DSA Anode Research Articles

Efficient and durable iridium-doped SnO2 anode for reactive chlorine species-mediated urine wastewater treatment

The prevalence of nitrogen pollutants in urine wastewater has become a pressing environmental issue. Among various methods for addressing this concern, electrochemical oxidation processes that generate reactive chlorine species (RCS) from chloride ions commonly found in urine wastewater stand out as a promising approach. Despite the exploration of diverse anode materials, existing options still suffer from low selectivity in RCS generation, poor stability, and considerable energy consumption. In this study, we synthesized iridium-doped tin oxide (Ir-SnO2) as an efficient, durable, and energy-conserving anode and systematically evaluated its electrochemical activity for RCS-mediated removal of nitrogen pollutants in urine wastewater. The Ir-SnO2 anode outperformed counterparts such as IrO2, SnO2, and Sb-SnO2, demonstrating its superior electrochemical performance characterized by high current density, low charge transfer resistance, and substantial active surface area. It also achieved exceptional current efficiency of 91.7 % and energy efficiency of 7.79 mmol/Wh for RCS generation at 30 mA cm−2 in diluted 0.1 M chloride solution. Computational analysis based on density functional theory additionally supported experimental results, revealing that Ir doping to SnO2 enhances chlorine adsorption through electronic structure modification, significantly lowering the overpotential and improving electrocatalytic activity for chlorine evolution reactions. In the electrolysis of synthetic urine wastewater at 30 mA cm−2 for 5 h, the Ir-SnO2 anode demonstrated remarkable efficacy in degrading ammonia nitrogen (NH3-N), total nitrogen (TN), and chemical oxygen demand (COD) with efficiencies of 100 %, 97.8 %, and 89.1 %, respectively. These results were comparable to those achieved by IrO2 (dimensional stable anode, DSA) and exceeded the performance of the boron-doped diamond (BDD) anode. Moreover, Ir-SnO2 exhibited the lowest energy consumption compared to benchmark DSA and BDD anodes in the treatment of urine wastewater. In stability assessments, furthermore, the Ir-SnO2 electrode maintained stable anodic cell potential for 100 h of continuous electrolysis in a 0.1 M NaCl electrolyte at 30 mA cm−2 and remained functional over five cycles without any signs of deactivation. This study provides valuable insights into the development of a suitable anode for energy-efficient urine wastewater treatment.

Novel use of the electrocatalytic oxidation process with Fe-DSA dual anode configuration for leachate treatment: Significance of in situ ferrate generation

The leachate produced by waste transfer stations (WTSs) contains substantial amounts of refractory organic matter and ammonia, necessitating on-site treatment. In this study, a novel electrocatalytic oxidation (ECO) process with Fe-DSA dual anode configuration was established for leachate pretreatment. In this configuration, chloride in the leachate was converted to active chlorine by the DSA anode, while ferric hydroxide (Fe(OH)3) was produced from Fe anode. As a result, Fe (VI) was in situ formed through the reactions between active chlorine and Fe(OH)3. Simultaneous and efficient removal of COD and NH4+-N in the ECO process with Fe-DSA dual anode configuration was achieved, significantly improving leachate biodegradability compared with the Fe–Fe and DSA-DSA dual anode configurations. The transformation characteristics of organic compounds in the ECO process were investigated through the electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) analysis. The ECO process with Fe-DSA dual anode configuration promoted the removal and transformation of lignins/carboxylic rich alicyclic molecules (CRAM)-like and tannins compounds with biologically refractory properties, as well as S-containing compounds with biological toxicity. Further X-ray photoelectron spectroscopy (XPS) analysis revealed that iron oxides, amorphous Fe-(oxy) hydroxide, and amorphous Fe(OH)3 produced by Fe (VI) decomposition in the ECO process with Fe-DSA dual anode configuration enhanced removal performance through coagulation. In addition, the contribution of different active species to organic matter removal in the ECO process was quantified by quenching experiments. High-valent iron oxidation dominated the ECO process with Fe-DSA dual anode configuration, while active chlorine oxidation, •OH oxidation and coagulation synergistically contributed to organic matter removal.

Enhanced electrochemical degradation of perfluorooctanoic acid by ligand-bridged PtII at Pt anodes

A new mechanism for the electro-oxidation (EO) degradation of perfluorooctanoic acid (PFOA) by Pt anode was reported. Using bridge-based ligand anions (SCN-, Cl- and N3-) as electrolytes, the degradation effect of PFOA by Pt-EO system was significant. Characterization of the Pt anode, the detection and addition of dissolved platinum ions, and the comparison of Pt with DSA anodes determined that the Pt- ligand complexes resulting from the specific binding of anodically dissolved PtII with ligand ions and C7F15COO- ((C7F15-COO)PtII-L3, L = SCN-, Cl- and N3-) on the electrode surface played a decisive role in the degradation of PFOA. Density functional theory (DFT) calculations showed that inside (C7F15-COO)PtII-L3 complexes, the electron density of the perfluorocarbon chain (including the F atom) compensated toward the carboxyl group and electrons in the PFOA ion transferred to the PtII-Cl3. Moreover, the (C7F15-COO)PtII-Cl3, as a whole, was calculated to migrate electrons toward the Pt anode, leading to the formation of PFOA radical (C7F15-COO•). Finally, with the detection of a series of short chain homologues, the CF2-unzipping degradation pathway of PFOA was proposed. The newly developed Pt-EO system is not affected by water quality conditions and can directly degrade alcohol eluent of PFOA, which has great potential for treating industrial wastewater contaminated with PFOA.

Degradation of the antibiotic ciprofloxacin in urine by electrochemical oxidation with a DSA anode

Ciprofloxacin (CIP) is a commonly prescribed fluoroquinolone antibiotic that, even after uptake, remains unmetabolized to a significant extent—over 70%. Unmetabolized CIP is excreted through both urine and feces. This persistent compound manages to evade removal in municipal wastewater facilities, leading to its substantial accumulation in aquatic environments. This accumulation raises concerns about potential risks to the health of various living organisms. Herein, we present a study on the remediation of CIP in synthetic urine by electrochemical oxidation in an undivided cell with a DSA (Ti/IrO2) anode and a stainless-steel cathode. Physisorbed hydroxyl radical formed at the anode surface from water discharge and free chlorine generated from Cl− oxidation were the main oxidizing agents. The effect of pH and current density (j) on CIP degradation was examined, and its total removal was easily achieved at pH ≥ 7.0 and j ≥ 60 mA cm−2 due to the action of free chlorine. The CIP decay always followed a pseudo-first-order kinetics. The components of the synthetic urine were also oxidized. The main nitrogenated species released was NH3. A very small concentration of free chlorine was quantified at the end of the treatment, thus demonstrating the good performance of electrochemical oxidation and its effectiveness to destroy all the organic pollutants. The present study demonstrates the simultaneous oxidation of the organic components of urine during CIP degradation, thus showing a unique perspective for its electrochemical oxidation that enhances the environmental remediation strategies.

Adsorption and in-situ electrochemical regeneration in a clay-packed continuous reactor for the removal of the antibiotic sulfamethoxazole

This study aims to investigate a reactor that allows the continuous adsorption of the antibiotic contaminant using clay as adsorbent and the in-situ electrochemical regeneration of the saturated absorbent. It is noteworthy that the electrochemical regeneration of adsorbents has not been widely investigated and studies that explore alternative adsorbents are rare. SpC clay and the antibiotic sulfamethoxazole were selected, through preliminary adsorption tests, to be investigated in this study. Density functional theory (DFT) calculations were conducted to understand the particularities of antibiotic adsorption. In the continuous system adsorption tests, the flow rate of 0.3 mL min−1 was selected to proceed with the electrochemical regeneration experiments. The influence of operating parameters on regeneration, such as anode type, electrolyte type and concentration, current density and time, was examined. Clay stability was investigated for five successive cycles, under operating conditions of 62.5 mA cm−2, DSA anode, 0.2 mol L−1 NaCl, and 15 min of electrolysis. The characterization analyses indicated that the electrochemical regeneration did not deteriorate the chemical surface of the clay. Electrolysis promoted the creation of new active sites in the clay after the first cycle, obtaining regeneration efficiency greater than 100 %. The reactor investigated here offered a promising approach for efficient removal of the emerging contaminant, since the process can be operated in-situ, with low energy consumption (0.42 kWh kg−1) over a short time-span (15 min).

Effect of Current Density on Preparation and Properties of TF/β-PbO2 in MSA Media.

The lead-based alloy and DSA anodes have drawbacks, such as poor corrosion resistance, easy peeling of coating, low electrocatalytic activity, and environmental pollution in electrode preparation processes. In this study, titanium foam/β-PbO2 (TF/β-PbO2) was prepared by electrodeposition in methanesulfonic acid (MSA) media. The current efficiency and the deposition rate were 89.7% and 5.36 v/(μm·min-1) at the best current density of 80 mA·cm-2, respectively. The TF/β-PbO2 was characterized by electrochemical tests, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The cyclic voltammetry (CV) test shows that the anodic peak potential of the optimum TF/β-PbO2 was as low as 2.135 V and anodic voltammetry charge was up to the maximum value of 3.564 × 10-2 C. The linear sweep voltammetry (LSV) test indicates that exchange current density of the optimum TF/β-PbO2 reached the maximum value of 8.284 × 10-6 A·cm-2. CV and LSV tests indicate that the optimum TF/β-PbO2 had a high electrocatalytic activity. Electrochemical impedance spectroscopy test Tafel polarization curves show that the optimum TF/β-PbO2 had better corrosion resistance. The XRD test shows that the crystal was mainly β-PbO2 of the optimum TF/β-PbO2 surface and the current density affected the preferential growth of the crystal surface of PbO2. SEM tests show that grains of the optimum TF/β-PbO2 coating prepared were tightly bound and uniform in size.

Electrochemical Reduction and Oxidation of Chlorinated Aromatic Compounds Enhanced by the Fe-ZSM-5 Catalyst: Kinetics and Mechanisms.

Devising cost-effective electrochemical catalyst system for the efficient degradation of chlorinated aromatic compounds is urgently needed for environmental pollution control. Herein, a Fe-ZSM-5 zeolite was used as a suspended catalyst to facilitate the degradation of lindane as a model chlorinated pesticide in an electrochemical system consisting of the commercial DSA (Ti/RuO2-IrO2) anode and graphite cathode. It was found that the Fe-ZSM-5 zeolite greatly accelerated the degradation of lindane, with the degradation rate constant more than 8 times higher than that without Fe-ZSM-5. In addition, the Fe-ZSM-5 zeolite widened the working pH range from 3 to 11, while efficient degradation of lindane in the absence of Fe-ZSM-5 was only obtained at pH ≤ 5. The degradation of lindane was primarily due to reductive dechlorination mediated by atomic H* followed by •OH oxidation. Fe-ZSM-5 zeolite could enrich lindane, H*, and •OH on its surface, thus provided a suitable local environment for lindane degradation. The Fe-ZSM-5 zeolite exhibited high stability and reusability, and reduced the energy consumption. This research provides a potential reduction–oxidation strategy for removing organochlorine compounds through a cost-efficient Fe-ZSM-5 catalytic electrochemical system.

Preparation of needle coke composite cathode and its treatment of RhB wastewater

A novel Fe-loaded needle coke composite electro-Fenton electrode was prepared, characterized, and investigated as the heterogeneous catalytic cathode for oxygen reduction and OH generation for the first time. The novel electro-Fenton system constructed with the cathode and DSA anode was employed to degrade rhodamine B (RhB) in an aqueous solution. Optimal conditions for electrode preparation for the treatment of RhB were obtained by single-factor experiments. The occurrence of the Fenton reaction was verified by hydroxyl radical quenching experiments, and the RhB degradation pathway was inferred by spectroscopic analysis. The decolorization rate of RhB of nearly 100% and the COD removal efficiency of 81.6% were achieved. RhB was degraded by N-de-ethylation, chromophore cleavage, opening-ring, and mineralization in the presence of reactive oxygen species, mainly OH. The cost of RhB simulated wastewater treatment was estimated at RMB 13 yuan per cubic meter of wastewater. As a cheap carbon cathode material, needle coke can catalyze the two-electron transfer of O2 to produce H2O2, reducing the material cost of the electrode, and also increasing the conductivity of the electrode, reducing the cost of water treatment. The needle coke composite electrode can serve as a cost-effective electro-Fenton cathode in the field of refractory organic wastewater treatment represented by dye wastewater.

Influence of anode material and chlorides in the new-gen solid polymer electrolyte cell for electrochemical oxidation – Optimization of Chloroxylenol degradation with response surface methodology

• Efficient removal of Chloroxylenol with BDD/SPE in low conductive solutions. • First application of Ti/RuO 2 (DSA) as anode coupled with solid polymer electrolyte. • Application of response surface methodology for process optimization. • Optimization allows decreasing the energy consumption preserving COD removal. • Promising results for DSA/SPE application in chlorinated environments. In this study the solid polymer electrolyte – based (SPE-based) system recently developed for electrochemical wastewater treatment is used for the degradation of Chloroxylenol (CXL). To the best of authors knowledge, this is the first study that deals the investigation of the effect of anode material in such electrochemical cell configuration. The most used BDD/SPE cell is compared with DSA/SPE (Ti/RuO 2 anode) system considering the effect of chlorides concentration to activate the process mediated by active chlorine. The preliminary tests to evaluate the feasibility of the process show that BDD/SPE is able to completely degrade the CXL reaching a COD removal close to 90 % also in absence of supporting electrolyte and in a low conductive solution (0.025 mS cm −1 ). The DSA anode suffers the lack of chlorides in solution but became more competitive when NaCl is added, with a maximum COD removal equal to 71.6 % with 50 mM NaCl. The response surface methodology based on three-factors Doehlert matrix is applied to optimize the operating conditions for both systems. The selected factors are the current density (2–20 mA cm −2 ), the NaCl concentration (0–20 mM), and CXL concentration (10–100 mg L −1 ). The optimization analysis allows identifying the operating conditions needed to maximize COD removal and to minimize energy consumptions for BDD/SPE and DSA/SPE setups. In particular, the RSM analysis shows that under peculiar conditions (i = 15.5 mA cm −2 ; NaCl > 13 mM) DSA/SPE can reach a COD removal analogous to those obtained with BDD electrode over 90%, suggesting the possibility to exploit this electrode material in solid polymer electrolyte electrochemical cells.

Oxychlorides Induced Over-Evaluation of Electrochemical Cod Removal Performance Over Dsa Anode: The Roles of Cathode Materials

Oxychlorides Induced Over-Evaluation of Electrochemical Cod Removal Performance Over Dsa Anode: The Roles of Cathode Materials

Electro-Fenton process for the removal of Direct Red 23 using BDD anode in chloride and sulfate media

• Degradation of dye DR23 by EF using BDD or DSA anode in chloride and sulfate media. • BDD/carbon graphite cell achieved efficient discoloration and mineralization. • Rapid and complete discoloration was obtained in chloride medium. • Sulfate medium led to the higher mineralization rates. • Combination of chloride and sulfate as supporting electrolyte provided a beneficial effect. This paper aims to study the degradation and mineralization of the dye Direct Red 23 (DR23) by electro-Fenton (EF) process for the first time using BDD and DSA anode and carbon graphite (CG) cathode in NaCl and Na 2 SO 4 media. The effect of different parameters such as the nature, concentration, and combination of the supporting electrolyte, the nature of the anode, the concentration of the catalyst and DR23 and the current density on H 2 O 2 generation and mineralization rate was investigated. The best treatment efficiencies were achieved by BDD/CG cell. The degradation of DR23 solution was faster in NaCl medium. The mineralization was more efficient in Na 2 SO 4 , where the main oxidizing species were the hydroxyl radicals, generated both in the bulk solution ( • OH) and at the anode surface (M( • OH)). The TOC removal, the energy consumption, and electrical cost per m 3 were 90%, 2.41 kWh g −1 TOC, and 3.21 US $ m −3 , respectively, after 6 h of electrolysis in sulfate medium while lower mineralization rate (83%) and higher energy consumption (2.86) and electrical cost per m 3 (3.27 US $ m −3 ) were achieved in chloride medium. As the textile wastewater contain generally sulfate and chloride ions, experiences were also performed in a medium formed of Na 2 SO 4 and NaCl. The following combination of these salts (75% Na 2 SO 4 + 25% NaCl) as supporting electrolyte was beneficial to further increase the mineralization rate of DR23 solution, current efficiency and reduce the energy consumption. Degradation of DR23 in the presence of different scavengers (methanol, 2-propanol, and tert-butanol) asserted that the elimination of DR23 is mainly attributed to the action of • OH/M( • OH) on the target pollutant.

Comparative degradation of 5-fluorouracil in aqueous solution by using H2O2-modified subcritical water, photocatalytic oxidation and electro-Fenton processes

This study investigated the degradation of the antineoplastic agent 5-fluorouracil (5-FU) widely applied to treat different cancers using different advanced oxidation processes such as electro-Fenton (EF), photocatalysis with TiO2, and H2O2-modified subcritical water oxidation. The treatment with the EF process was the most efficient compared to others. Interestingly, in the EF process, the oxidative degradation of 5-FU behaved differently depending on the anode used. At low currents (20 and 40 mA), Pt and DSA anodes performed better than BDD and Ti4O7 anodes. In contrast, at the higher current of 120 mA, the production of heterogeneous hydroxyl radicals (M(•OH)) became important and contributed significantly to the oxidation of 5-FU in addition to homogeneous •OH generated in the bulk solution. These latter have high O2-evolution overpotential leading to the high amount of physisorbed M(•OH) compared to Pt and DSA. The oxidative degradation of 5-FU was then performed by titanium dioxide-based photocatalytic oxidation and subcritical water oxidation processes, both of which showed a lower degradation efficiency and failed to achieve complete mineralization. Finally, a comparison was performed in laboratory-scale, taking into account the following performance indicators: the degradation efficiency, the mineralization power, the cost of equipment and reagents, and the energy required for the treatment of 5-FU.

Lead electrowinning from methane sulfonic acid

Currently lead is produced by conventional pyrometallurgical smelting route which is suitable for high grade sulfide ores and concentrates. The hydrometallurgical recovery of lead through methane sulfonic acid (MSA) medium provides a “green” lead production route with a potentially lower cost. Electrowinning is the most feasible and economic way to produce lead metal in the hydrometallurgical route. The current challenge for lead electrowinning from methane sulfonate solution is to produce a smooth and dense lead deposit without the significant formation of PbO2 on an anode. The use of proper leveling agents is the key for production of high-quality electrolytic lead. Various additives were first investigated using a Hull cell and then by electrowinning. Aloe has the best leveling effect. The combination of aloe and glue can produce smooth and dense lead deposits. Several DSA anodes have been evaluated and some of them have an oxygen evolution overpotential low enough to prevent the formation of PbO2. Although the current efficiency of PbO2 on graphite can be reduced to 3.6% in the presence of H3PO4, graphite anodes were not stable and degraded after extended time of electrowinning. With the use of aloe and glue as smoothing agents and suitable DSA anodes, smooth and dense lead deposits can be produced without the formation of PbO2 on the anodes. Lead can be depleted to 3 g/L from the electrolyte at a high efficiency. The presence of 5 g/L Fe in the electrolyte resulted in a decrease of 2.1% in the lead current efficiency. Chloride at its level of 50 mg/L or less practically has no effect on lead electrowinning.

Electro-enhanced heterogeneous activation of peroxymonosulfate via acceleration of Fe(III)/Fe(II) redox cycle on Fe-B catalyst

Heterogeneous catalytic oxidation based on iron species for peroxymonosulfate (PMS) activation is considered as one of the most attractive strategies for wastewater treatment. However, the rate-limiting regeneration of Fe(II) from Fe(III) heavily hampers the efficient activation of PMS. In this study, the introduction of electric field to the Fe-supported bentonite (Fe-B) activated PMS process was proposed to enhance the Fe(III)/Fe(II) redox cycle. The Fe-B catalyst performed well in the removal of Acid Orange 7 (AO7) through the synergistic effect of electrolysis and the continuous redox cycle of Fe(III)/Fe(II) for PMS activation. The use of 0.5 g L−1 Fe-B catalyst and 10 mM PMS yielded nearly complete removal of the AO7 (50 mg L−1) in 60 min at 2 mA cm−2 of current density. Based on the results of electron paramagnetic resonance (EPR) spectroscopy, chemical quenching tests, X-ray photoelectron spectroscopy (XPS) analysis, and electrochemical measurements, the decolorization of AO7 was dominantly attributed to surface-bound radicals (SO4•−ads and •OHads) and also the direct electron transfer at DSA anode. Moreover, the electro/Fe-B/PMS system showed an effective pH range from 2.6 to 9.0 and the abatement of AO7 was slightly affected in the presence of natural background anions. This work provides a feasible strategy of PMS activation by cost-effective Fe-B catalyst coupling with electric field and gives an insight into the accelerated oxidation of recalcitrant pollutants.

Long-chain phenols oxidation using a flow electrochemical reactor assembled with a TiO2-RuO2-IrO2 DSA electrode

The electrochemical degradation of long-chain phenols present in toxic residues from the cashew-nut processing industry was systematically investigated for the first time, using a flow electrochemical reactor assembled with a Ti/TiO2-RuO2-IrO2 DSA anode. After optimizing the current density (40 mA cm−2) and chloride concentration (0.028 mol L−1) in 0.5 mol L−1 Na2SO4 supporting electrolyte, it was achieved expressive total organic carbon (TOC) removal percentage for (un)saturated cardanol and cardol, either alone (85–92%) or in association/real industrial CNSL sample (82%), over 4 h of electrolysis. Evidently, the removal rate for the mixture changes (56–88% TOC removal) according to its starting concentration (0.005–0.100% residue), showing that the system performance can improve by increasing treatment time. Chromatography coupled to mass spectrometry (GC–MS) analysis showed that the first stage of the electrooxidation process was driven towards the formation of phenoxyl radicals, followed by the formation of polymeric dimers. These intermediates were continuously oxidized by different free and chemisorbed reactive species until obtaining short-chain organic acids, CO2 and H2O. The proposed system proved to be efficient, eco-friendly, and viable to treat industrial waste containing refractory phenolic compounds.

Treatment of wastewater effluents from Bogotá – Colombia by the photo-electro-Fenton process: Elimination of bacteria and pharmaceutical

In this work, the occurrences of bacteria families and relevant pharmaceuticals in municipal wastewater effluents from Bogotá (Colombia), and their treatment by the photo-electro-Fenton process were studied. Twenty-five representative pharmaceuticals (azithromycin, carbamazepine, ciprofloxacin, clarithromycin, diclofenac, enalapril, gabapentin, iopromide, metoprolol, sulfamethoxazole, trimethoprim, valsartan, clindamycin, erythromycin, levamisole, lincomycin, norfloxacin, oxolinic acid, phenazone, primidone, salbutamol, sulfadiazine, tetracycline, tramadol, and venlafaxine) were quantified in the effluent by LC-MS/MS analysis. Four of these target compounds (azithromycin, diclofenac, trimethoprim, norfloxacin) were found at concentrations that represent an environmental risk. In addition, several bacteria families related to water and foodborne diseases were identified in such effluents (e.g., Pseudomonadaceae, Campylobacteraceae, Aeromonadaceae, Enterobacteriaceae, and Bacteroidaceae), via shotgun-metagenomic technique. Then, a bench-scale photo-electro-Fenton (PEF) system equipped with a DSA anode (Ti/IrO2-SnO2) and a GDE cathode was applied to treat such effluents. After 60 min, this treatment led to a decrease in the ratio of the bacterial content in the original samples, ~150 thousand times, and a pondered removal of 66.12% for the pharmaceuticals. The study of the process pathways indicated that the bacteria and pharmaceuticals elimination mainly occurred through attacks of hydroxyl and chlorine radicals. Interestingly, in the case of pharmaceuticals, their environmental risk quotients were diminished after the PEF application. Furthermore, the prolonged action of this electrochemical process induced ~15% of mineralization and a significant reduction of the total DNA (removal >85%). Hence, the photo-electro-Fenton process showed to be a promising alternative to deal with municipal effluents for limiting the waterborne diseases, pollution by pharmaceuticals, and mobility/availability of genetic material coming from microorganisms.

Electrochemical removal of gaseous elemental mercury in liquid phase with a novel foam titanium-based DSA anode

The dimensional stable Ti/Sb-SnO2/PbO2 electrode was prepared by the impregnation method. To remove gaseous elemental mercury (Hg0) from coal combustion, the study of Hg0 oxidation was performed in a gas diffusion electrochemical reactor with the stainless steel mesh cathode and the Ti/Sb-SnO2/PbO2 anode. Hg0 is oxidized into highly water-soluble oxidation states of mercury as a result of the loss of electrons on the anode, which can be removed later utilizing WFGD and other devices. By investigating the effects of applied voltage, the concentration and pH of the electrolyte, reaction temperature, flue gas flow and initial Hg0 concentration on removal, the appropriate conditions for the experiment were obtained. At the pH of 3, the removal efficiency can reach over 90%, which is about 1.7 times the removal of a single foam Ti under the same conditions.

Stable boron and cobalt co-doped TiO2 nanotubes anode for efficient degradation of organic pollutants

Anode materials are crucial to anodic oxidation for wastewater treatment. In this regard, stable boron and cobalt co-doped TiO2 nanotube (B, Co-TNT) was prepared for the first time, and its lifetime was found increased significantly while electrocatalytic activity decreased with the increase of Co(NO3)2 in preparation from 1 to 10 mM. Characterized by scanning electron microscope (SEM), X-Ray Diffraction (XRD) and X-ray Photo-electronic Spectroscopy (XPS), B and Co content were optimized and successfully doped on TNT, which was more smooth without ripple with Co content of 0.038 mg/cm2 in a valence of +2, and B atomic content of 2.17 at.% in form of Ti-B-O. This optimized anode enhanced electrode lifetime 122.8 times while the electrochemical activity decreased slightly when compared to the undoped TNT. The effects of current density, initial pH and initial 2,4-dichlorophenoxyacetic acid (2,4-D) concentration were investigated, and the mainly responsible radical for degradation was confirmed to be the surface OH on B, Co-TNT anode. This anode had better performance on the TOC removal, mineralization current density (MCE) and energy consumption (Ec) when compared with BDD, PbO2, DSA and Pt anodes, and it also presented a very stable degradation for 10 cycles oxidation of 20 mg/L 2,4-D with allowable Co leaching. Therefore, B, Co-TNT anode is a promising, stable, safety and cost-effective anode for application in electrochemical advanced oxidation processes (EAOPs).

Pulsed electrochemical oxidation of acid Red G and crystal violet by PbO2 anode

Present work investigates the application of pulsed electrochemical oxidation technique using DSA anode, titanium coated with PbO2layer, for degradation of Acid Red G (anionic dye) and Crystal Violet (cationic dye). Decolorization efficiency, COD and TOC removal efficiency were measured and contrasted by varying process parameters such as current density, initial organic concentration, pulse frequency, pulse duty cycle and NaCl dosage. Furthermore, decay kinetics for color and COD removal process, average current efficiency and energy consumption were evaluated under diverse arguments. The results indicated that current density, pulse duty cycle and NaCl dosage exerted a positive influence on the performance of pulse electrochemical degradation for ARG and CV, namely, with the growth of relevant influencing factors, the corresponding removal efficiency, kinetic constant of decolorization and COD removal reaction, and specific energy consumption increased accordingly, whereas the average current efficiency gradually decreased. However, the initial concentration of ARG and CV had a negative influence on the pulse electrochemical degradation process, that is, with the increase of initial dye concentration could lead to the reduction of the corresponding removal efficiency, kinetic constant of decolorization and COD removal reaction and energy consumption, on the contrary, the average current efficiency went up. Being different from ARG degradation process, there were some substances adhering to the cathode during CV electrochemical degradation process due to its positive charge. Under same conditions, the degradation indexes of pulse constant current power supply mode were better than those of direct constant current mode, which was coincident for both ARG and CV.

Electrocatalytic generation of homogeneous and heterogeneous hydroxyl radicals for cold mineralization of anti-cancer drug Imatinib

The effective removal of anti-cancer drug Imatinib (IMA) from water was explored by electrochemical advanced oxidation processes electro-Fenton (EF) and anodic oxidation (AO-H2O2) using different kinds of anode material: Pt, DSA (Ti/RuO2-IrO2), BDD and sub-stoichiometric titanium oxide (Ti4O7) and carbon felt cathode. IMA was then destroyed by hydroxyl radicals (OH) generated in the system. A series of comparison experiments including oxidative degradation kinetics of IMA, total organic carbon (TOC) removal and mineralization efficiency were conducted at ambient temperature. In both cases, DSA and Pt anodes were less effective for the anodic oxidation and mineralization of IMA compared to Ti4O7 and BDD anodes. Complete mineralization of 0.07 mM (34.5 mg L−1) IMA solution (corresponding to 24.11 mg L−1 initial TOC) was obtained both in EF and AO-H2O2 processes with BDD anode at 300 mA. The Ti4O7 anode was proved not advantageous to decay kinetics of IMA under high current densities (12.5 and 20.8 mA cm−2), while exhibited better mineralization performance than DSA and Pt anode, reaching 82% TOC removal efficiency in EF and 73% in AO-H2O2 processes at 8 h electrolysis with 12.5 mA cm−2. Besides, the formation and evolution of intermediate products including short-chain carboxylic acids and N-based inorganic ions (NH4+, NO3−) during mineralization of IMA solution were monitored by GC–MS, ion exclusion HPLC and ion chromatography, respectively. Finally, a plausible degradation pathway for degradation of IMA by OH was proposed according to the intermediates detected by HPLC and GC–MS.