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 [Formula: see text] , leading to high CA degradation (>99.5%). The influence of different operational conditions, such as H(2)O(2) and Fe(2+) 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 × 10(−4) mol/L, [H(2)O(2)] = 2.2 × 10(−3) mol/L and [Fe(2+)] = 1.1 × 10(−4) mol/L (k(CA) = 0.694 min(−1)), with an electric energy per order ([Formula: see text]) 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 (θ = 0.04) in comparison to dissolved organic carbon (DOC) removal (θ = 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.