Application Of Electrochemical Oxidation Research Articles

Application of electrochemical oxidation for the enhancement of antibiotic resistant bacteria removal in stormwater bioretention cells

Recently, increasing attention has been paid to the removal of antibiotic resistant bacteria (ARB) during electrochemical advanced oxidation processes. However, there is still no available literature about the application of electrochemical oxidation (EO) to enhance ARB removal in stormwater bioretention cells. Batch experiments were conducted to investigate target ARB (E. coli K-12 carrying blaTEM, tetR and aphA) removals in bioretention cells with different current densities and ratios of air to water (A/W). ARB removals for bioretention cells with 17.6 μA/m2 of current density and 24:1 of A/W ratio was the largest with 5.28 log reduction, which was obviously higher than the one (3.68 log reduction) in the control (without EO). H2O2 production could be responsible for ARB removals in the used bioretention cells, where H2O2 levels increased at first and then decreased with the increase of current densities and A/W ratios. The evaluation for the application of EO implied that the highest antibiotic resistance (AR) conjugation frequency (3.8 × 10−3) at 3.5 μA/m2 of current density and 48:1 of A/W ratios was 124.5 % of the one in the control, while the largest AR transformation frequencies at 17.6 μA/m2 of current density and 48:1 of A/W ratios was 366.9 % (tetR) and 216.2 % (aphA) of the corresponding in the control, and there were still stable for both dominant microflora and metabolic activities in bioretention cells with electricity and aeration, suggesting that EO could be promising for the enhancement of ARB removals in bioretention cells.

Electrochemical oxidation technology to treat textile wastewaters

Dye-contaminated wastewater is hardly treated with conventional treatments. Consequently, there is an urgent need to develop powerful oxidation methods to ensure their removal and ensure water quality. In this framework, the scientific community is studying various treatment approaches, and this review aims to present important ideas on the applicability of electrochemical oxidation as an alternative to remove dyes from wastewater through the use of new carbon-based electrodes and dimensional stable anodes (DSAs) as commercial, environmentally friendly, and suitable electrocatalytic materials. In the discussion, the effect of the most important variables in this type of process is analyzed, namely, the type of dye, electrode material, and the different experimental conditions, that is, current density, electrolysis time, removal efficiency, color, or also abatement of the organic matter, such as total organic carbon (TOC) or chemical oxygen demand (COD).

3D hydrangea-like Mn3O4@(PSS/PDDA/Pt)n with ultrafine Pt nanoparticles modified anode for electrochemical oxidation of tetracycline

Three-dimensional (3D) hydrangea-like Mn3O4@(PSS/PDDA/Pt)n was prepared via in situ reduction of Pt4+ on sea-urchin-like MnO2 coated with lay-by-layer (LBL) films of polyelectrolytes. Combining of ultrafine Pt nanoparticles, 3D structure and manganese oxide support makes these Mn3O4@(PSS/PDDA/Pt)n particles suitable for anode-oxidation of tetracycline (TC) with both excellent mass activity and durability. The performance and possible mechanism of TC degradation on Mn3O4@(PSS/PDDA/Pt)n anode were investigated. The maximal TC removal efficiency on Mn3O4@(PSS/PDDA/Pt)n anode achieved 98.8% at a TC concentration of 60 mg L−1, pH 7.0 and 8 V in the presence of NaCl. The TC electrochemical oxidation on Mn3O4@(PSS/PDDA/Pt)n anode followed a pseudo-first-order kinetic. Additionally, the efficiency of TC removal on Mn3O4@(PSS/PDDA/Pt)1 anode maintained more than 95% after recycling for 5 times, indicating the considerable durability. We also evaluated the application for degradation of other antibiotics. Thus, our research provides a deep insight into the preparation of efficient anode based on 3D manganese oxides loaded with ultrafine Pt particles for potential application in electrochemical oxidation of TC and other antibiotics in contaminated water.

Application of electrochemical oxidation in cold climate regions – Effect of temperature, pH and anode material on the degradation of Bisphenol A and the formation of disinfection by-products

Abstract This study assessed the feasibility of electrochemical oxidation (EO) for the removal of organic compounds in cold climate regions. A two-level full factorial design was used to test the effect of three factors, temperature (6/20 °C), anode material (Pt/BDD) and pH (7/10) on the degradation of Bisphenol A. Due to the use of a chloride electrolyte, the formation of the disinfection by-products, perchlorate and trichloromethane was assessed too. The 90 % removal of the initial Bisphenol A concentration took up to 71 % (30 min) longer and up to 46 % more power input was required at 6 °C than at 20 °C. At pH 10, degradation and formation kinetics of Bisphenol A and trichloromethane were faster due to the higher oxidation power of OCl− than HOCl (pKa = 7.5) and the formation of bisphenolate ions (pKa = 9.6), which are more prone to electrophilic attack than Bisphenol A. Temperature and anode material were the two factors that significantly affect the trichloromethane formation. Trichloromethane was formed up to 45 % faster at 20 °C than at 6 °C and up to 23 % faster on Pt than on BDD anodes. However, higher trichloromethane concentration were reached on BDD anodes, but were formed at slower rates. The anode material was the only factor, which had a statistically significant influence on for the formation of perchlorate. On BDD anode up to 89 % more perchlorate was formed than on Pt anode. The present study shows that the application of EO for organic pollutant removal in regions with low average temperatures is a feasible treatment step although it is associated with higher energy demand and consequently higher costs. The formation of unwanted disinfection by-products in chloride containing waters could not be avoided, but it was shown in this study, that it can be limited by an adequate choice of treatment time, pH and anode material.

Improving the biodegradability of hospital urines polluted with chloramphenicol by the application of electrochemical oxidation

This work focuses on improving the biodegradability of hospital urines polluted with antibiotics by electrochemical advanced oxidation processes (EAOPs). To do this, chloramphenicol (CAP) has been used as a model compound and the influence of anodic material (Boron Doped Diamond (BDD) and Mixed Metal Oxide (MMO)) and current density (1.25–5 mA cm−2) on the toxicity and the biodegradability was evaluated. Results show that a complete CAP removal was attained using BDD anodes, being the process more efficient at the lowest current density tested (1.25 mA cm−2). Conversely, after passing 4 Ah dm−3, only 35% of CAP removal is reached using MMO anodes, regardless of the current density applied. Furthermore, a kinetic study demonstrated that there is a clear competitive oxidation between the target antibiotic and the organic compounds naturally contained in urine, regardless the current density and the anode material used. During the first stages of the electrolysis, acute toxicity is around 1% EC50 but it increases once CAP and its organic intermediates have been degraded. The formation and accumulation of inorganic oxidants may justify the remaining acute toxicity. This also helps to explain the trend observed in the rapid biodegradability assays. Finally, a 60% of standard biodegradability (Zahn-Wellens test) was achieved which suggests that electrochemical oxidation with BDD anodes could be the most appropriate technology to reduce the hazard of hospital urines at the operating conditions tested.

Electrochemical Oxidation of Acid Black 2 Dye Wastewater Using Boron-Doped Diamond Anodes: Multiresponse Optimization and Degradation Mechanisms

Azo dyes play an important role in the printing and dyeing industry. Acid Black 2 dye is one of the most representative dyes with significant toxicity on human health and aquatic organisms. Accordingly, appropriate technologies are needed to efficiently remove these compounds from aqueous environment. In this study, we examined the electrochemical oxidation (EO) of Acid Black 2 on a boron-doped diamond anode. A Box–Behnken design was used to determine experimental factors, namely current density (A), electrolysis time (B), pH (C), and electrolyte concentration (D), and optimize responses to chemical oxygen demand (COD) removal (R1), current efficiency (R2), and energy consumption (R3). Based on obtained models, a desirability function approach to multiresponse optimization was used to optimize response values. The results of response values, R1 = 90.01%, R2 = 80.77%, and R3 = 83.51 kWh/kg (COD), were obtained at optimized conditions. Furthermore, the influence of interactions among operating parameters on responses was analyzed using analysis of variance and three-dimensional surface plots. Finally, an Acid Black 2 degradation pathway was proposed according to intermediates detected by HPLC-MS. In short, these results have certain guiding significance for the energy conservation, technology development, and practical engineering application of EO.

Electro-oxidation of tetracycline by a Magnéli phase Ti4O7 porous anode: Kinetics, products, and toxicity

The goal of this study is to evaluate Magnéli phase titanium oxide (Ti4O7) as an anode material for potential application in electrochemical oxidation of organic pollutants in water. The removal of tetracycline (TC) was systematically investigated in terms of kinetics, reaction mechanisms and pathways, and multi-species toxicity. Application of 0.5–3mAcm−2 current densities resulted in >90% total removal of TC over a wide range of initial concentrations from 1ppm to 50ppm with half-lives between 28mins and 75mins. The oxidation mechanisms were further elucidated using salicylic acid (SA) as a hydroxyl free radical trap. At least 40% of total TC removal was attributable to reactions mediated by hydroxyl radicals, which were generated on Magnéli phase Ti4O7 at a rate of 2×10−9molcm−2min−1 under 0.5mAcm−2 applied current density. Tests on Escherichia coli culture indicated that electro-oxidation of TC by Magnéli phase Ti4O7 anode successfully reduced the original antimicrobial activity to a level below detection limit. However, for freshwater micro algae Scenedesmus obliquus, inhibitory effects persisted in the first couple of hours and then dramatically reduced during the last stage of treatment, likely due to intermediate products that later mineralized and detoxified. Reaction pathways were proposed based on the data of high-resolution mass spectrometry, and oxidation products with antibiotic potency similar to or greater than TC were identified in 1h treatment sample, but not detectable in the end-of-treatment solution.

Applicability of electrochemical oxidation using diamond anodes to the treatment of a sulfonylurea herbicide

In this work, the electrolysis of chlorsulfuron (ClSF, a sulfonylurea herbicide) with conductive-diamond anodes is studied. The influences of the nature of the supporting electrolyte (0.05moldm−3 NaCl and Na2SO4), the applied current density (30 and 100mAcm−2) and the initial herbicide concentration (20,50 ad 100mgdm−3) have been evaluated. Total mineralization of the herbicide was attained regardless of the supporting electrolyte medium used, although electrolyte clearly influenced on the efficiency and rate of the oxidation process. Likewise, the process was found to be more efficient at low current densities. Results point out the importance of mediated electrochemical processes in the removal of ClSF. This influence was confirmed by additional tests in which the electrolysis was combined with UV light or ultrasound irradiation: the use of UV irradiation results in a less efficient process, while US improves importantly the rate of the mineralization as compared to the single electrolytic process. The strong oxidation conditions of electrolysis leads to the formation of reaction intermediates (2-amino-4-methoxy-6-methyl-1,3,5-Triazine, 2-chlorobenzenesulfonamida and oxalic acid) in agreement with the mechanisms proposed in the literature for other AOPs.

Can electrochemical oxidation techniques really decontaminate saline dyes wastewater?

Formation of toxic chlorinated organic byproducts is of great concern when selecting electrochemical oxidation (EO) as decontamination technology for saline dye wastewater, but still not verified. To test the applicability of EO, methyl orange (MO) was used as a model dye for anodic contact glow discharge electrolysis (CGDE) and conventional electrolysis (CE) in the presence of chloride. The degradation kinetics and organic intermediates were analyzed. In the presence of chloride, the rates of dye degradation were significantly increased as CGDE and CE were applied. CE resulted in higher mineralization efficiency than CGDE which needs much energy input. Several refractory chlorinated aromatic and even aliphatic compounds were identified during MO degradation, as well as the other anthraquinone dye, alizarin red S (AR). Therefore, the issues of toxic chlorinated byproducts and energy cost should be preferentially evaluated prior to the selection of EO technologies.

Coupling digestion in a pilot-scale UASB reactor and electrochemical oxidation over BDD anode to treat diluted cheese whey.

The efficiency of the anaerobic treatment of cheese whey (CW) at mesophilic conditions was investigated. In addition, the applicability of electrochemical oxidation as an advanced post-treatment for the complete removal of chemical oxygen demand (COD) from the anaerobically treated cheese whey was evaluated. The diluted cheese whey, having a pH of 6.5 and a total COD of 6 g/L, was first treated in a 600-L, pilot-scale up-flow anaerobic sludge blanket (UASB) reactor. The UASB process, which was operated for 87 days at mesophilic conditions (32 ± 2 °C) at a hydraulic retention time (HRT) of 3 days, led to a COD removal efficiency between 66 and 97 %, while the particulate matter of the wastewater was effectively removed by entrapment in the sludge blanket of the reactor. When the anaerobic reactor effluent was post-treated over a boron-doped diamond (BDD) anode at 9 and 18 A and in the presence of NaCl as the supporting electrolyte, complete removal of COD was attained after 3-4 h of reaction. During electrochemical experiments, three groups of organochlorinated compounds, namely trihalomethanes (THMs), haloacetonitriles (HANs), and haloketons (HKs), as well as 1,2-dichloroethane (DCA) and chloropicrin were identified as by-products of the process; these, alongside free chlorine, are thought to increase the matrix ecotoxicity to Artemia salina.

Study of degradation intermediates formed during electrochemical oxidation of pesticide residue 2,6-dichlorobenzamide (BAM) at boron doped diamond (BDD) and platinum–iridium anodes

Electrochemical oxidation is a promising technique for degradation of otherwise recalcitrant organic micropollutants in waters. In this study, the applicability of electrochemical oxidation was investigated concerning the degradation of the groundwater pollutant 2,6-dichlorobenzamide (BAM) through the electrochemical oxygen transfer process with two anode materials: Ti/Pt90–Ir10 and boron doped diamond (Si/BDD). Besides the efficiency of the degradation of the main pollutant, it is also of outmost importance to control the formation and fate of stable degradation intermediates. These were investigated quantitatively with HPLC–MS and TOC measurements and qualitatively with a combined HPLC–UV and HPLC–MS protocol. 2,6-Dichlorobenzamide was found to be degraded most efficiently by the BDD cell, which also resulted in significantly lower amounts of intermediates formed during the process. The anodic degradation pathway was found to occur via substitution of hydroxyl groups until ring cleavage leading to carboxylic acids. For the BDD cell, there was a parallel cathodic degradation pathway that occurred via dechlorination. The combination of TOC with the combined HPLC–UV/MS was found to be a powerful method for determining the amount and nature of degradation intermediates.

Sequential treatment of diluted olive pomace leachate by digestion in a pilot scale UASB reactor and BDD electrochemical oxidation

The efficiency of the anaerobic treatment of olive pomace leachate (OPL) at mesophilic conditions was investigated. Daily and cumulative biogas production was measured during the operational period. The maximum biogas flowrate was 65 L/d, of which 50% was methane. In addition, the applicability of electrochemical oxidation as an advanced post-treatment method for the complete removal of chemical oxygen demand (COD) from the anaerobically treated OPL was evaluated. The diluted OPL, having a pH of 6.5 and a total COD of 5 g/L, was first treated in a 600 L, pilot-scale up-flow anaerobic sludge blanket (UASB) reactor. The UASB reactor was operated for 71 days at mesophilic conditions (32 ± 2 °C) in a temperature-controlled environment at a hydraulic retention time of 3 days, and organic loading rates (OLR) between 0.33 and 1.67 g COD/(L.d). The UASB process led to a COD removal efficiency between 35 and 70%, while the particulate matter of the wastewater was effectively removed by entrapment in the sludge blanket of the reactor. When the anaerobic reactor effluent was post-treated over a boron-doped diamond (BDD) anode at 18 A and in the presence of 0.17% NaCl as the supporting electrolyte, complete removal of COD was attained after 7 h of treatment predominantly through total oxidation reactions. During electrochemical experiments, three groups of organo-chlorinated compounds, namely trihalomethanes (THMs), haloacetonitriles (HANs) and haloketons (HKs), as well as 1,2-dichloroethane (DCA) and chloropicrin were identified as by-products of the process; these, along with the residual chlorine are thought to increase the matrix ecotoxicity to Artemia salina.

Synthesis of poly(sodium 4-styrenesulfonate) functionalized graphene/cetyltrimethylammonium bromide (CTAB) nanocomposite and its application in electrochemical oxidation of 2,4-dichlorophenol

Poly(sodium 4-styrenesulfonate) (PSS) intercalated graphene (PSS-GN) was prepared via in situ reduction of exfoliated graphite oxides in the presence of PSS, and then mixed with CTAB to form a stable PSS-GN-CTAB nanocomposite through electrostatic self-assembly. The prepared composites were characterized by Fourier transform infrared spectrometry (FT-IR), ultraviolet and visible spectrometry (UV–vis) and X-ray diffraction (XRD). A novel 2,4-dichlorophenol (2,4-DCP) electrochemical sensor was fabricated based on a PSS-GN-CTAB modified glassy carbon electrode. It was found that the composite of PSS-GN-CTAB exhibited excellent electrocatalytic activity towards the oxidation of 2,4-DCP. Linear sweep voltammetry (LSV) was used for the quantitative determination of 2,4-DCP. Under the optimum conditions, the peak current of 2,4-DCP was proportional to its concentration at the range of 1.0×10−8 to 2.0×10−6molL−1 with a detection limit 2.0×10−9molL−1. The newly developed method was successfully applied for the determination of 2,4-DCP in the waste water with good recoveries. The proposed electrode system represents a new platform for designing excellent electrochemical sensors with water-dispersed graphene.

Synthesis of Transition‐Metal Exchanged Nanocrystalline ZSM‐5 and Their Application in Electrochemical Oxidation of Glucose and Methanol

AbstractNanocrystalline ZSM‐5 was prepared using propyltriethoxysilane. Materials were characterized by a complementary combination of X‐ray diffraction, nitrogen sorption, and scanning electron microscopy. Transition‐metal ion exchanged nanocrystalline ZSM‐5‐modified electrodes were constructed for the electrocatalytic oxidation of glucose and methanol. A non‐enzymatic electrochemical sensor based on a Ni2+‐exchanged nanocrystalline ZSM‐5‐modified electrode exhibits the highest sensing ability, whereas the corresponding Cu2+‐exchanged electrode exhibits the highest current sensitivity for glucose oxidation. Among the variety of electrodes modified with transition‐metal ion exchanged nanocrystalline ZSM‐5, the Ni2+‐exchanged electrode exhibits high current sensitivity and sensing ability in methanol oxidation. Electrocatalytic activity of conventional ZSM‐5‐modified electrodes was significantly low compared to nanocrystalline ZSM‐5‐modified electrodes. Enhancement in the electrocatalytic activities of nanocrystalline ZSM‐5‐modified electrodes can be correlated with the enhanced accessibility of glucose/methanol to M2+ active centers in the nanocrystalline ZSM‐5 owing to its large specific surface area and intercrystalline mesopores. The sensor was applied directly to determine glucose concentration in adult human blood serum, and the precision of the method was found to be satisfactory. The non‐enzymatic sensor exhibited excellent reproducibility, repeatability, stability, and antifouling ability for direct determination of glucose in human blood serum.

Application of electrochemical oxidation as alternative treatment of produced water generated by Brazilian petrochemical industry

This paper presents the anodic oxidation of real produced water, generated by petroleum exploration of the Petrobras plant-Brazil, using platinum supported on Ti (Ti/Pt) and boron-doped diamond (BDD) anodes in an electrolytic batch cell. The influence of several operating parameters such as current, supporting electrolyte, agitation rate and temperature on the performance has been studied and the energy consumption has been also evaluated. Galvanostatic electrolysis at BDD leads to complete COD removal (98%) due to the high amounts of effective hydroxyl radicals and peroxodisulfates generated from water oxidation and the COD removal rate increases with rising applied current (from 15 to 60mAcm−2). Conversely, at Pt electrode, about 50% of COD removals were achieved by applying 15 and 30mAcm−2 of current density, and 80% of COD removal at 60mAcm−2. Although, the energy consumption and process time make useless anodic oxidation for complete treatment of petrochemical wastewaters; maybe, it can be a feasible process as a pre-treatment process reducing significantly the cost and time of treatment.

Electrochemical Degradation of Cyanobacterial Toxin Microcystin-LR Using Ti/RuO2Electrodes in a Continuous Tubular Reactor

Occurrence of cyanobacteria and their potent toxins has imposed a risk to human health and raised concerns in drinking water treatment. In this study, the applicability of electrochemical oxidation on microcystin-LR produced by cyanobacteria was examined using Ti/RuO2 as anodes. The experiments focused on the variation and elimination of extracellular and intracellular microcystin-LR during the cyanobacterial inactivation by electrooxidation. The effects of applied current density, cell density, as well as electrolyte type on toxin degradation have been studied. The complete elimination of extracellular and intracellular microcystin-LR was achieved and 100% removal for total microcystin-LR was obtained at current density 5 mA/cm2. The results showed that when the cell densities decreased or the applied current densities increased, the efficiency of total microcystin-LR removal could be increased. More than 98% removal for total microcystin-LR was also achieved even if the cyanobacteria were inoculated in lake water or drinking water without adding any chemicals. It can be concluded that electro-oxidation of microcystin-LR is quite an efficient method, and can be applied to remove microcystin-LR from waters during the cyanobacterial inactivation.

Ta/BDD Film Electrode for Electrochemical Oxidation Nitrophenol

The physical and electrochemical behaviors of the tantalum substrate born-doped diamond (Ta/BDD) electrode prepared by hot filament chemical vapor deposition (HFCVD) technique and its application in electrochemical oxidation of wastewater containing nitrophenol were studied. Raman spectroscopy and scanning electron microscopy (SEM) examinations demonstrated that the electrode had well-defined diamond features. It was observed that the Ta/ BDD electrode had a much higher overpotential for water electrolysis prohibiting the evolution of oxygen in the cyclic voltammetry test. During the electrochemical oxidation of wastewater containing nitrophenol, the results obtained by high performance liquid chromatography (HPLC) and chemical oxygen demand (COD) tests showed that the electrochemical process was suitable for completely degrading nitrophenol. The influence of current density, temperature, support electrolyte, and electrolyte concentration was investigated in order to find the best conditions for COD removal. Good electrochemical stability of Ta/BDD electrode was obtained in the accelerated life test. According to the results, Ta/BDD anode is consitered to be a unique electrode for the degradation of nitrophenol and COD simultaneously.

Electrochemical Oxidation as a Final Treatment of Synthetic Tannery Wastewater

Vegetable tannery wastewaters contain high concentrations of organics and other chemicals that inhibit the activity of microorganisms during biological oxidations, so biorefractory organics that are not removed by biological treatment must be eliminated by a tertiary or advanced wastewater treatment. In this paper, the applicability of electrochemical oxidation as a tertiary treatment of a vegetable tannery wastewater was investigated by performing galvanostatic electrolysis using lead dioxide (Ti/PbO2) and mixed titanium and ruthenium oxide (Ti/TiRuO2) as anodes under different experimental conditions. The experimental results showed that both the electrodes performed complete mineralization of the wastewater. In particular, the oxidation took place on the PbO2 anode by direct electron transfer and indirect oxidation mediated by active chlorine, while it occurred on the Ti/TiRuO2 anode only by indirect oxidation. Furthermore, the Ti/PbO2 gave a somewhat higher oxidation rate than that observed for the Ti/TiRuO2 anode. Although the Ti/TiRuO2 required almost the same energy consumption for complete COD removal, it was more stable and did not release toxic ions, so it was the best candidate for industrial applications. With the Ti/TiRuO2 anode, the rate of tannery wastewater oxidation increased with the current density, pH, and temperature of the solution. These results strongly indicate that electrochemical methods can be applied effectively as a final treatment of vegetable tannery wastewater allowing the complete removal of COD, tannin, and ammonium and decolorization.

SYNERGIC DEGRADATION OF REACTIVE BRILLIANT RED X-3B USING THREE DIMENSION ELECTRODE-PHOTOCATALYTIC REACTOR

A new reactor, three dimension electrode-photocatalytic reactor, was designed and used to investigate the photoelectrochemical degradation of reactive brilliant red X-3B (RBRX) in simulated wastewater. The reactor was characterized by a series of parameters, the current change, decolorization ratio, COD removal and degradation ratio. It was found that the three dimensional electrode-photocatalytic reactor could effectively destroy the RBRX within a reaction time of 30 min. The results also showed that the photoelectrochemical process is more efficient than the single application of electrochemical oxidation or photocatalytic degradation. The degradation reactions of RBRX conformed to pseudo first order kinetics in the three processes, and an apparent synergic effect in the increase of the photocurrent and the disappearance of RBRX was observed by combining the electrochemistry with photocatalytic process in the three dimension electrode-photocatalytic reactor.