Study on Electrochemical Degradation of Nicosulfuron by IrO2-Based DSA Electrodes: Performance, Kinetics, and Degradation Mechanism

Abstract

The widely used sulfonylurea herbicides have caused negative effects on the environment and human beings. Electrochemical degradation has attracted much attention in the treatment of refractory organic compounds due to its advantage of producing no secondary pollution. Three kinds of IrO2-based dimensionally stable anodes (DSAs) were used to degrade nicosulfuron by a batch electrochemical process. The results showed that a well-distributed crack network was formed on the Ti/Ta2O5-IrO2 electrode and Ti/Ta2O5-SnO2-IrO2 electrode due to the different coefficients of thermal expansion between the Ti substrate and oxide coatings. The oxygen evolution potential (OEP) increased according to the order of Ti/RuO2-IrO2 < Ti/Ta2O5-SnO2-IrO2 < Ti/Ta2O5-IrO2. Among the three electrodes, the Ti/Ta2O5-IrO2 electrode showed the highest efficiency and was chosen as the experimental electrode. Single factor experiments were carried out to obtain the optimum electrolysis condition, shown as follows: currency intensity 0.8 A; electrode spacing 3 cm, electrolyte pH 3. Under the optimum conditions, the degradation of nicosulfuron followed first-order kinetics and was mainly due to indirect electrochemical oxidation. It was a typical diffusion-controlled electrochemical process. On the basis of the intermediate identified by high performance liquid chromatograph-mass spectrometry (HPLC-MS), two possible degradation routes were proposed.

Electrochemical Degradation of Tetracycline Using a Ti/Ta2O5-IrO2 Anode: Performance, Kinetics, and Degradation Mechanism

“…The effects of the initial concentration of TC on electrochemical degradation were shown in Figure 4 d. TC was almost completely degraded at 70 min when the initial concentration was 20 mg/L, suggesting that the speed of the ·OH production was faster than that of the TC diffusion to the electrode surface [ 23 , 25 ]. Thus, the TC degradation on a Ti/Ta 2 O 5 -IrO 2 anode was a diffusion-controlled electrochemical process, which was in agreement with Zhao et al [ 26 , 27 ]. Due to the same galactic conditions, the direct or indirect oxidation processes produced similar concentrations of the electron transfer and reactive groups.…”

“…During the electrochemical process, initial solution pH affects not only the formation of free radicals, but also the existing state of organic matter in the solution. Thus, it is considered as one of the most important factors affecting the degradation process [ 27 , 28 , 30 , 31 ]. As can be seen in Figure 4 e, the optimum pH value was 4.74 and the Ka value was about 2 times higher than that at pH 6.57 and pH 7.78.…”

Mechanism of N,N-dimethylformamide electrochemical oxidation using a Ti/RuO2–IrO2 electrode

“…[19][20][21] Especially, in the processes of treating some refractory organic pollutants in complex wastewater, electrochemical oxidation has been found to exhibit satisfactory removal effect. 22 Electrochemical oxidation is classied into direct and indirect oxidation according to degradation mechanisms. 23 In the direct oxidation process, contaminants are rst adsorbed on the anode surface and then degraded by electron transfer without the generation of intermediate substances.…”

Fabrication and characterization of titanium‐based lead dioxide electrode by electrochemical deposition with Ti4O7 particles

“…Wei, 2019), Sb-SnO 2 electrode (Duan, Hu, Ji, Yang, & Sun, 2018;Shao et al, 2019;Zhang, Xu, He, & Zhang, 2014;Zhang, Shao, Lyu, Tan, & Ren, 2019;Zhou et al, 2019), Ir/Ru electrode (Kaur, Kushwaha, & Singh, 2019a, 2019bZhao, Zhang, Chen, Man, & Jiang, 2019), BDD electrode (Carneiro et al, 2018;Siedlecka et al, 2018;Zhu et al, 2018), noble metal electrode (Fernandes, Santos, Pacheco, Ciríaco, & Lopes, 2014), and graphite electrode (Mu'azu, Al-Yahya, Al-Haj-Ali, & Abdel-Magid, 2016).…”

“…Favorable anode materials are characterized as high stability, great corrosion resistance, good conductivity, strong catalytic activity, and relatively low cost (Shao et al., 2018). The anode types currently reported in literature include PbO 2 electrode (Jia, Kai, Hao, & Wei, 2019), Sb‐SnO 2 electrode (Duan, Hu, Ji, Yang, & Sun, 2018; Shao et al., 2019; Zhang, Xu, He, & Zhang, 2014; Zhang, Shao, Lyu, Tan, & Ren, 2019; Zhou et al., 2019), Ir/Ru electrode (Kaur, Kushwaha, & Singh, 2019a, 2019b; Zhao, Zhang, Chen, Man, & Jiang, 2019), BDD electrode (Carneiro et al., 2018; Siedlecka et al., 2018; Zhu et al., 2018), noble metal electrode (Fernandes, Santos, Pacheco, Ciríaco, & Lopes, 2014), and graphite electrode (Mu’azu, Al‐Yahya, Al‐Haj‐Ali, & Abdel‐Magid, 2016).…”