In recent years, the widespread use of pharmaceuticals and personal care products (PPCPs) has greatly improved the healthy life of human beings, but it has also caused potential safety risks to the ecological environment and ecosystems (Kurade et al., 2021.;Lu et al., 2021.; Shahriar et al., 2021.;Yxc et al., 2021.;Chaturvedi et al., 2021). Water environment serves as one of the major pollution transmitting carriers of the emerging organic pollutants, and more and more PPCPs are also frequently detected in the water(Shannon et al., 2008.;Ying et al., 2021.;Ren et al., 2021.;Meng et al., 2021.;Chen et al., 2021.;Chen et al., 2020.;Yang et al., 2020), both of which have attracted wide attention from researchers.
PPCPs mainly include antibiotics, hormones, anti-epileptic drugs and personal care products such as preservatives, fungicides, disinfectants, etc.(Yi et al., 2017.;N. et al., 2019). They have the characteristics of high toxicity, strong bioaccumulation, and refractory biodegradability. In the environmental media they can be absorbed and enriched by the human body or other organisms (Zhang et al., 2020), causing the feminization of biological organisms, increasing the cancer rate of the reproductive system, destroying the immune system and central nervous system and other hazards(Jl et al., 2019). Among antibiotics, sulfonamides (Sulfonamides, SAs), as a common medicine for both humans and animals, has been used frequently as an important chemotherapeutic drug(Dumont et al., 2006), and its dosage accounts for more than 12% of the total types of antibiotics(Xu et al., 2009). The removal efficiency of SAs in sewage treatment plants is very low(Yi et al., 2017.;N. et al., 2019.;K Jüttner et al., 2000), due to the fact that by means of the traditional treatment process, it is difficult to effectively remove the sulfonamide organics in the water(Yang et al., 2021.;Wang et al., 2016.;Dao et al., 2020.;Tarpani et al., 2018.;Samaras et al., 2013). Biological treatment technology requires many restrictions, the investment in operation and maintenance is large, and the effect is difficult to maintain for a long time(Oller et al., 2012). Physical and chemical methods are at high cost relatively and may cause secondary pollution and other risks. A majority of sulfonamides directly discharged into environment with the excrement of livestock and poultry and gradually accumulated in the groundwater due to its refractory property, and were detected in pig slurry(up to 500 mg/L), in surface water (up to 40 ng/L) and in groundwater (up to 20 ng/L)(Zhang et al.,2019), which caused serious environmental pollution including antibiotic resistance of bacterial pathogens and generation of superbacteria(Zhu et al., 2016;Teng et al., 2019).Therefore, it is an urgent demand to develop effective and economical methods for elimination of sulfonamide from wastewater to prevent water environment pollution (Liu et al., 2015;Muhammad et al.,2021).
In the past 20 years, the electrochemical method has been called clean processing technology due to its simple structure, small occupied area, and easy management(K Jüttner et al., 2000). In recent years the three-dimensional electrode system has been highly valued by scientific researchers. The three-dimensional electrode is the bipolar particles formed by filling with granular materials between the plates of the two-dimensional electrode electrolytic cell, and the filled particles are polarized under the action of an electric field. Each bipolar particle forms a micro electrolytic cell, and Hydroxyl radicals are generated on the surface of particle electrodes to undergo oxidation-reduction reactions with organics. These particle electrodes are usually some kind of granular or debris-like fillers. The choice of particle electrodes is also the key to design and improve the overall operating efficiency of the three-dimensional electrode system(Feng et al., 2015). The most common particle electrodes are metal particles, granular activated carbon (GAC)(Zhao et al., 2017.;Sun et al., 2014), carbon aerogel (GA), etc.(Zhuang et al., 2017.;Berenguer et al., 2010.;Zhang et al., 2013) .
Bimetallic catalysis has been widely concerned by researchers since the 1950s(Hai-Yan et al., 2018). Compared with single metal particles, bimetallic particles usually show higher catalytic activity(Chen et al., 2017). The reserve of metal nickel and iron in the earth is extremely abundant, and as a magnetic material, nickel is corrosion-resistant and has low cost. It can form a galvanic cell with iron to change the properties of ferroelectronics(Kuang et al., 2015.;Weng et al., 2014) and slow down its passivation(Lu et al., 2017.;Zhou et al., 2014.), both of which can effectively enhance the performance of each other, play a synergistic catalysis, and improve the performance of degrading organic pollutants(Gon?Alves et al., 2016.;Schrick et al., 2002.;Kadu et al., 2017).
In this study, GAC is used as the carrier, and the metal nickel and iron are loaded on the surface of the GAC by the liquid-phase reduction method to prepare a high-performance particle electrode with bimetallic synergistic catalytic function, which is used to degrade the typical SAs—sulfamethiadiazole (SMT). SEM, TEM, XRD, XPS, FTIR, etc. are used to characterize the particle electrode. Moreover, we discuss the synergistic catalysis of metal nickel's and iron's load ratio, the impact of key factors such as the initial voltage, particle electrode dosage, electrode plate spacing and SMT initial concentration on the degradation efficiency, so as to determine the optimal reaction conditions. The study also reveals the mechanism and possible degradation pathways of electrocatalytic degradation of SMT, providing more theoretical basis for the degradation of SMT by the three-dimensional electrode reactor, and offering a research foundation to its wide application in the future.