Water Remediation from Recalcitrant Pollution Using the Galvano-Fenton Process: A Modeling Approach of the Hydroxyl Radical Generation and the Energy Efficiency

Abstract

The hydroxyl radical is the most powerful oxidant after fluorine, and is the key reactant of the advanced oxidation processes AOP. Monitoring the kinetics of formation and reaction of this short life species is one of the challenging tasks from an experimental point of view. Thus, modelling is suggested to be one efficient tool for a comprehensive and predictive study of AOPs, particularly the Galvano-Fenton process. In the present study, mathematical modelling is used to describe the kinetics of hydroxyl radical 𝐻𝑂• generation and organic substrate 𝑅𝑂 degradation within the Galvano-Fenton process, based on the spontaneous galvanic corrosion of iron waste and in situ ferrous ion catalyst generation. A range of typical absolute kinetic constants of 106 à 1010 M-1.s-1 is considered to characterize the attack of 𝑅𝑂 species by 𝐻𝑂•. Phenol is presented as a model pollutant for a total mineralization model. The numerical simulations demonstration a quasi-linear evolution of hydroxyl radical production during the first stage of the Galvano-Fenton process. A comparison of the Galvano-Fenton process with the classic Fenton in terms of kinetics, and electro-Fenton in terms of energetic performance, revealed that the spontaneous galvanic generation of ferrous ions in the Galvano-Fenton process leads to a higher rate of the reaction a higher instantaneous concentration of ferric ions accompanying the release of hydroxyl radicals and hence a better oxidation efficiency, as well as a positive energy balance. A particular attention was given to the ratio of the degradation efficiency to the released energy.

Keywords

• Advanced oxidation
• Spontaneous corrosion
• Kinetics
• Chemical mechanism
• Energy efficiency.