Coupling photo and sono technologies to improve efficiencies in conductive diamond electrochemical oxidation

Souza, F.L.; Sáez, Cristina; Cañizares, Pablo; Motheo, Artur J.; Rodrigo, Manuel A.

doi:10.1016/j.apcatb.2013.07.003

Cited by 59 publications

(70 citation statements)

References 40 publications

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“…In all cases, complete mineralisation occurred after 600 min of electrolysis (corresponding to 31 Ah dm -3 of electrical charge passed), except for the treatment of caffeine solution in which 800 min were required to attain the complete mineralisation. These good results are opposed to the very low extent of degradation achieved by photolysis and sonolysis, which also demonstrated a strong dependence on the type of molecule studied [29]. In the experiments carried out with caffeine, sonolysis and photolysis showed negligible degradation of the compound, whereas the extent of degradation of SMX by sonolysis was almost nil and greater than 25 % by photolysis.…”

Section: Methodscontrasting

confidence: 74%

“…Taking into account the possibility of oxidant activation in the bulk, in single CDEO, SMX and intermediates are expected to be completely depleted near the electrode surface, whereas in CDPEO, bulk oxidation is expected [15,16,19,29,43]. The higher concentration of intermediates measured in CDSEO suggests that this technology mainly favours improvements in the mass transfer of pollutants (hence, organics are expected to be oxidised near the electrode surface, as in single CDEO).…”

Section: Resultsmentioning

confidence: 94%

“…To explain this unexpected antagonistic behaviour, it must be considered that in the application of coupled irradiation-assisted electrochemical technologies, an excessive formation of radicals may occur. In such cases, instead of attacking organic species, the radicals may combine to form more stable and less aggressive oxidants or even decompose oxygen that may be forming [28,29] …”

Section: Resultsmentioning

confidence: 98%

“…On the other hand, synergistic effects of the combination of photo irradiation and the electrochemical process, with greater removal efficiency over the expected separate contributions, was observed in recent studies [28,29]. Electrochemical oxidation of organic with conductivediamond anodes is not limited by electrode processes, an enhancement in the efficiency is only expected if homogeneous catalytic processes are promoted [14,[16][17][18]30].…”

Section: Introductionmentioning

confidence: 79%

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Irradiation-assisted electrochemical processes for the removal of persistent organic pollutants from wastewater

et al. 2015

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This work focused on the removal of persistent organic pollutants (POPs) from wastewater using irradiation-assisted electrochemical technologies, i.e. sonoelectrolysis, photoelectrolysis and sono-photoelectrolysis. Single-irradiation processes (sonolysis and photolysis) and electrochemical oxidation using conductive diamond anodes (current density of 30 mA cm -2 ) were also evaluated for comparison. Three POPs with different molecular structures (sulfamethoxazole, metoprolol and caffeine, initial concentration of 100 mg dm -3 ) were studied to evaluate the robustness of the selected technologies and the oxidation mechanisms involved in each case. Results show that the single application of the irradiation technologies led to the removal of only a small amount of POPs and no mineralisation, with the nature of the pollutant showing a marked effect; the opposite was observed for the single application of conductive diamond electrochemical oxidation (CDEO), which is a highly robust and efficient technology for the degradation of all types of POPs. Sonoelectrolysis, photoelectrolysis and sono-photoelectrolysis processes (ultrasound conditions: 200 W, ultraviolet conditions: 254 nm, 4 W) may show synergistic, antagonistic or nil effects with respect to a single electrochemical oxidation event, depending on the nature of the treated molecule. The differences observed may be related to the different chemical nature of the organic species studied, indicating an important role of mediated oxidation processes, which may be enhanced with ultrasounds and ultraviolet radiation techniques.

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Section: Methodscontrasting

confidence: 74%

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 79%

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Irradiation-assisted electrochemical processes for the removal of persistent organic pollutants from wastewater

et al. 2015

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“…These oxidants need to be activated in the solution in order to be effective, most likely as radicals, and this activation may occur either by combination of oxidants (f.i. formation of hydroxyl radicals when ozone and hydrogen peroxide are combined) or by irradiation of UV light or US [40][41][42]. In this latter case irradiation does not need to be focused on the anode surface but in the bulk volume of wastewater once oxidants have been produced.…”

Section: Introductionmentioning

confidence: 99%

Removal of pesticide 2,4-D by conductive-diamond photoelectrochemical oxidation

Souza

Sáez

Lanza

et al. 2016

Applied Catalysis B: Environmental

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a b s t r a c tIn this work, the removal of pesticide 2,4-D by single photolysis, electrolysis with BDD anode and a combined UV irradiation-electrolysis is studied. Results demonstrate that although photolysis is completely inefficient in the degradation of this pesticide, light irradiation improves significantly the results obtained by single electrolysis, leading to harsher oxidation conditions, which contribute to reduce the number of intermediates and promote mineralization. Electrolysis with diamond electrodes can attain the complete depletion of the pesticide and its mineralization regardless the current density applied and the light irradiation. In comparing the effect of current density, it was found that the process is much efficient operating at 10 mA cm −2 , attaining complete mineralization with specific current charges below 10 Ah dm −3 , in spite of being detected a lower concentration of oxidants. Under absence of chlorides in the supporting electrolyte main intermediates formed were hydroquinone and 4-chlororesorcinol. Under the presence of this anion, 2-chlorophenol and 4-chlorophenol were also observed at high concentrations. UV irradiation does not modify the intermediates formed although concentration is lower. An oxidation mechanism is proposed in agreement with other works shown in the literature.

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Coupling Ultrasound to the Electro‐Oxidation of Methyl Paraben Synthetic Wastewater: Effect of Frequency and Supporting Electrolyte

et al. 2018

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In this paper, electrooxidation of methyl paraben (MeP) is studied by electrolysis only and electrolysis coupled with sonolysis, using a diamond electrode. Complete mineralization of MeP was achieved for both processes, in chloride and sulfate media. Results showed that, although the oxidation of pollutant is faster in the presence of chloride, the mineralization is favored in sulfate medium. Ultrasound irradiation enhanced the removal of organic matter due to the activation of oxidant species in both supporting electrolytes. Moreover, the formation of chlorine gas in the chloride containing medium improves the ultrasound cavitation effect, promoting faster depletion of the total organic carbon in the first hour of treatment. Regarding the formation of more toxic products, all possible organochlorinated intermediates were removed, since complete mineralization was attained in less than 5 hours. Ultrasonic coupling to the electrolysis process accelerates the destruction of the intermediates and delays the formation of perchlorate, which only begins after the complete removal of the total organic carbon. Low and high ultrasound frequencies were evaluated and were found to produce different effects of cavitation, which affect the electrolysis in different ways. The final result will be a balance between these effects and thus, an optimum frequency can be established for different systems.

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Coupling photo and sono technologies to improve efficiencies in conductive diamond electrochemical oxidation

Cited by 59 publications

References 40 publications

Irradiation-assisted electrochemical processes for the removal of persistent organic pollutants from wastewater

Irradiation-assisted electrochemical processes for the removal of persistent organic pollutants from wastewater

Removal of pesticide 2,4-D by conductive-diamond photoelectrochemical oxidation

Coupling Ultrasound to the Electro‐Oxidation of Methyl Paraben Synthetic Wastewater: Effect of Frequency and Supporting Electrolyte

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