Kinetics Modeling for Degradation of Geosmin and 2-Methylisoborneol by Photo-Electrogenerated Radicals

Abstract

With the increasingly severe cyanobacterial blooms, the overflow of taste and odor (T/O) compounds represented by geosmin (GSM) and 2-methylisoborneol (2-MIB) is becoming a global water quality issue. As a promising alternative to generating HO• and Cl•, the advanced oxidation processes (AOPs) based on UV radiation and electro-oxidation mediated by active chlorine is considered to be an environmental-friendly technology for GSM and 2-MIB degradation. In this study, a kinetics model using the pseudo-first rate constants for the elimination of GSM and 2-MIB was developed in the UV photoelectrochemical process. The model can be applied successfully to predict the degradation of GSM and 2-MIB under different electrolyte concentrations, initial pH of the solutions, and current densities. The GSM and 2-MIB degradation rates improved with the increase in electrolyte concentration. With the increase of pH value from 5 to 11, the rate constants for the degradation of GSM and 2-MIB reduced by 52.9% and 69.5%, respectively. The degradation of GSM and 2-MIB showed positive correlations with the current density in the kinetic model. Furthermore, the significant role of HO• and Cl• were evaluated by scavenging experiments and kinetics modeling. The calculated rate constants for GSM and 2-MIB degradation were approximately consistent with the experimental values in the existence of different scavengers. Both HO• and Cl• made an important contribution to the GSM and 2-MIB removal. The results demonstrate that the UV photoelectrochemical AOPs with no extra oxidants addition could be an efficient way for the mineralization of T/O compounds.

Keywords: Geosmin, 2-Methylisoborneol, Kinetics model, UV photoelectrochemical process, Free radicals