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.
Highlights
Supercritical water oxidation (SCWO), first proposed by American scholar Modell in the 1980s [1], refers to the process, in which organics are completely decomposed into H2 O and CO2 as the homogeneous oxidation of organic matters and oxidants rapidly take place in supercritical water (SCW), water that is in a special state, where its temperature and pressure exceed critical points (374.15 ◦ C, 22.1 MPa), its density is close to that of liquid, and its viscosity, which is about 1–10% of the corresponding liquid is close to that of gas
With the improvement of molecular theory, the development of high-performance computing technologies and the rise of new calculation microscopic theory, the development of high-performance computing technologies and the rise of methods, quantum chemistry and molecular dynamics simulations as the auxiliary means of new calculation methods, quantum chemistry and molecular dynamics simulations as the auxiliary experimental research have been widely concerned by scholars, and have demonstrated their means of experimental research have been widely concerned by scholars, and have demonstrated outstanding advantages and guiding significance in the field of theoretical analysis [149]
SCWO is a promising wastewater treatment technology owing to its various advantages, such as rapid reactions and non-polluting products
Summary
Supercritical water oxidation (SCWO), first proposed by American scholar Modell in the 1980s [1], refers to the process, in which organics are completely decomposed into H2 O and CO2 as the homogeneous oxidation of organic matters and oxidants (usually excess oxidant) rapidly take place in supercritical water (SCW), water that is in a special state, where its temperature and pressure exceed critical points (374.15 ◦ C, 22.1 MPa), its density is close to that of liquid, and its viscosity, which is about 1–10% of the corresponding liquid is close to that of gas. Due to harsh SCWO reaction conditions, strong corrosion, high material requirements and salt deposition in operation have become the biggest obstacles to its commercialization. Li et al [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. 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]. The combination of accurate kinetic models and process simulations can predict the degradation of pollutants, and provide a reference for commercial amplifiers
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