Electroanalytical investigations on electrodeposited lead dioxide

Ti/PbO2 Electrode Efficiency in Catalytic Chloramphenicol Degradation and Its Effect on Antibiotic Resistance Genes

Livestock farming has led to the rapid accumulation of antibiotic resistance genes in the environment. Chloramphenicol (CAP) was chosen as a model compound to investigate its degradation during electrochemical treatment. Ti/PbO₂ electrodes were prepared using electrodeposition. The prepared Ti/PbO₂-La electrodes had a denser surface and a more complete PbO₂ crystal structure. Ti/PbO₂-Co electrodes exhibited improved electrochemical catalytic activity and lifetime in practice. The impact of different conditions on the effectiveness of CAP electrochemical degradation was investigated, and the most favorable conditions were identified (current density: I = 15.0 mA/cm, electrolyte concentration: c = 0.125 mol/L, solution pH = 5). Most importantly, we investigated the effects of the different stages of treatment with CAP solutions on the abundance of resistance genes in natural river substrates (intI1, cmlA, cmle3, and cata2). When CAP was completely degraded (100% TOC removal), no effect on resistance gene abundance was observed in the river substrate; incomplete CAP degradation significantly increased the absolute abundance of resistance genes. This suggests that when treating solutions with antibiotics, they must be completely degraded (100% TOC removal) before discharge into the environment to reduce secondary pollution. This study provides insights into the deep treatment of wastewater containing antibiotics and assesses the environmental impact of the resulting treated wastewater.

Co/La modified Ti/PbO2 anodes for chloramphenicol degradation: Catalytic performance and reaction mechanism

Chloramphenicol (CAP) is widely used in daily life, and its abuse hurts human health, so a suitable method is needed to solve the problem. In this study, the Ti/PbO₂ electrodes prepared by the electroplating method were characterized. The CAP degradation effect and mechanism were investigated. It was shown that the electrode surface had a dense plating with a characteristic peak of β-PbO₂ as the active component. The electrode had an oxygen precipitation potential of 1.695 V and a corrosion potential of 0.553 V, and a long service life (505.4 d). The degradation of CAP at Ti/PbO₂ electrode followed a first-order kinetic reaction. The optimal degradation conditions (current density of 12.97 mA cm^-2, electrolyte concentration of 50 mM, and solution pH of 6.38) were obtained by the response surface curve method. The degradation rate of CAP was 99.0% at 60 min. The results showed that the reactive groups leading to CAP degradation were mainly ·OH and SO₄^2-, and only a tiny portion of CAP was directly oxidized on the electrode surface. The addition of Cl^- favored the degradation of CAP, but reduced the mineralization rate. LC-MS analysis showed that ·OH mainly attacked the asymmetric centers (C1, C2) of weakly bound hydrogen atoms, resulting in underwent addition and substitution reactions. CAP was converted into two substances with m/z = 306 and m/z = 165. Finally, inorganic substances such as CO₂ and H₂O were generated. This study provided a new idea for preparing Ti/PbO₂ electrode with high performance and the safe and efficient degradation of CAP.

Coupling anodic oxidation, biosorption and alternating current as alternative for wastewater purification

Anodic oxidation process is considered as an effective solution for the treatment of refractory effluents. Its performance is strongly depending on the stability of the anodes used during the process. For this reason, we aim to enhance the stability of the SS/PbO₂ anodes electrodeposited by pulsed current while studying their performance for the anodic oxidation of methylene blue and industrial textile wastewater. The basic idea deals with the possibility to replace the expensive alternatives used for reinforcing the steadiness of the anodes during the anodic oxidation by a simple method based on coupling electrochemical oxidation with biosorption by vegetable material (Luffa cylindrica). The performance of the coupling process was optimized based on its performance in colored and industrial wastewater depollution. Results confirmed the efficiency of the coupling process where 98.7 and 80.02% of methylene blue were removed, respectively, after 60 and 120 min for alternating and direct current. Otherwise, 62.84 and 46.87% of methylene blue were removed by anodic oxidation, respectively, after 120 and 180 min for alternating and direct current. The % COD obtained for the anodic oxidation and the coupling process reached 57.45, 33.61, 91.32 and 75.48% respectively for alternating and direct current. The use of alternating current for both processes has enhanced the speed and the efficiency. Atomic absorption analysis has confirmed that the rates obtained of Pb²⁺ complied with those allowed by the Standards. LC/MS analysis allowed the identification of by-products generated and the germination tests proved the reuse of the treated water.

Use of alternating current for colored water purification by anodic oxidation with SS/PbO2 and Pb/PbO2 electrodes

This paper suggests a new alternative for the acceleration of dye removal by adopting alternating current instead of direct current in the treatment of methylene blue solutions and industrials effluents, using anodic oxidation on Pb/PbO₂ and stainless steel (SS)/PbO₂ anodes. A comparative study of the influence of electrolyte support (NaCl, NaNO₃, and Na₂SO₄) on the anodic oxidation performance and the anode stability was performed. The best results were obtained in presence of NaCl where the color removal percentage reached about 80.13% and 55.8%, for Pb/PbO₂ anodes, and 89.5% and 60.4% for the SS/PbO₂ anodes for alternating and direct current, respectively. Treatment in alternating current conditions enhanced the removal speed. Atomic absorption analysis confirmed the decrease of the release of (Pb²⁺) ions to much lower values compared with direct current and to those allowed by the Standards. LC/MS and phytotoxicity analyses confirmed the non-toxicity of the generated by-products during the anodic oxidation of methylene blue and the possibility of the reuse of the treated water.

Temperature effects on the kinetics of a PbO2 electrosynthesis process in an alkaline bath

An electrochemical investigation of temperature on the electrosynthesis of lead dioxide in alkaline solutions was performed using a rotating disk electrode (RDE).

High-performance Ti/Sb-SnO(2)/Pb(3)O(4) electrodes for chlorine evolution: preparation and characteristics

Chlorine evolution via electrochemical approach has wide application prospects in drinking water disinfection and wastewater treatment fields. Dimensional stable anodes used for chlorine evolution should have high stability and adequate chlorine evolution efficiency. Thus a novel and cost-effective Ti/Sb-SnO(2)/Pb(3)O(4)electrode was developed. The physicochemical and electrochemical properties as well as the chlorine evolution performances of the electrodes were investigated. The electrocatalytic activity and deactivation course of the electrodes were also explored. Results showed that this novel electrode had strong chlorine evolution ability with high current efficiency ranging from 87.3% to 93.4% depending on the operational conditions. The accelerated service life of Ti/Sb-SnO(2)/Pb(3)O(4) electrode could reach 180 h at a current density of 10,000 A m(-2) in 0.5 molL(-1) H(2)SO(4). During the electrolysis process, it was found that the conversion of Pb(3)O(4) into β-PbO(2) happened gradually on the electrode surface, which not only inhibited the leakage of hazardous Pb(2+) ion but also increased the anti-corrosion capacity of the electrode effectively.

Preparation and characterization of nano-structured lead oxide from spent lead acid battery paste

As part of contribution for developing a green recycling process of spent lead acid battery, a nanostructural lead oxide was prepared under the present investigation in low temperature calcination of lead citrate powder. The lead citrate, the precursor for preparation of this lead oxide, was synthesized through leaching of spent lead acid battery paste in citric acid solution. Both lead citrate and oxide products were characterized by means of thermogravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), and scanning electron microscope (SEM). The results showed that the lead citrate was sheet-shape crystal of Pb(C(6)H(6)O(7)) · H(2)O. When the citrate was calcined in N(2) gas, β-PbO in the orthorhombic phase was the main product containing small amount of Pb and C and it formed as spherical particles of 50-60 nm in diameter. On combusting the citrate in air at 370°C (for 20 min), a mixture of orthorhombic β-PbO, tetragonal α-PbO and Pb with the particle size of 100-200 nm was obtained, with β-PbO as the major product. The property of the nanostructural lead oxide was investigated by electrochemical technique, such as cyclic voltammetry (CV). The CV measurements presented the electrochemical redox potentials, with reversibility and cycle stability over 15 cycles.

Sonochemical-assisted synthesis of nano-structured lead dioxide

PbO(2) nano-powder was synthesized by the ultrasonic irradiation of an aqueous suspension of dispersed beta-PbO, as precursor, in the presence of ammonium peroxydisulfate as an oxidant. The reaction rate increased with an increase in temperature and ammonium peroxydisulfate concentration. In the presence of ammonium peroxydisulfate, the increased concentration of hydroxyl radical facilitated the oxidation of beta-PbO to PbO(2) under ultrasonic irradiation. The PbO(2) nano-powder was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the applied ultrasonic wave determines the particle size. PbO(2) samples prepared under optimized experimental conditions have lead dioxide particles in the range of 50-100 nm, as shown by SEM. The XRD results reveal that only beta-PbO(2) is formed under optimum conditions. When the reaction mixture was stirred instead of ultrasonically irradiated, only a fraction of the lead oxide was converted to lead dioxide, and lead sulfate was the main reaction product.