The demand for low-energy cost desalination technique is growing all around the world along with the water scarcity and energy crisis. Capacitive deionization (CDI) is a novel electrochemical technology for water desalination with several advantages such as low energy requirement, high water recovery, and environmental friendliness. Recently, investigation of different CDI operational charging modes (i.e., constant voltage and constant current operation) has drawn more attention due to that operational modes have crucial effects on energy consumption and desalination performance of CDI device, especially for the large-scale one. However, for electrode connection mode, only a few researchers have investigated the effect of unipolar- and bipolar-electrode connections on CDI performance, and little is known about the large-scale CDI stack operated in different electrode connections for desalination. A typical electrode for laboratory scale experiments is in the range of approximate 5 × 5 cm2. In this research, the operating optimization of a flow-through CDI stack in unipolar- and bipolar-electrode connections is investigated to achieve high-performance for desalination. The CDI stack is composed of 3 pairs of activated carbon electrodes separated by 2 mm spacer. The effective surface area of each electrode is 20 × 20 cm2. A continuous (single-pass mode) CDI experiment is carried out along with conductivity monitoring. As demonstrated, the CDI stack can successfully remove salts ions from water. Desalination performance is further analyzed by ion chromatography and inductively coupled plasma to detect the concentration change in Na+ and Cl- ions in the solution. Herein, it is expected that bipolar-electrode connection in CDI device will have shorter adsorption time, higher desalination ability, and lower energy consumption. Besides, the possible occurrence of side reactions in the charging stage (e.g., pH flocculation and water hydrolysis) will be discussed. Furthermore, the key performance parameters, including salt adsorption capacity (SAC), average salt adsorption rate (ASAR), and charge efficiency will be calculated to provide insight into desalination performance on the energetic and practical views. The obtained results can deliver important information for the development of operational modes for large-scale CDI devices in water desalination.

Performance optimization of a flow-through capacitive deionization stack using unipolar- and bipolar-electrode connections for desalination

254th National Meeting (2017)

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