Atmospheric-pressure plasma seawater desalination: Clean energy, agriculture, and resource recovery nexus for a blue planet

Water connects every aspect of life. Only 4% of the world's water is fresh water, as most water sources have different degrees of salinity. As a result, billions of people face water scarcity, which is a global challenge. Desalination technologies that separate fresh water from solvated salt ions in saline water are attracting major attention. However, conventional desalination processes including thermally and pressure driven processes are highly energy intensive. To address this issue we demonstrate that the atmospheric-pressure plasma (APP) treatment of saline water can be a new potential alternative low-energy and green desalination route. Valuable salts are recovered by direct salt crystal precipitation within a short plasma processing time. During desalination and salt precipitation, plasma activated desalinated water (PADW) is generated and can be used for clean energy processes such as water electrolysis and sustainable agriculture by enhanced plant seed germination. In addition, functional nanomaterials can be extracted from the precipitated salt. The PADW exhibited a low salinity of 5.6 mS/cm with a low pH value of 2.1. The unique intrinsic PADW chemistries enabled electrochemical water splitting for both the hydrogen evolution reaction (HER) at a Pt electrode and the oxygen evolution reaction (OER) at a RuO2 electrode. Moreover, the feasibility of using PADW in sustainable agriculture was demonstrated by enhancing mungbean seed germination using tap water mixed with PADW. At optimum mix concentration, both seed germination rates and germination percentages increased. Finally, we demonstrated the feasibility of synthesizing high-value 2D nanomaterials exemplified by Mg(OH)2 nanosheets via a single step thermal process using the salt precipitated from the seawater by the plasma process. Combined with straightforward use of renewable electricity to generate APPs, this study reveals the plasma potential for sustainable recovery of clean water, clean energy applications, sustainable agriculture, and manufacturing of advanced functional nanomaterials – all from the greatest treasure of our blue planet – seawater.</p

Utilization of plasma in water desalination and purification

© 2020 Elsevier B.V. Supplying fresh drinking water to the world population is a persistent global challenge. Therefore, effective and efficient desalination processes are becoming increasingly important. Oceans account for most of the water on Earth and the presence of salts and other contaminants in seawater prevents them from being used as a source of drinking water. Owing to this challenge, non-thermal plasma can be utilized in order to enhance the existing desalination processes via membrane or material modification while it can also be used as a direct tool for seawater desalination leading to significant process improvements. A direct non-thermal plasma-based desalination process is a new emerging area of research and recent efforts have shown its promise with many unexplored mechanisms, providing benefits that conventional desalination processes cannot offer. Here we critically review the use of plasma technologies in water desalination including membrane modification by plasma for pressure, thermal, photothermal processes and direct plasma-based desalination process. We also address the use of plasmas in water purification. Finally, the existing challenges and future prospects are outlined