Electrochemical oxidation of phenolic wastewaters using a batch-stirred reactor with NaCl electrolyte and Ti/RuO 2 anodes

Decentralized approach toward organic pollutants removal using UV radiation in combination with H2O2-based electrochemical water technologies

The current literature lacks a comprehensive discussion on the trade-off between pollutant degradation/mineralization and treatment time costs in utilizing UV light in combination with H2O2-based electrochemical advanced oxidation processes (EAOPs). The present study sheds light on the benefits of using the photoelectro-Fenton (PEF) process with UVA or UVC for methylparaben (MetP) degradation in real drinking water. Although light boosts the photodegradation of refractory Fe(III) complexes and the photolysis of H2O2 (with UVC only), the energy-intensive nature of light-based treatments is acknowledged. To help tackle the high energy consumption issue, a novel approach was employed: partial application of UVA or UVC light after a predetermined electro-Fenton electrolysis time. The proposed treatment approach yielded satisfactory comparable results to those obtained from the application of PEF/UVA or PEF/UVC in terms of total organic carbon removal (ca. 100%), with notably lower energy consumption (ca. 50%). The study delves into the combined method's feasibility, analyzing pollutant degradation/mineralization process and overall energy consumption. The research identifies possible degradation routes based on intermediate detection and radical quenching experiments. Finally, toxicological assessments evaluate the toxicity levels of MetP and its intermediates. The findings of this study bring meaningful contributions to the fore and point to the highly promising potential of the proposed approach, in terms of sustainability and cost-effectiveness, when applied for decentralized water treatment.

Electrochemical-based approaches for the treatment of pharmaceuticals and personal care products in wastewater

In recent times, emerging contaminants (ECs) like pharmaceuticals and personal care products (PPCPs) in water and wastewater have become a major concern in the environment. Electrochemical treatment technologies proved to be more efficient to degrade or remove PPCPs present in the wastewater. Electrochemical treatment technologies have been the subject of intense research for the past few years. Attention has been given to electro-oxidation and electro-coagulation by industries and researchers, indicating their potential to remediate PPCPs and mineralization of organic and inorganic contaminants present in wastewater. However, difficulties arise in the successful operation of scaled-up systems. Hence, researchers have identified the need to integrate electrochemical technology with other treatment technologies, particularly advanced oxidation processes (AOPs). Integration of technologies addresses the limitation of indiviual technologies. The major drawbacks like formation of undesired or toxic intermediates, s, energy expenses, and process efficacy influenced by the type of wastewater etc., can be reduced in the combined processes. The review discusses the integration of electrochemical technology with various AOPs, like photo-Fenton, ozonation, UV/H2O2, O3/UV/H2O2, etc., as an efficient way to generate powerful radicals and augment the degradation of organic and inorganic pollutants. The processes are targeted for PPCPs such as ibuprofen, paracetamol, polyparaben and carbamezapine. The discussion concerns itself with the various advantages/disadvantages, reaction mechanisms, factors involved, and cost estimation of the individual and integrated technologies. The synergistic effect of the integrated technology is discussed in detail and remarks concerning the prospects subject to the investigation are also stated.

A review on three-dimensional electrochemical technology for the antibiotic wastewater treatment

The potential genotoxicity and non-biodegradability of antibiotics in the natural water bodies threaten the survival of various living things and cause serious environmental pollution and destruction. Three-dimensional (3D) electrochemical technology is considered a powerful means for antibiotic wastewater treatment as it can degrade non-biodegradable organic substances into non-toxic or harmless substances and even completely mineralize them under the action of electric current. Therefore, antibiotic wastewater treatment using 3D electrochemical technology has now become a hot research topic. Thus, in this review, a detailed and comprehensive investigation was conducted on the antibiotic wastewater treatment using 3D electrochemical technology, including the structure of the reactor, electrode materials, the influence of operating parameters, reaction mechanism, and combination with other technologies. Many studies have shown that the materials of electrode, especially particle electrode, have a great effect on the antibiotic wastewater treatment efficiency. The influence of operating parameters such as cell voltage, solution pH, and electrolyte concentration was very significant. Combination with other technologies such as membrane and biological technologies has effectively increased antibiotic removal and mineralization efficiency. In conclusion, the 3D electrochemical technology is considered as a promising technology for the antibiotic wastewater treatment. Finally, the possible research directions of the 3D electrochemical technology for antibiotic wastewater treatment were proposed.

Electrochemical oxidation of styrene to benzaldehyde by discrimination of spin-paired π electrons

The oxidation of styrene to benzaldehyde has been a considerable challenge in the electrochemical synthesis of organic compounds because styrene is more easily oxidized to benzoic acid. In this work, MnO₂ with an asymmetric electronic configuration is designed to discriminate the spin-paired π electrons of styrene. One of these discriminated π electrons combined with reactive oxygen species (ROS), ˙OH, ˙OOH, etc., produced simultaneously on a MnO₂/(Ru_0.3Ti_0.7)O₂/Ti bifunctional anode, to form benzaldehyde via Grob fragmentation, rather than benzoic acid. However, only benzoic acid is obtained from the oxidation of styrene on the anodes MOs/(Ru_0.3Ti_0.7)O₂/Ti, where MOs are other metal oxides with symmetric electronic configurations.

Solar engineering of wastewater treatment for full mineralization of organic pollutants

Full mineralization of organic pollutants is a tough task with existing technologies. Even if all conventional energies and extremes are exhausted, high-temperature wastewater treatment is not worth the loss from the perspective of energy. Solar engineering holds promise for the full mineralization of organic pollutants to tackle the global fossil energy shortage. Here, we report solar engineering for full mineralization and efficient solar utilization. The solar energies and spectrum were fully utilized to initiate the solar heat and solar electricity. Two energies were applied to trigger the thermochemical and electrochemical oxidation of the organic pollutants. Our study bridges the gap between the energy and environment towards efficient solar utilization and effective water treatment. As a proof-of-concept study, this demonstrates a solar engineering of full phenol mineralization in wastewater. A record phenol mineralization rate was achieved to reach an oxidation rate of 98% and COD of 93% under a constant current density of 50mA/cm² at 150°C. UV and HPLC were used to detect the intermediate products during variable time intervals. The results showed that the intermediate products are composed of maleic acid, hydroquinone and p-benzoquinone. In the extreme high temperature (90°C), the solar oxidation time and pathway are greatly altered. The reaction rate constant at 150°C is about 11 times than that at 90°C. More solar heat significantly reduces the activated energy of the pollutant oxidation and lowers the potential of electrolysis.

Optimization and assessment of an electrochemical advanced oxidation system for synthetic stormwater treatment

Electrochemical advanced oxidation processes (eAOPs) such as the current advanced oxidation system (AOS) are a type of electrochemical wastewater treatment that creates oxidative species, such as iodide species, chloride species, and hydroxyl radicals, that can treat even the most recalcitrant contaminants. It is important to determine the concentrations and locations of oxidative species in eAOPs for optimization of the wastewater treatment process. In this study, a spectrophotometric methodology was used to determine concentrations of iodide and chloride oxidative species (starting at 10, 25, and 50 ppm) within an AOS under various input voltages (6, 12, and 24 V). Overall, it was found that iodate and chlorite were the dominant species created in their respective treatments. Additionally, the concentration of iodide oxidative species increased with increasing voltage, whereas the chloride species decreased with increasing voltage. The optimal conditions for the efficient creation of AOS oxidative species were 12 V and 10 ppm potassium iodide and 6 V and 10 ppm sodium chloride, respectively. In addition, the use of iodide is recommended for wastewater treatment using the AOS to effectively create oxidative species. Following optimization, the AOS performance was tested for synthetic stormwater. Results indicated that the AOS performed well for reduction of Escherichia coli; however, reduction of other contaminants was inconsistent as would be expected given the AOS was optimized for disinfection, not decontamination. Further AOS optimization for decontamination would be expected to result in improved decontamination performance.

Electrochemical oxidation process on palm oil mill effluent waste activated sludge: optimization by response surface methodology

Biological-based treatment as the conventional treatment for palm oil mill effluent (POME) in open-ponding system face a well known rate-limiting step which is hydrolysis. In this study, electrochemical oxidation (EO) by a ruthenium oxide-coated titanium (Ti/RuO₂) electrode was introduced as a pre-treatment for POME waste activated sludge (WAS). Surface morphology and elemental analysis were investigated using field emission scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively. Response surface methodology type central composite design was used in this study to understand the relationship between the independent and dependent variables. Analysis of variance (ANOVA) was used to validate the model of the studied variables. The correlation coefficients (R²) indicated a close agreement between the experimental results and the predicted values, with high R² values of 0.9044-0.9773. Multiple response optimization suggested that the range of current density (17-27 mA/cm²) and electrolysis time (55-75 min) at a fixed concentration of sodium chloride (10 g/L), resulted in mixed liquor volatile suspended solids (MLVSS) removal >20%, capillary suction timer (CST) reduction >43%, extracellular polymeric substances (EPS) increment <19% and soluble chemical oxygen demand (sCOD) increment >25%. EO appears to be an efficient pre-treatment as well as practical way to improve the POME WAS disintegration and dewaterability.

Toward efficient electrocatalytic degradation of iohexol using active anodes: A laser-made versus commercial anodes

The X-ray iodinated contrast medium iohexol is frequently detected in aquatic environments due to its high persistence and the inefficiency of its degradation by conventional wastewater treatments. Hence, the challenge faced in this study is the development of an alternative electrochemical treatment using active anodes. We investigate the oxidation of iohexol (16.42 mg L^-1) using different operating conditions, focusing on the role of different mixed metal oxide anodes in the treatment efficiency. The electrocatalytic efficiency of the Ti/RuO₂-TiO₂ anode prepared using a CO₂ laser heating and an ionic liquid is compared with Ti/RuO₂-TiO₂-IrO₂ and Ti/IrO₂-Ta₂O₅ commercial anodes. The hypochlorite ions generated by the anodes are also analyzed. The effect of the electrolyte composition (NaCl, Na₂SO₄, and NaClO₄) and current density (15, 30, and 50 mA cm^-2) on the iohexol degradation is also studied. The Ti/RuO₂-TiO₂ laser-made anode is more efficient than the commercial anodes. After optimizing experimental parameters, this anode removes 95.5% of iohexol in 60 min and displays the highest kinetic rate (0.059 min^-1) with the lowest energy consumption per order (0.21 kWh m^-3order^-1), using NaCl solution as the electrolyte and applying 15 mA cm^-2. Additionally, iohexol-intensified groundwater was used to compare the efficiency of anodes. The Ti/RuO₂-TiO₂ is also more efficient in removing the organic charge from the real water matrix (21.7% TOC) than the commercial anodes. Notably, the iohexol removal achieved is higher than all electrochemical treatments already reported using state-of-the-art non-active anodes in lower electrolysis time. Therefore, data from this study indicate that the electrochemical degradation of iohexol using the Ti/RuO₂-TiO₂ anode is efficient and has excellent cost-effectiveness; thus, it is a promising approach in the degradation of iohexol from wastewater. Furthermore, the Ti/RuO₂-TiO₂ active anode is competitive and can be an excellent option for treating effluents contaminated with recalcitrant organic compounds such as iohexol.

Recent progress on ultrasound-assisted electrochemical processes: A review on mechanism, reactor strategies, and applications for wastewater treatment

The electrochemical advanced oxidation processes (EAOPs) have received significant attention among the many other water and wastewater treatment technologies. However, achieving a desirable removal effect with a single technique is frequently difficult. Therefore, the integration of ultrasound technique with other processes such as electrocoagulation, electro-Fenton, and electrooxidation is a critical way to achieve effective organic pollutants decomposition from wastewater. This review paper is focused on ultrasound-assisted electrochemical (US/electrochemical) processes, so-called sonoelectrochemical processes of various organic pollutants. Emphasis was given to recently published articles for discussing the results and trends in this research area. The use of ultrasound and integration with electrochemical processes has a synergistic impact owing to the physical and chemical consequences of cavitation, resulting in enhancing the mineralization of organic pollutants. Various types of sonoelectrochemical reactors (batch and continuous) employed in the US/electrochemical processes were reviewed. In addition, the strategies to avoid passivation, enhanced generation of reactive oxygen species, and mixing effect are reviewed. Finally, concluding remarks and future perspectives on this research topic are also explored and recommended.

Direct electron transfer (DET) processes in a flow anode system-Energy-efficient electrochemical oxidation of phenol

In flow anode systems, surface-bound hydroxyl radicals (*OH) are generated at the solid-liquid interface of suspended particulate charge carriers at potentials well below that required for oxygen evolution as a result of water splitting. While these surface-bound radicals are powerful indiscriminant oxidants that often lead to complete mineralization of organic pollutants, the more selective process of direct electron transfer (DET) may also occur at the particle electrode interfaces and play a critical role in the degradation of some contaminants. In this study, we investigated DET processes in a flow anode system in which carbon black was utilized as the flow anode material and Pt, Ti, IrRu and IrTa meshes were used as the current collectors. The results indicate that the use of a carbon black flow anode enhanced the DET rate by 20 times at 1.0 V vs Ag/AgCl compared to the control experiment with no carbon black particles present. Low solution conductivity had a more obvious negative effect on the DET process (compared to *OH mediated oxidation) due to the high potential drop and inhibition of mass transfer processes at the solid-liquid interfaces of the anode particles. The DET rates were dependent on the particular anode current collector used (i.e., Ti, IrRu, IrTa or Pt mesh) with differences in rates ascribed to the electron transfer resistance of the current collectors in the flow anode system. Detailed investigation of the degradation of phenol in a flow anode system revealed that this widely studied contaminant could be degraded with an energy consumption of 3.08 kWh m^-3, a value substantially lower than that required with other techniques. Results of this study provide a better understanding of the DET mechanism at the solid-solid and solid-liquid interfaces with these insights expected to benefit the design of flow anode materials and current collectors and lead to the improvement in performance of flow anode systems.

Effect of current density and pH on the electrochemically generated active chloro species for the rapid mineralization of p-substituted phenol

The aim of present study is increasing the degradation and mineralization of 4-chlorophenol (4-CP) during electrochemical oxidation with Ti/RuO₂ anodes. Innovatively, the evolution of chlorine-related species and the formations of various inorganic ions were investigated by electrolytic analysis in order to set up whether the formation and consumption of these byproducts associated with either chemical or electrochemical reactions. The effect of operating parameters such as current density, solution pH, treatment time, and electrolyte concentration has been studied. The formation of Cl₂, chlorite (ClO₂^-), and chlorate (ClO₃^-) were detected by adding the known concentration of Cl^- ions at different pH and current densities. Concentration trends of active chloro-species indicate that the degradation of 4-CP and chemical oxygen demand (COD) removal was formed maximum at pH 6 and j of 225.2 Am^-2 in presence of 0.0085 M NaCl. Thus, the 4-CP degradation mainly depends on the radicals and active chlorine formation and a mineralization mechanism was proposed based on intermediates byproducts formation such as catechol, hydroquinone, 1, 4-benzoquinone, and organic acids identify by using the GC-MS and HPLC analysis at the optimum treatment condition. Total organic carbon (TOC) at different pH and current density, mass balance analysis of carbon and inorganic species formation were determined at the optimum treatment conditions of 4-CP. The degradation kinetic of 4-CP was followed the pseudo-first order kinetic model during the each parameters optimization. Specific energy consumption and current efficiency were also used to identify the technical feasibility of the process.

PVDF HFP_RuO2 Nanocomposite Aerogels Produced by Supercritical Drying for Electrochemical Oxidation of Model Tannery Wastewaters

A supercritical CO₂ drying process was used to prepare an innovative nanocomposite, formed by a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF HFP) aerogel loaded with RuO₂ nanoparticles. The produced nanocomposites, at 10% and 60% w/w of RuO₂, were tested for the electrochemical oxidation of model tannery wastewaters. The effect of the electrochemical oxidation parameters, like pH, temperature, and current density, on tannic acid, intermediates, and chemical oxygen demand (COD) removal, was investigated. In particular, the electrolysis of a simulated real tannery wastewater, using PVDF HFP_RuO₂ 60, was optimized working at pH 10, 40 °C, and setting the current density at 600 A/m². Operating in this way, surfactants, sulfides, and tannins oxidation was achieved in about 2.5 h, ammonium nitrogen oxidation in 3 h, and COD removal in 5 h. When chloride-containing solutions were tested, the purification was due to indirect electrolysis, related to surface redox reactions generating active chlorine. Moreover, sulfide ions were converted into sulfates and ammonium nitrogen in gaseous N₂.

Electrochemical degradation of psychotropic pharmaceutical compounds from municipal wastewater and neurotoxicity evaluations

Contaminants of emerging concern (CECs) are released daily into surface water, and their recalcitrant properties often require tertiary treatment. Electrochemical oxidation (EO) is often used as an alternative way to eliminate these compounds from water, although the literature barely addresses the neurotoxic effects of residual by-products. Therefore, this study investigated the performance of EO in the removal of five CECs (alprazolam, clonazepam, diazepam, lorazepam, and carbamazepine) and performed neurotoxicity evaluations of residual EO by-products in Wistar rat brain hippocampal slices. Platinum-coated titanium (Ti/Pt) and boron-doped diamond (BDD) electrodes were studied as anodes. Different current densities (13-75 A m^-2), pH values (3-10), electrolyte dosages (NaCl), and matrix effects were assessed using municipal wastewater (MWW). The drugs were successfully degraded after 5 min of reaction for both the Ti/Pt and BDD electrodes when a current density of 75 A m^-2 was applied. For Ti/Pt and BDD, neutral and acidic pH demonstrated better CEC removal performance, respectively. Compound degradation using MWW achieved 40% removal after 120 min for Ti/Pt and ranged between 33 and 52% for the BDD anode. For Ti/Pt, neurotoxicity studies using MWW indicated a decrease in reactive oxygen species (ROS) signals. However, when an artificial cerebrospinal fluid (ACSF) medium was reapplied, the signal recovered and increased to a value above the baseline, indicating that cells recovered part of their normal activity but remained in a different condition. For the BDD anode, the treated MWW did not cause significant ROS production variations, suggesting that he EO was effective in eliminating the toxicity of the treated solution.

Persulfate enhanced electrochemical oxidation of highly toxic cyanide-containing organic wastewater using boron-doped diamond anode

Cyanide-containing organic wastewater is discharged in large quantities by coking, electroplating and pharmaceutical industries, which seriously endangers environmental safety and human health. In this paper, Electrochemical Oxidation-Persulfate (EO-PS) Advanced Oxidation Process (AOP) was firstly used to treat high concentration cyanide-containing organic wastewater obtained from a chemical enterprise. The potential application of this process in the treatment of high concentration cyanide-containing organic wastewater was explored for the first time, and the effects of current density, initial pH, temperature and initial concentration on chemical oxygen demand (COD), total organic carbon (TOC) and total cyanide (CN^-) removal in wastewater were systematically investigated. The results shown that the EO-PS process had an excellent removal effect on organics and cyanide in high concentration cyanide-containing organic wastewater which contained 11,290 mg L^-1 COD, 4456 mg L^-1 TOC and 1280.15 mg L^-1 CN^-. The COD, TOC and CN^- removal at optimized operating parameters for 24 h were 95.8%, 87.8% and 98.4%, respectively. The corresponding electrical energy per order was only 41.6 kWh m^-3 order^-1. In addition, the pollutants removal can be accelerated under conditions of high current density, acidic solution, appropriate temperature and low pollutant concentration, among which low current density, low pH, appropriate temperature and low pollutant concentration can effectively diminish energy consumption. Cyanide, COD and TOC degradation in all reaction conditions followed the pseudo-first-order kinetic model.

Removal of styrene in air stream by absorption combined with electrochemical oxidation

Aqueous solution absorptions are widely used as an effective way for the treatment of noxious gases discharged from various industrial processes. However, this technology may encounter problems in removing gaseous pollutants with low Henry constants, such as styrene from contaminated air. In this study, a novel electrochemical absorption reactor was devised to remove these air pollutants. The reactor consists of five pairs of stacked mesh electrodes. Each pair of mesh electrodes consists of a Ti/RuO₂ anode and a Ti cathode. The dimension of mesh electrode is 100 mm × 100 mm with 3 mm × 5 mm rhombic holes evenly distributed. The distance between two neighbouring electrodes is 25 mm. The simulated gas was introduced into the reactor from the bottom of the reactor by a gas distributor. The experimental result shows that styrene in the air was effectively removed by the electrochemical absorption reactor, and the removal increased with the increase of current density applied to the reactor. It was found that almost 100% styrene removal was achieved in 1% NaCl solution with 1 pH value and a current density of 0.04 A/cm² applied to the reactor. The major liquid phase products from styrene oxidation were confirmed to be 1-Phenyl-1, 2-ethanediol and benzaldehyde.

Electrochemical removal of naphthalene from contaminated waters using carbon electrodes, and viability for environmental deployment

This work assesses the potential of electrochemical technologies for the treatment of groundwaters contaminated with petroleum hydrocarbons. Specific consideration was given to deployment in Antarctic regions where numerous fuel spills have occurred over the last two centuries, and resources and manual labour for remediation efforts are limited. The polycyclic aromatic hydrocarbon, naphthalene, was a used as a model contaminant and was treated with low-cost, active carbon electrodes to promote the active chlorine degradation pathway. Results showed that 20 mg/L naphthalene solutions could be treated to sufficient standards in less than 3 h of treatment, and that the formation of toxic and chlorinated by-products is not an issue of concern if the appropriate timeframes are used (4 h of treatment). The effects of the applied current (0-160 mA) and electrolyte concentration (0.01-0.1 M NaCl) were evaluated and a dynamic kinetic model proposed and found to be in good agreement with the experimental results. The energy consumption is an important limitation in remote environmental regions where resources are scarce. It was found that an energy usage of 104 kW h/kg of naphthalene removed could be achieved.

Electrochemical Oxidation-Membrane Distillation Hybrid Process: Utilizing Electric Resistance Heating for Distillation and Membrane Defouling through Thermal Activation of Anodically Formed Persulfate

This study reports distillation-based salt removal by Ohmic heating in a hybrid process, in which electrochemical oxidation (EO) and direct contact membrane distillation (DCMD) are performed sequentially. In addition to anodically destructing the organics, the hybrid process also separated the sulfate-based electrolytes from treated water through distillation, without consuming external energy, owing to the temperature of the aqueous sulfate solution being elevated to 70 °C via resistive heating. The hybrid process treated organic compounds in a nonselective fashion, whereas DCMD alone did not completely reject (semi)volatile organics. Integrating EO with DCMD made the hybrid process resistant toward the wetting phenomenon; the process exhibited a steady distillate flux and salt rejection as the initial loading of amphiphilic sodium dodecyl sulfate was increased to 0.3 mM. Anodic persulfate formation from the sulfate and Ohmic heating caused an in situ yield of the sulfate radical in the feed solution; this eliminated membrane fouling, according to the observation that the water flux, which was drastically reduced upon adding alginate, was recovered immediately after an electric current was applied. The hybrid process concurrently decomposed spiked organics and removed naturally present inorganic ions in actual flue gas desulfurization wastewater, without an external supply of electrolyte and heat energy.

Electrochemical oxidation treatment of coal tar wastewater with lead dioxide anodes

In this study, coal tar wastewater was treated by electrochemical oxidation technology using lead dioxide anodes. The influence of operating parameters, including applied current density, electrode gap and initial pH value, on the removal ratio of chemical oxygen demand (COD) was investigated. The results demonstrated that the COD removal ratio reached 90.5% after 3.5 h electrolysis with the current density at 3 A dm^-2 and electrode gap at 1.0 cm. Correspondingly, the COD decreased from 5,125 mg L^-1 to 487 mg L^-1, which fitted the wastewater discharge standards of China, and the specific energy consumption (SEC_COD) was 35.3 kWh kg_COD ^-1. Not only was the COD removal ratio only 77.1% after 2 h electrolysis but the BOD₅/COD ratio of the wastewater reached 0.44, which could be biochemically treated, and the SEC_COD decreased by 34.3%. Moreover, the main composition of pristine wastewater before and after 2 h electrolysis was analyzed by GC-MS, and the disappearance of macromolecules (such as ethyl-2-pyrenemethanol) and the production of small molecules (such as propane-1,3-diol) could improve the biodegradability of the wastewater. Therefore, electrochemical oxidation for 2 h is a promising alternative for pretreatment of coal tar wastewater prior to biological treatment.

The Degradation of Deoxynivalenol by Using Electrochemical Oxidation with Graphite Electrodes and the Toxicity Assessment of Degradation Products

Deoxynivalenol (DON) is a common mycotoxin, which is known to be extremely harmful to human and livestock health. In this study, DON was degraded by electrochemical oxidation (ECO) using a graphite electrode and NaCl as the supporting electrolyte. The graphite electrode is advantageous due to its electrocatalytic activity, reusability, and security. The degradation process can be expressed by first-order kinetics. Approximately 86.4% of DON can be degraded within 30 min at a potential of 0.5 V. The degradation rate reached 93.2% within 30 min, when 0.5 V potential was used for electrocatalyzing a 10 mg/L DON solution. The degradation rate of DON in contaminated wet distiller's grain with solubles (WDGS) was 86.37% in 60 min. Moreover, results from the cell counting kit-8 (CCK-8) and 4,6-diamidino-2-phenylindole dihydrochloride (DAPI) staining assay indicated that ECO reduced the DON-induced cytotoxicity and apoptotic bodies in a gastric epithelial cell line (GES-1) compared to the DON-treated group. These findings provide new insights into the application of ECO techniques for degrading mycotoxins, preventing food contamination, and assessing DON-related hazards.

Enhancement of municipal sludge dewaterability by electrochemical pretreatment

Electrolysis is a promising technology to improve sludge dewaterability efficiently with negligible environmental impact. To intensify the electrolytic efficiency, the effect of electrolytes (NaCl, Na₂SO₄, NaNO₃, and NaClO₄) on electrolysis pretreatment of municipal sludge and its mechanisms was investigated using Ti/PbO₂ electrodes. The electrolytes, which enhanced the production of oxidative radicals, showed a significant synergetic effect in reducing the capillary suction time (CST) of sludge. NaCl was distinguished from the other electrolytes since it formed a large amount of active chlorine species, which oxidized the sludge cells to improve the sludge dewaterability. The surface morphologies as well as the soluble proteins and polysaccharides were analyzed to unravel the underlying mechanisms of sludge dewaterability. Additionally, an economic assessment showed that NaCl addition in the electrolysis pretreatment can be a suitable technique for enhancing municipal sludge dewaterability.

Pollutants removal from synthetic wastewater by the combined electrochemical, adsorption and sequencing batch reactor (SBR)

Wastewater filtration is considered the main solution to water shortages. Here, we treated synthetic wastewater by combining treatment techniques, namely, electrochemical oxidation and adsorbent added sequencing batch reactor (SBR). One beaker with a working value of 1500 mL was applied in this contemporary study. In the upper part of the beaker, an anode and a cathode (Ti/RuO₂-IrO₂) were arranged in parallel for the electrochemical oxidation process. Sodium sulfate (Na₂SO₄) with a concentration of 2.5 g/L was added as the electrolyte. The voltage and current were set to 7.50 V and 0.40 A, respectively. Aeration was conducted at the bottom of the beaker. Then, 15% working value of the reactor was filled by activated sludge, and 85% working value of the reactor was added with synthetic wastewater. In addition, 1.50 g/L of powdered cockleshell was added in the reactor. Response surface methodology was used for statistical analysis. In synthetic wastewater, concentrations of COD, ammonia, phenols and chromium were 2500 mg/L, 2500 mg/L, 100 mg/L and 100 mg/L, respectively. pH and reaction time (h) were considered as independent factors. A total of 2430 mg/L biochemical oxygen demand, 2500 mg/L ammonia, 90.0 mg/L phenols, and 84.0 mg/L chromium were eliminated at the optimum reaction time (72.9 min) and pH (6.5). The energy consumption value was 6.5 (kWh kg^-1) at the optimum operating conditions. This study indicated that this combined treatment system exhibited high performance.

Electrical energy per order and current efficiency for electrochemical oxidation of p-chlorobenzoic acid with boron-doped diamond anode

Electrochemical oxidation (EO) is an advanced oxidation process for water treatment to mineralize organic contaminants. While proven to degrade a range of emerging pollutants in water, less attention has been given to quantify the effect of operational variables such applied current density and pollutant concentration on efficiency and energy requirements. Particular figures of merit were mineralization current efficiency (MCE) and electrical energy per order (E_EO). Linear increases of applied current exponentially decreased the MCE due to the enhancement of undesired parasitic reactions that consumed generated hydroxyl radical. E_EO values ranged from 39.3 to 331.8 kW h m^-3 order^-1. Increasing the applied current also enhanced the E_EO due to the transition from kinetics limited by current to kinetics limited by mass transfer. Further increases in current did not influence the removal rate, but it raised the E_EO requirement. The E_EO requirement diminished when decreasing initial pollutant loading with the increase of the apparent kinetic rate because of the relative availability of oxidant per pollutant molecule in solution at a defined current. Oxidation by-products released were identified, and a plausible degradative pathway has been suggested.

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).