Review on Mechanisms and Kinetics for Supercritical Water Oxidation Processes

Abstract

Supercritical water oxidation (SCWO) is a promising wastewater treatment technology owing to its various advantages such as rapid reactions and non-polluting products. However, problems like corrosion and salt decomposition set obstacles to its commercialization. To address these problems, researchers have been developing the optimal reactor design and strengthening measures based on sufficient understandings of the degradation kinetics. The essence of the SCWO process and the roles of oxygen and hydrogen peroxide are summarized in this work. Then, the research status and progress of empirical models, semi-empirical models, and detailed chemical kinetic models (DCKMs) are systematically reviewed. Additionally, this paper is the first to summarize the research progress of quantum chemistry and molecular dynamics simulation. The challenge and further development of kinetics models for the optimization of reactors and the directional transformation of pollutants are pointed out.

Pulsed Discharge Plasma in High-Pressure Environment for Water Pollutant Degradation and Nanoparticle Synthesis

“…Hence, the pyrrole monomer oxidation potential became higher than the pyrrole dimer oxidation potential. It is well known that higher-molecular-weight compounds, including pyrrole oligomers, are more easily oxidized than lower-molecular-weight compounds [85][86][87]. Therefore, as illustrated in Scheme 4, the oxidation reaction of pyrrole dimers took place more effectively than pyrrole monomers.…”

Effect of Process Conditions on Catalytic Hydrothermal Oxidation of p-Xylene to Terephthalic Acid

“…As the reaction temperature approaches near-critical water condition (T c 374 °C), the increase in p-xylene conversion to TPA was likely assisted by the availability of reactive oxygen species derived from hydrogen peroxide degradation. It was widely accepted that higher reactivity and yield observed in hydrogen peroxide assisted oxidation reaction system was closely related to the presence of OH and HO 2 free radicals (Croiset et al, 1997;Jiang et al, 2020). These short-lived radicals were responsible for activating the cracking of C-C and C=C bonds through a series of oxidation reactions leading to the TPA formation.…”

“…Around the critical conditions (T c 374 °C, P c :22.1 MPa, ρ c :320 kg.m -3 ), water characteristics such as diffusivity, viscosity, dielectric constant, and solvation properties change dramatically with small changes in pressure due to large compressibility of critical fluids. Consequently, favourable reaction kinetics and mechanisms (Brunner, 2014;Kwak et al, 2009), as well as an increase in the dissolution of oxygen and functionalised aromatic compounds (Kruse & Dinjus, 2007a) can be obtained to support various types of organic and aromatic chemical reactions (Eckert & Chandler, 1998;Daud et al, 2021;Kruse & Dinjus, 2007b) through free radical and ionic reactions (Kruse & Dinjus, 2007b;Jiang et al, 2020). From a chemical process perspective, hydrothermal is regarded as safe, non-toxic, environmentally benign, and easy to handle (Cocero, 2018;Dunn & Savage, 2005).…”

Oxidation of Per- and Polyfluoroalkyl Ether Acids and Other Per- and Polyfluoroalkyl Substances by Sulfate and Hydroxyl Radicals: Kinetic Insights from Experiments and Models

“…•− ) and hydroxyl radicals ( • OH) are generated in some destructive technologies. For example, • OH is generated in processes involving nonthermal plasmas, 27 electrochemical oxidation, 28 and supercritical water oxidation 29 that are being explored for PFAS destruction. 30,31 Furthermore, SO 4…”