Desalination by capacitive deionization in microchannel

Abstract

Water is a crucial factor for all living organisms. Although majority of the earth is covered by water, only small fraction the earth’s water is fresh water. The lacking of freshwater is an issue that every countries would like to solve. Desalination is one of the solutions. Unlike distillation and reverse osmosis, which require a lot of energy, capacitive deionization relies on removal of ions from water by applied potential. Hence it has potential to be cost effective. In this study, the capacitive deionization is applied in a microchannel. The experiments were conducted using NaCl solution. The 500-µm, 750-µm, and 1000-µm microchannel were formed between a graphite sheet used as anode and another graphite sheet used as cathode. The condition of the applied voltage was varied in the range of 0 - 5.0 V. Moreover, the graphite sheet was modified by steam activation at 1100°C for 30 minutes to increase its adsorption capacity. Activated graphites, gold sputtering on graphites and stainless steels were tested as electrodes. It was found that the use of the microchannel could significantly enhance the desalination efficiency by reducing mass transfer resistance. The salt removal would not increase as expected when operated over 2.06 volts, concerning electrolysis reaction. This objective of the study was to investigate behavior of the electrosorption of sodium ions and chloride ions within microchannel and study effect of electrode porosity in terms of desalinated efficiency.