Degradation of Agro-Industrial Wastewater Model Compound by UV-A-Fenton Process: Batch vs. Continuous Mode

The degradation of a model agro-industrial wastewater phenolic compound (caffeic acid, CA) by a UV-A-Fenton system was investigated in this work. Experiments were carried out in order to compare batch and continuous mode. Initially, batch experiments showed that UV-A-Fenton at pH 3.0 (pH of CA solution) achieved a higher generation of HO center dot, leading to high CA degradation (> 99.5%). The influence of different operational conditions, such as H2O2 and Fe2+ concentrations, were evaluated. The results fit a pseudo first-order (PFO) kinetic model, and a high kinetic rate of CA removal was observed, with a [CA] = 5.5 x 10(-4) mol/L, [H2O2] = 2.2 x 10(-3) mol/L and [Fe2+] = 1.1 x 10(-4) mol/L (k(CA) = 0.694 min(-1)), with an electric energy per order (EEO) of 7.23 kWh m(-3) order(-1). Under the same operational conditions, experiments in continuous mode were performed under different flow rates. The results showed that CA achieved a steady state with higher space-times (theta = 0.04) in comparison to dissolved organic carbon (DOC) removal (theta = 0-0.020). The results showed that by increasing the flow rate (F) from 1 to 4 mL min(-1), the CA and DOC removal rate increased significantly (k(CA) = 0.468 min(-1); k(DOC) = 0.00896 min(-1)). It is concluded that continuous modes are advantageous systems that can be adapted to wastewater treatment plants for the treatment of real agro-industrial wastewaters.

Automated summary

The degradation of caffeic acid in model agro-industrial wastewater was studied using a UV-A-Fenton system. Batch experiments showed that pH 3.0 achieved higher generation of HO center dot and thus higher caffeic acid degradation (>99.5%). The effects of H2O2 and Fe2+ concentrations were evaluated, and a pseudo first-order kinetic model was found to fit the results. Continuous mode experiments were performed at different flow rates, showing that increasing the flow rate resulted in significantly higher removal rates of caffeic acid and dissolved organic carbon (DOC). It is concluded that continuous modes are advantageous for treating real agro-industrial wastewaters.