Modeling Evaluation of Carbaryl Degradation in a Continuously Stirred Tank Reactor by Anodic Fenton Treatment

Abstract

Anodic Fenton treatment (AFT) has been shown to be effective in removing pesticides from aqueous solution in batch reactors with the formation of less toxic and more biodegradable products. To facilitate practical application of AFT, carbaryl degradation in a continuously stirred tank reactor (CSTR) by AFT was investigated under different experimental conditions, such as carbaryl inlet concentration, Fenton reagent concentration/ratio, and carbaryl feeding flow rate. A higher Fe2+ delivery rate and H2O2 to Fe2+ ratio (H2O2:Fe2+) were found to favor the carbaryl degradation process, whereas flow rate was shown to be a much less significant factor to influence the degradation rate under the evaluated experimental conditions. A kinetic-based semiempirical model was developed to simulate the experimental data, and a very good fit between the model and the raw data was found (R2 > 0.99). A dimensionless parameter (k/q2) was found to be a good indicator of the degradation rate; that is, the higher the k/q2value is, the faster the degradation process is. The rate parameter (k) can be used to evaluate the degradation rate when the flow rate is invariant for a given pesticide. The shape parameter (beta) is most likely related to the availability and reactivity of Fenton reagents and hydroxyl radicals. To compare the degradation rate of different pesticides, more information other than k/q2, k, and beta values, such as the instantaneous degradation rate vs time relationship, needs to be considered.