Project Description

Water and energy has been considered two critical issues facing humanity over the next 50 years because of rapid consumption of water and energy by continuously growing human population and increasing concern for the quality of life. To meet the demands, a seawater desalination process is one of the popular choices employed in many countries to make up deficient water supply.  However, traditional desalination processes are very energy intensive. Thus, an energy-saving desalination or desalination process producing an electric power has been recently emerged to save overall energy consumption required for operating the desalination process while recovering water. In addition to the issue of water and energy, an increase in the atmospheric CO₂ concentration is changing global climate as well as local weather, eventually threatening the security of possessing enough water, energy, and food locally and globally. In the Middle-East countries, many desalination plants are being operated together with fossil fuel based power plants, which contributes to additional release of CO₂. Therefore, a novel holistic strategy for securing water and energy and protecting climate change from CO₂ should be urgently developed and adopted especially at Qatar because “Water” and “Energy” security now ranks in the top research priority among the Qatar National Research Strategies (QNRS) of Qatar Foundation (QF) to pursuit the Qatar National Vision (QNV) 2030.      

To comply with the main strategy of the QNRS, the project proposed here will develop a technology that can utilize chloride ions from saline water (brackish water, seawater, RO brine water) using a solar-powered electrochemical desalination process (“SolEC-Desal Pro”) accompanying conversion of CO₂ into production of value-added solar chemicals (VASCs) and water purification for water reuse. Unlike the desalination process recently reported, this SolEC-Desal Pro will be able to convert CO₂ into solar chemicals and purify wastewater by maximally utilizing the salts (Cl^–, Na⁺) separated from saline water desalination through membranes. This holistic approach is promising to building an infrastructure particularly for an environment with a plenty of saline water or wastewater near resource points of saline water such as seashore.

Our proposed SolEC-Desal Pro will be composed of three chambers where the middle chamber for desalination (i.e., Desalinaton chamber) will be placed between the anode chamber and the cathode chamber under a given electric power supplied by photovoltaic (PV) system or sunlight as a source of renewable energy. The solar energy will initiate the movement of salt ions (e.g., Cl^– and Na⁺) from the desalination chamber to oppositely charged electrode chambers through an anionic exchange membrane (AEM) for Cl^– ion and a cationic exchange membrane (CEM) for Na⁺, respectively, finally leading to recovery of the desalinated water in the middle chamber. In order to maximally utilize both salt ions and electrically biased electrodes, chemical reactions that can drive water purification and production of VASCs will take place at anode and cathode, respectively. Herein, CO₂ gas will flow into the cathode chamber where cost-effective metal electrodes (e.g., Cu foam, 3D carbon nanotube sponge) or photoelectrode (CuAlO₂) will be used, coupled with an anode chamber where wastewater will be in contact with metal-doped oxides (e.g., Ni/Sb-co-doped SnO₂, Bi-TiO₂/IrO₂-Ta₂O₅/Ti) anodes or nanostructured oxides (e.g., hydrogen treated TiO₂ nanotube arrays) photoanodes or. In the anode chamber, wastewater will be purified by chemical oxidation using reactive chlorine species (e.g.,Cl^•, Cl₂^•-, HOCl/OCl^–), which are in-situ produced by (photo)electrochemical oxidation of the transferred Cl^– ions at the anode. The CO₂ purged to the cathode chamber will be converted into VASCs (e.g., H₂, CO, formate, etc) by taking electrons transferred from anode.

The performance of “Water Purification || Desalination || CO₂ conversion” at each chamber will be evaluated at first with simple lab-scale three compartment-configured reactors until the device configuration and electrode/membrane materials are optimized under various environmental conditions and operational parameters. The optimized SolEC-Desal Pro will be scaled up with an all-in-one tubular configuration of all chambers where a proton exchange membrane (PEM) will be placed along with the AEM and CEM between tubular-shaped anode and cathode. Herein, insertion of the PEM will boost the proton-coupled electron transfer reactions at the cathode. Apparently, the tubular configuration is to continuously produce VASCs at cathode as well as continuous water purification at anode while desalinating seawater at the tubular–shaped desalination chamber surrounded with AEM and CEM in order to provide Cl^– and Na⁺ to each electrode chamber.      

Major Project Accomplishments