Electrobiochemical skills of Pseudomonas aeruginosa species that produce pyocyanin or pyoverdine for glycerol oxidation in a microbial fuel cell.

Pseudomonas aeruginosa can produce pigments, which mediate external electron transfer (EET). Depending on the mediator, this species can be explored in bioelectrosystems to harvest energy or to obtain chemicals from residual organic compounds. This study has compared the performance of microbial fuel cells (MFCs) inoculated with a Pseudomonas aeruginosa isolate, namely EW603 or EW819, which produce pyocyanin and pyoverdine, respectively. The efficiency of these MFCs in glycerol, a typical residue of biodiesel production, were also compared. The MFCs exhibited different performances. The maximum voltage was 411 and 281 mV m2, the power density was 40.1 and 21.3 mW m-2, and the coulombic efficiency was 5.16 and 1.49% for MFC-EW603 and MFC-EW819, respectively. MFC-EW603 and MFC-EW819 achieved maximum current at 560 and 2200 Ω, at 141.2 and 91.3 mA m-2, respectively. When the system was operated at the respective maximum current output, MFC-EW603 consumed the total glycerol content (11 mmol L-1), and no products could be detected after 50 h. In turn, acetic and butyric acids were detected at the end of MFC-EW819 operation (75 h). The results suggested that P. aeruginosa metabolism can be steered in the MFC to generate current or microbial products depending on the pigment-producing strain and the conditions applied to the system, such as the external resistance. In addition, gene cluster pathways related to phenazine production (phzA and phzB) and other electrogenic-related genes (mexGHI-opmB) were identified in the strain genomes, supporting the findings. These results open new possibilities for using glycerol in bioelectrochemical systems.

Photocatalytic and mechanical properties of immobilized nanotubular TiO2 photocatalysts obtained by anodic oxidation: a novel combined analysis.

The photocatalytic and mechanical performance of TiO2 nanotubular coatings obtained by anodic oxidation of commercial titanium, using an NH4F and 3.5% v/v water in ethylene glycol solution as electrolyte was investigated. After the anodization, the coatings were thermally treated at 450 °C for 2 h. The effects of the anodizing voltage (40-80 V) and NH4F concentration (0.06, 0.15, 0.27 M) on the formation of the nanotube arrays were evaluated. Nanotube diameters (57 to 114 nm), wall thicknesses (4 to 13 nm), and lengths (5 to 17 µm) increased with the anodizing voltage and the NH4F concentration. The photocatalysts were characterized by scanning electron microscopy, glancing incidence X-ray diffraction, and UV-Vis diffuse reflectance spectroscopy. The mechanical properties of the photocatalysts were determined: adhesion using the tape test (ASTM D3359) and erosion resistance through a 3 h accelerated test. The photocatalytic activity of the nanotubes under UV irradiation was evaluated using hexavalent chromium (Cr(VI)) in the presence of ethylenediaminetetraacetic acid (EDTA), using a 1.25 EDTA/Cr(VI) molar ratio solution at pH 2. A complete Cr(VI) transformation after 3 h of irradiation was obtained for all samples, with a better performance than that of an immobilized P25 sample. The photocatalyst obtained with 0.27 M NH4F at 40 V presented a good behavior in adherence and erosion resistance, together with a very good photocatalytic activity. This novel analysis, combining photocatalytic and mechanical tests, proved that the new TiO2 nanotubular coatings could be successfully used as immobilized photocatalysts in photoreactors for water treatment.

Pharmaceuticals and personal care products in water streams: Occurrence, detection, and removal by electrochemical advanced oxidation processes.

Pharmaceutical and personal care products (PPCPs) are part of the emerging contaminants (ECs) in the environment due to their known or suspected adverse effects in aquatic and terrestrial organisms, as well as in human health. Presence of PPCPs in aquatic and terrestrial ecosystems has been mainly attributed to the effluents of wastewater treatment plants (WWTPs). Although several PPCPs have been detected in wastewater, their removal from wastewater via biological processes is limited. Removal of PPCPs depends on their chemical structure, concentration, solubility, and technology used to treat the wastewater. Electrochemical Advanced Oxidation Processes (EAOPs) are some of the most sought-after methods for dealing with organic pollutants in water including PPCPs, due to generation of strong oxidants such as •OH, H2O2 and O3- by using directly or indirectly electrochemical technology. This review is focused on the removal of main PPCPs via EAOPs such as, anodic oxidation, electro-Fenton, photoelectron-Fenton, solar photoelectron-Fenton, photoelectrocatalysis and sonoelectrochemical processes. Although more than 40 PPCPs have been identified through different analytical approaches, antibiotics, anti-inflammatory and antifungal are the main categories of PPCPs detected in different water matrices. Application of EAOPs has been centered in the removal of antibiotics and analgesics of high consumption by using model media, e.g. Na2SO4. Photoelectrocatalysis and Electro-Fenton processes have been the most versatile EAOPs applied for PPCPs removal under a wide range of operating conditions and a variety of electrodes. Although EAOPs have gained significant scientific interest due to their effectiveness, low environmental impact, and simplicity, further research about the removal of PPCPs and their by-products under realistic concentrations and media is needed. Moreover, mid-, and long-term experiments that evaluate EAOPs performance will provide knowledge about key parameters that allow these technologies to be scaled and reduce the potential risk of PPCPs in aquatic and terrestrial ecosystem.

Study of degradation of amitriptyline antidepressant by different electrochemical advanced oxidation processes.

Amitriptyline (AMT) is the most widely used tricyclic antidepressant and is classified as a recalcitrant emergent contaminant because it has been detected in different sources of water. Its accumulation in water and soil represents a risk for different living creatures. To remove amitriptyline from wastewater, the Advanced Oxidation Processes (AOPs) stands up as an interesting option since generate highly oxidized species as hydroxyl radicals (OH) by environmentally friendly mechanism. In this work, the oxidation and mineralization of AMT solution have been comparatively studied by 3 Electrochemical AOPs (EAOPs) where the OH is produced by anodic oxidation of H2O (AO-H2O2), or by electro-Fenton (EF) or photoelectro-Fenton (PEF). PEF process with a BDD anode showed the best performance for degradation and mineralization of this drug due to the synergistic action of highly reactive physiosorbed BDD (OH), homogeneous OH and UVA radiation. This process achieved total degradation of AMT at 50 min of electrolysis and 95% of mineralization after 360 min of treatment with 0.5 mmol L-1 Fe2+ at 100 mA cm-2. Six aromatic intermediates for the drug mineralization were identified in short time of electrolysis by GC-MS, including a chloroaromatic by-product formed from the attack of active chlorine. Short-chain carboxylic acids like succinic, malic, oxalic and formic acid were quantified by ion-exclusion HPLC. Furthermore, the formation of NO3- ions was monitored. Finally, the organic intermediates identified by chromatographic techniques were used to propose the reaction sequence for the total mineralization of AMT.

Electrochemical incineration of glyphosate wastewater using three-dimensional electrode.

Anodic oxidation of recalcitrant organic compounds is still challenging concerning to the anode material and mass transport limitations imposed by the low concentration. In this work, we studied the degradation of a real wastewater containing glyphosate using an electrode of PbO2 electrodeposited on a three-dimensional matrix of reticulated vitreous carbon (RVC). The high mass transfer rate provided by the RVC/PbO2 anode is demonstrated. A Box-Behnken factorial design was used for a systematic analysis of the effects of current density, flow rate and temperature on the degradation and mineralisation kinetics, current efficiency and specific energy consumption. The optimised degradation performance was achieved applying 30 mA cm-2, 3000 mL min-1 and 50°C. As the flow rate increases from 150 to 1500 mL min-1, the current efficiency increases from 18% to 65% and the energy consumption dropped from 72 to 33 kWh kg-1 due to the mass transfer enhancement promoted by the porous matrix. The efficacy of the electrochemical process for the treatment of real effluents using the three-dimensional PbO2 has been demonstrated.

Simultaneous degradation of 30 pharmaceuticals by anodic oxidation: Main intermediaries and by-products.

The anodic oxidation (AO) of 30 pharmaceuticals including antibiotics, hormones, antihistaminics, anti-inflammatories, antidepressants, antihypertensives, and antiulcer agents, in solutions containing different supporting electrolytes media (0.05 M Na2SO4, 0.05 M NaCl, and 0.05 M Na2SO4 + 0.05 M NaCl) at natural pH was studied. A boron-doped diamond (BDD) electrode and a stainless-steel electrode were used as anode and cathode, respectively, and three current densities of 6, 20, and 40 mA cm-2 were applied. The results showed high mineralization rates, above 85%, in all the tested electrolytic media. 25 intermediaries produced during the electrooxidation were identified, depending on the supporting electrolyte together with the formation of carboxylic acids, NO3-, SO42- and NH4+ ions. The formation of intermediates in chloride medium produced an increase in absorbance. Finally, a real secondary effluent spiked with the 30 pharmaceuticals was treated by AO applying 6 mA cm-2 at natural pH and without addition of supporting electrolyte, reaching c.a. 90% mineralization after 300 min, with an energy consumption of 18.95 kW h m-3 equivalent to 2.90 USD m-3. A degradation scheme for the mixture of emerging contaminants in both electrolytic media is proposed. Thus, the application of anodic oxidation generates a high concentration of hydroxyl radicals that favors the mineralization of the pharmaceuticals present in the spiked secondary effluent sample.

Comparing the electrochemical degradation of the fluoroquinolone antibiotics norfloxacin and ciprofloxacin using distinct electrolytes and a BDD anode: evolution of main oxidation byproducts and toxicity.

The effects of the supporting electrolytes (SEs) Na2SO4, NaCl, Na2CO3, NaNO3, and Na3PO4 on the anodic oxidation of norfloxacin (NOR) and ciprofloxacin (CIPRO), assessed by the respective degradation kinetics and byproducts and electrolyzed solution antimicrobial activity, are compared. Galvanostatic anodic oxidations were performed in a filter-press flow cell fitted with a boron-doped diamond anode. Removal rates higher than the theoretical one for a process purely controlled by mass transfer were found for all SEs, indicative of contribution by indirect oxidation processes. However, the removal rates for NaCl were about tenfold higher, with the lowest energy consumption per order (EC O) of targeted pollutant removal rate (ca. 0.7 kW h m-3 order-1), a very competitive performance. The TOC removal rates were also affected by the SE, but not as markedly. The antimicrobial activity of the electrolyzed solutions against Escherichia coli showed distinct temporal profiles, depending on the fluoroquinolone and SE. For instance, when Na3PO4 was used, the antimicrobial activity was completely removed for NOR, but none for CIPRO; conversely, when NaCl was used, complete removal was attained only for CIPRO. From LC-MS/MS analyses of Na3PO4 electrolyzed solutions, rupture of the fluoroquinolone ring leading to byproducts with no toxicity against E. coli occurred only for NOR, whereas exactly the opposite occurred for the NaCl solutions. Clearly, the nature of both the SE and the fluoroquinolone influence the oxidation steps of the respective molecule; this was also evidenced by the distinct short-chain carboxylic acids identified in the degradation of NOR and CIPRO.

Coupling of Anodic Oxidation and Soil Remediation Processes: A Review.

In recent years, due to industrial modernization and agricultural mechanization, several environmental consequences have been observed, which make sustainable development difficult. Soil, as an important component of ecosystem and a key resource for the survival of human and animals, has been under constant contamination from different human activities. Contaminated soils and sites require remediation not only because of the hazardous threat it possess to the environment but also due to the shortage of fresh land for both agriculture and urbanization. Combined or coupled remediation technologies are one of the efficient processes for the treatment of contaminated soils. In these technologies, two or more soil remediation techniques are applied simultaneously or sequentially, in which one technique complements the other, making the treatment very efficient. Coupling anodic oxidation (AO) and soil remediation for the treatment of soil contaminated with organics has been studied via two configurations: (i) soil remediation, ex situ AO, where AO is used as a post-treatment stage for the treatment of effluents from soil remediation process and (ii) soil remediation, in situ AO, where both processes are applied simultaneously. The former is the most widely investigated configuration of the combined processes, while the latter is less common due to the greater diffusion dependency of AO as an electrode process. In this review, the concept of soil washing (SW)/soil flushing (SF) and electrokinetic as soil remediation techniques are briefly explained followed by a discussion of different configurations of combined AO and soil remediation.

Electrochemical oxidation of indanthrene blue dye in a filter-press flow reactor and toxicity analyses with Raphidocelis subcapitata and Lactuca sativa.

Alternative routes to degrade dyes are of crucial importance for the environment. Hence, we report the electrochemical removal of indanthrene blue by using a boron-doped diamond anode, focusing on the toxicity of the treated solutions. Different operational conditions were studied, such as current density (5, 10, and 20 mA cm-2) and electrolyte composition (Na2SO4, Na2CO3, and NaNO3). Besides, the pH was monitored throughout the experiment to consider its direct influence on the ecotoxicity effects. The highest electrochemical oxidation efficiency, measured as color removal, was seen in the 180 min condition of electrolysis in 0.033 M Na2SO4, applying 20 mA cm-2, resulting in a color removal of nearly 91% and 40.51 kWh m-3 of energy consumption. The toxicity towards Lactuca sativa depends solely on pH variations being indifferent to color removal. While the inhibition concentration (IC50) for Raphidocelis subcapitata increases 20% after treatment (in optimized conditions), suggesting that the byproducts are more toxic for this specific organism. Our data highlight the importance of analyzing the toxicity towards various organisms to understand the toxic effect of the treatment applied.

Electrochemical oxidation of acetaminophen and its transformation products in surface water: effect of pH and current density.

Several studies have been conducted worldwide to develop effective and affordable methods to degrade pharmaceuticals and their metabolites/intermediates/oxidation products found in surface water, wastewater and drinking water. In this work, acetaminophen and its transformation products were successfully degraded in surface water by electrochemical oxidation using stainless steel electrodes. The effect of pH and current density on the oxidation process was assessed and the oxidation kinetics and mechanisms involved were described. Additionally, the results were compared with those obtained in acetaminophen synthetic solutions. It was found that conducting the electrochemical oxidation at 16.3 mA/cm2 and pH 5, good performance of the process was achieved and not only acetaminophen, but also its transformation products were totally degraded in only 7.5 min; furthermore, small number of transformation products were generated. On the other hand, degradation rates of acetaminophen and its transformation products in surface water were much faster (more than 2.5 times) and the reaction times much shorter (more than 4.0 times) than in synthetic solutions at all current densities and pH values evaluated. At pH 3 and pH 5, greater soluble chlorine formation due to the higher HCl amount used to acidify the surface water solutions could enhance the degradation rates of acetaminophen and its transformation products. However, constituents of surface water (ions and solids) could also have an important role on the oxidation process because at pH 9 (non-acidified solutions) the degradation rates were also much greater and the reaction times were much shorter in surface water than in acetaminophen synthetic solutions.

Influence of electrolysis conditions on the treatment of herbicide bentazon using artificial UVA radiation and sunlight. Identification of oxidation products.

The main objective of this work is to demonstrate the viability of solar photoelectro-Fenton (SPEF) process to degrade pesticides in urban wastewater matrix, selecting the herbicide bentazon as a model molecule. In order to provide a correct assessment of the role of the different oxidants and catalysts involved, bentazon was comparatively treated by anodic oxidation with electrogenerated H2O2 (AO-H2O2), electro-Fenton (EF) and UVA-assisted EF (i.e., PEF) processes as well, either in sulfate or chloride media. Trials were made in a stirred tank reactor with an air-diffusion cathode and a boron-doped diamond (BDD), RuO2-based or Pt anode. In chlorinated matrices, the herbicide disappeared more rapidly using a RuO2-based anode because of the generated active chlorine. The best mineralization performance was always obtained using BDD due to its higher oxidation power, which allowed the complete destruction of refractory chloroderivatives. A concentration of 0.50 mM Fe2+ was found optimal to catalyze Fenton's reaction, largely enhancing the mineralization process under the action of OH. Among photo-assisted treatments, sunlight was proven superior to a UVA lamp to promote the photolysis of intermediates, owing to its greater UV irradiance and contribution of visible photons, although PEF also allowed achieving a large mineralization. In all cases, bentazon decay obeyed a pseudo-first-order kinetics. SPEF treatment in urban wastewater using BDD at only 16.6 mA cm-2 yielded 63.2% mineralization. A thorough, original reaction pathway for bentazon degradation is proposed, including seven non-chlorinated aromatics, sixteen chloroaromatics and two chloroaliphatics identified by GC-MS, most of them not previously reported in literature. Ion-exclusion HPLC allowed the detection of seven short-chain linear carboxylic acids.

Treatment of winery wastewater by anodic oxidation using BDD electrode.

The effective removal of organics from winery wastewater was obtained in real residual effluents from the wine industry using anodic oxidation (AO). The effluent had an initial organic load of [COD]0 of 3490 mg L-1 equal to [TOC]0 of 1320 mg L-1. In addition, more than 40 organic compounds were identified by means of GC-MS. Different density currents as well as the addition of electrolytes were tested during electrolysis. The results show the decay of [COD]t by 63.6% when no support electrolyte was added, whereas almost total mineralization and disinfection was reached after adding of 50 mM of sodium sulfate and sodium chloride and applying higher density currents. The presence of sulfate and chloride in large concentration favors the production of oxidants such as hydroxyl radicals and active chlorine species that react with organics in solution. Moreover, the addition of a supporting electrolyte to industrial wastewater increases conductivity, reduces cell potential and therefore, decreases the energy consumption of the AO process.

Performance of (in)active anodic materials for the electrooxidation of phenolic wastewaters from cashew-nut processing industry.

This study investigated the anodic oxidation of phenolic wastewater generated by cashew-nut processing industry (CNPI) using active (Ti/RuO2-TiO2) and inactive (boron doped diamond, BDD) anodes. During electrochemical treatment, various operating parameters were investigated, such as current density, chemical oxygen demand (COD), total phenols, O2 production, temperature, pH, as well as current efficiency and energy consumption. After electrolysis under optimized working conditions, samples were evaluated by chromatography and toxicological tests against L. sativa. When both electrode materials were compared under the same operating conditions, higher COD removal efficiency was achieved for BDD anode; achieving lower energy requirements when compared with the values estimated for Ti/RuO2-TiO2. The presence of Cl- in the wastewater promoted the electrogeneration of strong oxidant species as chlorine, hypochlorite and mainly hypochlorous acid, increasing the efficiency of degradation process. Regarding the temperature effect, BDD showed slower performances than those achieved for Ti/RuO2-TiO2. Chromatographic and phytotoxicity studies indicated formation of some by-products after electrolytic process, regardless of the anode evaluated, and phytotoxic action of the effluent. Results encourage the applicability of the electrochemical method as wastewater treatment process for the CNPI, reducing depuration time.

Treatment of actual effluents produced in the manufacturing of atrazine by a photo-electrolytic process.

The photo-assisted electrochemical degradation of a real effluent of the atrazine manufacturing process containing atrazine, simazine, hydroxy-triazine and propazine was carried out galvanostatically using a pilot-scale tubular flow reactor prototype containing DSA® and Ti as cathode. The effluent was mainly characterized by a high amount of NaCl, required in the synthesis route used, and it was used as taken in the factory. The variables for process optimization were the current density (3.0, 6.0, and 9.0 mA cm-2) and flow rate (300 and 3,000 L h-1). These later values produces laminar and turbulent flow regimes, with Reynolds numbers of 1,100 and 11,000, respectively. None of the four organics contained in the waste is refractory to the photo-electrochemical treatment and they are depleted with the photo-electrolytic technology using large current densities and appropriate electric charge passed. Both direct electrochemical process and mediated anodic oxidation occur during the treatment. First process occurs at turbulent flow condition and low current densities, while the chemical oxidation process happens at laminar flow condition and high current densities. Atrazine and propazine are efficiently removed at laminar flow conditions, with an almost total depletion for the largest current densities. On the contrary, simazine is efficiently removed in turbulent flow conditions and intermediate current density, with removals higher than 90% for 20 kWh m-3. These results have great significance because they demonstrate the applicability of the electrochemical technology in the treatment of real industrial wastes with a cell specially designed to attain high efficiency in the removal of pollutants.

Decolorization and degradation of reactive yellow HF aqueous solutions by electrochemical advanced oxidation processes.

Textile manufacturing is the one responsible for water bodies' contamination through the discharge of colored wastes. This work presents the study of reactive yellow HF (RYHF) dye degradation under two different electrochemical advanced oxidation processes (EAOP), namely anodic oxidation (AO) and electro-Fenton (EF)/boron-doped diamond (BDD) process. For the AO, 100 and 300 mg/L solutions using Pt and BDD as anodes in a 100 mL stirred tank cell were used, with a supporting electrolyte of 0.05 mol/L of Na2SO4 at pH 3 under 30 and 50 mA/cm2 current density. The EF/BDD process was carried out in a flow reactor at 4 and 7 L/min to degrade 100, 200, and 300 mg/L RYHF solutions under 50 and 80 mA/cm2. UV-Vis determinations were used for decolorization evaluation, while high-performance liquid chromatography (HPLC) method provided information on dye degradation rate.

Treatment of paint manufacturing wastewater by coagulation/electrochemical methods: Proposals for disposal and/or reuse of treated water.

This paper describes and discusses an investigation into the treatment of paint manufacturing wastewater (water-based acrylic texture) by coagulation (aluminum sulfate) coupled to electrochemical methods (BDD electrode). Two proposals are put forward, based on the results. The first proposal considers the feasibility of reusing wastewater treated by the methods separately and in combination, while the second examines the possibility of its disposal into water bodies. To this end, parameters such as toxicity, turbidity, color, organic load, dissolved aluminum, alkalinity, hardness and odor are evaluated. In addition, the proposal for water reuse is strengthened by the quality of the water-based paints produced using the wastewater treated by the two methods (combined and separate), which was evaluated based on the typical parameters for the quality control of these products. Under optimized conditions, the use of the chemical coagulation (12 mL/L of Al2(SO4)3 dosage) treatment, alone, proved the feasibility of reusing the treated wastewater in the paint manufacturing process. However, the use of the electrochemical method (i = 10 mA/cm(2) and t = 90 min) was required to render the treated wastewater suitable for discharge into water bodies.

Diazo dye Congo Red degradation using a Boron-doped diamond anode: An experimental study on the effect of supporting electrolytes.

Diazo dye Congo Red (CR) solutions at 100mg/L, were degraded using different supporting electrolytes in an electrochemical advanced oxidation process (EAOPs), like the anodic oxidation (AOx/BDD). All experiments were carried out in a 3L flow reactor with a Boron-doped diamond (BDD) anode and stainless steel cathode (AISI 304), at 7.5, 15, 30 and 50mA/cm(2) current densities (j). Furthermore, each experiment was carried out under a flow rate of 7L/min. Additionally, HClO4, NaCl, Na2SO4, and H2SO4 were tested as supporting electrolytes at a 50mM concentration. The degradation process was at all times considerably faster in NaCl medium. Solutions containing SO4(2-) or ClO4(-) ions were less prompted to degradation due to the low oxidation power of these species into the bulk. Dissolved organic carbon (DOC) analysis, was carried out to evaluate the mineralization of CR. The degradation of CR, was evaluated with the HPLC analysis of the treated solutions.

Comparative study of the effect of pharmaceutical additives on the elimination of antibiotic activity during the treatment of oxacillin in water by the photo-Fenton, TiO2-photocatalysis and electrochemical processes.

Synthetic pharmaceutical effluents loaded with the ß-lactam antibiotic oxacillin were treated using advanced oxidation processes (the photo-Fenton system and TiO2 photocatalysis) and chloride mediated electrochemical oxidation (with Ti/IrO2 anodes). Combinations of the antibiotic with excipients (mannitol or tartaric acid), an active ingredient (calcium carbonate, i.e. bicarbonate ions due to the pH) and a cleaning agent (sodium lauryl ether sulfate) were considered. Additionally, urban wastewater that had undergone biological treatment was doped with oxacillin and treated with the tested systems. The evolution of antimicrobial activity was monitored as a parameter of processes efficiency. Although the two advanced oxidation processes (AOPs) differ only in the way they produce OH, marked differences were observed between them. There were also differences between the AOPs and the electrochemical system. Interestingly, each additive had a different effect on each treatment. For water loaded with mannitol, electrochemical treatment was the most suitable option because the additive did not significantly affect the efficiency of the system. Due to the formation of a complex with Fe(3+), tartaric acid accelerated the elimination of antibiotic activity during the photo-Fenton process. For TiO2 photocatalysis, the presence of bicarbonate ions contributed to antibiotic activity elimination through the possible formation of carbonate and bicarbonate radicals. Sodium lauryl ether sulfate negatively affected all of the processes. However, due to the higher selectivity of HOCl compared with OH, electrochemical oxidation showed the least inhibited efficiency. For the urban wastewater doped with oxacillin, TiO2 photocatalysis was the most efficient process. These results will help select the most suitable technology for the treatment of water polluted with ß-lactam antibiotics.

Coupling of solar photoelectro-Fenton with a BDD anode and solar heterogeneous photocatalysis for the mineralization of the herbicide atrazine.

Here, the synergetic effect of coupling solar photoelectro-Fenton (SPEF) and solar heterogeneous photocatalysis (SPC) on the mineralization of 200mL of a 20mg L(-1) atrazine solution, prepared from the commercial herbicide Gesaprim, at pH 3.0 was studied. Uniform, homogeneous and adherent anatase-TiO2 films onto glass spheres of 5mm diameter were prepared by the sol-gel dip-coating method and used as catalyst for SPC. However, this procedure yielded a poor removal of the substrate because of the low oxidation ability of positive holes and OH formed at the catalyst surface to destroy it. Atrazine decay was improved using anodic oxidation (AO), electro-Fenton (EF), SPEF and coupled SPEF-SPC at 100mA. The electrolytic cell contained a boron-doped diamond (BDD) anode and H2O2 was generated at a BDD cathode fed with an air flow. The removal and mineralization of atrazine increased when more oxidizing agents were generated in the sequence AO

Degradation of conazole fungicides in water by electrochemical oxidation.

The electrochemical oxidation (EO) treatment in water of three conazole fungicides, myclobutanil, triadimefon and propiconazole, has been carried out at constant current using a BDD/SS system. First, solutions of each fungicide were electrolyzed to assess the effect of the experimental parameters such as current, pH and fungicide concentration on the decay of each compound and total organic carbon abatement. Then a careful analysis of the degradation by-products was made by high performance liquid chromatography, ion chromatography and gas chromatography coupled with mass spectrometry in order to provide a detailed discussion on the original reaction pathways. Thus, during the degradation of conazole fungicides by the electrochemical oxidation process, aromatic intermediates, aliphatic carboxylic acids and Cl(-) were detected prior to their complete mineralization to CO2 while NO3(-) anions remained in the treated solution. This is an essential preliminary step towards the applicability of the EO processes for the treatment of wastewater containing conazole fungicides.