Electrochemical degradation of aspirin using a Ni doped PbO2 electrode

Energetic evaluation of phenol wastewater treatment by reverse electrodialysis reactor using different anodes

Efficient electrode materials are essential to convert salinity gradient energy into oxidative degradation energy and electrical energy by reverse electrodialysis reactor (REDR). In this context, comparative experiments of REDR using different anodes (Ti/IrO₂-RuO₂, Ti/PbO₂ and Ti/Ti₄O₇) were conducted. The effects of output current and electrode rinse solution (ERS) flowrate on mineralization efficiency and energy output were discussed. Results demonstrated that the COD removal rate(η_COD) rose almost linearly with output current and ERS flowrate when using Ti/Ti₄O₇ anode, but excessive operating conditions caused a slow increase or even decrease of η_COD when using Ti/IrO₂-RuO₂ or Ti/PbO₂ anodes. The order of electrode system potential loss (E_ele) for the three anodes was Ti/Ti₄O₇> Ti/PbO₂> Ti/IrO₂-RuO₂. High E_ele was beneficial to η_COD but had a negative effect on the net output power (P_net) of REDR. Regardless of the applied anodes, increasing the current and decreasing the ERS flowrate was detrimental to P_net due to higher E_ele. Based on these findings, four energy efficiency parameters were defined to evaluate energy recovery from multiple perspectives by linking energy output with mineralization capacity. They were electrode efficiency (η_ele), energy efficiency (EE), general current efficiency (GCE) and energy consumption (EC), respectively. Results showed that REDR with Ti/Ti₄O₇ anodes and suitable operating conditions achieved the optimal energy indicators and mineralization efficiency, which provided an efficient and economical option for wastewater treatment and energy recovery.

Mechanism of highly efficient electrochemical degradation of antibiotic sulfadiazine using a layer-by-layer GNPs/PbO2 electrode

A PbO₂ electrode integrating electrocatalytic and adsorptive functions was successfully fabricated by embedding layer-by-layer graphene nanoplatelets (GNPs) into β-PbO₂ active layer (GNPs/PbO₂) and employed as anode for high-efficient removal of sulfadiazine (SDZ). In electrochemical degradation experiments, SDZ was quickly enriched on the surface of GNPs/PbO₂ film via adsorption and then oxidized by ⋅OH in-site. In terms of the electrocatalytic performance and adsorption of electrode, the optimal electrodeposition time for each β-PbO₂ outer layer was 4 min (GNPs/PbO₂-4). Compared with conventional PbO₂ electrode, the layer-by-layer GNPs resulted in the smaller crystal size and denser surface of PbO₂ electrode, thus facilitating the generation of active oxygen species. At the same time, the specific surface area, oxygen evolution potential (OEP) of the anode were enhanced and the charge-transfer resistance was reduced. For GNPs/PbO₂-4 anode, the optimal conditions of electrochemical oxidation of SDZ were identified as initial pH 9, 50 mg/L of SDZ and 20 mA/cm² of current density using response surface methodology (RSM), 98.15% of SDZ could be removed in this case. The contribution of radical oxidation and non-radical oxidation to SDZ removal was about 79% and 21%, respectively. Moreover, the reaction pathways of SDZ on the GNPs/PbO₂-4 electrode involving hydroxylation, radical reaction and ring cleavage were speculated. Finally, the continuous SDZ degradation and accelerated service lifetime test suggested that the GNPs/PbO₂-4 electrode was shown to be stable and repeatable, and the Pb²⁺ concentration was measured to ensure the safety of the treated solution. Consequently, the above findings provide an innovative way to design and prepare an effective and stable PbO₂ electrode for electrochemical degradation of antibiotic wastewater.

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.

Robust and Self-Cleaning Electrochemical Production of Periodate

Periodate, a platform oxidizer, can be electrochemically recycled in a self-cleaning process. Electrosynthesis of periodate is well established at boron-doped diamond (BDD) anodes. However, recovered iodate and other iodo species for recycling can contain traces of organic impurities from previous applications. For the first time, it was shown that the organic impurities do not hamper the electrochemical re-oxidation of used periodate. In a hydroxyl-mediated environment, the organic compounds form CO₂ and H₂ O during the degradation process. This process is often referred to as "cold combustion" and provides orthogonal conditions to periodate synthesis. To demonstrate the strategy, different dyes, pharmaceutically active ingredients, and iodine compounds were added as model contaminations into the process of electrochemical periodate production. UV/Vis spectroscopy, NMR spectroscopy, and mass spectrometry (MS) were used to monitor the degradation of organic molecules, and liquid chromatography-MS was used to control the purity of periodate. As a representative example, dimethyl 5-iodoisophthalate (2 mm), was degraded in 90, 95, and 99 % while generating 0.042, 0.054, and 0.082 kilo equiv. of periodate, respectively. In addition, various organic iodo compounds could be fed into the periodate generation for upcycling such iodo-containing waste, for example, contrast media.

Hydroxyl radicals in anodic oxidation systems: generation, identification and quantification

Anodic oxidation has emerged as a promising treatment technology for the removal of a broad range of organic pollutants from wastewaters. Hydroxyl radicals are the primary species generated in anodic oxidation systems to oxidize organics. In this review, the methods of identifying hydroxyl radicals and the existing debates and misunderstandings regarding the validity of experimental results are discussed. Consideration is given to the methods of quantification of hydroxyl radicals in anodic oxidation systems with particular attention to approaches used to compare the electrochemical performance of different anodes. In addition, we describe recent progress in understanding the mechanisms of hydroxyl radical generation at the surface of most commonly used anodes and the utilization of hydroxyl radical in typical electrochemical reactors. This review shows that the key challenges facing anodic oxidation technology are related to i) the elimination of mistakes in identifying hydroxyl radicals, ii) the establishment of an effective hydroxyl radical quantification method, iii) the development of cost effective anode materials with high corrosion resistance and high electrochemical activity and iv) the optimization of electrochemical reactor design to maximise the utilization efficiency of hydroxyl radicals.

Electrochemical Ni-EDTA degradation and Ni removal from electroless plating wastewaters using an innovative Ni-doped PbO2 anode: Optimization and mechanism

In this work, a novel Ni-doped PbO₂ anode (Ni-PbO₂) was prepared via a co-electrodeposition method and used to remove Ni-ethylenediaminetetraacetic acid (Ni-EDTA) from solutions typical of electroless nickel plating wastewater. Compared with a pure PbO₂ electrode, Ni doping increased the oxygen evolution potential as well as the reactive surface area and reactive site concentration and reduced the electron transfer resistance thereby resulting in superior Ni-EDTA degradation performance. The 1% Ni-doped PbO₂ electrode exhibited the best electrochemical oxidation activity with a Ni-EDTA removal efficiency of 96.5 ± 1.2%, a Ni removal efficiency of 52.1 ± 1.4% and an energy consumption of 2.6 kWh m^-3. Further investigations revealed that 1% Ni doping enhanced both direct oxidation and hydroxyl radical mediated oxidation processes involved in Ni-EDTA degradation. A mechanism for Ni-EDTA degradation is proposed based on the identified products. The free nickel ion concentration initially increased as a result of the degradation of Ni-EDTA complexes and subsequently decreased as a consequence of nickel electrodeposition on the cathode surface. Further characterization of the cathode deposits by X-ray diffraction and X-ray photoelectron spectra indicated that the deposition products were a mixture of Ni⁰, NiO and Ni(OH)₂ with elemental Ni accounting for roughly 80% of the deposited nickel. Results of this study pave the way for the application of anodic oxidation processes for efficient degradation of Ni-containing complexes and recovery of Ni from nickel-containing wastewaters.

Co/Sm-modified Ti/PbO2 anode for atrazine degradation: Effective electrocatalytic performance and degradation mechanism

In this work, Ti/PbO₂-Co-Sm electrode has been successfully prepared using electrodeposition and further applied for the electrocatalysis of atrazine (ATZ) herbicide wastewater. As expected, Ti/PbO₂-Co-Sm electrode displays highest oxygen evolution potential, lowest charge transfer resistance, longest service lifetime and most effective electrocatalytic activity compared with Ti/PbO₂, Ti/PbO₂-Sm and Ti/PbO₂-Co electrodes. Orthogonal and single factor experiments are designed to optimize the condition of ATZ degradation. The maximum degradation efficiency of 92.6% and COD removal efficiency of 84.5% are achieved in electrolysis time 3 h under the optimum condition (current density 20 mA cm^-2, Na₂SO₄ concentration 8.0 g L^-1, pH 5 and temperature 35 °C). In addition, Ti/PbO₂-Co-Sm electrode exhibits admirable recyclability in degradation progress. The degradation of ATZ is accomplished by indirect electrochemical oxidation and ∙OH is tested as the main active substance in ATZ oxidation. The possible degradation mechanism of ATZ has been proposed according to the degradation intermediates detected by LC-MS. This research suggests that Ti/PbO₂-Co-Sm is a promising electrode for ATZ degradation.

A Novel Porous Ni, Ce-Doped PbO2 Electrode for Efficient Treatment of Chloride Ion in Wastewater

The porous Ti/Sb-SnO2/Ni-Ce-PbO2 electrode was prepared by using a porous Ti plate as a substrate, an Sb-doped SnO2 as an intermediate, and a PbO2 doped with Ni and Ce as an active layer. The surface morphology and crystal structure of the electrode were characterized by scanning electron microscope(SEM), energy dispersive spectrometer(EDS), and X-Ray diffraction(XRD). The electrochemical performance of the electrodes was tested by linear sweep voltammetry (LSV), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and electrode life test. The results show that the novel porous Ni-Ce-PbO2 electrodes with larger active surface area have better electrochemical activity and longer electrode life than porous undoped PbO2 electrodes and flat Ni-Ce-PbO2 electrodes. In this work, the removal of Cl− in simulated wastewater on three electrodes was also studied. The results show that the removal effect of the porous Ni-Ce-PbO2 electrode is obviously better than the other two electrodes, and the removal rate is 87.4%, while the removal rates of the other two electrodes were 72.90% and 80.20%, respectively. In addition, the mechanism of electrochemical dechlorinating was also studied. With the progress of electrolysis, we find that the increase of OH- inhibits the degradation of Cl−, however, the porous Ni-Ce-PbO2 electrode can effectively improve the removal of Cl−.

The "Green" Electrochemical Synthesis of Periodate

High-grade periodate is relatively expensive, but is required for many sensitive applications such as the synthesis of active pharmaceutical ingredients. These high costs originate from using lead dioxide anodes in contemporary electrochemical methods and from expensive starting materials. A direct and cost-efficient electrochemical synthesis of periodate from iodide, which is less costly and relies on a readily available starting material, is reported. The oxidation is conducted at boron-doped diamond anodes, which are durable, metal-free, and nontoxic. The avoidance of lead dioxide ultimately lowers the cost of purification and quality assurance. The electrolytic process was optimized by statistical methods and was scaled up in an electrolysis flow cell that enhanced the space-time yields by a cyclization protocol. An LC-PDA analytical protocol was established enabling simple quantification of iodide, iodate, and periodate simultaneously with remarkable precision.

Electrochemical oxidation of Acid Orange 7 azo dye using a PbO2 electrode: Parameter optimization, reaction mechanism and toxicity evaluation

In this study, electrochemical oxidation of Acid Orange 7 (AO 7) azo dye has been investigated using a Fe-doped PbO₂ electrode. The degradation of AO 7 followed pseudo-first-order reaction kinetics. The removals of AO 7, chemical oxygen demand (COD) and total organic carbon (TOC) were 87.15%, 49.88% and 44.94% after 60 min of electrolysis at the optimal conditions (Na₂SO₄ concentration 0.1 M, initial pH 5, initial AO 7 concentration 100 mg L^-1 and applied current density 20 mA cm^-2), respectively. And the corresponding degradation rate constant was 0.035 min^-1. The intermediates formed during electrochemical process were identified, and a possible degradation pathway was proposed, which was initiated by the oxidation of azo bond (-NN-), hydroxylation and substitution reaction of -NH₂ and -SO₃H under the attack of OH, and ended with the formation of mineralization products such as NH₄⁺, NO₃^-, SO₄^2-, CO₂ and H₂O. The toxicity of treated AO 7 solution towards Vibrio fischeri increased slightly at first and then rapidly reduced to non-toxicity with prolonging time. The results indicate that electrochemical oxidation of AO 7 using Fe-doped PbO₂ electrode is a promising way.

Electrochemical degradation of safranine T in aqueous solution by Ti/PbO2 electrodes

The electrochemical degradation of safranine T (ST) in aqueous solution was studied. The effects of current density, initial concentration of ST, initial pH values, and Na2SO4 concentration on electrocatalytic degradation of ST in the aqueous solution by Ti/PbO2 electrode were analyzed. The experimental results showed that the electrochemical oxidization reaction of ST fitted a pseudo first order kinetics model. By using the Ti/ PbO2 electrode as the anode, 99.96% of ST can be eliminated at 120 min. It means that the electrochemical degradation of ST in aqueous solution by the Ti/PbO2 electrode was very effective. The optimal reaction conditions were as follows: current density, 40 mA cm−2; initial ST concentration, 100 mg L−1; Na2SO4 concentration, 0.20 mol L−1; initial pH, 6. It can be known from the test of UV–vis and HPLC in the reaction process that the intermediates will be generated, and the possible intermediate structure was studied by HPLC–MS test. However, with the progress of degradation reaction, the intermediates will eventually be oxidized into CO2 and H2O. Cyclic voltammetry and fluorescence experiments proved that ST was indirectly oxidized through the generation of hydroxyl radicals. Under the optimal reaction conditions, the energy required to completely remove ST was 17.92 kWh/m3.

From bimetallic PdCu nanowires to ternary PdCu-SnO2 nanowires: Interface control for efficient ethanol electrooxidation

At present, although a large number of palladium-based nanowire electrocatalysts have been prepared, there are few reports on nanowires containing rich metal oxides. Herein, porous PdCu alloy nanowires and PdCu-SnO₂ nanowires were prepared by using a galvanic displacement synthesis method. Due to their one-dimensional structure, rough surfaces with non-homogeneous edges, electronic effect, and the advanced PdCu/SnO₂ interface of the as-synthesized PdCu-SnO₂ nanowire catalysts, they exhibited a mass activity of 7770.0 mA mg^-1 towards ethanol oxidation, which was 7.6-fold higher than that of Pd/C catalysts (1025.0 mA mg^-1). In addition, they behaved strong durability upon chronoamperometry and continuous cyclic voltammetry tests. The electrochemical measurements demonstrated that SnO₂ was introduced into the PdCu/SnO₂ interface, which promoted the oxidation of ethanol at a lower potential and accelerated the oxidation of Pd-CO_ads via SnO₂-OH_ads to regenerate the active sites. This research highlights the significance of introducing metal oxides into the nanostructure interface, and the performance of Pd-containing catalysts towards ethanol oxidation reaction was greatly improved.

Differential control of anode/cathode potentials of paired electrolysis for simultaneous removal of chemical oxygen demand and total nitrogen

Paired electrolysis can take advantage of both anodic oxidation and cathodic reduction, and thus improve current efficiency for electrochemical wastewater treatment. In this work, differential control of anode/cathode potentials of paired electrolysis for simultaneous removal of chemical oxygen demand (COD) and total nitrogen (TN, including ammonia, nitrate, and nitrite) was studied. We first determined the optimal potentials for anodic oxidation of COD/NH₄⁺ or cathodic reduction of NO₃^-/NO₂^- (minimization of over-oxidation or over-reduction) by preliminary cyclic voltammetry and constant-potential electrolysis experiments, i.e., 1.6 V for anodic oxidation and -1.26 V for cathodic reduction in this case. The optimal working potential of the cathode was achieved at appropriate current density in the paired electrolysis system, the working potential of the anode was independently controlled by adjusting the ratio of its surface area to that of the cathode. In this way, both the cathode and anode could work under optimal potentials. At an optimized cathodic current density of 5.0 mA cm^-2 and cathode/anode surface area ratio of 2:1, the removal efficiencies of COD and TN from simulated wastewater reached 91.9% and 86.2%, respectively. Additionally, the developed paired electrolysis system was validated by treating an actual pharmaceutical wastewater, results for which showed that a total current efficiency of 84.8% was achieved, which was at least twice as high as that of traditional electrochemical processes.

Electrochemical Oxidation of Para-Aminophenol With Rare Earth Doped Lead Dioxide Electrodes: Kinetics Modeling and Mechanism

In this study, La and Ce doped PbO₂ electrodes were prepared and the characteristic of the electrodes were discussed with the help of structure analysis. The catalytic effects of the doped electrodes were explored through the degradation of para-aminophenol wastewater. The results showed that the para-aminophenol removal was 96.96%, 89.34%, and 77.55% after 180 min treatment with Ce-PbO₂, La-PbO₂, and PbO₂, respectively. The para-aminophenol enhanced degradation mechanism was discussed with rare earth element doping electrodes and a kinetic model was established based on radical reactions mechanism with genetic algorithm (GA) calculation. The reaction constants of these electrodes were calculated and the results showed that the reaction constant of Ce-PbO₂ electrode was the highest, which indicated that Ce-PbO₂ electrode could have a better treatment effect. The EE/O was used as the index of energy consumption efficiency and the results were calculated and compared. This paper could provide basic data and technique reference of the prediction the oxidation reaction process of different electrodes for the electrochemical oxidation application in wastewater treatment.

Enhanced oxidation potential of Ti/SnO2-Cu electrode for electrochemical degradation of low-concentration ceftazidime in aqueous solution: Performance and degradation pathway

In order to develop an efficient electrode to remove pharmaceutical and personal care products from wastewater, copper and antimony doped Ti/SnO₂ electrode were prepared by thermal decomposition. Electrochemical characterization was undertaken on Ti/SnO₂-Cu using cyclic voltammetry and linear sweep voltammetry, indicating an ultra-high 2.1 V of oxygen evolution potential, better stability, and superior corrosion resistance rather than traditional Ti/SnO₂-Sb electrode. Competitive degradation experiments showed more efficient removal rate was achieved on Ti/SnO₂-Cu electrode, which could remove more than 90% ceftazidime within 60 min. The microstructure and crystal orientation of the modified electrodes were investigated by scanning electron microscopy, which indicated that the crystal of the Ti/SnO₂-Cu electrode grew in more porous and uniform condition, covered with closely arranged layers of the coating. X-ray photoelectron spectroscopy and X-ray diffractions suggested that Cu₂O was successfully coated on the Ti/SnO₂-Cu electrode surface. The operating parameters of electrochemical degradation process were also investigated, including current density, initial concentration, electrode distance, stirring rate and supporting electrolyte. Consequently, the intermediate products of electrochemical degradation were monitored by liquid chromatography-mass spectrometry and a major degradation pathway was proposed.

Ti/PbO2-Sm2O3 composite based electrode for highly efficient electrocatalytic degradation of alizarin yellow R

In this work, a novel Ti/PbO₂-Sm₂O₃ composite electrode with high electrocatalytic activity is successfully fabricated via simple electrodeposition method and further investigated for electrochemical degradation of alizarin yellow R (AYR) wastewater. The test results of X-ray diffraction, field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy confirm that Sm₂O₃ is successfully composited with PbO₂. The coating of Ti/PbO₂-Sm₂O₃ composite electrode stacked by typical pyramid-like micro-particles exhibits smooth and compact surface morphology which is conducive to enhancing the corrosion resistance of electrode. Furthermore, electrochemical performance tests indicate that Ti/PbO₂-Sm₂O₃ composite electrode has advantages of higher oxygen evolution potential, lower charge transfer resistance and longer lifetime over Ti/PbO₂ electrode. Electrolyte concentration, plate space, initial pH and cell voltage are assessed to optimize the degradation condition of AYR. The results show that COD removal efficiency and degradation efficiency of AYR on Ti/PbO₂-Sm₂O₃ composite electrode reach up to 79.90% and 80.00% under the optimal conditions (Na₂SO₄ electrolyte concentration 9.0 g L^-1, plate space 3.0 cm, initial pH 5, cell voltage 3.0 V and electrolysis time 150 min), respectively. The degradation of AYR follows pseudo-first-order reaction kinetics, and a plausible mineralization pathway of AYR is proposed on the basis of the identification of major intermediate products. These results suggest that Ti/PbO₂-Sm₂O₃ composite electrode is a promising candidate for electrocatalytic degradation of AYR wastewater.

A Broad-Spectrum Sweet Taste Sensor Based on Ni(OH)₂/Ni Electrode

A broad-spectrum sweet taste sensor based on Ni(OH)₂/Ni electrode was fabricated by the cyclic voltammetry technique. This sensor can be directly used to detect natural sweet substances in 0.1 M NaOH solution by chronoamperometry method. The current value measured by the sensor shows a linear relationship with the concentration of glucose, sucrose, fructose, maltose, lactose, xylitol, sorbitol, and erythritol (R² = 0.998, 0.983, 0.999, 0.989, 0.985, 0.990, 0.991, and 0.985, respectively). Moreover, the characteristic value of this sensor is well correlated with the concentration and relative sweetness of eight sweet substances. The good correlation between the characteristic value of six fruit samples measured by the sensor and human sensory sweetness measured by sensory evaluation (correlation coefficient = 0.95) indicates that it can reflect the sweetness of fruits containing several sweet substances. In addition, the sensor also exhibits good long-term stability over 40 days (signal ratio fluctuation ranges from 91.5% to 116.2%). Thus, this broad-spectrum sensor is promising for sweet taste sensory application.

Hydrophobic networked PbO2 electrode for electrochemical oxidation of paracetamol drug and degradation mechanism kinetics

A hydrophobic networked PbO₂ electrode was deposited on mesh titanium substrate and utilized for the electrochemical elimination towards paracetamol drug. Three dimensional growth mechanism of PbO₂ layer provided more loading capacity of active materials and network structure greatly reduced the mass transfer for the electrochemical degradation. The active electrochemical surface area based on voltammetric charge quantity of networked PbO₂ electrode is about 2.1 times for traditional PbO₂ electrode while lower charge transfer resistance (6.78 Ω cm²) could be achieved on networked PbO₂ electrode. The electrochemical incineration kinetics of paracetamol drug followed a pseudo first-order behavior and the corresponding rate constant were 0.354, 0.658 and 0.880 h^-1 for traditional, networked PbO₂ and boron doped diamond electrode. Higher electrochemical elimination kinetics could be achieved on networked PbO₂ electrode and the performance can be equal to boron doped diamond electrode in result. Based on the quantification of reactive oxidants (hydroxyl radicals), the utilization rate of hydroxyl radicals could reach as high as 90% on networked PbO₂ electrode. The enhancement of excellent electrochemical oxidation capacity towards paracetamol drug was related to the properties of higher loading capacity, enhanced mass transfer and hydrophobic surface. The possible degradation mechanism and pathway of paracetamol on networked PbO₂ electrode were proposed in details accordingly based on the intermediate products.

Highly efficient electro-oxidation catalyst under ultra-low voltage for degradation of aspirin

A novel cryptomelane-Ir (cry-Ir) electrode is prepared for Ir to enter into the cryptomelane (named as cry-Mn) structure and used for aspirin degradation. This catalyst can efficiently reduce the Ir usage from 85 to 34%. Also, the onset potential of cry-Ir is about 1.40 V and the over potential is about 0.34 V at 10 mA cm^-2, indicating that cry-Ir has an excellent oxygen evolution reaction (OER) activity to produce oxidizing species and can decrease electrolytic voltage during the electro-oxidation process. So, the electrical efficiency per log order (EE/O) for cry-Ir electrode is only 5% of PbO₂ electrode, which is the best electrode for organic degradation. Also, cry-Ir has large tunnel size which favors insertion of aspirin molecule into cry-Ir structure and enhances the contact between reactive intermediates and the contaminant. Using cry-Ir as anode, 100% aspirin removal and 55% chemical oxygen demand (COD) removal could be obtained at 4 V. We also compare cry-Ir electrode with IrO₂ and find that IrO₂ anode can only eliminate 20% aspirin under the same condition. As a result, cry-Ir is a promising anode material for organic pollutant degradation. Graphical abstract Aspirin removal after 4h under different voltages. Aspirin removal on IrO₂/Ti-f and cry-Ir/Ti-f after 4h.

OH-initiated transformation and hydrolysis of aspirin in AOPs system: DFT and experimental studies

Advanced oxidation processes (AOPs) are widely used in wastewater treatment of pharmaceutical and personal care products (PPCPs). In this work, the OH-initiated transformation as well as the hydrolysis of a typical PPCPs, aspirin, was investigated using density functional theory (DFT) calculations and laboratory experiments. For DFT calculations, the frontier electron densities and bond dissociation energies were analyzed. Profiles of the potential energy surface were constructed, and all the possible pathways were discussed. Additionally, rate constants for each pathway were calculated with transition state theory (TST) method. UV/H₂O₂ experiments of aspirin were performed and degradation intermediates were identified by UPLC-MS-MS analysis. Different findings from previous experimental works were reported that the H-abstraction pathways at methyl position were dominated and OH-addition pathways on benzene ring were also favored. Meantime, hydroxyl ASA was confirmed as the main stable intermediate. Moreover, it was the first time to use DFT method to investigate the hydrolysis mechanisms of organic ester compound.

Preparation and characterization of a novel porous Ti/SnO2–Sb2O3–CNT/PbO2 electrode for the anodic oxidation of phenol wastewater

Porous Ti/SnO₂–Sb₂O₃–CNT/PbO₂ electrodes were successfully fabricated using a thermal decomposition technique and electro-deposition technologies.