Effects of operational conditions on the electrosorption efficiencies of Capacitive deionization

Capacitive deionization (CDI) represents a novel electrosorption process for the desalination of brackish water. The CDI working principle depends on the use of porous carbon materials as electrodes. CDI electrodes possess a charged surface that results in adsorption of salt ions by being charged in low voltage and it desorbing the salt ions by applying a reverse potential to the electrodes. CDI has many advantages due to its low energy consumption, low environmental pollution, and low fouling potential. The objective of this study is to investigate the effect of different operational conditions (TDS concentration, temperature, flow rate) on the CDI electrosorption efficiency and energy consumption and to investigate the effect of silica on the treatment efficiency. Laboratory scale experiments were conducted by using a commercial CDI with activated carbon electrodes developed by Aque EWP. CDI achieves TDS removal efficiency of 95.26% and 54.37% at TDS influent concentration of 500 and 3500 mg/l respectively. TDS removal efficiency decreased from 90.43% to 65.79% by increasing the flow rate from 1 to 4.5 l/min. By raising the influent temperature from 20 to 50 °Celsius, the TDS removal efficiency decreases from 90.43% to 79.25%. The electrosorption removal efficiency is inversely proportional to the flow rate, TDS concentration and the temperature. Silica does not have any effect on the CDI electrosorption efficiency and does not lead to scaling of electrodes. CDI energy consumption is inversely proportional to the flow rate and directly proportional to the TDS concentration.