Session 11 - Advanced oxidation processes

[CEST2019_00518] Degradation of Cylindrospermopsin using Advanced Non-Thermal Plasma Technologies
by Schneider M., Rataj R., Kolb J.F., Bláha L.

The application of non-thermal plasmas in wastewater and air purification received a lot of attention, but their potential application in drinking water treatment has scarcely been investigated. Classified as Advanced Oxidation Processes, plasmas ignited in water or at the air-water interface generate a vast range of reactive species capable of removing water contaminants.
The efficiency to degrade cylindrospermopsin (CYN, cyanobacterial toxin) was compared for six different plasma sources. A spark discharge showed the most energy-efficient degradation, followed by the other investigated systems, which showed similar trends.
Two approaches were selected for further in-depth study of the degradation efficiency and underlying mechanisms. For a follow-up detailed study, a corona-like and a dielectric barrier discharge were selected based on the CYN degradation efficiency, usability of the reactors and plasma-chemistry. For the corona-like plasma, the degradation efficiency increased with increasing voltage and solution pH. After 15 min of plasma treatment at pH ≥ 7.5, degradation of CYN even progressed without further plasma application. The pH-dependency was not observed for the dielectric barrier discharge (DBD), whose degradation efficiency increased with decreasing operating voltage. The corona-like plasma promotes degradation primarily via OH, whereas the DBD produces mainly O3 and NOx.

Session: 11, Room: E, at Thu, 09/05/2019 - 12:00 to 12:15
Oral presentation in Advanced oxidation processes
[CEST2019_00497] Cavitation Based Advanced Oxidation Processes for Wastewater Treatment – Comparison of Hydrodynamic and Sonocavitation Systems
by Boczkaj G., Gągol M., Fedorov K., Cako E.

Cavitation based advanced oxidation processes (Cav-AOPs), are a promising alternative to currently used wastewater treatment technologies. Amplified interest in this “hot” topic results in increased number of research on several aspects relating to formation of cavitation phenomena and its utilization for wastewater treatment as well as hybrid processes based of application of external oxidants effectively converted to radical species in cavitation conditions. The paper discusses a state of the art of cavitation based AOPs, as well as presents recent developments in this field of our research group. The principles of cavitation combined with AOPs will be presented followed by evaluation of their effectiveness in oxidation of organic contaminants and comparison of hydrodynamic and acoustic cavitation processes used for same type of pollutants. An examples of degraded particular pollutants will include chlorinated and nitro derivatives as well as other emerging environmental pollutants. Applications for disinfection of water will be also addressed. The paper will present also results of studies on degradation of pharmaceuticals as well as pre-treatment of real post-oxidative effluents formed during bitumen production as an examples of possible implementation of cavitation based processes in real industrial scenario.

Session: 11, Room: E, at Thu, 09/05/2019 - 11:45 to 12:00
Oral presentation in Advanced oxidation processes
[CEST2019_00350] Ozonation, advanced oxidation and hydrodynamic cavitation for removal of persistant pollutants
by Čehovin M., Žgajnar Gotvajn A.

Ozone is commonly used in advanced oxidation processes (AOPs) in combinations with hydrogen peroxide (H2O2) and UV radiation (UV). Hydrodynamic cavitation (HC) has been experimentally proven to result in effects, typical of AOPs. Combinations of AOPs with O3, H2O2 and UV, and HC (with cavitation numbers less than 0.2, generated by various orifice plates and nozzles, with number of passes up to 12) were experimentally assessed on model water, containing organic matter. Various synthetic organic micropollutants (iohexol, diatrizoic acid and metaldehyde with concentrations of 10 μg L–1) were selected as the target compounds. At dosages of O3, H2O2 and UV above 2 mg L–1, 4 mg L–1 and 450 mJ cm–2, respectively, herein applied HC had no beneficial effect on target pollutants removal. At lower dosages of the aforementioned oxidants, HC was able to improve the removal rate of the target pollutants by as much as 15 %. Moreover, in terms of electrical energy consumption, the hybrid process with HC was found to be as efficient per order (90 %) of removal (EEO, kWh m–3 order–1).

Session: 11, Room: E, at Thu, 09/05/2019 - 11:30 to 11:45
Oral presentation in Advanced oxidation processes
[CEST2019_00228] Evaluation of phytotoxic effects and decolorization of simulated and real textile wastewaters by UV/H2O2
by Quiceno L.I., Hernández M., Cardona L., Arroyave C., Aristizábal A.

In the present study textile dyes (Methylene Blue, Eliamine Blue F, Indigo) were used as model pollutants in water (ranging from 5 – 5000 mg/L) and real wastewater containing the Indigo dye was studied. The dyes in solution and the wastewater were treated by UV/H2O2 to study the influence of the type of dye, the initial concentrations of dye, the initial concentration of H2O2, the initial pH of the solution and the irradiation time in the dye decolorization of the treated solutions. The phytotoxic effect in Raphanus sativus of the treated and untreated dyes and wastewater in solution were evaluated.

Session: 11, Room: E, at Thu, 09/05/2019 - 12:33 to 12:36
Flash presentation in Advanced oxidation processes
[CEST2019_00064] Effect of iron catalyst on caffeine oxidation by sono-Fenton technology
by Villota N., Sardón L., Ferreiro C., Lomas J.M., Camarero L.M.

Oxidation of waters containing 100.0 mg L-1 of caffeine was conducted by a sono-Fenton treatment employing an ultrasound power of 720W at pH=3.0 and T=25°C. The catalytic action of ferrous ion was studied in a range of [Fe2+]0=0-100.0 mg L-1, using oxidant ratios of [H2O2]0=250.0 mM. The oxidation of caffeine was fitted to second order kinetic model, with the oxidation kinetic constant showing a linear dependence with iron dosage. During oxidation, the water acquired yellow-brown colour, along with an increase of turbidity and aromaticity degree. This is due to byproducts formation of uric acid-derived that has strongly aromatic structures that contain chromophore groups. Iron could give rise to a reaction mechanism with organic matter through the formation of (hydro)peroxo iron complexes. The molar ratio of 1 mol Fe2+: 0.5 mol C8H10N4O2 : 250 mol H2O2 : 720W promotes the formation of coloured species that generate high turbidity in the water.

Session: 11, Room: E, at Thu, 09/05/2019 - 12:36 to 12:39
Flash presentation in Advanced oxidation processes
[CEST2019_00070] Effect of hydrogen peroxide on caffeine oxidation by sono-Fenton technology
by Villota N., Sardón L., Ferreiro C., Lomas J.M., Camarero L.M.

Oxidation of waters containing 100.0 mg L-1 of caffeine was conducted by a sono-Fenton treatment employing an ultrasound power of 720W at pH=3.0 and T=25°C. The oxidizing action of hydrogen peroxide was studied in a range between [H2O2]0=0-250.0 mM, using iron ratios of 0.7 mol Fe2+/mol C8H10N4O2. The oxidation of caffeine was fitted to second order kinetics, obtaining removals of 98% when dosing 485 mol H2O2/mol C8H10N4O2. During the oxidation, the water acquired a strong brown colour at the same time as there was a strong increase in turbidity and degree of aromaticity. The interaction of (hydro)peroxo-iron complexes with the byproducts of caffeine degradation (1,3,7-trimethyluric acid, theobromine, paraxanthine, theophylline) generated supramolecular structures responsible for this phenomenon, being 116 mol H2O2/mol C8H10N4O2, the relationship that induced colour and aromaticity, while the formation of turbidity was favoured by using 29 and 116 mol H2O2/mol C8H10N4O2.

Session: 11, Room: E, at Thu, 09/05/2019 - 12:39 to 12:42
Flash presentation in Advanced oxidation processes
[CEST2019_00071] Changes of dissolved oxygen during the caffeine oxidation by photo-Fenton
by Villota N., Coralli I.,Lomas J.M.

The aim of this work is to analyse the changes of dissolved oxygen ([DO], mg/L) during the oxidation of caffeine waters by photo-Fenton treatment. The concentration of dosed hydrogen peroxide would be the addition of the stoichiometric [H2O2], which reacts with organic matter ([H2O2]esteq=2.0 mM), plus the concentration in excess of [H2O2]exc that decomposes, generating O2 through radical processes, according to a ratio R=0.8164 mmol H2O2/mg O2). Operating at doses lower than the stoichiometric value [H2O2]0<2.0 mM, O2 is not emitted, as there is no excessive oxidant. Besides, it is verified that the Fe2+ ion is oxidized to Fe3+, with subsequent regeneration to Fe2+. Applying higher doses than the stoichiometric [[H2O2]0>2.0 mM, oxygen is released, and regeneration of Fe3+ to Fe2+does not occur. The highest oxygen generation output is obtained when dosing [Fe]0=10.0 mg/L, conducting at pH=3.0 and 25ºC. The evolution of DO formation is adjusted to zero-order kinetics, the kinetic constant of oxygen generation being kf=29.48 [Fe]0-1.25 (mg O2 L-1 min -1) and oxygen consumption kd=-0.006 [Fe]02.0 + 0.244 [Fe]0-3.7 (mg O2 L-1 min-1).

Session: 11, Room: E, at Thu, 09/05/2019 - 12:15 to 12:30
Oral presentation in Advanced oxidation processes
[CEST2019_00079] Colour changes during the carbamazepine oxidation by photo-Fenton
by Villota N., Qullatein H., Lomas J.M.

Oxidation of waters containing 50.0 mg L-1 of carbamazepine was conducted by a photo-Fenton reagent employing a UV lamp of 150W, at pH=3.0 and T=40°C. The oxidising action of hydrogen peroxide was studied in a range between [H2O2]0=0-15.0 mM. When applying stoichiometric ratios of 2 mol C15H12N2O:20 mol H2O2:1.8 mol Fe2+, the maximum formation of colour (0.381 AU) is promoted. The colour may be generated by by-products of degradation of carbamazepine that have chromophore groups in its internal structure, such as oxo and dioxo-carbazepines, which would generate colour during the first minutes of oxidation, while the formation of acridones would slowly induce colour to the water.

Session: 11, Room: E, at Thu, 09/05/2019 - 12:42 to 12:45
Flash presentation in Advanced oxidation processes
[CEST2019_00014] Fenton reagent in combination with UV light and ultrasound waves applied for caffeine oxidation
by Villota N., Lomas J.M.

The oxidation of aqueous caffeine solutions ([Ca]0=100.0 mg L-1) was analyzed, operating at pH=3.0 and 25ºC using different AOPs, which combine the Fenton reagent ([H2O2]0=15.0 mM and [Fe2+]0=20.0 mg L-1) with low power UV light (15W,), medium (150W), and high (720 W). The Fenton reagent, combined with 150W UV light, was the most energetic treatment, proving that at 20 min it completely degrades caffeine and 80% of the water aromaticity. This hard oxidative process is accompanied by a high oxygen consumption, up to concentrations of [DO]=0.9 mg L-1 at the time when the caffeine contained in the water is completely degraded. On the other hand, 150W UV light is the only treatment capable of decreasing the concentration of total solids dissolved in water, according to a ratio of 0.0035 min-1. US waves allow degrading caffeine by 35%. This treatment leads to the emission of high oxygen concentrations ([DO]=20.0 mg L-1), which subsequently decreases along time. The UV lamp of 15W allows degrading caffeine by 12%, but does not affect the rest of the parameters analyzed.

Session: 11, Room: E, at Thu, 09/05/2019 - 12:30 to 12:33
Flash presentation in Advanced oxidation processes