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

Abstract

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 , 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 × 10−4 mol/L, [H2O2] = 22 × 10−4 mol/L and [Fe2+] = 1.1 × 10−4 mol/L (kCA = 0.694 min−1), with an electric energy per order () 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 (kCA = 0.468 min−1; kDOC = 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.

Treatment of Winery Wastewater by Combined Almond Skin Coagulant and Sulfate Radicals: Assessment of HSO5− Activators

“…The range of PMS and Co 2+ concentrations was consistent with those previously assayed in the treatment of agro-industrial wastewaters by other authors [45,46]. The LED lamps were selected as radiation sources due to (1) the LED efficiency, (2) the LED price and (3) the maximum emission wavelength [47,48].…”

Olive Washing Wastewater Treatment by Coagulation/Flocculation/Decantation and UV-A LEDs/Fenton

“…Thus, the increase in iron concentration improved the H 2 O 2 decomposition into hydroxyl radicals [4]. However, excessive iron can cause the consumption of HO • radicals by Fe 2+ , which negatively affects the degradation of organic pollutants and increases the operational cost [9].…”

“…In Figure 2d, it can be observed that the increase in H 2 O 2 concentration was responsible for an improvement in DOC efficacy removal, i.e., 60.6% of 77.6 mM, 68.9% of 97.0 mM, 75.1% of 116.4 mM, 76.3% of 135.8 mM, and 76.6% of 155.3 mM. An excessive H 2 O 2 concentration can cause scavenging reactions between H 2 O 2 and HO • , causing the generation of hydroperoxyl and superoxide anion radicals [9]. However, with the gradual addition of 116.4 mm of H 2 O 2 at 0, 15, 30, 60, and 90 min, an improvement in DOC removal from 75.1 to 80.5% was verified.…”

Advanced Oxidation Processes and Their Application in the Treatment of Different Types of Wastewater Samples

“…Conventional methods are not much effective in removing and/or degrading these compounds due to the persistence related to their molecular properties and chemical structures 3 . Although these chemicals are detected in trace amounts, prolonged exposure can cause adverse effects on human health as well as aquatic life.Therefore, treating these pollutants from wastewater is obligatory before discharging them 4 .…”