Mechanisms of Advanced Oxidation Processes, the Principle of Detailed Balancing, and Specifics of the UV/Chloramine Process

Abstract

Advanced oxidation processes tend to have very complex reaction mechanisms, and models containing over 150 steps have been developed to describe the chemistry. Without the aid of automation, it is extremely difficult to avoid the development of kinetic mechanisms that violate the principle of detailed balancing. Here, we apply DETBAL, a computer application, to systematically identify many violations of the principle of detailed balancing in a model proposed for the UV/chloramine process. We then show that these violations can also be found in dozens of other proposed models for advanced oxidation processes. Suggested repairs to these violations are provided. These repairs lead to no significant changes in the model predictions because the illegal loops include steps that are unnecessary under the conditions modeled. The model omits certain steps that do have significant effects on the model predictions.

Mechanistic and Kinetic Understanding of the UV254 Photolysis of Chlorine and Bromine Species in Water and Formation of Oxyhalides

“…The Bulman- and Sun-models underpredicted the k chlorine and [ • OH] ss values because of the presence of some illegal loops (Figure S18). Overall, the use of large kinetic models requires careful checking for any violations of the detailed balancing …”

“…The kinetic model contained photochemical and chemical reactions obtained from the current study and literature. − , Sensitivity analysis of the kinetic model was conducted using Atropos 1.20 . Detailed balancing analysis was applied to the kinetic model to identify reversible and illegal reaction loops using DETBAL …”

“…46 Detailed balancing analysis was applied to the kinetic model to identify reversible and illegal reaction loops using DETBAL. 47 ■ RESULTS AND DISCUSSION Quantum Yields for Halogen Oxidant Decomposition and Radical Generation. Halogen oxidant Decomposition.…”

New Mechanistic Insights into the Transformation of Reactive Oxidizing Species in an Ultraviolet/Sulfite System under Aerobic Conditions: Modeling and the Impact of Mn(II)

“…An input reaction with a high overall S indicates that the rate constant of this reaction has a crucial influence on the overall simulation results. Detailed balancing analysis using DETBAL (Text S6) was also applied to identify the reversible and illegal reaction loops that possibly exist in the kinetic models. − …”

The principle of detailed balancing, the iron-catalyzed disproportionation of hydrogen peroxide, and the Fenton reaction

“…The principle of detailed balancing has been the topic of several of the author's recent publications, [39][40][41][42] but its history extends back almost a century. It is a fundamental principle of chemical kinetics that has both qualitative and quantitative implications.…”