(Digital Presentation) Electrochemical Degradation of Acrylamide in Industrial Sewage Via a Modified PbO2 Electrode
Authors: Lu Shun 
Published: September 2023

Acrylamide (C3H5NO) (AA) is an important monomer for the synthesis of polyacrylamide, is often used as flocculant, thickener, or moisturizer in industrial production, but it is highly toxic. Once it enters the human body, it can lead to nerve center and liver function disorder, chromosome mutation and even cancer. In industrial production, improper treatment and wanton discharge may result in water and soil pollution, which is harmful to human health. In general, the content of AA should be less than 0.2% and less than 0.05% in direct drinking water, while many factories produce AA above the standard. Thus, it is necessary to find an efficient method to degrade AA.[1]

Advanced oxidation processes (AOP) include photocatalysis, Fenton reaction, and Fenton-like processes, ozone oxidation, and electrochemical catalysis have been used for drinking water treatment. AOP can produce highly active substances like hydroxyl (·OH), quickly and non-selectively combine with and oxidize electron-rich sites on contaminants and decompose contaminants into carbon dioxide and water.[2-4]

In this study, OP-10 and rGO co-doping were used for the first time to modify the PbO2 electrode (Figs. 1a-b).[5] The results showed that rGO was doped into PbO2 with success and improved the OEP of the PbO2 electrode, thus the electrode had better electrochemical performance and more active sites. The degradation experiments on AA showed that the OP-10&rGO-PbO2 electrode was more effective in degrading AA with a removal rate of 91%, which was 1.5 times higher compared to the PbO2 electrode (Figs. 1c-d). The practical application and evaluation of a dye wastewater pair electrode showed that OP-10&rGO-PbO2 electrode can discolor all industrial effluents within 120 min, and the COD elimination is up to 89% (Figs. 1e-f). The electrode degradation mechanism of AA was mainly the indirect oxidation of ·OH (carboxylation and cyanidation). In detail, used gas chromatography-mass spectrometry (GC-MS) to determine the mechanism of acrylamide degradation by OP-10&rGO-PbO2 electrode. The interval for the determination of the intermediate product was 30 min for a total degradation time of 120 min. The possibility of degradation routes of AA on OP-10&rGO-PbO2 electrode. In the process of AA degradation, AA molecules were activated under the action of ·OH with strong oxidation ability to form a series of 3-methyl-2,5-cyclobutyl amide and acetic acid, followed with opening 3-methyl-2,5-cyclobutyl amide to form a series of cyano and carboxyl compounds, which were finally oxidized to CO2, H2O, NO3
− and N2 (Fig. 1g). The enhanced lifetime test showed that the OP-10&rGO-PbO2 electrode had a higher service life than the PbO2 electrode. In summary, the potential use for treating wastewater of OP-10&rGO-PbO2 electrodes warrants further investigation.

Figure insert

Figure 1. (a) XRD patterns of PbO2 and OP-10&rGO-PbO2 electrode; (b) Contact angles of OP-10&rGO-PbO2 electrodes; (c) AA removal rate and (d) Dynamic curve of PbO2 and OP-10&rGO-PbO2
electrodes in 30 mg L−1 AA; (e) COD removal and (f) ICE of PbO2 and OP-10&rGO-PbO2 electrodes in 30 mg L−1 AA and (g) Proposed degradation mechanism of AA via OP-10&rGO-PbO2 electrode.

References:

[1] S. Garabagiu et al.
Journal of Electroanalytical Chemistry
, 2011, 659(2): 196-200.

[2] S. Lu et al.
ACS Sustainable Chemistry & Engineering
, 2021, 9(4): 1703-1713.

[3] S. Lu et al.
ACS Omega,
2021, 6(22): 14648-14654.

[4] T. Mandal et al.
Desalination
, 2010, 250(1): 87-94.

[5] C. Yan et al.
Industrial & Engineering Chemistry Research
2023. In press. DOI: 10.1021/acs.iecr.3c00479

Figure 1