Theoretical Modeling And Preparation Of Modified Carbon Electrode Materials For Capacitive Deionization

Capacitive deionization (CDI) is an emerging and appealing technique for desalination of saline water due to its low energy consumption, no polluting and low cost. Electrode material is the core component in CDI technology and porous carbon materials are used as electrodes widely. The properties of electrode materials determine the salt adsorption ability of CDI directly. We hope that through theoretical simulation combined with experiment to study the effect of hydrophilicity and pore structure properties of electrodes on the CDI performance. By improving the properties of electrodes to achieve a high efficiency and low energy consumption CDI.In this paper a batch-mode dynamic CDI process model was modified to describe the transport of ions and charge in porous electrodes based on the modified Donnan (mD) model and porous-electrode theory. Stern layer capacity, effective micropore volume, and other dynamic parameters were used to describe the enhancement of hydrophilicity of electrodes and its effect on the CDI performance. Theoretical results illustrate that the improvement of hydrophilicity can effectively increase the Stern layer capacity and effective micropore volume and reduce ions diffusion resistance, thereby enhancing the CDI performance. Experiments were applied to confirm the theoretical results obtained by the batch-mode dynamic CDI process model, in which a series of high hydrophilic activated carbons were prepared by a green method. The experimental results indicate that the increase of hydrophilicity is important to enhance the performance of CDI, which is consist with the results of theory.Based on the modified Donnan theory, we modified the simplified dynamic model to describe the CDI process. Stern layer capacity, total transmission coefficient, and effective pore volume were used to describe the increase of micropore and mesopore of electrodes and its effect on the CDI performance. Theoretical results illustrate that the improvement of micropores and mesopores can increase the Stern layer capacity, total transport coefficient, and effective pore volume, thereby enhancing the CDI performance effectively. Experiments were applied to confirm the theoretical results obtained by the modified dynamic CDI process model, in which the carbon xerogels with enhanced surface areas and pore volumes were synthesized using ionic liquid template combined with KOH activation without CO2 supercritical drying. The experimental results indicate that suitable availability of the pores is important to the enhancement of the CDI performance, which is consist with the results of theory.