输情况，考虑到过长的流道长度会增强电流密度的极化现象，降低装置除氨性能，提出了串联装置的建议。保持流道长度和工况条件不变，串联的装置可以比原装置的去除效率提升32.9%，同时去除单位质量N的能耗降低22.0%，表明装置的改进是有效的。优化后的FCDI除氨工艺比同类处理工艺更有优势，NH{}_{\mathrm{4}}^{+}去除效率更高，能耗更低，具有广泛应用前景。

关键词: 流动电极电容去离子, 电化学, 模型, 废水, 氨氮