Dimensional Stable Lead Electrode Modified by SDS for Efficient Degradation of Bisphenol A

Robust PbO2 modified by co-deposition of ZrO2 nanoparticles for efficient degradation of ceftriaxone sodium

In recent years, PbO2 electrodes have received widespread attention due to their high oxygen evolution reaction (OER) activity. However, due to the brittle nature of the plating layer, it is easy to cause the active layer to fall off. Pb2+ will leach out with the electrochemical process causing secondary pollution. The starting point of this study is established to improve the stability and adhesion of the electrode coating. Electrochemical oxidation technology has the characteristics of high treatment efficiency, wide range of applications, and non-polluting environment. In this study, conventional PbO2 electrodes were modified by using co-deposition of ZrO2 nanoparticles. In addition, α-PbO2 was added to increase the stability of the electrodes. At a high current density of 1 A/cm2, the accelerated life of the pure PbO2 electrode is 648 h, the accelerated life of the PbO2-ZrO2 electrode is 1.37 times that of the pure PbO2, and the electrode with an added α-PbO2 layer is 1.69 times that of the pure PbO2 electrode. The amount of dissolved Pb2+ was only 29% of that of pure PbO2. The electrochemical performance of the electrode is evaluated by studying the degradation effect of ceftriaxone sodium (CXM). The addition of ZrO2 nanoparticles alters the particle size and deposition content of PbO2, leading to a unique crystal structure distinct from pure PbO2. Compared to conventional PbO2 electrodes, the PbO2-ZrO2 can remove chemical oxygen demand (COD) and pollutants more efficiently, removing for 59% increased by 38.47%. Therefore, PbO2-ZrO2 is of great value in the field of electrochemical degradation of industrial pollutants.

Development of SDS-Modified PbO2 Anode Material Based on Ti3+ Self-Doping Black TiO2NTs Substrate as a Conductive Interlayer for Enhanced Electrocatalytic Oxidation of Methylene Blue

Efficient and stable electrode materials are urgently required for wastewater treatment in the electrocatalytic degradation of toxic and refractory organic pollutants. Ti3+ self-doping black TiO2 nanotube arrays (Ti/B-TiO2-NTs) as an interlayer were used for preparing a novel PbO2 electrode via an electrochemical reduction technology, and a sodium dodecyl sulfate (SDS)-modified PbO2 catalytic layer was successfully achieved via an electrochemical deposition technology. The physicochemical characterization tests showed that the Ti/B-TiO2-NTs/PbO2-SDS electrodes have a denser surface and finer grain size with the introduction of Ti3+ in the interlayer of Ti/TiO2-NTs and the addition of SDS in the active layer of PbO2. The electrochemical characterization results showed that the Ti3+ self-doping black Ti/TiO2-NTs/PbO2-SDS electrode had higher oxygen evolution potential (2.11 V vs. SCE), higher electrode stability, smaller charge-transfer resistance (6.74 Ω cm-2), and higher hydroxyl radical production activity, leading to it possessing better electrocatalytic properties. The above results indicated that the physicochemical and electrochemical characterization of the PbO2 electrode were all enhanced significantly with the introduction of Ti3+ and SDS. Furthermore, the Ti/B-TiO2-NTs/PbO2-SDS electrodes displayed the best performance on the degradation of methylene blue (MB) in simulated wastewater via bulk electrolysis. The removal efficiency of MB and the chemical oxygen demand (COD) could reach about 99.7% and 80.6% under the optimal conditions after 120 min, respectively. The pseudo-first-order kinetic constant of the Ti/B-TiO2-NTs/PbO2-SDS electrode was 0.03956 min-1, which was approximately 3.18 times faster than that of the Ti/TiO2-NTs/PbO2 electrode (0.01254 min-1). In addition, the Ti/B-TiO2-NTs/PbO2-SDS electrodes showed excellent stability and reusability. The degradation mechanism of MB was explored via the experimental identification of intermediates. In summary, the Ti3+ self-doping black Ti/TiO2-NTs/PbO2-SDS electrode is a promising electrode in treating wastewater.

Electrochemical degradation of indigo carmine, P-nitrosodimethylaniline and clothianidin on a fabricated Ti/SnO2-Sb/Co-βPbO2 electrode: Roles of radicals, water matrices effects and performance

In this study, the kinetic degradation of several typical organic pollutants was performed on a synthetic electrode (Ti/SnO₂-Sb/Co-βPbO₂). The surface structure and the electrochemical properties of the prepared electrode were investigated, confirming the successful preparation of the electrode using an electrochemical deposition method. The outer layer (Co-βPbO₂) played an important role in reducing the resistance of the electrode and improving its degradation efficiency. The results showed that indigo carmine (IC), p-nitrosodimethylaniline (RNO), and clothianidin (CLO) were effectively degraded within 20 min of electrolysis. Their degradation in the electrochemical process followed the first-order kinetic model with the degradation rate constant of IC being higher than that of RNO and CLO. This was proved by the difference in the reactivity of the target pollutants toward oxidizing radicals (i.e., •OH, SO₄^•-, and Cl•). Their second-order rate constant towards radicals were in the range of 10⁹ - 10¹⁰ M^-1 s^-1 with the highest value being that for IC: k_·OH,IC = 15.1 × 10⁹ M^-1 s^-1 and [Formula: see text]  = 7.4 × 10⁹ M^-1 s^-1. The study calculated the contribution of some oxidizing species, including direct electron transfer (DET), •OH, SO₄^•-, and other reactive oxygen species (ROS). Solution pH, supporting electrolyte, and water matrix affected the degradation efficiency of pollutants and the contribution of the oxidizing species. Br^- and I^- ions enhanced the degradation rate of organic pollutants, while Fe²⁺, HCO₃^-, and humic acid (HA) reduced it. In addition, the toxicity, total organic carbon (TOC) removal, mineralization current efficiency (MCE), energy consumption, recyclability and stability of the prepared electrode were studied, suggesting that the prepared Ti/SnO₂-Sb/Co-βPbO₂ is a good candidate for treating organic pollutants using the electrochemical oxidation process.

Optimized Mo-doped IrOx anode for efficient degradation of refractory sulfadiazine

Electrochemical advanced oxidation processes (EAOPs) is considered to be an efficacious method to degrade antibiotics. However, the performance of the anode has become the main limiting factor of this technology. In this study, due to the electron-deficient characteristics and the improvement of OER performance of Mo, we chose to use thermal decomposition to incorporate Mo into IrO₂ to prepare anodes with industrial applicability. Under the optimal ratio of Ir to Mo is 7:3, (Ir_0.7Mo_0.3)O_x electrode's particular pore structure can expose more active sites and create a channel for the transportation of electrons, thereby promoting the formation of free radicals and degrading pollutants more efficiently. (Ir_0.7Mo_0.3)O_x electrode also has a higher mass activity (6.332 A g^-1, three times that of the IrO₂ electrode) and a larger electrochemical active area (ECSA, 375.43 cm², seven times that of the IrO₂ electrode). In addition, the optimal conditions of (Ir_0.7Mo_0.3)O_x electrode for degrading sulfadiazine(SDZ) were explored, which achieved a higher removal than traditional electrodes (90% removal within 4 h) when the Ti plate was the substrate. Through the intermediate products of SDZ degradation and related literatures, two possible degradation pathways of SDZ were speculated. This research provides a new type of anode catalyst for the degradation of sulfonamide antibiotics, which is possible for industrial application.

Electrocatalytic synthesis of adipic acid coupled with H2 production enhanced by a ligand modification strategy

Adipic acid is an important building block of polymers, and is commercially produced by thermo-catalytic oxidation of ketone-alcohol oil (a mixture of cyclohexanol and cyclohexanone). However, this process heavily relies on the use of corrosive nitric acid while releases nitrous oxide as a potent greenhouse gas. Herein, we report an electrocatalytic strategy for the oxidation of cyclohexanone to adipic acid coupled with H₂ production over a nickel hydroxide (Ni(OH)₂) catalyst modified with sodium dodecyl sulfonate (SDS). The intercalated SDS facilitates the enrichment of immiscible cyclohexanone in aqueous medium, thus achieving 3.6-fold greater productivity of adipic acid and higher faradaic efficiency (FE) compared with pure Ni(OH)₂ (93% versus 56%). This strategy is demonstrated effective for a variety of immiscible aldehydes and ketones in aqueous solution. Furthermore, we design a realistic two-electrode flow electrolyzer for electrooxidation of cyclohexanone coupling with H₂ production, attaining adipic acid productivity of 4.7 mmol coupled with H₂ productivity of 8.0 L at 0.8 A (corresponding to 30 mA cm⁻²) in 24 h.

Adipic acid is an important building block of polymers, although its production relies on harmful reagents. Here, authors examined surfactant-modified nickel hydroxide for adipic acid electrosynthesis coupled with hydrogen gas evolution.

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.

Electrochemical oxidation of chloramphenicol with lead dioxide-surfactant composites

The PbO₂ -2 wt.% sodium dodecyl sulfate composite formed from methanesulfonate electrolyte consists of 93.1% of α-phase PbO₂ in contrast to the similar one synthesized from nitrate electrolyte, which contains 73.3% of β phase. The electrocatalytic activity of the obtained composites in the oxygen evolution reaction and oxidation of chloramphenicol was investigated. It was found that the Tafel slope significantly exceeds the theoretical value, which indicates a decrease in the degree of filling of the electrode surface with oxygen-containing particles. In the presence of organic compound and chloride ions in the solution, irreversible adsorption of the intermediate is observed, which leads to additional blocking of active centers on the oxide surface, which are involved in the oxidation of organic substance. It was established that the maximum rate of chloramphenicol conversion is 83.5% and 85% at 50 and 80 mA cm^-2 , respectively, under kinetic control. The heterogeneous oxidation rate constant of chloramphenicol is 0.0035 min^-1 . Oxidation of chloramphenicol occurs through the formation of 4-(-2-amino-1,3-dihydroxy-propanyl)-nitrobenzene with cleavage of dichloroacetic acid. Next, the amino group is oxidized to the nitro group to form 4-(2-nitro-1,3-dihydroxy-propanyl)-nitrobenzene. Subsequent electrolysis produces nitrobenzoic acid, which is oxidized to benzoic acid, later hydroquinone, then benzoquinone and a set of aliphatic compounds. PRACTITIONER POINTS: The PbO₂ -2 wt.% SDS composite consists of 93.1% of α phase of PbO₂ in contrast to those synthesized from nitrate electrolyte. The Tafel slope indicates a decrease of surface filling with oxygen-containing particles. Irreversible adsorption of the intermediate is observed in the presence of chloride ions.