Reactive Transport of Ozone Micro-Nano Bubbles in Multiphase Environments (Environmental Chemistry)
Abstract
Ozone is a powerful oxidant often used for environmental applications, including disinfection and remediation. However, ozone applications in soil and groundwater remediation are still limited, which is mainly attributed to the limited spatial impact of such reactive and unstable gas in the subsurface. The limited spatial impact of ozone in the subsurface is driven by both mass transfer limitations and competing ozone consumption. Delivery of ozone through micro-nano bubbles (MNBs) in porous subsurface media may be a key to overcoming the major limitations of such processes and to increasing their practical utility. Particularly, introduction of ozone through micro (<100 µm) and nanoscale (<1 µm) MNBs, which allow high gas-liquid contact areas, increase ozone mass transfer to the treated water, and enable protection of ozone molecules from competing reactions. Despite this high application potential for ozone MNB, the research on ozone MNBs in porous media is quite limited: physical and chemical stabilities of ozone MNB in complex multiphase systems and their confluence have not been studied to date. The overarching goal of this proposed study is to reveal the governing mechanisms of reactive transport of ozone in porous media and to advance our knowledge regarding the effect of ozone physical states (i.e., dissolved ozone vs. ozone MNBs) on its physicochemical interactions at the solid-liquid interface. Specific objectives and corresponding work packages are: (i) Explore the physical stability of inert MNBs in relevant porous media conditions. In this work, we will quantify the role of porous media characteristics (size, roughness, hydrostatic pressure, and composition) and solution chemistry (focusing on salinity effects) on the size, concentration, and phase distribution (bulk vs. surface) of non-reactive MNBs in batch mode. (ii) Assess ozone chemical decomposition and associated radical formation in porous media. We will compare the chemical stability of ozone molecules in bubble and dissolved forms, determine the nature (i.e., finite vs. catalytic reactions) and extent (reaction kinetics and rates) of ozone reactions in porous media, and characterize the radicals formed (type and concentration). (iii) Characterize ozone reactive transport in porous media and identify the controlling parameters of MNB retention. Ozone MNB retention, chemical stability, and mobility in porous media will be examined in a set of column experiments at various physical and chemical conditions. This will allow quantification of the potential effectiveness of ozone-MNBs ozonation in the time-distance dimensions. (iv) Demonstrate contaminant removal in porous media by ozone MNBs. In this work, we will provide a proof of concept for groundwater remediation through comparison of organic contaminant degradation using conventional ozonation and ozone MNB. The primary intellectual contribution of this project will be a foundational understanding of ozone stability and reactivity in multiphase environments. This work will expand the knowledge of ozone reactivity in porous media by experimentally characterizing ozone bubble stabilities, determining the nature and extent of ozone processes in the subsurface, and controlling ozone reactive transport. The knowledge gained through this work will inform the design of both subsurface ozonation processes (e.g., for remediating petroleum- and explosive-contaminated groundwater) as well as other applicative venues (e.g., reactive, multifunctional filters), and outline the fundamentals required for controlled release of reactive gases in microenvironments. Lastly, either through higher transport distances of the oxidant in bubble form or through better oxidant dissolution at shorter distances, this work will result in a win-win situation in which the reactive oxidant will be better delivered to the subsurface, illustrating the significance of this research and its high-impact results.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Nov 17, 2022
- Source ID
- W911NF2310002
Entities
People
- Ines Zucker
Organizations
- Army Contracting Command
- Office of the Secretary of Defense
- Tel Aviv University