电容去离子脱盐中离子输运及吸脱附的多尺度研究

The improvement of desalination capacity and rate of porous carbon electrode is of great significance to the capacitive deionization. Currently, the characteristics and mechanisms of ion transport and adsorption/desorption in the desalination process are not fully clear. The approach of numerical simulation with experiment complemented for verification is adopted to investigate the multiscale ion transport and adsorption/desorption processes in capacitive deionization. The finite volume method (FVM) and lattice Boltzmann method (LBM) is combined to develop the multiscale numerical framework. The FVM is used in the flow channel between electrodes and the LBM is used in the macropores of the electrode with actual porous structures. The ion transport from macro-to-micropores is described by the adsorption model with finite transport rate. The mechanism of multiscale ion transport and adsorption/desorption in the desalination process is comprehensively studied, and the coupling mechanism of convection, diffusion and electromigration is revealed. The influence mechanisms of pore proportions and spatial distribution on the ion transport and adsorption/desorption in porous electrodes are studied, and the influence of velocity, ion concentration and potential on the desalination capacity and rate is analyzed. The aim is to obtain the electrode pore configurations with both high salt adsorption capacity and rate, providing theoretical references for the preparation of efficient electrodes and the design of capacitive deionization device.

提升多孔电极脱盐容量及速率对电容去离子海水淡化技术至关重要。本项目针对电容去离子脱盐过程中离子输运及吸脱附特性和规律尚不清楚的现状，拟采用数值模拟为主，辅以实验验证的研究手段，开展电容去离子脱盐过程中离子输运及吸脱附的多尺度研究。项目基于电极真实孔隙结构重构多孔电极模型，电极间流动通道采用有限体积法，电极内大尺度孔隙使用格子玻尔兹曼方法，电极中大尺度至微尺度孔隙的离子传质输运采用有限速率吸附模型描述，建立基于有限体积法-格子玻尔兹曼法的多尺度计算体系；研究电容去离子过程中各个尺度上的离子输运及吸脱附特性，揭示对流、扩散、电迁移等各过程间的耦合机制；探明电极中各尺度孔隙的占比及空间分布对离子输运及吸脱附的影响机理；并分析流速、浓度、电势等因素对脱盐容量及速率的影响，以期获得兼具高脱盐容量及脱盐速率的电极孔隙构型。该研究可充实电极制备及电容去离子海水淡化装置设计的理论基础。

围绕电容去离子脱盐过程中离子输运及吸脱附的多物理化学多尺度科学问题开展研究，项目发展了多孔电极孔隙结构随机重构方法、多孔电极孔隙尺度反应吸脱附分析模型及数值算法和电容去离子单元宏观尺度多场耦合模型及算法，深入研究了颗粒尺度下颗粒外大孔至内部微孔离子输运吸附及其传递阻力特性并构建了大孔至微孔离子有限速率吸附模型，通过多孔电极孔隙尺度模拟，揭示了多孔电极孔隙结构、孔隙率、颗粒尺寸、电流密度等关键参数对离子输运、反应吸附过程的影响并构建孔隙构型优化方案用以提升多孔电极反应输运过程，查明了单元结构尺度参数（电极厚度、流道宽度、进出口位置）和外部操作参数（电流、电压、浓度、流速）对脱盐性能的影响，项目多尺度研究分析及结论可为高脱盐性能电极制备及电容去离子海水淡化装置优化设计提供理论指导。基于项目研究成果发表了基金第一标注论文12篇，其中SCI论文9篇（包括第一作者5篇，通讯作者3，共同作者1篇），中文核心论文第一作者3篇，授权发明专利1件。参加国际会议1次，国内会议2次，培养研究生3名。