Let’s imagine rupturing the electrons or ions from a gas or vapor. It certainly sounds like an energy intensive process, perhaps requiring a highly specialized and sophisticated experimental setup. I thought the same before joining the Soft Matter & Interface Research Group at the University of Alberta. In reality, this can be achieved just by applying a tiny electrical energy (discharge) to a gas or air.
An electrical discharge can partially break down the gas into ions and electrons. The induction of an electric discharge preferentially heats the electrons in the surrounding air or any gaseous phase, owing to their much smaller mass compared to ions and neutral molecules. The excited electrons are accelerated and activate the surrounding gas molecules creating new and ionic species and radicals. The cocktail of these ionized species forms the fourth state of matter, which is generally known as plasma. Similar phenomena can be commonly observed during lightning or thunderstorms. In fact, plasma formation is responsible for most of the visible matter in our universe. Fascinatingly, the process can be mimicked in a small-scale laboratory setting by ionizing different gases (air, nitrogen, oxygen, etc.) without requiring any specialized experimental conditions. Ionization at low energy forms a non-thermal bright and intense pink to purple color light, which is known as cold plasma. Unlike hot environmental or thermal reactions, cold plasma technology is gaining immense interest due to its ability to use low-temperature and low-pressure chemical reactions for conversion of stable molecules into several value-added products (H2 and NH3 formation). Since, this technology uses electrical power and is ideal for several chemical conversions, it is also referred as “power-to-X (P2X). Besides gaseous-phase reactions, the cold plasma has huge potential in water-based chemical reactions such as nitrogen fixation, and removal of organics, pathogens, and persistent pollutants.
Being a young water professional, specialized in the field of advanced water treatment, I feel that cold plasma is a fascinating scientific frontier, which is novel, unconventional, and rich with untapped potential. At UofA, we explore the potential of cold plasma in the field of water treatment and nitrogen fixation. A plasma device (corona needles) initiates a discharge in air that subsequently activates the neighboring gas molecules (O2, N2, CO2, etc.) via several ionization and dissociation reactions. This chain of reactions among excited molecules lead to the formation of reactive oxygen and nitrogen species (RONS), thereby creating localized, highly reactive environment-like conditions. The cocktail of these RONS is widely explored for several intended applications; however, the diffusion of these species in the liquid phase is limited. This limitation restricts the effectiveness for RONS to be applied in a water medium.
To address the challenges of the RONS technology, we introduced the microbubble enhanced cold plasma activation (MB-CPA) technology. This innovative strategy involves a 3D printed Venturi tube that self-sucks the plasma activated air from the plasma-glow zone by the Bernoulli effect. The formation and subsequent bursting of plasma-carrying bubbles in the flow system intensifies the gas-to-liquid mass transfer and assists their rapid transportation into liquid medium. We recently tested the application of MB-CPA on removing methyl orange (MO), multiple stubborn organic micropollutants, and microbial pathogens from contaminated water. As we predicted, it was easier to remove these pollutants from simple water environments (e.g. tap water) compared to a complex system (e.g. real wastewater). For such a complex system, we integrated conventional flotation and coagulation-flocculation as a pre-treatment that helped reduce the interfering organic species. A subsequent intermittent exposure to MB-CPA demonstrated higher treatment efficiency for food processing wastewater compared to continuous direct exposure. While pathogen removal can be expected due to reactive oxygen species (ROS) in plasma activated water (PAW), we are also considering nitrogen species such as nitrate (NO3−), nitrite (NO2−) and peroxynitrite (ONOO−) to contribute to pathogen removal. Moreover, such N-containing species are known for their fertilizing capability, which motivated us to investigate the application of MB-CPA for agricultural purposes. Intriguingly, we observed substantial beneficial effects of MB-CPA activation on promoting vegetable growth in hydroponics. Recognizing the potential of cold plasma in the field of nitrogen fixation, we consolidated a review explaining how plasma-assistance can help the industrial fertilizer sector minimize its global carbon footprint. Additionally, the microbubble enhanced plasma-catalysis is an emerging technology for ammonia (NH3) generation which can transform several chemical industrial sectors and act as a promising hydrogen carrier as well.
Inspired by such findings, we believe that cold plasma is a next-generation technology fulfilling current world needs in the field of water treatment and nitrogen fixation. With such possibilities, we envision that cold plasma-assisted technology can unfold several research horizons with a joint effort from multi-disciplinary scientific communities worldwide.
References
- Panchal, D., Lu, Q., Saedi, Z., Luk, H., Yu, T., & Zhang, X*. (2025). Integrate bubble flotation and intermittent microbubble-enhanced cold plasma activation for scalable disinfection of food processing wastewater. Separation and Purification Technology, 131677.
- Panchal, D., Lu, Q., Sakaushi, K., & Zhang, X*. (2024). Advanced cold plasma assisted technology for green and sustainable ammonia synthesis. Chemical Engineering Journal, 154920.
- Saedi, Z., Panchal, D*., Lu, Q., Kuddushi, M., Pour, S. E., & Zhang, X*. (2025). Integrating multiple cold plasma generators and Bernoulli-driven microbubble formation for large-volume water treatment. Sustainable Materials and Technologies, 44, e01300.
- Saedi, Z., Kuddushi, M., Gao, Y., Panchal, D., Zeng, B., Pour, S. E., Shi, H. & Zhang, X*. (2024). Stable and efficient microbubble-enhanced cold plasma activation for treatment of flowing water. Sustainable Materials and Technologies, 40, e00887.
- Lu, Q., Panchal, D., Yang, L., Saedi, Z., El-Din, M. G., & Zhang, X*. (2025). Simultaneous degradation of multiple micropollutants in flowing water by mild and strong microbubble-enhanced cold plasma activation. Water research, 280, 123435.
Written by: Deepak Panchal
Department of Chemical and Materials Engineering, University of Alberta, Alberta T6G 1H9, Canada
Deepak Panchal is a Postdoctoral research fellow at the Department of Chemical and Materials Engineering, University of Alberta working with Professor Xuehua Zhang, Soft Matter and Interfaces Research Group. His research focuses on microbubble enhanced cold plasma activation technology for water & wastewater treatment, particularly targeting organic pollutants, as well as nitrogen fixation. Outside of his academic pursuits, Deepak is passionate about sports and enjoys cooking.
IWA YWP Canada 