# Review on Mechanisms and Kinetics for Supercritical Water Oxidation Processes
## 1 Introduction
[20] studied the effect of salt deposits on corrosion behavior of Ni-based alloys during the SCWO of high-salinity organic wastewater. Since the salt deposit layer restricted the transport of corrosion products and formed a local acidic environment, the corrosion rate of nickel-based alloys accelerated. Meanwhile, obstacles formed by the salt deposit layer for the oxygen transport suppressed the lateral migration of metallic elements and promoted the longitudinal growth of the oxides, thus further roughing the oxide scales. [PERSON] et al. [21] found that the under-deposit corrosion mechanism of Ni-based alloys was affected by environmental temperature. The dissolution-precipitation mechanism was principal at 400 \({}^{\circ}\)C while the solid-growth mechanism was primary at 500 \({}^{\circ}\)C. Sufficient understandings of organics' degradation kinetics can determine the optimal reaction conditions, which is conducive to the remission of harsh reaction conditions and the reduction of reaction time, so as to further reduce the requirement and corrosion tendency of materials. Some scholars have reviewed the reactor concepts, industrial status and research status of different pollutants, as well as problems like corrosion and salt deposition in the SCWO system, and provided some possible solutions [6; 7; 8; 22; 23; 24; 25; 26]. In terms of reaction mechanism and reaction kinetics, [PERSON] et al. [27] summarized the chemical reactions of C1 compounds in the near-critical and supercritical water, including carbon dioxide, carbon monoxide, formaldehyde, formic acid, methanol, methane and chlorinated methane. [PERSON] [22] introduced the experimental studies of model compounds and waste materials. [PERSON] et al. [28] made a detailed comparative analysis of the kinetic data on methanol and found that the kinetic data were affected by the preheating condition of methanol, the initial oxygen-to-methanol ratio, oxidant type, H\({}_{2}\)O\({}_{2}\) decomposition, hot zones at high feed concentrations and wall catalysis. [PERSON] and [PERSON] [29] reviewed the process simulation in supercritical fluids and pointed out that molecular dynamics may be the basis for the process simulation which is still based on empirical or semi-empirical approaches. However, the empirical models, semi-empirical models and DCKMs in the SCWO process have not been systematically compared and analyzed. Additionally, although quantum chemistry and molecular dynamics simulations are important for revealing the nature and microscopic mechanism of SCWO reactions, previous reviews did not mention their progress due to the limited computational power. This article summarizes the essence of the SCWO process and elucidates the roles of oxygen and hydrogen peroxide. Then, the research status and progress of empirical models, semi-empirical models and DCKMs are discussed. Furthermore, this paper is the first to summarize the research progress of quantum chemistry and molecular dynamics simulation. The combination of accurate kinetic models and process simulations can not only predict the degradation of pollutants, but also provide a reference for commercial amplifiers.