Electrodialysis based waste utilization methodology for the desalination industry

Abstract

High salinilty wastewater and carbon dioxide are major hurdles in implementing a sustainable desalination technology. This study proposes an electrodialysis (ED) technique for onsite utilization of desalination reject brine into value-added products, such as carbonate salts and inorganic acid. The parameters that defined the overall system performance included the current efficiency, the mass of captured CO2, metal removal percentage, total energy consumption, and specific energy consumption. Sodium chloride (NaCl) is used as representative of saline wastewater. The effects of NaCl concentration, CO2 flow rate, and voltage on the process performance are evaluated. A six-chamber ED cell with a batch circulation process for the CO2 chamber with a cathodic chamber is adopted to investigate the process. The ED cell contained cation-exchange membranes, anion-exchange membranes, and electrodes. Membranes are arranged in a specific pattern to collect hydrochloric acid and carbonate salts in separate chambers. NaCl solution and a gas mixture containing 10% CO2 and 90% N2 are used as feed to the ED cell. The cathodic and CO2 chambers are linked to each other through the batch circulation mode. The anode and cathode are made of titanium, and the anode is coated with mixed oxides of iridium and platinum. The current efficiency, mass of captured CO2, metal (sodium) removal percentage, specific energy consumption, and total energy consumption ranged from 81.4%-99.8%, 3.88 g-8.2 g, 12.8%-38.7%, 352.9 g/kWh-435.2 g/kWh, and 0.023kWh-0.070kWh, respectively.