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To achieve the purpose of treating waste by waste, in this study, a nitrogen-doped Fe/Mn bimetallic biochar material (FeMn@N-BC) was prepared from chicken manure for persulfate activation to degrade Bisphenol A (BPA). The FeMn@N-BC was characterized by scanning electron microscopy (SEM), X-ray diffract meter (XRD), fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectrometer (XPS) and found that N doping can form larger specific surface area. Catalytic degradation experiments showed that Fe/Mn bimetal doping not only accelerated the electron cycling rate on the catalyst surface, but also makes the biochar magnetic and easy to separate, thus reducing environmental pollution. Comparative experiments was concluded that the highest degradation efficiency of BPA was achieved when the mass ratios of urea and chicken manure, Fe/Mn were 3:1 and 2:1, respectively, and the pyrolysis temperature was 800 °C, which can almost degrade all the BPA in 60 min. FeMn@N-BC/PS system with high catalytic efficiency and low consumables is promising for reuse of waste resources and the remediation of wastewater.

activation, biochar, bisphenol A, Fe/Mn bimetallic, nitrogen doping, persulfate
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Bisphenol A (BPA) is a phenolic compound and widely used in industrial production of fibers, electronics, medical devices and leather tanning (Bao et al. 2021; Xing et al. 2022). In recent years, BPA has been detected in soil, sediment, air, water, food, and even in wildlife and aquatic species. It is widely recognized as an endocrine disruptor that poses a harmful threat to human health by causing many health defects, such as heart disease, obesity, cytotoxicity, hormonal imbalances, cancers, and malformations (Gu et al. 2022; Tarafdar et al. 2022). Therefore, there is an urgent need to investigate an effective and reliable method for BPA removal. In previous studies, physical adsorption (Łukasik et al. 2023), biodegradation (Li et al. 2022), advanced oxidation processes (AOPs), and other technologies have been widely adopted in the treatment of BPA (Xu et al. 2020), but physical adsorption only transfers the pollutant from the aqueous environment to the adsorbent and does not achieve complete removal of the pollutant or require further treatment of the adsorbent, with adsorption saturation also being one of the shortcomings of the process. BPA is usually very stable in the environment, which also limits the further application of biodegradation technologies. In contrast, AOPs are widely used in recent years to degrade refractory contaminations from aquatic environments due to their high efficiency and wide operative pH range (Rodriguez-Narvaez et al. 2017; Lee et al. 2020).

Among AOPs, sulfate radical-based advanced oxidation process has received much attention for its ability to produce with higher redox potential and longer half-life than •OH (Zhu et al. 2020; Cui et al. 2021). Because of its relative stability under normal conditions, PS needs to be catalyzed by external conditions to produce radicals with strong oxidization (Kakavandi et al. 2022). activation methods mainly contain external energy (thermal activation, Potakis et al. 2017 photocatalysis, Liu et al. 2022 ultrasonic activation, Wang et al. 2019) and catalyst activation (metal-based catalysts, Gao et al. 2018 carbon-based catalysts Li et al. 2023a). However, there are several problems of using energy activation methods such as high energy consumption and cost, limiting its wide application, and the use of catalyst activation will inevitably cause secondary environmental pollution. Thus, it is necessary to develop cost-effective and environmentally friendly activation methods.

Carbon-based materials, especially biochar materials, are considered as promising activation materials due to their easy availability and excellent catalytic properties (Wang & Wang 2019), but it is usually difficult to reach a satisfactory effect without a further treatment, evidence from recent studies suggests that nitrogen doping can increase the surface area of original biochar and greatly improve its activation properties (Wang et al. 2018a). The main types of N in biochar are pyrrole nitrogen (N-5), pyridine nitrogen (N-6), graphite nitrogen (N-Q), and pyridine type nitrogen oxide (N-X), among which N-Q has strong thermal stability, it helps to improve the catalytic performance, stability and conductivity of the material. With the increase of carbonization temperature (>700 °C), N-5 and N-6 will be converted to stable N-X and N-Q, respectively (Lv et al. 2018,; Ji et al. 2021; Ma et al. 2021), so the pyrolysis temperature has a significant effect on the catalytic properties of the material. However, single nitrogen-doped modified biochar materials are difficult to recover in actual water bodies, so it is necessary to load metal materials based on nitrogen doping to make the materials have excellent magnetic recycling ability. Previous studies have shown that biochar materials loaded with single metals not only have good magnetic recycling ability, but also have high charge transfer and activation efficiency (Hu et al. 2020; Ma et al. 2020). Due to the slow recovery of monometallic ions, the addition of bimetals accelerates the rate of electron cycling on the catalyst surface, thus speeding up the catalytic reaction (Duan et al. 2020). N-doping on the one hand gives the catalyst a large specific surface area, and on the other hand the loading of Fe/Mn bimetals accelerates the speed of electron cycling on the catalyst surface and greatly improves the catalytic effect.

Although nitrogen-doped bimetallic biochar composites have been studied in recent years, the reaction mechanism and influencing factors (e.g., pyrolysis temperature, N-doping content, and Fe/Mn mass ratio) have been relatively less explored. In the study, a nitrogen-doped bimetallic biochar composite (FeMn@N-BC) was successfully fabricated utilizing chicken manure, urea, FeSO4·7H2O, and MnCl2 to activate PS for BPA degradation. The materials were characterized by using scanning electron microscopy (SEM), X-ray diffract meter (XRD), Fourier transform infrared spectroscopy (FT-IR) spectra, and X-ray photoelectron spectrometer (XPS) and the effects of key factors (type of catalyst, catalyst dosage, PS concentration, and initial pH) on BPA degradation were investigated to determine the optimal conditions for the application of FeMn@N-BC catalysts. Finally, the main radical species in the FeMn@N-BC/PS system were identified by quenching and electron paramagnetic resonance (EPR) experiments. Subsequently, the possible activation mechanisms in the system were explored. This research can provide practical strategies for the development of water purification technologies and the design of biochar functional materials for the efficient removal of novel pollutants from water.

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Materials and chemicals

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The chicken manure was collected from a local organic fertilizer plant in Nanchang, China. Sodium persulfate (PS), urea (CH4N2O), ferrous sulfate heptahydrate (FeSO4•7H2O, 99%), Manganese chloride (MnCl2, 99%), sodium hydroxide (NaOH), hydrochloric acid (HCl), tert-butyl alcohol (TBA), methanol (MeOH), BPA, humic acid (HA) 5,5-Dimethyl-1-pyrroline N-oxide (DMPO, ≥97%), 2,2,6,6-tetramethyl-4-piperidinol(TEMP, 99%). All reagents belonged to analytical reagent grade and employed directly without purification. Deionized water (DI) was obtained from an ultra-pure purification system to prepare solutions.

Synthesis of catalytic materials

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Nitrogen-doped Fe/Mn bimetallic biochar was prepared as follows: chicken manure was dried and ground by a blast drier and pestle, FeSO4•7H2O and MnCl2 in mass ratios of 1:1, 2:1, and 3:1 were mixed with chicken manure and stirred by magnetic stirring for 1 h. Then, a certain amount of urea (the mass ratios of urea and chicken manure were 1:2, 1:1, and 2:1) was added to the mixed solution, and the mixture was stirred magnetically at 80 °C until the water evaporated to get a brown viscous substance, which was transferred to a quartz boat and dried in an oven at 65 °C overnight. The final products were heated in a tube furnace to 600, 700, 800, and 900 °C in an N2 atmosphere at a heating rate of 5 °C/min for 2 h. Finally, they were ground and sieved, then cleaned with ethanol and DI. The synthesized catalyst was labeled as FexMn1@N-BCy-z, where x denotes the addition ratio of Fe to Mn (x = 1, 2, and 3), y the mass ratio of urea to chicken manure (y = 0.5, 1, and 3), and z denotes the pyrolysis temperature of the material (z = 600, 700, 800, and 900). N-free doped (without urea addition) and metal-free doped biochar materials were prepared according to the same steps and labeled as BC-z, N-BCy-800, and FexMn1@BC-z, respectively.

Catalyst characterization and degradation experiment

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The surface morphology and structure of the catalysts were characterized by SEM, XRD, and XPS were used to analyze the crystal structure and surface chemical composition of the catalysts, respectively. FT-IR spectra was used to characterize the surface functional groups of the catalysts. In the experiments, a certain dose of catalyst (0.01–0.5 g·L−1) and PS (0.5–5.0 mmol·L−1) were added to a 10 mg·L−1 solution of BPA to start the reaction, the initial pH (3.1–11.1) was adjusted by adding HCl or NaOH. The mixed solution was placed in a constant temperature shaker at 25 °C with magnetic shaking and stirring, and samples were collected, then filtered through a 0.45 μm membrane. Finally, the absorbance of BPA was measured by using an ultraviolet spectrophotometer at a wavelength of 278 nm and its corresponding concentration was derived from the standard curve. The BPA removal rate R was calculated from the following equation:
(1)
The pseudo-first-order kinetic equation is shown in the following equation (Cai et al. 2016):
(2)
where Ct is the concentration of BPA (mg·L−1) after the reaction time t min, and C0 is the concentration of BPA before the reaction (mg·L−1). kobs is a quasi-primary dynamic constant (min−1).
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Characterization of materials

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Microscopic morphology analysis of biochar materials

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SEM can be used to analyze the surface micro morphologies of materials. In this section, the surface micro morphologies of primary biochar (BC-800), nitrogen-doped biochar (N-BC3-800), and nitrogen-doped iron-manganese bimetallic biochar (Fe2Mn1@N-BC3-800) were mainly analyzed. As shown in Figure 1(a), It can be observed that the surface of the original biochar is smooth, the void is less, and the structure is compact. After nitrogen doping (Figure 1(b)), it can be found that obvious folds appear on the surface of the material, the surface becomes rough, and defect sites increase, mainly because nitrogen atoms enter the carbon network to break the chemical inertness of the carbon material and form a large number of defect sites, resulting in a significant increase in the roughness of the surface of the carbon material (Sun et al. 2019).
Figure 1
SEM images of (a) BC-800, (b) N-BC3-800, (c) Fe2Mn1@N-BC3-800, and (d) Fe2Mn1@N-BC3-800 used 4 times.
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SEM images of (a) BC-800, (b) N-BC3-800, (c) Fe2Mn1@N-BC3-800, and (d) Fe2Mn1@N-BC3-800 used 4 times.

Figure 1
SEM images of (a) BC-800, (b) N-BC3-800, (c) Fe2Mn1@N-BC3-800, and (d) Fe2Mn1@N-BC3-800 used 4 times.
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SEM images of (a) BC-800, (b) N-BC3-800, (c) Fe2Mn1@N-BC3-800, and (d) Fe2Mn1@N-BC3-800 used 4 times.

Close modal

After Fe/Mn bimetal was loaded on N-doped biochar (Figure 1(c)), the catalyst surface became more fluffier and the fold state was more obvious. In addition, there were spherical aggregates on the biochar surface, which could be presumed to be Fe/Mn oxides, indicating that the in situ formation of Fe/Mn metal particles further improved the roughness of the catalyst surface (Li et al. 2023b). In Fe/Mn/N co-doped biochar materials, the formation of these special forms is mainly the result of the collaborative catalysis of Fe/Mn and N in the calcination process. Therefore, SEM images show that nitrogen doping is conducive to improving the roughness of the surface of the material, while the loading of iron and manganese bimetal increases the active site of the material, which is conducive to the removal of pollutants. Figure 1(d) is the SEM image of activated PS degradation of BPA after four reactions. It can be observed that Fe/Mn particles on the surface of the material have decreased significantly, and the defect sites and roughness of the surface have also decreased significantly, indicating that Fe/Mn metal participates in the catalytic reaction. In addition, N-doping can also increase the defect sites of biochar substrate, thus exposing more Fe/Mn active sites, which is conducive to the loading of iron and manganese metal and the subsequent catalytic active sites and the improvement of degradation performance (Duan et al. 2020; Hu et al. 2022).

Crystal structure and surface functional groups analysis of biochar materials

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XRD can observe the composition and crystal phase changes of materials, as shown in Figure 2(a), a diffraction peak appears, respectively, at 2θ = 26.3° in BC-800 and Fe2Mn1@N-BC3-800, which corresponds to the (0 0 2) crystal face of graphitic carbon (Ding et al. 2020), indicating the existence of graphitic carbon structure. However, the peak strength of the crystal face decreases after Fe/Mn metal was loaded, because Fe/Mn and its oxides were covered on the surface of the material, thereby reducing the peak strength of the crystal face (Chen et al. 2018). Characteristic peaks belonging to SiO2 (JCPDS(Joint Committee on Powder Diffraction Standards):79-1906) (2θ = 21.5°, 28.6°, and 38.6°) were observed in both BC-800 and Fe2Mn1@N-BC3-800 (Wang et al. 2011), mainly due to the presence of undigested stones and sand in chicken manure. In addition, a variety of crystal faces were also observed in Fe/Mn-loaded materials. The diffraction peaks at 58.3° and 65.7° were attributed to FeSi2 (JCPDS, No.72-1982) (Li et al. 2021), and the peaks at 34.9° (3 1 1) were corresponding to Fe3O4 crystal faces. Peaks at 43.2° and 49.6° correspond to the (4 0 0) and (1 2 4) crystal faces of Mn3O4 and Fe2O3, respectively, and 48.2° corresponds to the (3 1 1) crystal faces of FeMn4 PDF(Powder Diffraction Files)#03-1180 (Li et al. 2019a). From the XRD crystal surface detection, it can be found that the nitrogen-doped iron-manganese bimetallic catalyst contains a variety of crystal components and contains a variety of active substances.
Figure 2
(a) XRD patterns of BC-800 and Fe2Mn1@N-BC3-800 catalysts, (b) FT-IR spectra of BC-800, N-BC3-800 and Fe2Mn1@N-BC3-800 catalysts.
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(a) XRD patterns of BC-800 and Fe2Mn1@N-BC3-800 catalysts, (b) FT-IR spectra of BC-800, N-BC3-800 and Fe2Mn1@N-BC3-800 catalysts.

Figure 2
(a) XRD patterns of BC-800 and Fe2Mn1@N-BC3-800 catalysts, (b) FT-IR spectra of BC-800, N-BC3-800 and Fe2Mn1@N-BC3-800 catalysts.
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(a) XRD patterns of BC-800 and Fe2Mn1@N-BC3-800 catalysts, (b) FT-IR spectra of BC-800, N-BC3-800 and Fe2Mn1@N-BC3-800 catalysts.

Close modal

The FT-IR spectra of BC-800, N-BC3-800, and Fe2Mn1@N-BC3-800 are shown in Figure 2(b). The O–H stretching vibration peaks were found at 3,423 cm−1 in all three materials, which may be related to the presence of interlayer crystal water or surface hydroxyl groups in the materials. The 1,620 cm−1 absorption peak corresponds to the telescopic vibrational peak of C = O, the vibrational absorption peak of C–O–H at 1,090 cm−1 (Li et al. 2019b), and the intensity of this characteristic peak is weakened after Fe/Mn doping, which may be attributed to the fact that Fe/Mn complexed with C–O–H on the surface of the biochar during the modification process, changing into an iron-manganese oxide after high temperature pyrolysis (Pierri et al. 2020). In addition, C–N can be found in the N-doped material compared to BC-800, and Fe–O and Mn–O are present in the Fe/Mn-loaded material, indicating that the N atoms have been successfully doped and loaded with Fe/Mn in the carbon skeleton (Lv et al. 2015).

Elemental composition analysis of Fe2Mn1@N-BC3-800 biochar materials

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The surface elements of Fe2Mn1@N-BC3-800 were analyzed by using XPS and the elements of Fe, Mn, O, N, and C can be found (Figure 3(a)), which further indicates that Fe, Mn, and N were successfully loaded onto the biochar. The high-resolution C1s spectra of Fe2Mn1@N-BC3-800 had four main peaks at 288.91, 285.83, and 284.76 eV, which corresponded to C = O(18.78% C), C − O/C − N (36.13% C) and C − C/C = C (45.24% C), respectively (Figure 3(b)) (Lu et al. 2019). C–C/C = C peaks decreased after the reaction, suggesting that they participated in the reaction and provided active sites for BPA degradation (Chen et al. 2022). The N1s spectrum of Fe2Mn1@N-BC3-800 can be fitted with four peaks at 402.25, 401.12, 400.03, and 398.35 eV (Figure 3(d)) for nitrogen oxides (25.6% N), graphite N (34.2% N), pyrrolyl nitrogen (23.7% N), and pyridine N (16.5% N), respectively (Oh & Lim 2019). The peaks of graphite N and pyridine N, especially graphite N, showed a decrease after the reaction, further confirming that graphite N and pyridine N are the main active sites during the reaction. In addition, the O1s spectrum at 533.76, 531.69, 530.87, and 529.56 eV can be fitted with four peaks (Figure 3(c)), they are C–O (10.23% O), C = O(33.24% O), O–H (34.12% O), and Fe/Mn oxide (referred to as M–O) (22.41%O) (Gao et al. 2018). After the reaction, the content of the M–O group decreased from 22.41 to 15.24%, and Fe/Mn was successfully loaded on the biochar and participated in the catalytic reaction, which played a role in promoting the catalytic reaction, they are in good agreement with the XRD and FT-IR characterization results.
Figure 3
(a) XPS survey spectra, (b) high-resolution C1s, (c) O1s, and (d) N1s spectra of Fe2Mn1@N-BC3-800 catalysts.
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(a) XPS survey spectra, (b) high-resolution C1s, (c) O1s, and (d) N1s spectra of Fe2Mn1@N-BC3-800 catalysts.

Figure 3
(a) XPS survey spectra, (b) high-resolution C1s, (c) O1s, and (d) N1s spectra of Fe2Mn1@N-BC3-800 catalysts.
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(a) XPS survey spectra, (b) high-resolution C1s, (c) O1s, and (d) N1s spectra of Fe2Mn1@N-BC3-800 catalysts.

Close modal

Comparison of the degradation effect of BPA in different catalytic systems

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As shown in Figure 4, under the conditions of pH 5.6, temperature 25 °C, catalyst dosage of 0.30 g·L−1, PS concentration of 1.0 mmol·L−1, and target pollutant BPA concentration of 10 mg·L−1, the activation properties of PS and the removal efficiency of BPA of different materials were evaluated. Figure 4(a) shows the effect of biochar materials with different N-doping ratios on activating PS to degrade BPA. Compared with original biochar, the catalytic effect is gradually enhanced with the increase of nitrogen doping ratio, and the removal efficiency of BPA by original biological carbon is only about 20%. Within 60 min, the removal rate of BPA was the highest, 35.21%, and the reaction rate constant was 0.0072 min−1, indicating that the modification of biochar by nitrogen doping significantly promoted the catalytic effect of PS, which was mainly due to the porous structure formed by urea doping in chicken manure biochar, so that it had more PS active sites. In addition, it can be found that with the increase of the nitrogen doping ratio, the adsorption performance of the material for BPA becomes better during the adsorption period of 30 min before PS is added. This is because nitrogen doping can effectively improve the electronegativity of the surface of the original biochar, resulting in more positive charges on the surface. Improve the adsorption capacity of pollutants. Figure 4(b) shows the effect of nitrogen-doped biochar material activating PS to degrade BPA at different pyrolysis temperatures. It can be seen that when the pyrolysis temperature is 600 °C, BPA degrades by only 16%, with the temperature rising to 800 °C, the removal rate of BPA rises to 36.37% within 60 min, and the reaction rate constant also increased from 0.0029 to 0.0077 min−1, which was mainly due to the decomposition and conversion of unstable nitrogen-containing functional groups into other nitrogen-containing functional groups at higher temperatures (such as the conversion of pyridine N to graphite N), gradually increased the degree of graphitization of biochar and increased its activation properties. However, the removal effect of N-doped biochar material pyrolysis at 900 °C was slightly lower than that at 800 °C, which may be due to the adverse effects of higher pyrolysis temperature on the number and properties of functional groups on the surface of biochar. Therefore, biochar material pyrolysis at 800 °C was selected for subsequent experiments.
Figure 4
The degradation of BPA by PS activated by FeMn@N-BC with different (a) nitrogen-doping ratios, (b) pyrolysis temperatures, (c) Fe/Mn doping ratios, and (d) degradation systems. Reaction conditions: [BPA] = 10 mg·L−1, [PS] = 1.0 mmol·L−1, pH = 5.6, [catalyst] = 0.30 g·L−1, and temperature = 25 °C.
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The degradation of BPA by PS activated by FeMn@N-BC with different (a) nitrogen-doping ratios, (b) pyrolysis temperatures, (c) Fe/Mn doping ratios, and (d) degradation systems. Reaction conditions: [BPA] = 10 mg·L−1, [PS] = 1.0 mmol·L−1, pH = 5.6, [catalyst] = 0.30 g·L−1, and temperature = 25 °C.

Figure 4
The degradation of BPA by PS activated by FeMn@N-BC with different (a) nitrogen-doping ratios, (b) pyrolysis temperatures, (c) Fe/Mn doping ratios, and (d) degradation systems. Reaction conditions: [BPA] = 10 mg·L−1, [PS] = 1.0 mmol·L−1, pH = 5.6, [catalyst] = 0.30 g·L−1, and temperature = 25 °C.
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The degradation of BPA by PS activated by FeMn@N-BC with different (a) nitrogen-doping ratios, (b) pyrolysis temperatures, (c) Fe/Mn doping ratios, and (d) degradation systems. Reaction conditions: [BPA] = 10 mg·L−1, [PS] = 1.0 mmol·L−1, pH = 5.6, [catalyst] = 0.30 g·L−1, and temperature = 25 °C.

Close modal

Loading metal substances on N-doped biochar further explored its catalytic activation properties. As shown in Figure 4(c), when only single metal Fe was loaded in the material, the degradation efficiency of BPA was 76.2% lower than that of bimetallic materials. When the Fe/Mn doping ratio increased from 1:1 to 2:1, the degradation efficiency of BPA increased from 89.2 to 99.3%, and the corresponding reaction rate constant also increased from 0.0368 to 0.0768 min−1, 60 min almost completely degraded BPA, which was mainly due to the acceleration of the electron cycling rate of Fe/Mn bimetal in the system. However, as the Fe/Mn doping ratio continued to increase 3:1, the degradation efficiency decreased to 90.1%, mainly due to the accumulation and deposition of Fe/Mn and its oxides on the surface of the material, resulting in a decrease in the active site and catalytic efficiency (Guo et al. 2020). Therefore, a 2:1 Fe/Mn loading ratio was adopted in subsequent experiments. To further visually compare the degradation performance of BPA by different systems, the catalytic performance of various materials and different catalytic degradation systems were compared in Figure 4(d). The removal rate of BPA in the system with only PS added was only 5.16%, showing almost no degradation effect, indicating that PS is difficult to oxidize and degrade BPA in the absence of catalyst activation. The removal rates of BC-800 and N-BC3-800 for BPA were 11.25 and 15.76%, respectively, mainly due to the relatively smooth surface of the original BC, low porosity and specific surface area, which limited the adsorption capacity of BC for BPA, while N-BC3-800 had a larger specific surface area than BC-800, a new nitrogen-containing functional group is formed with strong adsorption affinity (Wang et al. 2018b). When PS was added to the reaction system, the degradation efficiency was further improved. Compared with the BC-800/PS system, Fe2Mn1@N-BC3-800/PS system had higher catalytic performance and could almost completely remove BPA within 60 min, indicating that Fe/Mn might be the main active substance in the system. Nitrogen doping and bimetal loading can further improve the activity of the catalyst. Through the above degradation experiments, it can be concluded that the catalyst material synthesized by pyrolysis has the best activation and degradation effect under the conditions of urea: chicken manur e = 3:1, Fe:Mn = 2:1, and the pyrolysis temperature is 800 °C.

Analysis of catalytic degradation influencing factors

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Influence of PS concentration and catalyst dosage

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Figure 5(a) shows the effect of the initial concentration of PS on the degradation of BPA in Fe2Mn1@N-BC3-800/PS system. It can be found that when the PS concentration increased from 0.5 to 1.0 mmol·L−1, the degradation rate of BPA increased significantly, from 89 to 99.3%, and the reaction rate constant also increased from 0.0261 to 0.0768 min−1. When the PS concentration continued to increase to 2.0 mmol·L, there was no significant change in the removal rate of BPA, which was mainly due to the limited active sites provided by the catalyst surface. Further increasing the amount of PS did not significantly promote the catalytic effect, but the reaction rate was improved when the amount of PS was further increased to 3 and 5 mmol·L−1. The system can almost completely remove BPA from the solution in about 30 min, mainly because a high enough PS concentration can accelerate the corrosion of Fe/Mn and the electron transfer exchange rate in the catalyst at the initial stage of the reaction, so BPA can be completely removed in a short time. Although some studies have shown that when the amount of PS in the system is too high, self-quenching reaction (Equations (3) and (4)) may occur or react with excessive PS in the system, resulting in a decrease in the degradation efficiency of pollutants (Qiu et al. 2021), such a situation did not occur in this experiment, this may be because the amount of PS in this experiment has not reached a certain limit. Taking comprehensive consideration, the optimal reaction concentration of PS is 1.0 mmol·L−1.
Figure 5
Effects of (a) PS concentration, (b) catalyst dosage on the degradation of BPA in the Fe2Mn1@N-BC3-800/PS system. Reaction conditions: [BPA] = 10 mg·L−1, PS concentration = 1.0 mmol·L−1 (except (a)), catalyst dosage = 0.30 g·L−1 (except (b)) and temperature = 25 °C.
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Effects of (a) PS concentration, (b) catalyst dosage on the degradation of BPA in the Fe2Mn1@N-BC3-800/PS system. Reaction conditions: [BPA] = 10 mg·L−1, PS concentration = 1.0 mmol·L−1 (except (a)), catalyst dosage = 0.30 g·L−1 (except (b)) and temperature = 25 °C.

Figure 5
Effects of (a) PS concentration, (b) catalyst dosage on the degradation of BPA in the Fe2Mn1@N-BC3-800/PS system. Reaction conditions: [BPA] = 10 mg·L−1, PS concentration = 1.0 mmol·L−1 (except (a)), catalyst dosage = 0.30 g·L−1 (except (b)) and temperature = 25 °C.
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Effects of (a) PS concentration, (b) catalyst dosage on the degradation of BPA in the Fe2Mn1@N-BC3-800/PS system. Reaction conditions: [BPA] = 10 mg·L−1, PS concentration = 1.0 mmol·L−1 (except (a)), catalyst dosage = 0.30 g·L−1 (except (b)) and temperature = 25 °C.

Close modal
Figure 5(b) shows the effects of different catalyst dosages on BPA degradation. When the dosage of catalyst increased from 0.01 to 0.50 g·L−1, the degradation efficiency of BPA also increased from 75.2 to 88.3%, and the amount of catalyst continued to increase to 0.30 g·L−1, the removal rate of BPA was further improved, BPA was almost completely removed from the system within 60 min of reaction, the reaction rate constant also increased to 0.0768 min−1, mainly because increasing the amount of catalyst could provide more reactive sites for activated PS, thus generating more oxidizing active substances to degrade pollutants (Duan et al. 2020). However, when the catalyst concentration continued to increase to 0.50 g·L−1, the removal rate of BPA did not increase significantly, but the reaction rate increased in the first 30 min, mainly because there was enough catalyst to activate PS at the beginning of the reaction, which accelerated the free radical production rate (Jonidi Jafari et al. 2017). Therefore, 0.30 g·L−1 catalyst dosage was selected in this experiment.
(3)
(4)

Effects of initial pH, co-existing ions, and humic acids

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Initial pH is one of the key factors influencing the degradation of pollutants, which affects not only the stability of PS and the morphology of free radicals, but also the release of manganese and iron ions from Fe2Mn1@N-BC3-800. In general, the free radicals produced during activation of persulfate at acidic pH are dominated by ⁠, while at alkaline pH they are mainly dominated by •OH, and will be converted to •OH under strong alkaline conditions (Devi et al. 2016), so it is needed to evaluate the effect of different initial pH on the removal of BPA. As shown in Figure 6(a), the degradation rate of BPA reached more than 90% at pH 3.1, 5.6, 6.7, and 9.3, while decreased to 23.26% at increasing pH 11.1. It was mainly due to the fact that the free radicals (⁠⁠) generated in the PS system have the strongest oxidizing properties under acidic conditions (Jiang et al. 2018; Wang & Wang 2018), but compared with the conventional Fenton process, the Fe2Mn1@N-BC3-800/PS system has a wide working pH range (3–9).
Figure 6
Effects of (a) initial pH, (b) co-existing ions and humic acids on the degradation of BPA in the Fe2Mn1@N-BC3-800/PS system. Reaction conditions: [BPA] = 10 mg·L−1, [PS] = 1.0 mmol·L−1, pH = 5.6, [catalyst] = 0.30 g·L−1 and temperature = 25 °C.
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Effects of (a) initial pH, (b) co-existing ions and humic acids on the degradation of BPA in the Fe2Mn1@N-BC3-800/PS system. Reaction conditions: [BPA] = 10 mg·L−1, [PS] = 1.0 mmol·L−1, pH = 5.6, [catalyst] = 0.30 g·L−1 and temperature = 25 °C.

Figure 6
Effects of (a) initial pH, (b) co-existing ions and humic acids on the degradation of BPA in the Fe2Mn1@N-BC3-800/PS system. Reaction conditions: [BPA] = 10 mg·L−1, [PS] = 1.0 mmol·L−1, pH = 5.6, [catalyst] = 0.30 g·L−1 and temperature = 25 °C.
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Effects of (a) initial pH, (b) co-existing ions and humic acids on the degradation of BPA in the Fe2Mn1@N-BC3-800/PS system. Reaction conditions: [BPA] = 10 mg·L−1, [PS] = 1.0 mmol·L−1, pH = 5.6, [catalyst] = 0.30 g·L−1 and temperature = 25 °C.

Close modal
Furthermore, since actual water often contains many anions (e.g., chloride (Cl−), nitrate (⁠⁠), bicarbonate ions (⁠⁠), dihydrogen phosphate ions (⁠⁠), and humic acid (HA)), they may affect the degradation performance of the Fe2Mn1@N-BC3-800/PS system. From Figure 7(b), it can be seen that Cl− and had no significant effect on the degradation effect of the system, this is consistent with the study of Li et al. (2020) while and have obvious inhibition on the degradation effect of BPA, which is partly due to the fact that the surface precipitates generated from and with Mn(II) and Fe(II) covering the catalyst surface and hindering the catalytic reaction, resulting in a decrease in a degradation efficiency (Chen et al. 2020). On the other hand, reacts with the active site on the catalyst surface, resulting in poor catalytic reactivity (Li et al. 2019c). HA is a type of natural organic matter, and the degradation efficiency of BPA was significantly affected when the concentration of HA was increased from 5 to 10 mmol·L−1, which was mainly attributed to the free radical competition reaction between HA and BPA on the surface of Fe2Mn1@N-BC3-800 (Wang et al. 2016).
Figure 7
(a) BPA degradation after several runs of the Fe2Mn1@N-BC3-800 catalyst. (b) The degradation rate of various organic pollutants by the Fe2Mn1@N-BC3-800/PS system. Reaction conditions: [organics] = 10 mg·L−1, [PS] = 1.0 mmol·L−1, pH = 5.6, [catalyst] = 0.30 g·L−1 and temperature = 25 °C.
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(a) BPA degradation after several runs of the Fe2Mn1@N-BC3-800 catalyst. (b) The degradation rate of various organic pollutants by the Fe2Mn1@N-BC3-800/PS system. Reaction conditions: [organics] = 10 mg·L−1, [PS] = 1.0 mmol·L−1, pH = 5.6, [catalyst] = 0.30 g·L−1 and temperature = 25 °C.

Figure 7
(a) BPA degradation after several runs of the Fe2Mn1@N-BC3-800 catalyst. (b) The degradation rate of various organic pollutants by the Fe2Mn1@N-BC3-800/PS system. Reaction conditions: [organics] = 10 mg·L−1, [PS] = 1.0 mmol·L−1, pH = 5.6, [catalyst] = 0.30 g·L−1 and temperature = 25 °C.
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(a) BPA degradation after several runs of the Fe2Mn1@N-BC3-800 catalyst. (b) The degradation rate of various organic pollutants by the Fe2Mn1@N-BC3-800/PS system. Reaction conditions: [organics] = 10 mg·L−1, [PS] = 1.0 mmol·L−1, pH = 5.6, [catalyst] = 0.30 g·L−1 and temperature = 25 °C.

Close modal

Reusability and application of Fe2Mn1@N-BC3-800

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To explore the potential use of Fe2Mn1@N-BC3-800 in practical applications, the material was separated from water by an applied magnetic field and rinsed with ultra-pure water 4 times in the experiment. Finally, the material was dried in a vacuum oven at 60 °C. It can be concluded from the cycle experiment that the degradation rate of BPA decreased after 4 times of repeated use of the material (Figure 7(a)), this may be due to the fact that the intermediates of BPA converted into smaller molecules covered the surface of the material during the degradation process, thus occupying part of the adsorption and catalytic sites, thereby reducing the removal rate of BPA (Xu et al. 2020). However, after 4 times of recycling, the removal rate of BPA in Fe2Mn1@N-BC3-800/PS system was still more than 75%, which proves that Fe2Mn1@N-BC3-800 has good stability and reusability and has certain application prospects. In addition, another three types of refractory organic pollutants (phenol, rhodamine B (Rh B), tetracycline (TC)) were selected as target pollutants to test the application potential of the material, and the results are shown in Figure 8(b). Within 60 min, the removal rates of phenol, Rh B and TC with concentrations of 10 mg·L−1 in Fe2Mn1@N-BC3-800/PS system reached 98.4, 95.3, and 94.2%, respectively, indicating a wide range of applicability of the catalyst.
Figure 8
(a) Influence of free radical quencher on BPA degradation efficiency. Effect of using DMPO and TEMP as a spin trapping agent on the EPR spectra at different time intervals for (b) and •OH, (c) and (d) .
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(a) Influence of free radical quencher on BPA degradation efficiency. Effect of using DMPO and TEMP as a spin trapping agent on the EPR spectra at different time intervals for (b) and •OH, (c) and (d) ⁠.

Figure 8
(a) Influence of free radical quencher on BPA degradation efficiency. Effect of using DMPO and TEMP as a spin trapping agent on the EPR spectra at different time intervals for (b) and •OH, (c) and (d) .
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(a) Influence of free radical quencher on BPA degradation efficiency. Effect of using DMPO and TEMP as a spin trapping agent on the EPR spectra at different time intervals for (b) and •OH, (c) and (d) ⁠.

Close modal

Analysis of BPA removal mechanism in Fe2Mn1@N-BC3-800/PS system

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Qualitative and quantitative identification of active oxidizing species

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Radical and non-radical pathways are the main pathways for degradation of pollutants in catalyst/PS systems, thus, to explore the reaction mechanism of Fe2Mn1@N-BC3-800/PS system for the degradation of BPA. In this experiment, methanol (MeOH), tert-butanol (TBA), benzoquinone (BQ), and furfuryl alcohol (FFA) were chosen as the quenching agents for the free radical species identification experiments, in which MeOH could scavenge both and •OH with reaction rates of (0.9–1.3) × 107M−1s−1 and (8–10) × 108 M−1s−1, respectively, whereas the ability of TBA to capture is much lower than that of •OH (kMeOH,•OH = (3.8–7.6) × 108M−1s−1, kMeOH, = (4.9–9.1) × 105M−1s−1) (Zhang et al. 2020), so TBA was used as a •OH trapping agent. As shown in Figure 8(a), under the conditions of BPA concentration of 10 mg·L−1, pH of 6.75, temperature of 25 °C, catalyst dosing of 0.30 g·L−1 and PS concentration of 1.0 mmol·L−1, the degradation of BPA was slightly inhibited by the addition of 300 mmol·L−1 of TBA to the solution, whereas after the addition of the same dose of MeOH, the removal rate of BPA decreased from 96.45 to 71.32%, which showed an obvious inhibitory effect, indicating that both and •OH were generated in the system, and •OH played a dominant role in the degradation of BPA. FFA was a quencher of ⁠, the removal of BPA was significantly inhibited with a removal rate of 50.65% when 1 mmol·L−1 of FFA was added, suggesting the yield of in system. It has been shown that the generation of during PS activation is usually associated with superoxide radicals (⁠⁠) (Long et al. 2019), so BQ was chosen as an (k = 0.9–1.0 × 109 M−1s−1) inhibitor, it can be found that the degradation rate of BPA was only 33.16% in 120 min, indicating that was produced in the system. Hence, it is hypothesized that the degradation mechanism of BPA in the Fe2Mn1@N-BC3-800/PS system includes both radical pathways and non-radical pathways, with the non-radical pathway predominating.
Figure 9
(a) Mn2p and (b) Fe2p spectra.
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(a) Mn2p and (b) Fe2p spectra.

Figure 9
(a) Mn2p and (b) Fe2p spectra.
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(a) Mn2p and (b) Fe2p spectra.

Close modal

To further identify the reactive species involved in BPA degradation in the Fe2Mn1@N-BC3-800/PS system, EPR assays were performed by using DMPO and TEMP as the free radicals (⁠⁠, •OH, ⁠) and single-linear oxygen (⁠⁠) traps, respectively. As shown in Figure 8(b), the DMPO- characteristic peak (1: 2: 2: 1) and the DMPO-•OH characteristic peak (1: 1: 1: 1) can be observed, DMPO- was significantly stronger than DMPO-•OH. The presence of and is confirmed by the signals of DMPO-and TEMP- in Figure 8(c) and 8(d), which agree with the results of the free radical quenching experiments.

Analysis of activation and degradation mechanisms

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The preliminary characterization results of the materials and the adsorption degradation performance experiments can lead to a preliminary conclusion on the synergistic activation mechanism between Fe/Mn and N on Fe2Mn1@N-BC3-800. The specific surface area of the nitrogen-doped biochar material increased, which was favorable to improving the adsorption performance of the material for pollutants. The chemical valence changes of Mn/Fe before and after the reaction were further analyzed by XPS, and the XPS spectra of the Mn2p and Fe2p regions of the catalysts before and after use were analyzed (Figure 9). Two peaks of 710.07 eV Fe(II) and 713.26 eV Fe(III) were fitted to Fe2Mn1@N-BC3-800 (Yang et al. 2021), and the Fe(II) and Fe(III) contents were 54.58 and 28.61%, respectively. The Fe (III) content increased from 28.61 to 35.81% after reaction, which may be related to the Reduction-Oxidation (REDOX) between Fe (III) and Fe(II). Similarly, Mn(IV), Mn(III), and Mn(II) were observed in the Mn2p XPS energy spectrum, after the reaction, the contents of Mn(III) and Mn(IV) increased from 37.21 to 39.48% and 24.25 to 28.42%, respectively, while the content of Mn(II) decreased from 37.26 to 30.89%, which was mainly due to the redox cycling between Fe and Mn, inducing the successive activation of PS (Equations (5)–(9)) (Du et al. 2016).
(5)
(6)
(7)
(8)
(9)
The mechanism of BPA degradation by Fe2Mn1@N-BC3-800/PS system can be derived from the free radical detection experiments, which include the free radical pathway (⁠⁠, •OH, ⁠) and non-free radical pathway (⁠ and electron transfer), the possible processes can occur as shown in the following equation:
(10)
(11)
(12)

Therefore, the main factors leading to the degradation of BPA include adsorption and electron transfer on the surface of the material, and the activation reaction is accelerated by the redox cycle between bimetallic Fe and Mn (Equations (13) and (14)).

Free radical pathways:
(13)
Non-free radical pathways:
(14)
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In this study, FeMn@N-BC catalysts were successfully prepared using agricultural waste chicken manure as a precursor, which were used to activate PS for degrading the target pollutant BPA and showed excellent catalytic performance. Fe/Mn and N co-doping improved the structural properties of the biochar and enhanced the catalytic activity of the biochar for PS with certain adsorption properties. More importantly, the Fe2Mn1@N-BC3-800 material is of practical significance in removing a wide range of difficult-to-degrade pollutants with good reusability and a wide pH working range. Under the optimal conditions, 10 mg/L of BPA was almost completely removed after 60 min of reaction, and the degradation process of BPA basically conformed to the proposed first-order kinetic equation. Fe2Mn1@N-BC3-800/PS system can maintain high catalytic activity in the wide pH range of 3.1–9.3, and the materials had good reusability. The free radical quenching experiments and EPR showed that both free radical pathways and non-free radical pathways existed in the reaction system, ⁠, •OH, ⁠, were involved in the degradation process, and the doping of Fe/Mn bimetallic not only made the catalytic materials easy to be separated from the water, but also accelerated the redox rate, which led to the improvement of reaction activation performance. This work opens up new pathways for mitigating BPA contamination in water treatment processes and agricultural wastes, and further research should be conducted on the wide range of applications of this synthetic material, including economic cost estimates, toxicity migration, and other possible issues.

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Z. C. and W. Z. conceptualized the study; C. Y. performed the methodology; Z. C. did software analysis; Z. C., W. Z., and H. S. validated the study; Z. C. did formal analysis; W. Z. investigated the study; C. Y. collected the resources; Z. C. did data curation; Z. C. prepared and wrote the original draft; Z. C. wrote, reviewed , and edited the article; W. Z. visualized the study; C. Y. supervised the study; C. Y. did project administration.

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This work was supported by the Natural Science Youth Fund of Jiangxi Provincial Department of Science and Technology (2007 gZC0075) and the Science and Technology Research Project of Jiangxi Provincial Department of Education ([2007] 51).

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All relevant data are included in the paper or its Supplementary Information.

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The authors declare there is no conflict.

Bao
T.
,
Damtie
M. M.
,
Wei
W.
,
Phong Vo
H. N.
,
Nguyen
K. H.
,
Hosseinzadeh
A.
,
Cho
K.
,
Yu
Z. M.
,
Jin
J.
,
Wei
X. L.
,
Wu
K.
,
Frost
R. L.
 &
Ni
B.-J.
2021
Simultaneous adsorption and degradation of bisphenol A on magnetic illite clay composite: Eco-friendly preparation, characterizations, and catalytic mechanism
.
J. Cleaner Prod.
287
,
125068
.
Google Scholar
Crossref
Search ADS
 
Cai
M.
,
Su
J.
,
Zhu
Y.
,
Wei
X.
,
Jin
M.
,
Zhang
H.
,
Dong
C.
 &
Wei
Z.
2016
Decolorization of azo dyes orange G using hydrodynamic cavitation coupled with heterogeneous Fenton process
.
Ultrason. Sonochem.
28
,
302
–
310
.
Google Scholar
Crossref
Search ADS
PubMed
 
Chen
L.
,
Jiang
X.
,
Xie
R.
,
Zhang
Y.
,
Jin
Y.
 &
Jiang
W.
2020
A novel porous biochar-supported Fe-Mn composite as a persulfate activator for the removal of acid red 88
.
Sep. Purif. Technol.
250
,
117232
.
Google Scholar
Crossref
Search ADS
 
Chen
C.
,
Pang
X.
,
Chen
Q.
,
Xu
M.
,
Xiao
Y.
,
Wu
J.
,
Zhang
Y.
,
Liu
Y.
,
Long
L.
 &
Yang
G.
2022
Tetracycline adsorption trajectories on aged polystyrene in a simulated aquatic environment: A mechanistic investigation
.
Sci. Total Environ.
851
,
158204
.
Google Scholar
Crossref
Search ADS
PubMed
 
Cui
X.
,
Zhang
S.
,
Geng
Y.
,
Zhen
J.
 &
Zhan
J.
2021
Synergistic catalysis by Fe3O4-biochar/peroxymonosulfate system for the removal of bisphenol A
.
Sep. Purif. Technol.
276
,
119351
.
Google Scholar
Crossref
Search ADS
 
Du
J.
,
Bao
J.
,
Liu
Y.
,
Ling
H.
,
Zheng
H.
,
Kim
S. H.
 &
Dionysiou
D. D.
2016
Efficient activation of peroxymonosulfate by magnetic Mn-MGO for degradation of bisphenol A
.
J. Hazard. Mater.
320
,
150
–
159
.
Google Scholar
Crossref
Search ADS
PubMed
 
Duan
P.
,
Qi
Y.
,
Feng
S.
,
Peng
X.
,
Wang
W.
,
Yue
Y.
,
Shang
Y.
,
Li
Y.
,
Gao
B.
 &
Xu
X.
2020
Enhanced degradation of clothianidin in peroxymonosulfate/catalyst system via core-shell FeMn@N-C and phosphate surrounding
.
Appl. Catal.
267
,
118717
.
Google Scholar
Crossref
Search ADS
 
Gu
J.
,
Guo
M.
,
Yin
X.
,
Huang
C.
,
Qian
L.
,
Zhou
L.
,
Wang
Z.
,
Wang
L.
,
Shi
L.
 &
Ji
G.
2022
A systematic comparison of neurotoxicity of bisphenol A and its derivatives in zebrafish
.
Sci. Total Environ.
805
,
150210
.
Google Scholar
Crossref
Search ADS
PubMed
 
Guo
C.
,
Zhou
R.
,
Li
Z.
,
Si
Y.
,
Liao
W.
,
Sun
W.
,
Xiang
S.
,
Luo
X.
,
Luo
M.
 &
Luo
Z.
2020
Molten-salt/oxalate mediating Fe and N-doped mesoporous carbon sheet nanostructures towards highly efficient and durable oxygen reduction electrocatalysis
.
Microporous Mesoporous Mater.
303
,
110281
.
Google Scholar
Crossref
Search ADS
 
Hu
W.
,
Tong
W.
,
Li
Y.
,
Xie
Y.
,
Chen
Y.
,
Wen
Z.
,
Feng
S.
,
Wang
X.
,
Li
P.
,
Wang
Y.
 &
Zhang
Y.
2020
Hydrothermal route-enabled synthesis of sludge-derived carbon with oxygen functional groups for bisphenol A degradation through activation of peroxymonosulfate
.
J. Hazard. Mater.
388
,
121801
.
Google Scholar
Crossref
Search ADS
PubMed
 
Ji
R.
,
Wu
Y.
,
Bian
Y.
,
Song
Y.
,
Sun
Q.
,
Jiang
X.
,
Zhang
L.
,
Han
J.
 &
Cheng
H.
2021
Nitrogen-doped porous biochar derived from marine algae for efficient solid-phase microextraction of chlorobenzenes from aqueous solution
.
J. Hazard. Mater.
407
,
119932
.
Google Scholar
Crossref
Search ADS
 
Jonidi Jafari
A.
,
Kakavandi
B.
,
Jaafarzadeh
N.
,
Rezaei Kalantary
R.
,
Ahmadi
M.
 &
Akbar Babaei
A.
2017
Fenton-like catalytic oxidation of tetracycline by AC@Fe3O4 as a heterogeneous persulfate activator: Adsorption and degradation studies
.
J. Ind. Eng. Chem.
45
,
323
–
333
.
Google Scholar
Crossref
Search ADS
 
Li
L.
,
Lai
C.
,
Huang
F.
,
Cheng
M.
,
Zeng
G.
,
Huang
D.
,
Li
B.
,
Liu
S.
,
Zhang
M.
,
Qin
L.
,
Li
M.
,
He
J.
,
Zhang
Y.
 &
Chen
L.
2019a
Degradation of naphthalene with magnetic bio-char activate hydrogen peroxide: Synergism of bio-char and Fe–Mn binary oxides
.
Water Res.
160
,
238
–
248
.
Google Scholar
Crossref
Search ADS
PubMed
 
Li
L.
,
Deng
Y.
,
Ai
J.
,
Li
L.
,
Liao
G.
,
Xu
S.
,
Wang
D.
 &
Zhang
W.
2021
Fe/Mn loaded sludge-based carbon materials catalyzed oxidation for antibiotic degradation: Persulfate vs H2O2 as oxidant
.
Sep. Purif. Technol.
263
,
118409
.
Google Scholar
Crossref
Search ADS
 
Li
Z.
,
Chen
H.
,
Dong
C.
,
Jin
C.
,
Cai
M.
,
Chen
Y.
,
Xie
Z.
,
Xiong
X.
 &
Jin
M.
2023b
Nitrogen doped bimetallic sludge biochar composite for synergistic persulfate activation: Reactivity, stability and mechanisms
.
Environ. Res.
229
,
115998
.
Google Scholar
Crossref
Search ADS
PubMed
 
Łukasik
N.
,
Wikarska
S.
,
Świątek
H.
,
Łapiński
M.
,
Klimczuk
T.
 &
Hemine
K.
2023
The influence of magnetic particle incorporation on bisphenol A removal by β-cyclodextrin-derived sorbent
.
Chemosphere
338
,
139538
.
Google Scholar
Crossref
Search ADS
PubMed
 
Lv
Q.
,
Si
W.
,
He
J.
,
Sun
L.
,
Zhang
C.
,
Wang
N.
,
Yang
Z.
,
Li
X.
,
Wang
X.
,
Deng
W.
,
Long
Y.
,
Huang
C.
 &
Li
Y.
2018
Selectively nitrogen-doped carbon materials as superior metal-free catalysts for oxygen reduction
.
Nat. Commun.
9
,
3376
.
Google Scholar
Crossref
Search ADS
PubMed
 
Ma
Q.
,
Nengzi
L.-c.
,
Zhang
X.
,
Zhao
Z.
 &
Cheng
X.
2020
Enhanced activation of persulfate by AC@cofe2o4 nanocomposites for effective removal of lomefloxacin
.
Sep. Purif. Technol.
233
,
115978
.
Google Scholar
Crossref
Search ADS
 
Ma
Q.
,
Chen
W.
,
Jin
Z.
,
Chen
L.
,
Zhou
Q.
 &
Jiang
X.
2021
One-step synthesis of microporous nitrogen-doped biochar for efficient removal of CO2 and H2S
.
Fuel
289
,
124785
.
Google Scholar
 
Pierri
L.
,
Gemenetzi
A.
,
Mavrogiorgou
A.
,
Borges Regitano
J.
,
Deligiannakis
Y.
 &
Louloudi
M.
2020
Biochar as supporting material for heterogeneous Mn(II) catalysts: Efficient olefins epoxidation with H2O2
.
Mol. Catal.
489
,
110946
.
Google Scholar
Crossref
Search ADS
 
Potakis
N.
,
Frontistis
Z.
,
Antonopoulou
M.
,
Konstantinou
I.
 &
Mantzavinos
D.
2017
Oxidation of bisphenol A in water by heat-activated persulfate
.
J. Environ. Manage.
195
,
125
–
132
.
Google Scholar
Crossref
Search ADS
PubMed
 
Rodriguez-Narvaez
O. M.
,
Peralta-Hernandez
J. M.
,
Goonetilleke
A.
 &
Bandala
E. R.
2017
Treatment technologies for emerging contaminants in water: A review
.
Chem. Eng.
323
,
361
–
380
.
Google Scholar
Crossref
Search ADS
 
Sun
B.
,
Ma
W.
,
Wang
N.
,
Xu
P.
,
Zhang
L.
,
Wang
B.
,
Zhao
H.
,
Lin
K.-Y. A.
 &
Du
Y.
2019
Polyaniline: A new metal-free catalyst for peroxymonosulfate activation with highly efficient and durable removal of organic pollutants
.
Environ. Sci. Technol.
53
,
9771
–
9780
.
Google Scholar
Crossref
Search ADS
PubMed
 
Tarafdar
A.
,
Sirohi
R.
,
Balakumaran
P. A.
,
Reshmy
R.
,
Madhavan
A.
,
Sindhu
R.
,
Binod
P.
,
Kumar
Y.
,
Kumar
D.
 &
Sim
S. J.
2022
The hazardous threat of bisphenol A: Toxicity, detection and remediation
.
J. Hazard. Mater.
423
,
127097
.
Google Scholar
Crossref
Search ADS
PubMed
 
Wang
A.
,
Fan
R.
,
Pi
X.
,
Zhou
Y.
,
Chen
G.
,
Chen
W.
 &
Yang
Y.
2018a
Nitrogen-doped microporous carbons derived from pyridine ligand-based metal-organic complexes as high-performance SO2 adsorption sorbents
.
ACS Appl. Mater. Interfaces
10
,
37407
–
37416
.
Google Scholar
Crossref
Search ADS
PubMed
 
Wang
L.
,
Yan
W.
,
He
C.
,
Wen
H.
,
Cai
Z.
,
Wang
Z.
,
Chen
Z.
 &
Liu
W.
2018b
Microwave-assisted preparation of nitrogen-doped biochars by ammonium acetate activation for adsorption of acid red 18
.
Appl. Surf. Sci.
433
,
222
–
231
.
Google Scholar
Crossref
Search ADS
 
Xing
J.
,
Zhang
S.
,
Zhang
M.
 &
Hou
J.
2022
A critical review of presence, removal and potential impacts of endocrine disruptors bisphenol A
.
J. Comp. Biochem. Physiol., Part C: Toxicol. Pharmacol.
254
,
109275
.
Google Scholar
 
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