Conversion of Saline Water and Carbon Dioxide into Value-Added Chemicals By Electrodialysis

Tuesday, 3 October 2017: 11:20
National Harbor 10 (Gaylord National Resort and Convention Center)
A. Bonakdarpour, S. Dara (University of British Columbia, Mangrove Water Technologies), M. Ho (University of British Columbia), A. Lam (Mangrove Water Technologies), and D. P. Wilkinson (University of British Columbia, Mangrove Water Technologies)
A multi-compartment electrochemical reactor, which simultaneously converts carbon dioxide (dissolved or gaseous CO2) and high salinity waste-water to value-added chemicals, in the form of inorganic acids, carbonate salts and desalinated water, is demonstrated. The electrocehmical approach operates in electrodialysis or electrolytic mode and uses anion exchange and cation exchange membranes, and a Pt/Ir-coated Ti anode and Ti mesh cathode (for dissolved CO2) or Pt/C-coated gas diffusion cathode electrodes (for gaseous CO2) to produce acid and base products from CO2 (or CO2/O2) and an aqueous NaCl feed. The electrodialysis mode operates with carbonic acid feed while the electrolytic approach electrochemically converts carbon dioxide from the gas phase. With the gaseous conversion of carbon dioxide, a non-selective catalyst (carbon-supported Pt) was used to reduce the oxygen into hydroxyl ions which further reacted with CO2feed to form bicarbonate and carbonate species.

Under an applied voltage (~ 6 V) clear production of inorganic carbon salts and acids was observed. The product fluxes for HCl and NaHCO3 were ~ 0.05 mM cm-2 hr-1 on average for the case of dissolved CO2 and ~ 3.50 mM cm-² hr-1 for the case of gaseous CO2 showing an enhancement factor of about 70x in the flux rates with the use of gaseous CO2.

The bench-top (3.24 cm2 electrodes) cell has been successfully scaled up (1,500x) to a 5,000 cm² NORASCAND® commercial-scale electrolytic cell. Chemicals such as hydrochloric acid and bicarbonate salts have potential uses in many applications including oil and gas exploration and production where the chemicals as well as the desalinated water can be used in resource extraction. Coupling of CO2 removal and water treatment as presented here has potential applications in both conventional and unconventional oil and gas operations. Evolution of the technology from the conceptual bench-top reactor to initial scale up efforts and the current status of technology will be presented during the meeting.