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In an attempt to improve the capacitive deionization (CDI) performance and develop an efficient CDI electrode material, the effect of carbon characteristics on CDI was investigated. Activated carbon (AC) and ordered mesoporous carbon (OMC) materials synthesized by template method were used for the electrode manufacture. The capacitive deionization performance of AC and OMC based electrodes was investigated and compared. We found that when the specific surface areas of AC materials increased from 712 to 1347 m2/g, the electrosorption capacities of AC electrodes increased slightly from 9.43 to 10.14 mg/g. The characteristics of OMC materials can be optimized by the adjustment of the mesoporous silica beads template proportion, resulting in a maximum average pore size of 11.35 nm and total pore volume of 2.101 cm3/g. The optimum electrosorption capacity obtained with OMC4 electrode was 10.83 mg/g, which was not only higher than that of AC electrodes, but obviously higher than the values of most carbon-based electrodes in other studies. In conclusion, these results provide important insights into the effect of carbon characteristics on capacitive deionization and suggest that OMC synthesized by template method could be a promising carbon material for the CDI electrode manufacture.

The capacitive deionization (CDI) performance of activated carbon electrodes with various anions and competitive electrosorption between two anions in mixed solution were studied. It was found that the electrosorption capacity was strongly dependent on the ionic charge and hydrated radius. With the same concentration, smaller monovalent anions showed their size-affinity to access the pores. The order of normalized equivalent capacity was as follows: trivalent anion > divalent anion > monovalent anion. In mixed Cl− and NO3− solution, Cl− is preferably electrosorped over NO3− in early period of the electrosorption process. However, during the end of the electrosorption process, part of Cl− would be exchanged by NO3− due to the stronger competitiveness of NO3− than Cl−. There was no obvious selectivity between Cl− and SO42 −.