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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., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The appearance of pharmaceutical compounds and their bioactive transformation products in aquatic environments is becoming an issue of increasing concern. In this study, the electrochemical oxidation of the widely used antibiotic sulfamethoxazole (SMX) was investigated using a commercial mixed oxide anode (Ti/Ru0.3Ti0.7O2) and a single compartment filter press-type flow reactor. The kinetics of SMX degradation was determined as a function of electrolyte composition, applied current density, and initial pH. Almost complete (98 %) degradation of SMX could be achieved within 30 min of electrolysis in 0.1 mol L(-1) NaCl solution at pH 3 with applied current densities ≥20 mA cm(-2). Nine major intermediates of the reaction were identified by LC-ESI-Q-TOF-MS (e.g., C6H9NO2S (m/z = 179), C6H4NOCl (m/z = 141), and C6H6O2 (m/z = 110)). The degradation followed various routes involving cleavage of the oxazole and benzene rings by hydroxyl and/or chlorine radicals, processes that could occur before or after rupture of the N-S bond, followed by oxidation of the remaining moieties. Analysis of the total organic carbon content revealed that the antibiotic was partially mineralized under the conditions employed and some inorganic ions, including NO3 (-) and SO4 (2-), could be identified. The results presented herein demonstrate the efficacy of the electrochemical process using a Ti/Ru0.3Ti0.7O2 anode for the remediation of wastewater containing the antibiotic SMX.

The electrooxidation of the dimethyl phthalate (DMP) ester was galvanostatically carried out in a filter-press reactor using a fluoride-doped lead dioxide (β-PbO2,F) film electrodeposited on a Ti substrate. The variables investigated were the nature of the supporting electrolyte (NaCl and Na2SO4), pH (3, 7, and 10), current density (10, 20, 40, 60, and 80mAcm(-2)), and temperature (10, 20, 30, 40, and 50°C). The removal of DMP was monitored through high performance liquid chromatography (HPLC) and total organic carbon (TOC) analysis. The best conditions were obtained using Na2SO4 and at low current densities, independent of the solution pH or temperature. These conditions led to the highest levels of current efficiencies and complete combustion. However, the TOC removal levels were low, due to the generation of highly oxidized intermediates, which was confirmed by the intermediates detected by HPLC., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The breakdown of pesticides has been promoted by many methods for clean up of contaminated soil and wastewaters. The main goal is to decrease the toxicity of the parent compound to achieve non-toxic compounds or even, when complete mineralization occurs, carbon dioxide and water. Therefore, electrochemical degradation (potentiostatic and galvanostatic) of both the pesticide atrazine and cyanuric acid (CA) at boron-doped diamond (BDD) and Ti/Ru0.3Ti0.7O2 dimensionally stable anode (DSA) electrodes, in different supporting electrolytes (NaCl and Na2SO4), is presented with the aim of establishing the influence of the operational parameters on the process efficiency. The results demonstrate that both the electrode material and the supporting electrolyte have a strong influence on the rate of atrazine removal. In the chloride medium, the rate of atrazine removal is always greater than in sulfate under all conditions employed. Furthermore, in the sulfate medium, atrazine degradation was significant only at the BDD electrode. The total organic carbon (TOC) load decreased by 79% and 56% at the BDD and DSA electrodes, respectively, in the chloride medium. This trend was maintained in the sulfate medium but the TOC removal was lower (i.e. 33% and 13% at BDD and DSA electrodes, respectively). CA, a stable atrazine degradation intermediate, was also studied and it is efficiently removed using the BDD electrode in both media, mainly when high current densities are employed. The use of the BDD electrode in the chloride medium not only degrades atrazine but also mineralized cyanuric acid leading to the higher TOC removal.

This study presents the results of the degradation of the pesticide atrazine using electrochemical and photo-assisted electrochemical degradation techniques using SnO(2)-containing electrode of nominal composition electrodes of composition Ti/Ru(X)Sn(1-X)O(2) (where X=0.10, 0.15, 0.20, 0.25 and 0.30). The materials were characterized ex situ and in situ in order to correlate the observed atrazine removal rates with electrode morphology/composition. The results obtained demonstrate the effectiveness of the photo-assisted electrochemical degradation. Using purely electrochemical methods the rate of atrazine removal is almost zero at all the electrodes studied. However, the application of photo-assisted degradation results in almost complete atrazine removal in 1h of electrolysis. The efficiency of atrazine degradation does not seem to be greatly affected by the electrode material or by SnO(2) content, but the overall COD removal is dependent on the SnO(2) content. Overall, the SnO(2)-containing electrodes do not reach the level of COD removal (maximum approximately 21%) seen for the Ti/Ru(0.3)Ti(0.7)O(2) electrode. An interesting correlation between the morphology factor (phi) and chemical oxygen demand removal is observed., (Copyright 2010 Elsevier B.V. All rights reserved.)

This paper presents a degradation study of the pesticide atrazine using photo-assisted electrochemical methods at a dimensionally stable anode (DSA(®)) of nominal composition Ti/Ru(0.3)Ti(0.7)O(2) in a prototype reactor. The effects of current density, electrolyte flow-rate, as well as the use of different atrazine concentrations are reported. The results indicate that the energy consumption is substantially reduced for the combined photochemical and electrochemical processes when compared to the isolated systems. It is observed that complete atrazine removal is achieved at low current densities when using the combined method, thus reducing the energy required to operate the electrochemical system. The results also include the investigation of the phytotoxicity of the treated solutions.

This paper presents the results concerning the degradation of the pesticide carbaryl comparing two methods: electrochemical (EC) and photo-assisted electrochemical (PAEC). The experimental variables of applied current density, electrolyte flow-rate and initial carbaryl concentration were investigated. The results demonstrate that the electrochemical degradation of carbaryl was greatly enhanced when simultaneous UV light was applied. The greatest difference between the PAEC and EC method was apparent when lower current densities were applied. The extent of COD removal was much enhanced for the combined method, independent of the applied current density. It should be noted that the complete removal of carbaryl was achieved with out the need to add NaCl to the reaction mixture, avoiding the risk of chlorinated organic species formation.

The present paper presents the study of the decolourisation of real textile effluent by constant current electrolysis in a flow-cell using a DSA type material. The effect of using different anode materials (Ti/Ru(0.3)Ti(0.7)O(2); Ti/Ir(0.3)Ti(0.7)O(2); Ti/Ru(X)Sn(1-X)O(2), where X=0.1, 0.2 or 0.3) on the efficiency of colour removal is discussed. Attempts to perform galvanostatic oxidation (40 and 60 mA cm(-2)) on the as-received effluent demonstrate that colour removal and total organic carbon (TOC) removal are limited. In this case the greatest degree of colour removal is achieved when anode containing 90% SnO(2) is used. If the conductivity of the effluent is increased by adding NaCl (0.1 mol L(-1)) appreciable colour/TOC removal is observed. The efficiencies of colour and TOC removal are discussed in terms of the energy per order (E(EO)/kW h m(-3)order(-1)) and energy consumption (E(C)/kW h kg(-1)TOC), respectively. Finally, the extent of colour removal is compared to consent levels presented in the literature.

This paper presents the study of the degradation of the pesticide atrazine, employing photoassisted electrochemical methods at a dimensionally stable anode of nominal composition Ti/Ru0.3Ti0.7O2. All experiments were performed in a flow cell, and the effects of current density, electrolyte flow rate, as well the use of different supporting electrolytes are reported. The results indicate that the energy per order (E(EO)/kW h m(-3) order(-1)) is substantially reduced when the photochemical and electrochemical techniques are combined. It is observed that complete atrazine removal is achieved at low current densities when the combined method is employed, thus reducing the energy required to operate the electrochemical system. The study of the electrolyte flow rate through the cell indicates that the photoassisted removal of atrazine is controlled by mass transfer. The degradation of commercial atrazine solutions is also presented, and the results show that the efficiency of atrazine removal is reduced compared with that of simulated solutions, due to the presence of the additional components present in the commercial formula.

The present paper presents the study of the decolorisation of real textile effluent by constant current electrolysis in a flow-cell using a Ti/Ru(0.3)Ti(0.7)O(2) DSA type electrode. The effect of increasing the chloride ion concentration on the efficiency of colour removal is discussed. Attempts to perform galvanostatic oxidation (40 and 60 mA cm(-2)) on the as-received effluent demonstrate that colour removal and total organic carbon (TOC) removal are limited. If the conductivity of the effluent is increased by adding 0.033 mol L(-1) Na(2)SO(4), little increase in the extent of colour/TOC removal is observed. However, when Na(2)SO(4) is substituted, stepwise, with NaCl (while maintaining the ionic strength constant) appreciable colour/TOC removal is observed. The study of the effect of increasing the current density demonstrates that total colour removal is possible at high currents. The efficiencies of colour and TOC removal are discussed in terms of the Energy per order (E(EO)/kWh m(-3)order(-1)) and Energy consumption (E(C)/kWh kg(-1)TOC), respectively. Finally, the extent of colour removal is compared to consent levels presented in the literature.

This work presents an electrochemical investigation of the benzene oxidation process in aqueous solution on boron-doped diamond (BDD) electrodes. Additionally, in order to determine the main products generated during the oxidation process, electrolysis and high performance liquid chromatography experiments were carried out. The complete degradation of this compound was performed aiming to a further application in waste water treatment. The cyclic voltammetry studies indicate that benzene is irreversibly oxidized in acid medium (H2SO4 0.5 M) on the BDD electrode surface at 2.0 V versus Ag/AgCl in a diffusion controlled process. During the cycling, other products are generated, and a pair of peaks was observed that can be associated with the oxi-reduction of anyone of the following species: hydroquinone, benzoquinone, resorcinol or catechol. The electrolysis experiments were carried out at 2.4 and 2.5 V on the BDD electrode surface in a solution containing 1x10(-2) M of benzene (below the saturation concentration in aqueous solution), for 3 and 5 h, respectively. The main products measured were: hydroquinone, resorcinol, p-benzoquinone, catechol and phenol. The complete electrochemical benzene degradation was performed in the electrolysis experiments using a rotating BDD disc electrode (2.5 V for 5 h) and the main products detected were all measured at concentrations lower than 10(-5) M in this condition. The boron-doped diamond electrode had proved to be a valuable tool for the electrochemical degradation of the benzene, a very stable chemical compound.

This paper presents the study of a prospective electrochemical treatment system for the pesticide carbaryl. Three different dimensionally stable anodes were employed (Ti/Ru0.3 Ti0.7 O2, Ti/Ru0.3 Sn0.7 O2 and Ti/Ir0.3 Ti0.7 O2) and the effect of current density (10, 20, 40 and 60 mA cm(-2)) and supporting electrolyte (0.1 mol L(-1) NaCl and 0.033 mol L(-1) H2SO4) is discussed. All the electrodes present a low level of carbaryl and total organic carbon removal in H2SO4, even at highly positive potentials, indicating that the application of current is not, in itself, sufficient to promote effective oxidation of the pesticide and its products. However, in the presence of NaCl all the electrodes used present rapid diminishing of the carbaryl and total organic carbon content, thus suggesting enhanced activity. The results demonstrate the participation of partially oxidised Cl- species at the electrode surface, which act as an intermediate in the electron transfer between the pesticide molecule and the electrode. Thus, under such conditions, the feasibility of the electrochemical route for the treatment (total or partial) of waste that contains carbaryl is evident.

This paper presents the study of the electrochemical oxidation of the pesticide atrazine at a Ti/Ru(0.3)Ti(0.7)O(2) dimensionally stable anodes (DSA). The effect of using different supporting electrolytes (NaCl, NaOH, NaNO(3), NaClO(4), H(2)SO(4) and Na(2)SO(4)) during the galvanostatic electrolysis of atrazine was investigated. It was observed that the removal of atrazine and total organic carbon (TOC) was only achieved at appreciable rates when NaCl was used as the supporting electrolyte, due to the oxidising species formed in this electrolyte (e.g. ClO(-)). Variation of the NaCl concentration demonstrated that, although only low concentrations of NaCl are necessary to result in the complete removal of atrazine in solution, TOC removal is almost linearly dependent on the quantity of NaCl in solution. Examination of the applied current density indicates that the efficiency of TOC removal reaches a maximum at 60 mA cm(-2). Testing of alternative electrode materials containing SnO(2) did not improve the efficiency of atrazine removal in Na(2)SO(4), but in NaCl a small increase was observed. Overall there appears to be no great advantage in using SnO(2)-containing electrodes over the Ti/Ru(0.3)Ti(0.7)O(2) electrode.

The main purpose of this study was to evaluate the performance of the electrochemical oxidation process as a post-treatment for the effluents of a bench-scale UASB reactor treating simulated wastewater from an unbleached pulp plant. The oxidation process was performed using a single compartment cell with two plates as electrodes. The anode was made of Ti/Ru0.3Ti0.7O2 and the cathode of stainless steel. The following variables were evaluated: current density (75, 150 and 225 mA cm(-2)) and recirculation flow rate in the electrochemical cell (0.22, 0.45 and 0.90 L h(-1)). The increase in current density from 75 to 225 mA cm(-2) did not increased the color removal efficiency for the tested flow rates, 0.22, 0.45 and 0.90 L h(-1), however the energy consumption increased significantly. The results indicated the technical feasibility of the electrochemical treatment as post-treatment for UASB reactors treating wastewaters from pulp and paper plants.