Electrochemical degradation of tricyclazole in aqueous solution using Ti/SnO2–Sb/PbO2 anode

Synergistic effect between Ce-doped SnO2 and bio-carbon for electrocatalytic degradation of tetracycline: Experiment, CFD, and DFT

Carbon-based sandwich-like electrocatalyst with a hierarchical structure, carbon sheet (CS)-loaded Ce-doped SnO₂ nanoparticles, were successfully prepared using a simple method, which presented a high-efficiency electrocatalytic performance for tetracycline decomposition. Among them, Sn_0.75Ce_0.25O_y/CS exhibits superior catalytic activity, such as more than 95% of tetracycline was removed (120 min), and over 90% of total organic carbon was mineralized (480 min). It is found from morphology observation and computational fluid dynamics simulation that the layered structure is conducive to improving the mass transfer efficiency. Through X-Ray powder diffraction, X-ray photoelectron spectroscopy, Raman spectrum, and density functional theory calculation analyze that the structural defect in Sn_0.75Ce_0.25O_y caused by Ce doping is considered to play the key role. Moreover, electrochemical measurements and degradation experiments further prove that the outstanding catalytic performance is attributable to the initiated synergistic effect established between CS and Sn_0.75Ce_0.25O_y. These results explain the effectiveness of Sn_0.75Ce_0.25O_y/CS for the remediation of tetracycline-contaminated water and mitigating the potential risks and imply that the Sn_0.75Ce_0.25O_y/CS composite has a deeply practical value in tetracycline wastewater degradation and a promise for further application.

PbO2 materials for electrochemical environmental engineering: A review on synthesis and applications

Lead dioxide (PbO₂) materials have been widely employed in various fields such as batteries, electrochemical engineering, and more recently environmental engineering as anode materials, due to their unique physicochemical properties. Key performances of PbO₂ electrodes, such as energy efficiency and space-time yield, are influenced by morphological as well as compositional factors. Micro-nano structure regulation and decoration of metal/non-metal on PbO₂ is an outstanding technique to revamp its electrocatalytic activities and enhance environmental engineering efficiency. The aim of this review is to comprehensively summarize the recent research progress in the morphology control, the structure constructions, and the element doping of PbO₂ materials, further with many environmental application cases evaluated. Concerning electrochemical environmental engineering, the lead dioxide employed in chemical oxygen demand detection, ozone generators, and wastewater treatment has been comprehensively reviewed. In addition, the future research perspectives, challenges and the opportunities on PbO₂ materials for environmental applications are proposed.

Performance and mechanism of removal of antibiotics and antibiotic resistance genes from wastewater by electrochemical carbon nanotube membranes

Electrochemical carbon nanotube (CNT) and carboxylated carbon nanotube (CNT-COOH) membranes were prepared by vacuum filtration for the removal of antibiotics and antibiotic resistance genes (ARGs) from water. Scanning electron microscopy and energy-dispersive spectroscopy were used to analyze the performances of the two electrochemical membranes in the removal of antibiotics and ARGs, to determine the effects of different factors on removal rates, and to explore the mechanisms of the removal of antibiotics and ARGs. The results showed that CNT-COOH formed a porous mesh structure on the surface of polytetrafluoroethylene membrane and contained more oxygen than CNT. The electrochemical CNT-COOH membrane showed higher antibiotic and ARG removal rates than the electrochemical CNT membrane, with an antibiotics removal rate of 82% after 60 min of reaction and an ARGs concentration decrease by 1.85 log. The removal rate of antibiotics and ARGs increased with the increase in electrolyte concentration and anode voltage but decreased with the increase in the influent flow rate. The removal rate of antibiotics decreased with the increase in pH, while the best removal rates of ARGs were observed in a neutral environment. The degradation mechanism of antibiotics on the electrochemical CNT-COOH membrane was analyzed, and possible antibiotic degradation pathways were proposed. The removal of antibiotics and ARGs mainly occurred through electrochemical degradation, where hydroxyl radicals (-OH) played a dominant role.

Degradation of carbendazim in aqueous solution by different settings of photochemical and electrochemical oxidation processes

The present study analyzed the performance of photochemical and electrochemical techniques in the degradation and mineralization of the pesticide carbendazim (CBZ). Direct photolysis (DP), heterogeneous photocatalysis (HP), photoelectrocatalysis (PEC), and electrochemical oxidation (EO) were tested, and the influence of UV radiation, current density (j), and supporting electrolyte concentration were evaluated. The results suggest that CBZ is only degraded by DP when UV-C_254nm is used. For HP, the CBZ degradation was observed both when UV-A_365nm or UV-C_254nm were used, which is related to the reactive oxygen species (ROS) formed by the photocatalytic activity (photon-ROS). Neither DP nor HP were able to mineralize CBZ, demonstrating its resistance to photomediated processes. For EO, regardless of the j, there were higher CBZ degradation and mineralization than those observed when using DP and HP. The increase in the supporting electrolyte concentration (Na₂SO₄) did not affect the levels of degradation and mineralization of CBZ. Concerning the PEC, a CBZ mineralization of 52.2% was accomplished. These findings demonstrate that the EO is the main pathway for CBZ mineralization, suggesting an additional effect of the electro-ROS on the photon-ROS and UV-C_254nm. The values of mineralization, kinetics, and half-life show that PEC UV-C_254nm with a j of 15 mA cm^-2 was the best setting for the degradation and mineralization of CBZ. However, when the values of specific energy consumption were considered for industrial applications, the use of EO with a j of 3 mA cm^-2 and 4 g L^-1 of Na₂SO₂ becomes more attractive. The assessment of by-products formed after this best cost-efficient treatment setting revealed the presence of aromatic and aliphatic compounds from CBZ degradation. Acute phytotoxicity results showed that the presence of sodium sulfate can be a representative factor regarding the toxicity of samples treated in electrochemical systems.

Research trends in the development of anodes for electrochemical oxidation of wastewater

The review focuses on the recent development in anode materials and their synthesis approach, focusing on their compatibility for treating actual industrial wastewater, improving selectivity, electrocatalytic activity, stability at higher concentration, and thereby reducing the mineralization cost for organic pollutant degradation. The advancement in sol–gel technique, including the Pechini method, is discussed in the first section. A separate discussion related to the selection of the electrodeposition method and its deciding parameters is also included. Furthermore, the effect of using advanced heating approaches, including microwave and laser deposition synthesis, is also discussed. Next, a separate discussion is provided on using different types of anode materials and their effect on active •OH radical generation, activity, and electrode stability in direct and indirect oxidation and future aspects. The effect of using different synthesis approaches, additives, and doping is discussed separately for each anode. Graphene, carbon nanotubes (CNTs), and metal doping enhance the number of active sites, electrochemical activity, and mineralization current efficiency (MCE) of the anode. While, microwave or laser heating approaches were proved to be an effective, cheaper, and fast alternative to conventional heating. The electrodeposition and nonaqueous solvent synthesis were convenient and environment-friendly techniques for conductive metallic and polymeric film deposition.

Study of the chlorfenvinphos pesticide removal under different anodic materials and different reactor configuration

The present manuscript focuses on the study of the electrochemical oxidation of the insecticide Chlorfenvinphos (CVP). The assays were carried out under galvanostatic conditions using boron-doped diamond (BDD) and low-cost tin dioxide doped with antimony (Sb-doped SnO₂) as anodes. The influence of the operating variables, such as applied current density, presence or absence of a cation-exchange membrane and concentration of supporting electrolyte, was discussed. The results revealed that the higher applied current density the higher degradation and mineralization of the insecticide for both anodes. The presence of the membrane and the highest concentration of Na₂SO₄ studied (0.1 M) as a supporting electrolyte benefited the oxidation process of CVP using the BDD electrode, while with the ceramic anode the elimination of CVP was lower under these experimental conditions. Although the BDD electrode showed the best performance, ceramic anodes appear as an interesting alternative as they were able to degrade CVP completely for the highest applied current density values. Toxicity tests revealed that the initial solution of CVP was more toxic than the samples treated with the ceramic electrode, while using the BDD electrode the toxicity of the sample increased.

Application of lead oxide electrodes in wastewater treatment: A review

Electrochemical oxidation (EO) based on hydroxyl radicals (·OH) generated on lead dioxide has become a typical advanced oxidation process (AOP). Titanium-based lead dioxide electrodes (PbO₂/Ti) play an increasingly important role in EO. To further improve the efficiency, the structure and properties of the lead dioxide active surface layer can be modified by doping transition metals, rare earth metals, nonmetals, etc. Here, we compare the common preparation methods of lead dioxide. The EO performance of lead dioxide in wastewater containing dyes, pesticides, drugs, landfill leachate, coal, petrochemicals, etc., is discussed along with their suitable operating conditions. Finally, the factors influencing the contaminant removal kinetics on lead dioxide are systematically analysed.

Recent insights into SnO2-based engineered nanoparticles for sustainable H2 generation and remediation of pesticides

Due to the ongoing industrial revolution and global health pandemics, solar-driven water splitting and pesticide degradation are highly sought to cope with catastrophes such as depleting fossil reservoirs, global warming, and environmental degradation.

Pesticide production wastewater treatment by Electro-Fenton using Taguchi experimental design

In this study, the electro-Fenton (EF) method was applied to remove total organic carbon (TOC) from the pesticide production wastewater containing tricyclazole (TC). Statistical Taguchi method was used to optimize the treatment performance. Analysis of variance (ANOVA) indicated that the polynomial regression model fitted experimental data with R² of 0.969. The optimal conditions for eliminating 75.4% TOC and 93.7% TC were 0.2 mM of Fe²⁺, 990 mg/L of Na₂SO₄, 180 min of reaction time at pH 3 with 2.22 mA/cm² of current density. The removal of TC present in the wastewater followed the first-order reaction kinetic model (R² = 0.993); while that was the second-order kinetic model in the case of the TOC removal (R² = 0.903). In addition, the experimental results and theory approaches (density functional theory and natural bond orbital calculations) also showed the C-N bond breaking and nitrate ions cleavage to ammonia. Acute toxicity of the pesticide wastewater after treatment (PWAT) on microcrustaceans showed that the treated wastewater still exhibited high toxicity against D. magna, with LC₅₀ values of 3.84%, 2.68%, 2.05%, and 1.78% at 24 h, 48 h, 72 h, and 96 h, respectively.

Electro-catalytic membrane reactors for the degradation of organic pollutants – a review

Electro-catalytic membrane reactor exhibiting electro-oxidation degradation of organic pollutants on anodic membrane.

The role of the anode material and water matrix in the electrochemical oxidation of norfloxacin

The roles of the anode material, boron-doped diamond (BDD), with different boron (B) and substrate Silicon (Si) or Niobium (Nb) content, and one dimensionally stable anode (DSA^®), were evaluated in the oxidation of norfloxacin (NOR) by electrochemical advanced oxidation process (EAOP). The effect of other components in real wastewater on the performance of EAOP was also studied. The anode materials were characterized by cyclic voltammetry, regarding diamond quality, electro-generation of oxidants and NOR oxidation mechanism (direct and/or indirect). The results showed that the anode material influences on the NOR oxidation pathway, due to distinct characteristics of the substrate and the coating. Apparently, low difference in diamond-sp³/sp²-carbon ratio (Si/BDD₁₀₀ × Si/BDD₂₅₀₀) does not leads to significant differences in the EAOP. On the other hand, the variation in the sp³/sp² ratio seems to be higher when Si/BDD₂₅₀₀ and Nb/BDD₂₅₀₀ are compared, which would explain the best current efficiency result for Si substrate. However, the Nb substrate presented a similar current efficiency and a 60% lower energy consumption. Dissolved organic matter (DOM) present in the real wastewater affect the EAOP-Nb/BDD due to HO and persulfate ions scavenged. However, when supporting electrolyte was added to a real wastewater spiked with NOR, the NOR decay reaches similar values found to the synthetic one. Due to the energy saving and mechanical properties, Nb substrate presents some technological advantages in relation to Si, which can facilitate the application to industrial levels.

Effective Removal of Sulfanilic Acid From Water Using a Low-Pressure Electrochemical RuO2-TiO2@Ti/PVDF Composite Membrane

Removal of sulfanilic acid (SA) from water is an urgent but still challenging task. Herein, we developed a low pressure electrochemical membrane filtration (EMF) system for SA decontamination using RuO₂-TiO₂@Ti/PVDF composite membrane to serve as not only a filter but also an anode. Results showed that efficient removal of SA was achieved in this EMF system. At a charging voltage of 1.5 V and a electrolyte concentration of 15 mM, flow-through operation with a hydraulic retention time (HRT) of 2 h led to a high SA removal efficiency (80.4%), as expected from the improved contact reaction of this compound with ROS present at the anode surface. Cyclic voltammetry (CV) analysis indicated that the direct anodic oxidation played a minor role in SA degradation. Electron spin resonance (ESR) spectra demonstrated the production of ^•OH in the EMF system. Compared to the cathodic polarization, anodic generated ROS was more likely responsible for SA removal. Scavenging tests suggested that adsorbed ^•OH on the anode (>^•OH) played a dominant role in SA degradation, while O2•- was an important intermediate oxidant which mediated the production of ^•OH. The calculated mineralization current efficiency (MCE) of the flow-through operated system 29.3% with this value much higher than that of the flow-by mode (5.1%). As a consequence, flow-through operation contributed to efficient oxidation of SA toward CO₂ and nontoxic carboxylic acids accounting for 71.2% of initial C. These results demonstrate the potential of the EMF system to be used as an effective technology for water decontamination.

Bioaugmentation potential of a newly isolated strain Sphingomonas sp. NJUST37 for the treatment of wastewater containing highly toxic and recalcitrant tricyclazole

In order to develop an effective bioaugmentation strategy for the removal of highly toxic and recalcitrant tricyclazole from wastewater, a tricyclazole degrading strain was firstly successfully isolated and identified as Sphingomonas sp. NJUST37. In batch reactors, 100 mg L^-1 tricyclazole could be completely removed within 102 h, which was accompanied by significant biomass increase, TOC and COD removal, as well as toxicity reduction. Chromatography analysis and density functional theory simulation indicated that monooxygenation occurred firstly, followed by triazole ring cleavage, decyanation reaction, hydration reaction, deamination, dihydroxylation and final mineralization reaction. Tricyclazole biodegradation condition by NJUST37 was optimized in terms of temperature, pH, tricyclazole concentration and additional carbon and nitrogen sources. After the inoculation of NJUST37 into a pilot-scale powdered activated carbon treatment tank treating real fungicide wastewater, tricyclazole removal efficiency increased to higher than 90%, demonstrating the great potential of NJUST37 for bioaugmentation particularly on tricyclazole biodegradation in practice.

Electrochemical Oxidation of EDTA in Nuclear Wastewater Using Platinum Supported on Activated Carbon Fibers

A novel Pt/ACF (Pt supported on activated carbon fibers) electrode was successfully prepared with impregnation and electrodeposition method. Characterization of the electrodes indicated that the Pt/ACF electrode had a larger effective area and more active sites. Electrochemical degradation of ethylenediaminetetra-acetic acid (EDTA) in aqueous solution with Pt/ACF electrodes was investigated. The results showed that the 3% Pt/ACF electrode had a better effect on EDTA removal. The operational parameters influencing the electrochemical degradation of EDTA with 3% Pt/ACF electrode were optimized and the optimal removal of EDTA and chemical oxygen demand (COD) were 94% and 60% after 100 min on condition of the electrolyte concentration, initial concentration of EDTA, current density and initial value of pH were 0.1 mol/L, 300 mg/L, 40 mA/cm² and 5.0, respectively. The degradation intermediates of EDTA in electrochemical oxidation with 3% Pt/ACF electrode were identified by gas chromatography-mass spectrum (GC-MS).

Electrochemical oxidation of perfluorinated compounds in water

Perfluorinated compounds (PFCs) are persistent and refractory organic pollutants that have been detected in various environmental matrices and municipal wastewater. Electrochemical oxidation (EO) is a promising remediation technique for wastewater contaminated with PFCs. A number of recent studies have demonstrated that the "non-active" anodes, including boron-doped diamond, tin oxide, and lead dioxide, are effective in PFCs elimination in wastewater due to their high oxygen evolution potential. Many researchers have conducted experiments to investigate the optimal conditions (i.e., potential, current density, pH value, plate distance, initial PFCs concentration, electrolyte, and other factors) for PFCs elimination to obtain the maximal elimination efficiency and current efficiency. The EO mechanism and pathways of PFCs have been clearly elucidated, which undergo electron transfer, Kolbe decarboxylation or desulfonation, hydrolysis, and radical reaction. In addition, the safety evaluation and energy consumption evaluation of the EO technology have also been summarized to decrease toxic ion release from electrode and reduce the cost of this technique. Although the ultrasonication and hydrothermal techniques combined with the EO process can improve the removal efficiency and current efficiency significantly, these coupled techniques have not been commercialized and applied in industrial wastewater treatment. Finally, key challenges facing EO technology are listed and the directions for further research are pointed out (such as combination with other techniques, treatment for natural waters contaminated by low levels of PFCs, and reactor design).

Sonoelectrochemical mineralization of perfluorooctanoic acid using Ti/PbO 2 anode assessed by response surface methodology

BACKGROUND

Perfluorocarboxylic acids (PFCAs) are emerging pollutant and classified as fully fluorinated hydrocarbons containing a carboxylic group. PFCAs show intensively resistance against chemical and biological degradation due to their strong C-F bond. The Sonoelectrochemical mineralization of the synthetic aqueous solution of the perfluorooctanoic acid (PFOA) on Ti/PbO2 anode was investigated using the response surface methodology based on a central composite design with three variables: current density, pH, and supporting electrolyte concentration.

METHODS

The defluorination ratio of PFOA was determined as an indicator of PFOA mineralization. Fluoride ion concentration was measured with an ion chromatograph unit. The Ti/PbO2 electrode was prepared using the electrochemical deposition method. The ultrasonic frequency was 20 kHz.

RESULTS

The optimum conditions for PFOA mineralization in synthetic solution were electrolyte concentration, pH, and current density of 94 mM, 2, and 83.64 mA/cm(2), respectively. The results indicated that the most effective factor for PFOA mineralization was current density. Furthermore, the PFOA defluorination efficiency significantly enhanced with increasing current density. Under optimum conditions, the maximum mineralization of PFOA was 95.48 % after 90 min of sonoelectrolysis.

CONCLUSIONS

Sonoelectrolysis was found to be a more effective technique for mineralization of an environmentally persistent compound.