Operating regimes, scaling laws, and optimization of selectivity in plasma-liquid reactions
Chemical Engineering Science, vol.335, 2026 (SCI-Expanded, Scopus)
- Publication Type: Article / Article
- Volume: 335
- Publication Date: 2026
- Doi Number: 10.1016/j.ces.2026.124342
- Journal Name: Chemical Engineering Science
- Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Chemical Abstracts Core, Chimica, Compendex, INSPEC, zbMATH, Academic Search Ultimate (EBSCO), Engineering Source (EBSCO)
- Keywords: Chemical reaction engineering, Dimensional analysis, Plasma-liquid interactions, Radical chemistry, Reaction–diffusion
- Middle East Technical University Affiliated: Yes
Abstract
Plasmas in contact with liquids enable challenging liquid-phase chemical transformations through the injection of highly reactive radicals, but achieving high selectivity and efficiency remains challenging due to competition between desired radical-substrate and undesired side reactions, as well as mass transport limitations. Here, we present a unified non-dimensional framework to analyze the reaction-transport problem at a plasma-liquid interface through the introduction of three dimensionless groups: a Hatta number (Ha), a Damköhler number (Da), and a kinetic competition factor (Ω). Our analysis reveals three distinct operating regimes—kinetically-limited, transport-limited, and selective operation—under asymptotic limits and corresponding scaling laws for reaction rate and selectivity, valid within each regime along with criteria for regime transitions. Experiments on chloroacetate reduction via a direct-current plasma in aqueous and ethylene glycol solutions further support the simple selectivity scaling law derived for the transport-limited regime. Finally, an operating regime map, parameterized by Da/Ha and Ω, is constructed to visually provide the requirements for operating within a given regime and transitioning into another. The framework provides a rigorous foundation that can guide the optimization of plasma-liquid processes for a wide-range of reactions and applications.