Evaluation of total dissolved solids removal characteristics by recycling concentrated water in membrane capacitive deionization process

초록

The present study evaluated the removal characteristics of total dissolved solids (TDS) using recycled concentrated water generated through desorption in a membrane capacitive deioni-zation (MCDI) process. As a result of 40-cycle experiments of the conventional MCDI process, stable adsorption and desorption were performed. In MCDI circulation process, TDS concentra-tion in concentrated water increased; however, this did not affect the adsorption capacity, and treated water was obtained stably. The energy consumption as a function of the number of cycles in conventional MCDI process kept constant, but it gradually increased in the MCDI circulation process. The reason for this increase is that the amount of current changes with the concentra-tion of feed water. Finally, as a result of comparing the yield of treated water per feed water, we observed that the conventional MCDI process requires an influent for both adsorption and desorp-tion; however, the production of treated water is constant because it is produced only through the adsorption process. By contrast, the MCDI circulation process does not require a separate influent because it uses the concentrated water stored in the concentrated water tank during the desorption process. Thus, we observed that the yield gradually increased with the number of cycles.