Conductive-diamond Electrochemical Oxidation Research Articles

Remediation of groundwater polluted with lindane production wastes by conductive-diamond electrochemical oxidation

This work studies the remediation of groundwater saturated with dense non-aqueous phase liquid (DNAPL) from lindane production wastes by electrochemical oxidation. DNAPL-saturated groundwater contains up to 26 chlorinated organic compounds (COCs), including different isomers of hexachlorocyclohexane (HCH). To do this, polluted groundwater was electrolysed using boron-doped diamond (BDD) and stainless steel (SS) as anode and cathode, respectively, and the influence of the current density on COCs removal was evaluated in the range from 5 to 50 mA cm−2. Results show that current densities higher than 25 mA cm−2 lead to the complete removal and mineralisation of all COCs identified in groundwater. The higher the current density, the higher the COCs removal rate. At lower current densities (5 mA cm−2), chlorobenzenes were completely removed, and degradations above 90 % were reached for COCs with more than five chlorine atoms in their molecules. The use of BDD anodes promotes the electrochemical generation of powerful reactive species, such as persulfate, hypochlorite or hydroxyl radicals, that contribute to the degradation and mineralisation of COCs. The applied current density also influences the generation of these species. Finally, no acute toxicity towards Vibrio fischeri was observed for the treated groundwater after the electrochemical oxidation performed at 5 and 10 mA cm−2. These findings demonstrate that electrochemical oxidation with BDD anodes at moderate current densities is a promising alternative for the remediation of actual groundwater contaminated with DNAPLs.

Modelling of the treatment of wastewater by photovoltaic solar electrochemical oxidation (PSEO) assisted by redox-flow batteries

This work aims at the formulation of simple and pragmatic models to predict the behaviour of a photovoltaic solar electrochemical oxidation treatment assisted by an energy storage system. Those models will be later integrated in a software tool that allows the optimization and the management of the energy provided by solar panels to power electrochemical advanced oxidation processes coupled with a redox flow battery as energy storage system. Models for a PV panel, a redox flow battery stack and a conductive diamond electrochemical oxidation electrolyzer have been proposed and fitted to experimental data. Results showed a huge accuracy of the models to predict the electric and remediation parameters. Validation analyses reported high regression coefficients above 0.96 which confirm the precision of all the proposed models. Thus, once known the solar radiation in a located place, the level of remediation of a wastewater effluent treated by electrolysis may be estimated. Furthermore, it must be pointed out that the operational conditions of the treatment could be optimized and adjusted by means of an energy storage in the redox flow battery. Considering those facts, the sustainability and efficiency of electrochemically-assisted remediation processes could be highly increased.

Does intensification with UV light and US improve the sustainability of electrolytic waste treatment processes?

This work aims to assess the influence of ultrasounds (US) application or ultraviolet (UV) light irradiation on the efficiency and sustainability of the treatment of wastes by conductive diamond electrochemical oxidation (CDEO). To do this, a life cycle assessment (LCA) is carried out in order to quantify the environmental impacts of the intensified CDEO processes. Inventories of three bench scale remediation plants (CDEO, Sono-CDEO and Photo-CDEO) in which the different technologies are implemented are performed by means of Ecoinvent 3.3 data base. AWARE, USEtox, IPPC and ReCiPe methodologies are used to quantify the environmental burden into 5 midpoint (water footprint, global warming 100a, ozone layer depletion, human toxicity, freshwater ecotoxicity) and 17 endpoint impact categories. Photo-CDEO attains the faster and more efficient removal in terms of energy consumed. All impact categories are lower in the case in which UV light irradiation is coupled to the CDEO treatment, particularly if the electrolyte does not contain chloride anions. From the point of view of toxicity and ecotoxicity, it is essential to achieve a complete mineralization, because of the intermediates generated into wastes containing chloride anions can become more hazardous than the initial pesticide. The operation of these technologies at large current densities shows positive results from the sustainability point of view, despite the huge environmental impact related to the energy production. Data notice that almost a 99.0% of the total global warming potential is mainly due to the electricity required during the electrochemical treatment, being higher by the sono and photo CDEO treatments because of the use of additional devices. Nevertheless, this issue can be overcome by means of using renewable energies as power sources of these remediation treatments. According to results, it can be claimed that the electrochemical technologies may successfully compete with other AOPs in terms of sustainability.

Effects of coupling hybrid processes on the treatment of wastewater containing a commercial mixture of diuron and hexazinone herbicides

This work evaluates the effects of coupling Conductive Diamond Electrochemical Oxidation (CDEO) with electrogenerated peroxide (CDEO-H2O2), iron (II) catalyst (electro-Fenton, EF) and UV irradiation (photoelectron-Fenton, PEF) techniques for the treatment of wastewater containing a commercial mixture of Diuron and Hexazinone herbicides. Although the techniques employed in this study exhibited significant differences in terms of current charge, energy consumption and amounts of byproducts formed, they have shown to be capable of degrading and mineralizing both herbicides (Diuron and Hexazinone). The application of electrooxidation technique with and without hydrogen peroxide generation led to the oxidation of both herbicides, where removal rates ranging from 74% to 99% and 77%–92% were obtained for Hexazinone and Diuron, respectively. Hexazinone and Diuron were completely removed after 90 min in the EF process. PEF was found to be the most efficient technique for having drastically reduced the time for complete degradation of the herbicides, although 25% of organic carbon remained in solution after 120 min of electrolysis. Higher rates of herbicides degradation were obtained in this order: PEF > EF > CDEO/H2O2/UV > CDEO/H2O2 > CDEO > UV. The result indicates that the production of oxidants is promoted by the hybrid processes, and this leads to an improvement in the oxidation of the pollutants. The synergistic coefficient obtained for the coupled techniques were higher than one in terms of both herbicides degradation and Total Organic Carbon (TOC) removal. Two important sub-products of reaction were identified, and their degradation route is in agreement with the reports published in the literature. Essentially, this work draws attention to the synergistic effect caused by the coupling of techniques involving the treatment of chemical agents in wastewater and sheds light on how to use this coupling technique for the development of more efficient treatment processes.

The role of Toll-like receptor 3 on the pathogenesis of murine malaria during pregnancy

This work aims to assess the influence of ultrasounds (US) application or ultraviolet (UV) light irradiation on the efficiency and sustainability of the treatment of wastes by conductive diamond electrochemical oxidation (CDEO). To do this, a life cycle assessment (LCA) is carried out in order to quantify the environmental impacts of the intensified CDEO processes. Inventories of three bench scale remediation plants (CDEO, Sono-CDEO and Photo-CDEO) in which the different technologies are implemented are performed by means of Ecoinvent 3.3 data base. AWARE, USEtox, IPPC and ReCiPe methodologies are used to quantify the environmental burden into 5 midpoint (water footprint, global warming 100a, ozone layer depletion, human toxicity, freshwater ecotoxicity) and 17 endpoint impact categories. Photo-CDEO attains the faster and more efficient removal in terms of energy consumed. All impact categories are lower in the case in which UV light irradiation is coupled to the CDEO treatment, particularly if the electrolyte does not contain chloride anions. From the point of view of toxicity and ecotoxicity, it is essential to achieve a complete mineralization, because of the intermediates generated into wastes containing chloride anions can become more hazardous than the initial pesticide. The operation of these technologies at large current densities shows positive results from the sustainability point of view, despite the huge environmental impact related to the energy production. Data notice that almost a 99.0% of the total global warming potential is mainly due to the electricity required during the electrochemical treatment, being higher by the sono and photo CDEO treatments because of the use of additional devices. Nevertheless, this issue can be overcome by means of using renewable energies as power sources of these remediation treatments. According to results, it can be claimed that the electrochemical technologies may successfully compete with other AOPs in terms of sustainability.

Enhanced electrolytic treatment for the removal of clopyralid and lindane

In this work, it is evaluated the more critical point of a new electrochemical technology for the removal of organic pollutants based on the regeneration of granular active carbon (GAC) (that can be used efficiently to concentrate aqueous wastes) with methanol and in the electrochemical treatment of methanol with conductive diamond electrochemical oxidation (CDEO). The system proposed was studied with lindane and clopyralid. Results show that it is possible the complete removal of the raw pesticides and intermediates formed by electrolyzing these species in methanol media and that both sodium chloride and sodium hydroxide can be used as supporting electrolyte to increase the conductivity of methanol. The cell voltages obtained are quite similar to those obtained during the electrolysis of aqueous wastes. The electrolysis of these dilute solutions does not generate significant concentrations of intermediates and the depletion of the raw pollutant fits well to a pseudo-first order kinetic model. Oxidants capable to oxidize iodide to iodine are produced during the electrolysis in methanol media and they have an important influence on the degradation of the pollutants. The new technology, based on the concentration of the pollutant before electrolysis, allows to remove completely pollutants from soil and soil washing fluids in a more efficient way, although the concentration of pollutant attained and, hence, the efficiency of the overall removal process depends on the adsorption equilibria of the pollutant in aqueous and methanol media.

Comparison and Predesign Cost Assessment of Different Advanced Oxidation Processes for the Treatment of 1,4-Dioxane-Containing Wastewater from the Chemical Industry

The predesign cost analysis of the industrial implementation of several advanced oxidation processes (AOPs) as the pretreatment of 1,4-dioxane-containing wastewater from the chemical manufacturing industry is herein assessed and discussed. Aiming to maximize biodegradability and minimize the generation of residues, ozonation (O3), conductive diamond electrochemical oxidation (CDEO), and zerovalent iron-based heterogeneous photo-Fenton processes were tested. Sufficient biodegradability (≈60%) was reached by all the studied AOPs when the pretreatment was performed until obtaining a 40% removal of the chemical oxygen demand (COD). The design criteria consisted of reaching this 40% COD reduction in a unit with a treatment capacity of 43 800 m3·y–1. Considering the limitations inherent to this type of assessment, it resulted, from the analysis of capital investment and annual operational spending, that the cost of all the assessed AOPs was about 5 €·m–3.

Evidence for the production of hydroxyl radicals at boron-doped diamond electrodes with different sp3/sp2 ratios and its relationship with the anodic oxidation of aniline

In this work, the electrochemical production of hydroxyl radicals on boron-doped diamond (BDD) electrodes with different sp3/sp2 ratios was studied, together with the relationship between the level of production of hydroxyl radicals and the degradation and mineralization of aniline, taken as a model organic compound. A higher sp3/sp2 ratio on the BDD surface produces a greater number of hydroxyl radicals, as previously stated; however, for the first time the difference in the production of hydroxyl radicals for different levels of sp2-impurities on BDD surface was established and its importance in determining the nature of the BDD surface (semi-active or inactive) is demonstrated. The results are of great relevance in interpreting the real effect of conductive diamond electrochemical oxidation on the treatment of organic wastes described in the literature.

Disinfection of urine by conductive-diamond electrochemical oxidation

This work focuses on the application of electrolysis with diamond anodes for the disinfection of urine. To do this, a synthetic human urine was polluted with Escherichia coli and Pseudomonas aeruginosa and then, it was electrolyzed at current densities within the range 0–100 A m−2. Results show that it is possible to disinfect completely the effluent even at applied electric charges lower than 2 kAh m−3, regardless the current density applied. This good performance is related to the production of powerful oxidants from the oxidation of the ions present in synthetic urine. Likewise, these species also react with the organics contained in urine (urea, creatinine and uric acid), favoring their degradation. The process efficiency for both microorganisms and organics is higher when working at low current densities. The removal of organics leads to the release of significant amounts of nitrogen in the form of nitrate which are later electroreduced to ammonium, that, in turn, reacts with the electrogenerated hypochlorite, favoring the production of chloramines (which can also contribute to the disinfection process). Regarding the mineralization, TOC removal higher than 90% can be achieved but higher applied electric charges than those required for disinfection have to be applied (around 30 kAh m−3).

Removal of Procion Red MX-5B dye from wastewater by conductive-diamond electrochemical oxidation

In this work, the removal of Procion Red MX-5B dye by electrochemical oxidation with boron doped diamond (BDD) anodes was investigated. The impact of current density, flow rate, initial pH, and supporting electrolyte was evaluated on dye and organic matter removal. Furthermore, the use of dimensionally stable anodes (DSA) was tested to evaluate process performance. Results show that after 240 min, it is possible to achieve full dye and COD (Chemical Oxygen Demand) removal, regardless of applied current density. This is due to the generation of powerful oxidants – i.e. hydroxyl radicals and peroxodisulfate–, which attack the organic matter in the wastewater, promoting its complete degradation. However, process efficiency increases when using lower current densities (10 mA cm−2): electric charges of about 5 Ah dm−3 are sufficient to fully remove both dye and COD, while charges higher than 15 Ah dm−3 are required when working at higher current densities (>30 mA cm−2). This fact is related to the production of large amounts of hydroxyl radicals, which are wasted in other reactions at higher current densities. On the other hand, higher flow rates (300 dm3 h−1) promote Procion Red MX-5B and organic matter degradation, due to improved mass transfer within the system. Regarding the impact of initial pH on dye removal, no significant differences were observed. Conversely, COD is clearly affected by this parameter: it is only possible to fully remove the organic matter when working at natural pH.Finally, with DSA anodes, higher dye removal efficiencies are attained than with BDD electrodes, when 100 mg dm−3 chlorides are added to the supporting electrolyte. Likewise, higher chloride concentration (100–1000 mg dm−3) was observed to enhance process efficiency when using DSA as anode material. However, during electrolysis with both BDD and DSA, chloride ions in the supporting electrolyte promote the production of intermediate organochlorinated compounds. Therefore, under these conditions, no full organic matter removal can be achieved, regardless of the anode material employed.

Electrolytic and electro-irradiated technologies for the removal of chloramphenicol in synthetic urine with diamond anodes

Hospital effluents are a major source for the occurrence of pharmaceuticals in the environment. In this work, the treatment of synthetic urine polluted with chloramphenicol is studied by using three different conductive-diamond electrochemical oxidation technologies: electrolysis (single electrolysis), photoelectrolysis and high-frequency ultrasound sonoelectrolysis. These technologies were evaluated at 10 and 100 mA cm−2. Results shows that not only chloramphenicol but also other organics contained in urine are completely mineralized by electrolysis. Ammonium is the main inorganic nitrogen species formed and it can react with the electrogenerated hypochlorite, favouring the formation of chloramines. These species prevent the potential formation of perchlorate from chlorides contained in urine at low current densities (10 mA cm−2) and delay its occurrence at high current densities (100 mA cm−2). On the other hand, irradiation of ultraviolet (UV) light or high-frequency ultrasound (US) produce changes in the performance of the electrolytic treatment, but these changes are not as important as in other cases of study shown in the literature. Nonetheless, the effect of electroirradiated technologies seems to be higher and depends on the type of pollutant when working at low current densities (10 mA cm−2). It is positive in the case of the degradation of the antibiotic and the uric acid and negative in the case of urea where there is a clear antagonistic effect. Production of oxidants increases with the current density although in lower ratio than expected. These results are of great importance because clearly point out that electrolytic technologies can be applied to minimize the diffuse pollution associated to pharmaceuticals before discharge into municipal sewers.

Irradiated-assisted electrochemical processes for the removal of persistent pollutants from real wastewater

Abstract In this work, it is studied the treatment of real wastewater (intensified with two target compounds) using electro-irradiated technologies. Two types of effluents coming from an organic-synthesis pharmaceutical industry and the outlet of a municipal wastewater treatment plant were intensified with metoprolol (β-blocker) and caffeine (stimulant), respectively. Conductive diamond electrochemical oxidation (CDEO), photolysis, sonolysis and all possible combinations among these technologies were evaluated for the treatment of both wastes. Results demonstrate that complete oxidation of the target compounds, as well as mineralization of the organic compounds contained in the matrixes, can be attained by all electro-irradiated technologies and no salt addition was needed to obtain an efficient treatment. Single irradiated technologies were inefficient in the oxidation but their combination with CDEO improves significantly the efficiency of the process showing clear synergistic effects. However, due to the large energy requirement of ultrasound irradiation, this combination is only cost-effective in the case of ultraviolet irradiation.

Scale-up of electrolytic and photoelectrolytic processes for water reclaiming: a preliminary study.

This work focuses on the scale-up of electrochemical and photoelectrochemical oxidation processes with diamond anodes for the removal of organic pollutants and disinfection of treated urban wastewater, two of the most important parameters for the reclaiming of wastewater. The removal of organics was studied with actual biologically treated urban wastewater intensified with 100mgdm(-3) of caffeine, added as a trace organic pollutant. The disinfection was also studied with biologically treated urban wastewater, and Escherichia coli was used to monitor the efficiency of the process. Results obtained with a single DiaCell® 101 were compared with those obtained with a single-stack DiaCell® 1001 and with a pilot plant made up of five of these stacks. Results obtained demonstrate that scale-up is not a simple but a very complex process, in which not only the electrode and the irradiation dose are important but also mass transfer conditions. Enhanced mass transport conditions have a determining and very positive effect on the removal of organics and a negative effect on the disinfection. Likewise, ultraviolet (UV) irradiation affects in a different way in the different setups used, having a great influence on the removal of complex organics and on the speciation of oxidants produced during disinfection. This works helps to understand the key differences observed in the scale-up, and it is a first approach for future works focused on the real application of conductive diamond electrochemical oxidation.

Mechanism and kinetics of electrochemical degradation of uric acid using conductive-diamond anodes

ABSTRACTUric acid (UA) is one of the principal effluents of urine wastewaters, widely used in agriculture as fertilizer, which is potentially dangerous and biorefractory. Hence, the degradation of UA (2,6,8-trihydroxy purine) in aqueous solution of pH 3.0 has been studied by conductive-diamond electrochemical oxidation. Hydroxyl radicals formed from water oxidation at the surface of boron-doped diamond anodes were the main oxidizing agents. Effects of current density and supporting electrolyte on the degradation rate and process efficiency are assessed. Results show that the increase of current density from 20 to 60 mA cm–2 leads to a decrease in the efficiency of the electrochemical process. In addition, the best degradation occurred in the presence of NaCl as conductive electrolyte. Interestingly, an almost total mineralization of 50 ppm UA was obtained when anodic oxidation was performed at low current densities (20 mA cm–2) and in the presence of NaCl. This result confirmed that the electrolysis using diamond anodes is a very interesting technology for the treatment of UA. The identification of UA transformation products was performed by high-performance liquid chromatography (HPLC). HPLC analysis of treated solutions revealed that oxalic acid and urea were the two intermediates found. Oxalic acid was the most persistent product. Based on detected intermediates and bibliographic research, a mechanism of UA mineralization by anodic oxidation has been proposed. Ionic chromatography analysis confirmed the release of and ions during UA mineralization.

What happens to inorganic nitrogen species during conductive diamond electrochemical oxidation of real wastewater?

This work describes the oxidation of caffeine, metoprolol, SMX and progesterone in real wastewater in terms of inorganic nitrogen speciation and help clarify the mechanisms that affect inorganic nitrogen species as final products. In synthetic solutions containing ammonium or nitrate ions, it has been confirmed that reduction of nitrates is a very favored process while oxidation of ammonium is negligible. Role of chloride is demonstrated to be important in the formation of chloramines, as well. These results allow the clarification of the production of nitrates as main products of the oxidation of organic chemicals and the occurrence of ammonium and chloramines in the reaction media, as well as the depletion of nitrogen by gaseous nitrogen production. Results are of a great relevance to interpret the mechanisms proposed in the literature for the treatment of organic wastes by conductive diamond electrochemical oxidation.

Removal of herbicide glyphosate by conductive-diamond electrochemical oxidation

This work focuses on the removal of herbicide glyphosate by electrolysis with boron doped diamond anodes. Both the electrolysis of the pure reagent and that of a commercial dispersion (RoundUp) are evaluated. Results show that it is possible to attain a complete mineralization of this herbicide and point out the key role of the supporting electrolyte in the efficiency of the process. This role is explained in terms of the electrogeneration of oxidants. The electrolysis of glyphosate also leads to the release of phosphate and nitrate anions. Further electrochemical and chemical reactivity explains the occurrence of ammonium and other nitrogen species in the electrolyte during the process. Regarding the influence of the type of herbicide (chemical or commercial), competitive reactions have been observed between the electrolysis of herbicide and surfactant, which help to explain the lower efficiency observed in the degradation of RoundUp. Regarding the influence of the operation current density, the process is found to be more efficient at low current densities but at these conditions it is not possible to attain the complete mineralization of pollutant.

CONDUCTIVE-DIAMOND ELECTROCHEMICAL OXIDATION OF A PHARMACEUTICAL EFFLUENT WITH HIGH CHEMICAL OXYGEN DEMAND (COD). KINETICS AND OPTIMIZATION OF THE PROCESS BY RESPONSE SURFACE METHODOLOGY (RSM)

Conductive-diamond electrochemical oxidation processes are promising technologies for treating biorefractory industrial wastes with organic loads below 20000 mg L-1. In this work, electrochemical oxidation of a real industrial pharmaceutical wastewater with conductive-diamond anodes has been studied. The electrolyses were carried out in discontinuous operation mode under galvanostatic conditions, using a bench-scale plant equipped with a single compartment electrochemical flow cell. For optimizing the process and studying the interaction between the operating conditions, different experiments were performed by modifying the current density (from 25 to 180 mA cm-2) and recirculation flow rate (from 105 to 565 ml min-1) with residence times between 0 and 570 minutes. The corresponding contribution of these two operative parameters on COD removal and its evolution versus residence time was studied. A time of 98 minutes was obtained in order to evaluate the highest influence of operative parameters. For this time, the current density was found to have a considerable positive effect, while the flow rate proved to be a statistically insignificant variable. ANOVA test reported significance for three of the five involved variables and Response Surface Methodology technique was used to optimize COD removal.

Conductive diamond electrochemical oxidation of caffeine-intensified biologically treated urban wastewater

In this work, the usefulness of Conductive Diamond Electrochemical Oxidation (CDEO) to degrade caffeine in real urban wastewater matrixes was assessed. The oxidation of actual wastewater intensified with caffeine (from 1 to 100mgL−1) was studied, paying particular attention to the influence of the initial load of caffeine and the differences observed during the treatment of caffeine in synthetic wastewater. The results showed that CDEO is a technology that is capable of efficiently degrading this compound even at very low concentrations and that it can even be completely depleted. Profiles of the ionic species of S (SO42−), N (NH4+, NO3−) and Cl (ClO−, ClO3− and ClO4−) were monitored and explained for plausible oxidation mechanisms. It was observed that the efficiency achieved is higher in the treatment of real wastewater than in the oxidation of synthetic wastewater because of the contribution of electrogenerated oxidant species such as hypochlorite. The formation of chlorate and perchlorate during electrochemical processes was observed, and a combined strategy to prevent this important drawback was successfully tested based on the application of low current densities with the simultaneous dosing of hydrogen peroxide.

Solar-powered CDEO for the treatment of wastewater polluted with the herbicide 2,4-D

In this work, the remediation of wastewater polluted with 2,4-D via conductive-diamond electrochemical oxidation using solar energy as a direct electrical power source has been investigated. The changes in operating conditions during the solar test are clearly related to the day–night cycle, with a maximum solar irradiation intensity of 450Wm−2 at noon and an average daily charge supplied of 22.5Ahm−2d−1. A solar irradiation intensity greater than 100Wm−2 is necessary to produce current, and values over 200Am−2 are required for efficient solar-powered processes. Despite fluctuations in the intensity supplied to the electrochemical cell, electrolysis with diamond electrodes can attain complete depletion of 2,4-D and its mineralization, although the changing operating conditions applied during the electrolysis powered by solar energy favor the accumulation of many intermediates. In contrast, only very low concentrations of two intermediates were detected during electrolysis powered galvanostatically with a power supply at 3.0A, indicating that the intensity highly influences the oxidation rate involved in the electrolysis.

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

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.