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/lp/springer-journals/unveiling-the-synergistic-effect-of-internal-fe-single-atoms-and-ZC0ooA9HdS
- Publisher
- Springer Journals
- Copyright
- Copyright © The Author(s) 2023
- ISSN
- 2524-7972
- eISSN
- 2524-7867
- DOI
- 10.1007/s42773-023-00221-1
- Publisher site
- See Article on Publisher Site
Abstract
1 Introduction attracted the attention of researchers (Cai et al. 2022). Nitenpyram (NTP) is a neonicotinoid pesticide that PMS-AOPs can remove refractory organic pollutants has been promoted to replace highly toxic organophos- with high efficiency and easy operation by the highly phorus pesticides. In recent years, some reports have reactive oxygen species (ROS) like hydroxyl radical ·− shown that NTP has frequently appeared in tea (Li (·OH, 1.8–2.7 V) and sulfate radical ( SO , 2.5–3.1 V ) et al. 2020b). Not only that, NTP has been detected in (Wang et al. 2020a). During the process of PMS-AOPs infants (2.8% of children had a hazard index between on organic pollutants removal, the core issue is how to −1 0.1 and 1.0) and adolescents (1.79 μg g creatinine) improve the activation efficiency of PMS. Therefore, (Wang et al. 2020b; Zhou et al. 2021b), and tap water various transition metal-based catalysts have been and fresh vegetables are presumed to be potential researched for the activation of PMS, especially iron, a sources. Although the researchers suggest it is not very common, reactive and inexpensive element (Han et al. harmful to human health, NTP is highly toxic to bees, 2020). However, there have been disadvantages of metal an agriculturally important organism. Moreover, it is ion leaching and unsatisfactory catalytic performance highly toxic to silkworms, which is significant in biol - in a long term (Pan et al. 2021). Hence how to improve ogy and possesses great economic benefits for agri - the anchor and catalytic efficiency of iron is the current culture (Yu et al. 2016; Zhu et al. 2020). Therefore, the hot pot. residual harm of NTP in the water environment should Fortunately, the emergence of single-atom catalysts not be underestimated. (SACs) can solve the problem of the low activation effi - Up to date, the NTP removal methods mainly include ciency of PMS. Compared with mononuclear metal low-temperature plasma process, microbial process, compounds and metal nanoparticles (NPs), SACs own and photocatalytic degradation (Li et al. 2013; Pang extraordinary catalytic activity, selectivity and stability, et al. 2020; Tang et al. 2020c), however, these meth- including oxidation and water–gas conversion (Li et al. ods possess many disadvantages such as high energy 2021c). So far, abundant work of single-Fe-atoms on PMS consumption, limited reaction conditions and low activation for organic pollutants degradation have been efficiency. In this case, the advanced oxidation pro - reported (Wang et al. 2021; Yang et al. 2022; Zhang et al. cess based on persulfate activation (PMS-AOPs) has 2022). However, the introduction of the single iron atom Xiong et al. Biochar (2023) 5:19 Page 3 of 18 into the material is difficult because of the extremely application. This work proposed an in-depth insight high surface energy of isolated atoms and the strong ten- into the synergistic mechanism of iron single atoms and dency for atoms to aggregate (Cui et al. 2021). The com - iron compounds and a feasible scheme for the functional mon strategy is to use N defects to anchor the dispersed transformation and efficient utilization of EP. Fe atoms and construct a catalyst containing transition iron–nitrogen coordination in a metal-nitrogen-carbon 2 Material and methods (Fe–N–C) framework, which is usually accompanied by 2.1 Materials and chemicals the consumption of nitrogen precursors (Sun et al. 2020). All chemicals were purchased from Sinopharm Chemi- Moreover, when using this method in biochar, the iron cal Regent Co. Ltd (Shanghai, China), including NTP compounds will concomitantly generate with the intro- (purity > 96.5%), iron acetylacetonate (Fe(acac)), Fe C, duction of Fe atoms, especially the iron carbide (Fe C) 3 3 γ-Fe O , peroxymonosulfate (PMS), tert-butyl alco- due to the high temperature pyrolysis and anoxic atmos- 2 3 hol (TBA), methanol (MeOH), furfuryl alcohol (FFA), phere. However, most studies focus on the activation of and p-benzoquinone (p-BQ). Unless otherwise stated, PMS by the interaction between single-atom catalysis or all experiments in this work used ultrapure water (Eco- the transition metal compounds and biochar (Gao et al. S15Q, Hitech Instruments Co. Ltd., Shanghai, China). 2021; Pang et al. 2021; Zhang et al. 2022). Some works are concerned with the interaction of Fe with N doping (Yao et al. 2022), or with the interaction of different sizes of 2.2 Catalyst preparation iron, such as the comparison of nanoscale Fe with single- Two grams of EP powder was dispersed in 50 mL etha- atom Fe (Li et al. 2021c). But those works neglect the syn- nol, and then Fe(acac) was added. The mixed precur - ergistic activation of PMS by single-atom and compound. sor was ultrasonicated for fully uniform for 5 min. Then Especially in biochar, it is inevitable that some Fe-rich it was transferred to a constant temperature water bath biomass produces internal Fe single atoms during high and stirred vigorously at 40 °C until ethanol was com- temperature pyrolysis (Peng et al. 2021). In this case, the pletely evaporated. After that, the prepared precursor introduced Fe compound will interact with the internal was placed in a tube furnace, and heated to 900 °C at a Fe single atoms. However, the synergistic mechanism of −1 rate of 5 °C·min with a nitrogen atmosphere for 3 h. iron single atoms and iron compounds on enhanced PMS After cooling, it was taken out and washed 3 times with activation is still confusing and needs further investiga- ultrapure water and ethanol, respectively. Then it was tion. In this case, in situ N-rich Enteromorpha (EP) was dried in an oven at 60 °C for 24 h. In the order of the selected (Xiong et al. 2021b). The abundant inner N of EP amount of Fe(acac) added (0.019 g, 0.038 g, 0.076 g and possesses huge potential for N defect formation, thereby 0.152 g), the obtained biochar was named as SFB900-1, easily forming a Fe–N–C framework with the introduced SFB900-2, SFB900-3 and SFB900-4. For comparison, the iron during the pyrolysis process to achieve the anchor- blank biochar without Fe(acac) was prepared and named ing of Fe single atoms (Peng et al. 2021). Besides, EP is SFB900-0. one of the causes of red tides in the Yellow Sea, China (Qiu et al. 2020). Its impact on the local marine ecol- ogy and surrounding economy cannot be underesti- 2.3 Characterization and analytical methods mated, so it has great significance to find a way for EP The morphologies of all as-prepared materials were functionalization. characterized by transmission electron microscope In this work, biochar loaded with single Fe atoms and (TEM) using a Tecnai F20 (FEI, USA). XPS patterns the iron compound was prepared and used for efficient were obtained using a K-Alpha spectrometer (Thermo PMS activation for NTP removal. The batch experiment Fisher Scientific, USA) equipped with monochro - showed that the synergy of Fe single atoms and their matic Al Kα X-rays at 1486.6 eV. The Fourier transform compounds greatly enhanced the performance of NTP infrared (FT-IR) spectra of the nanocomposites were removal. The removal ratio was raised from 53.6% to obtained with a Nicolet iS10 spectrometer (Thermo 89.5%. This is attributed to the fact that the internal Fe Nicolet, USA) as KBr (mass ratio of 1:200) pellets. The single atom increases the adsorption energy of the cata- crystal structures of the nanocomposites were analyzed lyst to the PMS and the tendency of electron transfer to by X-ray diffraction (XRD) (Bruker, Germany) with the PMS, which is conducive to the PMS decomposi- Cu Kα radiation (λ = 1.54 nm) over a 2θ range of 10° to tion. Then, the combination of Fe C further intensifies −1 80° at a scanning rate of approximately 10°·min . The the process. Free radical and non-radical pathways were Raman spectra were analyzed using Raman spectros- explained in detail. Finally, the experiment of effecting copy (Thermo Fischer DXR, USA). A300 EMXplus-10/12 factors verified the ability of the material in practical EPR spectrometer (Bruker, Germany) was 0.1 mol Xiong et al. Biochar (2023) 5:19 Page 4 of 18 which are the stand of pristine biochar and the best per- L−15,5-dimethyl-1-pyrroline N-oxide (DMPO) was used formance modified biochar, respectively. As shown in as a capture agent. Fig. 1a, some pure iron clusters (dark dots) were exhib- ited on SFB900-0. Figure 1b further points out the lattice 2.4 Catalysis experiments of the Fe clusters, which is referred to the high percent- The NTP removal by SFB900 on PMS activation was in −1 age of in situ Fe elements in EP. Therefore, without intro - a 25 °C constant temperature stirrer (160 r min ). The duced Fe, the SFB900-0 still has Fe single atoms existing porous structure is expected to give SFB900 a superior in the form of Fe–N–C. This result is in line with previ - adsorption capacity, which is not negligible for the over- ous research (Peng et al. 2021), due to the EP possessing all catalytic performance. Therefore, in the SFB900/PMS/ abundant iron and nitrogen elements. After being modi- NTP system, the test experiment was divided into two fied with Fe(acac) , more iron compounds were produced parts: adsorption and degradation. In the first 30 min, −1 −1 on SFB900-3 (the bigger dark dots in Fig. 1c). Further- the SFB900 (0.2 g L ) can adsorb NTP (40 mg L ) to −1 more, Fig. 1d indicates the lattice of the pure Fe clus- reach equilibrium. Then, with PMS (0.5 g L ) added, ter, Fe O and Fe C on SFB900-3. This finding suggests SFB900 can activate PMS to degrade NTP within 60 min. 2 3 3 that more iron compounds and carbide species were gen- Without other states, all experiments were performed at erated with the introduction of Fe(acac) . So there were the initial pH = 5.87 without adjustment. The samples both Fe single atoms and iron compounds on SFB900-3. were extracted at 0.5 mL and filtered with a 0.22 μm fil - Then, the HAADF-STEM image and corresponding ele - ter membrane at selected intervals. Then, the collected ments mapping profiles for C, N and Fe in SFB900-0 and sample was detected by high performance liquid chroma- SFB900-3 are presented in Fig. 1e, f, respectively. Both tography (HPLC, Agilent 1100, USA). All control experi- figures exhibit the uniform distribution of C, N, and Fe in ments without PMS and/or catalysts were performed SFB900-0 and SFB900-3. Besides, the C and N elements under the same reaction conditions. In order to verify the possess approximate density. The abundant in situ N pro - reuse performance of the prepared materials, the used vides the possibility for the N defects to further generate materials were collected and dried after being washed the Fe–N–C in both pristine biochar and modified bio - with water and ethanol. The cycle experiment was char (Xiong et al. 2021c; Xu et al. 2020). As for iron ele- repeated for 3 rounds. All experiments were performed ments, they are distributed uniformly in SFB900-0, which in duplicate or triplicate, and the average value was taken is also consistent with previous work (Peng et al. 2021). for analysis. Naturally, the percentage of Fe in SFB900-3 is much higher than in SFB900-0, which indicates the successful 2.5 Computational details introduction of Fe. Therefore, abundant N defects and Fe The first-principles calculations based on DFT were car - elements ensure the possibility of the coexistence of Fe ried out on the Vienna Ab initio Simulation Package single atoms and iron compounds. (VASP) code, using the Perdew-Burke-Ernzerh function The BET results, porosity characterizations and for the exchange–correlation potential. The interaction nitrogen adsorption–desorption isotherms of all as- between ions and electrons was described by projec- prepared catalysts are shown in Table 1 and Additional tor augmented wave pseudopotential. The cutoff energy file 1: Fig. S1. Notably, the specific surface area (SSA) of was 400 eV for the valence electrons. For structure opti- all samples was small. It is maybe due to the collapse of mization, a vacuum space of 15 Å along the z-direction porous structures at high temperature (900 °C). Besides, was used to avoid the periodic image interaction between the SSA of the as-prepared material was significantly neighboring slabs, and a 4 × 4 × 1 k-point Γ-centered negatively correlated with the amount of Fe(acac) , mesh was used for the calculation. The energy crite - –5 indicating that the generated Fe-products blocked rion was 10 eV/atom for each step, and all atoms were the porous structure of the biochar. The SEM images fully relaxed until the force on each atom was less than -1 of all as-prepared catalysts intuitively exhibited this 0.03 eV Å . In this work, a 1 × 1 × 1 supercell of F e C (0 result (Additional file 1: Fig. S2). SFB900-0 possessed 3 1) binding with the functionalized graphene plane with a smooth surface with few pores and hence the SSA a rectangular boundary (10.08 Å × 9.60 Å × 20.00 Å) was was small. With the increasing of Fe(acac) amounts, used as the substrate for the adsorption of PMS. All pre- the iron compounds on the catalyst surface gradually sented models were drawn by VESTA. increased leading to the pores being blocked. The total pore volume of all as-prepared samples in Additional 3 Results and discussion file 1: Fig. S1a has confirmed this hypothesis. The initial 3.1 Characterization volume is small, and becomes progressively smaller as The morphology and elemental mapping of two typi - Fe(acac) increases. Then, the pore size analysis showed cal biochar SFB900-0 and SFB900-3 are shown in Fig. 1, 3 Xiong et al. Biochar (2023) 5:19 Page 5 of 18 Fig. 1 TEM images of (a, b) SFB900-0 and (c, d) SFB900-3 samples at 50 nm and 5 nm. HAADF-STEM image and corresponding EDS mapping profiles for C, N and Fe in (e) SFB900-0 and (f) SFB900-3 Table 1 BET results and porosity characterizations of as-prepared materials 2 −1 2 −1 2 −1 3 −1 3 −1 Materials S (m g ) S (m g ) S* (m g ) V (cm g ) V (cm g ) Ave-pore BET mic mes total mic radius (nm) SFB900-0 27.1 14.6 12.5 0.022 0.006 3.16 SFB900-1 24.6 12.7 11.9 0.019 0.006 3.21 SFB900-2 18.5 11.4 7.1 0.015 0.005 2.85 SFB900-3 12.3 8.1 4.2 0.008 0.003 2.97 SFB900-4 10.7 6.6 4.1 0.007 0.003 3.08 *S = S − S mes BET mic that all samples had a similar porous structure with an were consistent with type-IV isotherms, characteristic average pore radius of 3.05 nm and a standard devia- of mesoporous adsorption. This result is also consist - tion of 0.15. This result can also obtain by pore size ent with the pore size analysis. Given the unsatisfactory distribution images in Additional file 1: Fig. S1b–f. All porous structure in all samples, its excellent adsorp- these images exhibited a sharp peak at 2–4 nm, indicat- tion capacity for NTP may be related to the surface ing the presence of abundant mesopores with smaller Fe-products. sizes inside those as-prepared catalysts. Moreover, the XRD pattern in Fig. 2a further ensures the existence corresponding nitrogen adsorption–desorption curves of iron compounds on SFB900-3. In fact, due to the Xiong et al. Biochar (2023) 5:19 Page 6 of 18 Fig. 2 (a) XRD pattern, (b) Raman spectrum and (c) FT-IR of all as-prepared materials. XPS high-resolution (d) Fe 2p and (e) N 1 s of all as-prepared materials. ( The next column refers to the total Fe or total N content) introduction of Fe (SFB900-1), F e O and Fe C were biochar and has little effect on the carbon skeleton struc - 2 3 3 generated in the material. As shown in Fig. 2a, all as- ture. Namely, the introduction of iron does not affect the prepared samples had typical peaks of carbon at 2θ = 27°, defect in pristine biochar. The defects in all samples pre - which indicates successful carbonization. Besides, except sented few influences on their ability to activate persul - for SFB900-0, all samples exhibited typical peaks of Fe O fate for NTP removal. Additionally, the result of FT-IR 2 3 (JCPDS No. 39-1346) and Fe C (JCPDS No. 35-0772). exhibited a similar finding to Raman spectra, which Furthermore, it can be seen that the peaks of F e O and eliminates the role of surface functional groups of those 2 3 Fe C evolved sharper with the increase of introduced-Fe as-prepared catalysts in PMS activation. Figure 2c shows content. This result infers that the higher concentration that all as-prepared samples possess similar surface func- of iron added during the preparation process, the bet- tional groups, including the O–H bond and C=C bond ter crystallinity of the Fe O and Fe C in the as-prepared (Shi et al. 2019; Wu et al. 2016). This result suggests that 2 3 3 materials. the introduction of iron had little influence on the surface The D band and G band in the Raman spectrum reflect functional groups in all samples. Although the peak of the disorder and defects in the carbon layer, and graph- the C–O bond in SFB900-3 and SFB900-4 appeared split, ite structure in biochar, respectively (Fig. 2b). The D band which only indicates that the increase of introduced-Fe and G band were observed in all as-prepared samples, snatched the oxygen in biochar, so the part of the C–O indicating the presence of defects and graphite structures bond split into the C–H bond (Li et al. 2019). in them. The intensity ratio (I /I ) was commonly used The XPS spectrum was provided to exhibit the chemi - D G to evaluate the degree of defect for biochar (Xiong et al. cal bonds of Fe 2p and N 1 s in all as-prepared materials. 2021a). In this case, the I /I value of the five samples In Fig. 2d, there are only two typical peaks in 714.1 eV and D G was almost no different. This finding indicates that the 710.4 eV in SFB900-0, which correspond to the Fe (III) addition of Fe(acac) does not affect the defect state of EP and Fe (II), respectively (Lawrinenko et al. 2017; Yang 3 Xiong et al. Biochar (2023) 5:19 Page 7 of 18 et al. 2019). With the increasing Fe content in SFB900, As shown in Fig. 2e, all materials had four typical peaks more peaks emerged in SFB900-1 and SFB900-2. This in 400.8 eV, 399.6 eV, 398.1 eV and 397.0 eV with or with- finding suggests that a variety of iron compound species out little fluctuation. Those four peaks are referred to are generated due to the externally introduced iron. Fur- the graphite N, pyrrolic N, Fe–N bond and pyridinic N, thermore, there was even a typical Fe peak and satellite respectively. The appearance of the Fe–N bond proved peak in SFB900-3 and SFB900-4 because of the higher the existence of Fe–N–C, as well as the existence of single content of introduced Fe (Xiong et al. 2020a). The change Fe atoms (Li et al. 2016). Similarly, the volatility of Fe–N in total Fe content in SFB900 intuitively showed this pro- bond content may be the result of the irregular distribu- cess. The total Fe content kept increasing attributed to tion of N defects. In fact, compared with other elements, the modification process, which also: proved the iron was the ratio of N content is very low (< 3.53%). So this vola- successfully loaded. On the contrary, the total N content tility of Fe–N bond content is ignorable (0.40–0.75%). did not change significantly in SFB900 (Fig. 2e). Because In other words, the content of iron compounds species there was a shortage of introduction of external nitrogen. played an important role in the synergy effect. Besides, the weak volatility of total N content in materials may be attributed to the uneven distribution of in situ N. Fig. 3 a Adsorption and degradation performance of all as-prepared materials on NTP and (b) the related k . c Correlation analysis of iron app content and adsorption/ degradation capacity of all as-prepared materials. The effect of (d) PMS dosage and (e) catalyst dosage on NTP removal. f Quenching experiment on NTP removal by prepared materials. EPR detection of (g) hydroxyl radical, sulfate radical, (h) superoxide radical and (i) −1 −1 −1 singlet oxygen during the test of NTP removal. Conditions: [Biochar] = 0.2 g L , [PMS] = 0.5 g L , [NTP] = 40 mg L , [temperature] = 25 °C, [initial pH] = 5.87, [ TBA] = [MeOH] = 0.5 M, [FFA] = [p-BQ] = 0.1 M Xiong et al. Biochar (2023) 5:19 Page 8 of 18 3.2 Catalytic performance To comprehensively consider the reaction efficiency NTP was selected as a target pollutant to evaluate the and economic cost in practical applications, the dosage of catalytic performance of all as-prepared materials for PMS and material were studied. As shown in Fig. 3d, the PMS activation. As shown in Fig. 3a, compared with non- SFB900-3/PMS system possessed the worst NTP removal −1 modified SFB900-0, all iron-loaded materials showed rate (60.4%) when the PMS dosage was 0.2 g L . While it a higher removal effect on NTP. In addition, the mate - raised to the highest when the PMS dosage reached 0.5 g −1 rial with higher iron content possessed better catalytic L . Besides, from the k shown in Additional file 1: Fig. app ability. These results indicate that there is a certain syn - S3, the rate is also the highest when the PMS dosage is −1 ergistic effect between EP biochar and iron (Liu et al. 0.5 g L . Thereafter, the removal efficiency of NTP was 2021). According to the previous analysis, the defect and negatively correlated with the concentration of PMS. functional groups on catalysts present few differences. This is maybe caused by the excess PMS agglomeration Besides, all as-prepared materials possessed similar con- that reduces the reaction efficiency of the SFB900-3/PMS tent of a single Fe atom due to the approximative in situ system (Jiang et al. 2019; Tian et al. 2020). Therefore, a −1 N ratio. Therefore, this improvement may be attributed PMS concentration of 0.5 g L had the highest efficiency to the synergy of a single Fe atom captured by in situ N and lowest economic cost. Then, the effect of SFB900-3 and abundant iron oxide species that were externally dosage on NTP removal is exhibited in Fig. 3e. The introduced. However, SFB900-4, the material with the SFB900-3 had excellent adsorption capacity for NTP, so highest iron content, had a similar removal ratio of NTP it could completely remove NTP by adsorption when its −1 (90.1%) to SFB900-3 (89.5%). This result further confirms dosage reached 2.0 g L . However, based on the result the synergy of the single iron atom and iron oxide spe- of the NTP removal rate within 90 min, the SFB900-3 −1 cies in modified catalysts and indicates that this synergy dosage of 0.2 g L possessed the best economic ben- is related to the content of iron oxide species. Curiously, efits. Because the NTP removal rate at this concentration in the adsorption stage, the iron content in the materi- was only ~ 6% lower than the highest efficiency. Moreo - −1 als showed a clear correlation with its adsorption capac- ver, despite the k of 0.2 g L in the adsorption stage app −1 ity for NTP. This finding is consistent with BET analysis, being poorer than the dosage of 2.0 g L , it possessed the porous structure is poorer as the Fe(acac) increases, the highest k in the degradation stage (Additional 3 app −1 −1 and hence the Fe products play a more important role. file 1: Fig. S4). The dosage between 0.2 g L and 2.0 g L Furthermore, Fig. 3b exhibits the related apparent rate exhibited a similar performance, and the NTP removal −1 constant (k ) of materials on NTP removal in the rate by SFB900-3 at 0.1 g L was only 73%. Hence the app −1 adsorption stages. The value of k increased with the optimum dosage of PMS and SFB900-3 was 0.5 g L and app −1 higher iron content. However, the k of degradation rate 0.2 g L , respectively. The subsequent experiments were app showed a poor correlation with iron content. Moreover, carried out with these dosages. Fig. 3c further reveals the relation of adsorption or deg- radation performance with iron content. In the adsorp- 3.3 Active species detection of NTP removal on SFB900-3 tion step, the linear correlation coefficient (R ) reached a After revealing the intuitive reaction performance very significant level (n = 3, R = 0.9765 > 0.959) and a sig- of the SFB900-3/NTP/PMS system, the quenching nificant level (n = 4, R = 0.9476 > 0.878) in different cases experiments are helpful to explore more in-depth reac- (Xiong et al. 2020b). This result indicates that the Fe-load tion mechanisms in the process of NTP degradation greatly enhanced the adsorption capacity of SFB900 on (Tang et al. 2022a; Zheng et al. 2022). In this work, the NTP. In the degradation step, the linear correlation coef- tert-butanol (TBA), methanol (MeOH), furfuryl alco- ficient between the NTP degradation rate and loaded-Fe hol (FFA), and p-benzoquinone (p-BQ) were selected ·− amount (R = 0.8238) was much higher when the loaded- to quench ·OH, both SO and ·OH, singlet oxygen Fe amount was below (SFB900-3, 0.076 g). When the ( O ), and superoxide radicals (·O ), respectively (Tang loaded-Fe amount further increased (SFB900-4, 0.152 g), et al. 2022b). As shown in Fig. 3f, after the addition the linear correlation coefficient value largely decreased of TBA and MeOH, the NTP removal rate decreased (R = 0.5920). Considering that the different SFB900 own to 74.3% and 67.8%, respectively. Because TBA reacts ·− a similar amount of internal single iron atom, while the with ·OH more preferent than SO (k = (3.8– TBA/·OH 8 −1 −1 ·− 5 −1 −1 higher introduced iron compounds (SFB900-4 compared 7.6) × 10 M s; k = (4.0–9.1) × 10 M s ), TBA/SO 4 ·− to SFB900-3) cannot further improve the removal rate but MeOH with ·OH and SO in a relatively compa- 8 −1 −1 of NTP. This finding infers that the iron species possess rable kinetic manner (k = 9.7 × 10 M s ; MeOH/·OH ·− 6 −1 −1 a limited promotion effect on NTP removal by SFB900. k = 3.2 × 10 M s )(Fang et al. 2021). There - MeOH/SO Moreover, it indicates the potential synergistic effect of fore, the results in Fig. 3f indicate the few contributions of ·− ·− iron single atoms and iron species on NTP degradation. SO and ·OH, but the contribution of SO was higher 4 Xiong et al. Biochar (2023) 5:19 Page 9 of 18 ·− finding of Fig. 3a, pure SFB900-0 possessed poor adsorp- than that of ·OH. Hence the strong peaks of SO and tion ability on NTP removal, while the introduced Fe was ·OH were detected in EPR (Fig. 3g). Notably, the NTP beneficial for NTP adsorption. However, in Fig. 4a–c, all removal rate decreased to 17.6% and 14.5% after the addi- those mixed systems of SFB900-0/iron-compounds had tion of FFA and p-BQ, respectively. It was almost com- bad adsorption ability on NTP removal, and the k in pletely inhibited in the degradation stage, and the k app app the adsorption stage was much lower than that of the of NTP removal after the addition of FFA and p-BQ was SFB900-3 (Additional file 1: Fig. S6–S8). This result indi - nearly zero (Additional file 1: Fig. S5). This result suggests cates that the free iron compounds can hardly influence the great contributions of O and ·O . However, the EPR 2 2 the surface property of SFB900-0, and the improvement detection exhibited a weak peak of ·O (Fig. 3h), which of adsorption capacity is mainly due to the strong posi- may be related to its rapid conversion to O due to a fast 2− 1 − tive charge brought by the iron that is immobilized on reaction: ·O + ·OH → O + OH (Tang et al. 2022c). the surface of biochar (Feng et al. 2021). After the addi- Therefore, O may be the most significant active species tion of PMS, the SFB900-0/Fe O system exhibited the in the SFB900-3/PMS/NTP system. Encouragingly, the 2 3 worst NTP degradation rate at 52.1% (2 wt%), 58.6% (4 EPR detection was consistent with this hypothesis via the wt%) and 63.5% (8 wt%), respectively. The NTP removal strong peak of O (Fig. 3i). rate was greatly decreased compared with the SFB900-3 The main active species in the SFB900-3/PMS/NTP result. The k in the degradation stage was greatly system have been revealed. Then, which iron com - app reduced, which was at most 3.29 times lower than that pounds play a significant role in NTP removal needs to of the SFB900-3 (Additional file 1: Fig. S6). The results be carefully screened. This is helpful to further explore of the SFB900-0/Fe C system were better, those materi- the synergistic effect of iron compounds and iron single als with different amounts showed the fine NTP removal atoms on the activation of PMS by SFB900-3. As shown rate as 69.1% (2 wt%), 72.9% (4 wt%) and 77.6% (8 wt%), in Fig. 4, the NTP removal rate on mixed SFB900-0 and respectively. In addition, the k in the degradation stage various stable iron compounds was detected. As the app Fig. 4 SFB900-0/PMS system for NTP removal after supplemented with different amounts (a) Fe O , (b) Fe C and (c) calcined Fe(acac) . d XRD 2 3 3 3 −1 −1 −1 pattern of calcined Fe(acac) . Conditions: [Biochar] = 0.2 g L , [PMS] = 0.5 g L , [NTP] = 40 mg L , [temperature] = 25 °C, [initial pH] = 5.87 3 Xiong et al. Biochar (2023) 5:19 Page 10 of 18 was almost double the value of SFB900-0/Fe O (Addi- completely carbonized into Fe C in the hypoxic atmos- 2 3 3 tional file 1: Fig. S7). This finding indicates that the main phere under high temperatures. To sum up, there existed role of the iron compounds for PMS activation is F e C. both Fe O and F e C in the SFB900-3, and the latter 3 2 3 3 Besides, the decreased NTP removal rate may be caused played a significant role in the PMS activation. Moreover, by the hardly interactive free F e C and the single-Fe the NTP removal rate on the mixed SFB900-0/calcined atom embedded in SFB900-0. Subsequently, considering Fe(acac) was poor than that of the SFB900-3, which indi- that the preparation method of SFB900-3 in this work cates the potential synergy of iron single atoms and iron is related to the addition of Fe(acac) . The pure calcined compounds, and mainly the Fe C. 3 3 Fe(acac) was prepared under the same pyrolysis condi- tions. The NTP removal rate on the SFB900-0/calcined- 3.4 Investigation of interfacial interaction and active sites Fe(acac) system was 67.1% (2 wt%), 71.0% (4 wt%) and with DFT calculation 74.6% (8 wt%), respectively. Curiously, this result was To further explore the potential synergistic effect of similar to the value of the SFB900-0/Fe C system. Even single Fe atoms and F e C, and reveal the possible active 3 3 the k of those two systems were similar (Additional sites in the three systems, C/PMS, Fe–N–C/PMS and app file 1: Figs. S7 and S8). This finding is reasonable when Fe–N–C/Fe C/PMS, the adsorption of PMS on dif- the XRD pattern revealed the crystal structure of cal- ferent systems were analyzed by DFT calculations. cined Fe(acac) (Fig. 4d). The calcined Fe(acac) has Meanwhile, to reveal the electron transfer at the PMS- 3 3 almost coincided with the standard PDF card of Fe C. substrate interface, charge density analysis and Bader It is speculated that Fe(acac) may deprive some of charge analysis were performed, as shown in Fig. 5. The the oxygen in the biomass and partly produced F e O amount of electron transfer can be visualized by the 2 3 when pyrolyzed together with the EP powder, while it is three-dimensional charge density difference, as shown Fig. 5 Adsorption energies and the corresponding three-dimensional charge density difference calculated by DFT with different structures: (a) C/ PMS, (b) Fe–N–C/PMS and (c) Fe–N–C/Fe C/PMS. d Profile of the planar averaged charge density difference as a function of the position in the z direction. e Charge variation of O atoms and active sites in different structures by using the Bader method Xiong et al. Biochar (2023) 5:19 Page 11 of 18 in Fig. 5a–c. In all three configurations, there is a sig - adsorption sites or active sites tend to lose electrons, and nificant electron transfer between PMS and catalyst, the values of C, Fe–N–C and Fe–N–C/Fe C are 0.050 eV, indicating that PMS is through chemisorption on the 1.174 eV and 0.658 eV, respectively. The results are con - substrate, and the interaction of Fe–N–C/Fe C/PMS sistent with the findings of the charge density difference. is the strongest, followed by Fe–N–C/PMS. The differ - These phenomena indicate that Fe atoms as active sites ence in the average charge density of the correspond- greatly enhance the adsorption capacity of the as-pre- ing plane perpendicular to the carbon layer direction pared material for PMS. further confirms the larger amount of charge transfer The dissociation process of PMS in the three systems, in Fe–N–C/Fe C/PMS (Fig. 5d). In addition, the elec- from the initial state to the final state, is shown in Fig. 6a– tron depletion region is almost uniformly distributed in c. During this process, the l (O –O length) in PMS O-O 1 2 the C/PMS system, while it is concentrated around Fe was used to measure the ease of O–O bond breaking atoms in Fe–N–C/PMS and Fe–N–C/Fe C/PMS, while for each system (Additional file 1: Table S2). The reason the electron accumulation region appears in the PMS for the O–O bond elongation is that the electron distri- closest to the catalyst. On the O atom, this means that bution on the PMS changes when interacting with the electrons are more easily transferred to the PMS (Li three different materials. In the three systems, the O–O et al. 2020a; Liu et al. 2020). bond length changes is in the order: Fe–N-C/Fe C/PMS Bader charges (Fig. 5e and Additional file 1: Table S1) (from 1.467 Å to 3.890 Å) > Fe–N–C/PMS (from 1.468 Å further provide quantitative results of the charge trans- to 2.786 Å) > C/PMS (from 1.411 Å to 2.557 Å). The find - fer, where a clear charge redistribution can be observed. ing indicates that the Fe–N–C/Fe C system may be the Both O atoms of the O–O bond in PMS accepts electrons most favorable for PMS activation. Furthermore, Fig. 6d of three structures, in the order of Fe–N–C/Fe C > Fe– indicates that the dissociation of PMS on the surface of N–C > C. The C atoms or Fe atoms in the corresponding C is an endothermic reaction, while it is an exothermic Fig. 6 Structure of PMS molecules adsorbed on (a) C, (b) Fe–N-C and (c) Fe–N-C/Fe C. d Schematic illustration and calculated potential energy profiles of PMS dissociation processes over the different systems Xiong et al. Biochar (2023) 5:19 Page 12 of 18 Scheme 1 Mechanism of the synergistic promotion of PMS activation by Fe single atoms and Fe C in SFB900-3 reaction on the surfaces of Fe–N–C and Fe–N–C/Fe C, the addition of Fe C, the change of O–O bond in PMS is 3 3 with ΔE of 1.025 eV, −0.584 eV and −1.158 eV, respec- further enlarged, and l reaches the maximum value. O-O tively. This result indicates that the PMS dissociation step Meanwhile, Fe–N–C/Fe C exhibited the largest adsorp- is favorable in thermodynamics in all systems (except the tion energy (−4.214 eV) for PMS. In this case, Bader C/PMS system) (Meng et al. 2020). Besides, the change charge analysis showed that the electron transfer abil- in the energy barrier indicates that the O–O bond break- ity of Fe atoms in Fe C is much smaller than that of Fe– ing in PMS is fastest on the Fe–N–C/Fe C surface (Xue N–C, while the electron transfer occurring on O (from 3 1 et al. 2021). Taken together, the DFT calculation results −0.568 e to −0.577 e), O (from −0.581 e to −0.573 e) in showed that the Fe–N–C/Fe C system possessed the both systems is similar. This indicates that Fe single atoms optimal PMS activation performance, which sufficiently in Fe–N–C/Fe C play a synergistic role with Fe C on PMS 3 3 supported the synergistic promotion of PMS activation adsorption, resulting in a further increase in adsorption by Fe–N–C and F e C. energy. Finally, the analysis of the energy barrier pointed out that the activation process of PMS in the C/PMS sys- tem is unfavorable in thermodynamics. The Fe single atom 3.5 S ynergy of Fe single atoms with F e C to the enhanced turns the PMS cracking process favorable in thermody- PMS activation namics (ΔE from 1.025 eV to −0.584 eV), which greatly After comprehensively analyzing the results of ROS improves the PMS activation performance of the material. detective experiments and DFT calculations, the syner- The synergistic effect of Fe–N–C and Fe C further pro- gistic mechanism of iron single atoms and F e C is shown moted the dissociation process of PMS, and the energy in Scheme 1. At first, the introduction of Fe single atoms barrier was reduced from −0.584 eV to −1.158 eV. This in pure carbon material (Fe–N–C) greatly enhances result indicates that Fe–N–C/Fe C has the optimal PMS the adsorption capacity of the material for PMS (from activation performance. Considering the whole reaction −0.953 eV to −3.252 eV), because the original electron dis- process, a total exothermic of 1.158 eV indicates that O tribution is disturbed (Fig. 5a, b). The strong electron loss could be easily generated in Fe–N–C/Fe C/PMS system, as ability of the Fe atom makes the O–O bond in PMS gains shown in Eqs. (1)–(6). more electrons. This process further leads to l increase O-O − ·− − in Fe–N–C-adsorbed PMS (Additional file 1: Table S2), 2HSO + SFB900−3 → 2SO + OH (1) 5 4 which is beneficial to the cleavage of PMS. Second, with Xiong et al. Biochar (2023) 5:19 Page 13 of 18 − ·− 2− adsorption of PMS due to the increase of positive charges 2HSO + SFB900−3 → SO + 2 · OH + SO 5 4 4 (Fig. 7b) (Wang et al. 2020c). As for the alkaline condi- (2) 2− tions, PMS will self-decompose to HSO , which cannot − 2− + 2− ·− HSO + SFB900−3 + H O →·O + 3H + SO 5 4 generate SO . Therefore, the pH value of the reaction (3) environment has less interference with the SFB900-3. − − − ·− + Inorganic anions such as HCO , Cl and NO are HSO + SFB900−3 + H O → SO + H (4) 3 3 5 5 widely present in wild aquatic environments, and can ·− react with reactive species (SO and ·OH) and affect the ·− ·− 1 2SO + SFB900−3 → 2SO + O (5) 5 4 catalytic reaction (Fig. 7c)(Li et al. 2021a; Yin et al. 2020). The results showed that the addition of these ions was 2− 1 − not conducive to the degradation of NTP, because they (6) ·O + ·OH → O + OH would react with PMS to form less active substances ·− 2− − · Then, NTP is degraded into various intermediate prod - (CO , ·Cl, ·Cl , ·ClOH and NO ) (Zhou et al. 2021a). ucts under the attack of O , and finally degraded into 2 Besides, they possess a similarly decreased k (Addi- app H O and C O which is confirmed by TOC results (Addi - 2 2 tional file 1: Fig. S11). tional file 1: Fig. S9). Further, the tap water (TW) and wild water (from Liuy- ang River (LW) and paddy water (PW), Changsha, China) were selected to confirm of ions influence. As the left part 3.6 En vironmental factors and applications shown in Fig. 7d, compared with the result of the con- To explore the stability and application capability of the trol team (ultrapure water), the NTP removal rate in TW, SFB900-3/PMS/NTP system, several environmental fac- LW and PW decreased by 8.6%, 20.2% and 18.9%, respec- tors were studied (Tang et al. 2022c). As shown in Fig. 7a, tively. The removal rate in PW was higher than that the the NTP removal rate was negatively correlated with the LW. Based on the composition analysis of LW and PW pH value of the system in both the adsorption and deg- (Table S3), it is speculated that the higher concentration radation stages. As shown in Additional file 1: Fig. S10, of chloride ions in PW may lead to the formation of more the k decreases as the pH value increases. Under app active species during the SFB900/PMS reaction (Qiu acidic conditions, the catalyst surface will enhance the Fig. 7 a pH value effect on NTP removal by SFB900-3. b Zeta potential of SFB900-3 under different pH values. c Common coexistent ion influence on NTP removal by SFB900-3. d Application of SFB900-3 to remove NTP in different aquatic environments and its cycle test in the laboratory −1 environment. The comparison of (e) Raman spectra and (f) XPS spectra of used and fresh SFB900-3. Conditions: [Biochar] = 0.2 g L , [PMS] = 0.5 g −1 −1 L , [NTP] = 40 mg L , [temperature] = 25 °C, [initial pH] = 5.87, [ions] = 2 mM Xiong et al. Biochar (2023) 5:19 Page 14 of 18 et al. 2019). Nevertheless, the NTP removal rate in LW attack of O , which makes it finally degraded to H O and 2 2 and PW still reached 69.1% and 72.4%, indicating that the CO . In Route 2, O is attacks the edge methyl groups 2 2 SFB900-3/PMS system possesses application potential in from the amino group to produce P2 (m/z = 256.09). wild aquatic remediation for NTP. Then, the most distal nitro group is replaced by a Moreover, the cycle utilization of the SFB900-3/PMS hydroxyl group and occurs to generate P4 (m/z = 227.69). system for NTP removal was tested. The NTP removal Meanwhile, the novel hydroxyl group may dehydrogenate rate was still 73.6% after three rounds. The decreased due to the strong oxidation ability of O and generate the removal rate may be due to the inevitable partial loss of P5 (m/z = 227.05) (Tang et al. 2020a, 2020b). Then, the surface active sites on SFB900-3 during PMS activation follow-up is consistent with Route 1 again. (Li et al. 2021b; Ye et al. 2021). This result suggests the To further explore the fate of intermediate products in stability of SFB900-3 in the process of NTP remediation. the process of NTP degradation, the abundance of NTP At last, the Raman and XPS spectra were selected and its products was intuitively exhibited (Additional for revealing the stability of SFB900-3’s structure. As in file 1: Fig. S13b, c). In Route 1, the NTP’s abundance was Fig. 7e, the I /I value indicates that the carbon skeleton decreased constantly with the catalytic process, while G D and structural defects in SFB900-3 exhibited few changes the trends of its intermediate products were chaotic. after PMS activation. Besides, Fig. 7f reveals the variation The evolution of the P1 (m/z = 300.03) was striking. Its of Fe in fresh and used SFB900-3, indicating there existed abundance increased soon in 0–20 min, then decreased the Fe(III)/Fe(II) cycle in SFB900-3 with some loss of Fe quickly until it disappeared completely in 20–60 min. ions (Fu et al. 2019; Zhen et al. 2021). This finding maybe Besides, the abundance of P1 was the highest in all NTP’s is the reason for the decrease in the NTP removal rate intermediate products in Route 1, which suggests that P1 on used SFB900-3. In this case, the iron leaching concen- was the main intermediate product. Notably, the inten- tration during the NTP removal on the SFB900-3/PMS sity of P3 (m/z = 242.04) appeared in 0 min, which can be system was detected by ICP-MS (Additional file 1: Fig. explained by the spontaneous degradation of NTP. More- S12). The results showed that the maximum iron con - over, the strong oxidation of O greatly increases its −1 centration was 0.109 mg L within 60 min, which meets decomposition rate. The abundance of P6 (m/z = 199.05) −1 the national emission standard (≤ 0.3 mg L ). Moreo- increased briefly and disappeared rapidly. This finding ver, this finding confirmed the former hypothesis of the implies that this product is a transient intermediate and decreased NTP removal rate, and it also indicated that transformed rapidly. The evolution of the remaining two the SFB900-3 possessed the stable ability for PMS activa- intermediates P7 (m/z = 170.07) and P8 (m/z = 113.01) in tion. In general, the SFB900-3/PMS system possesses the Route 1 was similar. The abundance of those intermedi - application potential in wild aquatic remediation. ate products showed a steady uptrend during the degra- dation process, which indicates that P7 and P8 were the most important products in the late stage of NTP deg- 3.7 P otential degradation pathways of NTP and toxicity radation. Then, in Route 2 (Additional file 1: Fig. S13c), analysis of its intermediates the P4 (m/z = 227.69) was the main intermediate product High-performance liquid chromatography-mass spec- in this NTP degradation pathway. Because its abundance trometry (HPLC/MS) was used to explore the interme- was the highest in all NTP’s intermediates, and its varia- diate products and the possible degradation pathways tion trend was similar to the P1 in Route 1. The finding of NTP (m/z = 270.07) by the SFB900-3/PMS system suggests a potential degradation mode on NTP degrada- (Additional file 1: Fig. S14–S20). There are two differ - tion in the SFB900-3/PMS system. The evolution of the ent potential degradation routes of NTP on SFB900-3/ P2 (m/z = 256.09) and P5 (m/z = 227.05) in Route 2 was PMS (Additional file 1: Fig. S13). In Route 1, the N-linked similar. The abundance of those intermediate products methyl groups are oxidized to carboxyl groups to gen- showed few changes during the degradation process. This erate P1 (m/z = 300.03). Then, the C–C bond attached finding implies that these products are transient interme - to the carboxyl group is broken under the continuous 1 diates and transformed rapidly. oxidation of the O , and the methyl group attached to At last, the Toxicity Estimation Software Tool (T.E.S.T.) the distal amino group is also removed. Those two reac - was introduced to further research the potential toxic- tions both cause P3 (m/z = 242.04) generation. After ity of NTP’s intermediates (Tao et al. 2020). The data of that, the distal nitro group is removed to generate P6 Daphnia LC (48 h), Fathead minnow LC (96 h) and 50 50 (m/z = 199.05). After that, a large group of branched Oral rat LD in the Consensus method was used to esti- chains connected by N is removed under the constant 1 mate the acute toxicity of those intermediates. As Table 2 attack of O , and the P7 (m/z = 170.07) is formed (Tang showed, the overall acute toxicity of these intermediates et al. 2020c; Zheng et al. 2022). At last, P8 (m/z = 113.01) exhibited a trend that the value increased first and then is gradually oxidized and broken under the continuous Xiong et al. Biochar (2023) 5:19 Page 15 of 18 Table 2 Toxicological of NTP and its intermediates predicted by T.E.S.T decreased. This result indicates that the acute toxicity of Furthermore, the main degradation pathways of NTP NTP intermediates was reduced during the degradation were explained through LC/MS analysis. The toxicity of process. Notably, the later appearance of NTP intermedi- the intermediate product was simulated and analyzed to ates, the greater the bioconcentration factor. It is specu- show that the catalytic system is effective in degrading lated that the early intermediates are normally unstable NTP and has practical application potential. This work and they will constantly degrade thereby possessing less put forward the synergy of Fe single atoms and Fe C for bioconcentration factor. Then, the developmental toxic - efficient PMS activation and provided novel guidance ity of all NTP intermediates was defined as a toxicant, for constructing efficient biochar on organic pollutant which emphasized the importance of remediation with remediation. NTP contamination in the aquatic environment. To our delight, with the process of NTP degradation, the final Supplementary Information NTP intermediate exhibited negative mutagenicity. All The online version contains supplementary material available at https:// doi. org/ 10. 1007/ s42773- 023- 00221-1. the above analyses indicate that the SFB900-3/PMS sys- tem is effective for NTP removal and has practical appli - Additional file 1: Fig. S1 (a) Specific surface area and total pore volume cation potential. of allas-prepared samples. Pore size distribution by non-linear density functionaltheory (NLDFT ) (inserts are corresponding nitrogen adsorption and desorptionisotherms) of (b) SFB900-0, (c) SFB900-1, (d) SFB900-2, 4 Conclusion (e) SFB900-3 and (f )SFB900-4. Fig. S2 SEM images of (a) SFB900-0, (b) SFB900-1, (c) SFB900-2, (d) SFB900-3 and (e) SFB900-4 at 500 nm. Fig. In summary, the SFB900-3/PMS system with high and S3The apparent rate constants (k ) of NTP degradation in theSFB900/ app stable NTP degradation efficiency was presented. The PMS system under different PMS concentration. Conditions: [Biochar] -1 -1 excellent performance of the system for PMS activation =0.2 g L , [NTP] = 40 mg L , [temperature] = 25°C, [initial pH]= 5.87. Fig. S4 The apparent rate constants (k ) of NTPdegradation in the SFB900/ originates from the synergistic effect of internal Fe single app PMS system under different catalyst dosage.Conditions: [PMS] = 0.5 g atoms and the introduced Fe compounds, which greatly -1 -1 L , [NTP]= 40 mg L , [temperature] = 25°C,[initial pH] = 5.87. Fig. S5 improve the adsorption capacity of SFB900-3 for per- The apparent rate constants (k )of NTP degradation in the SFB900/ app PMS system with different quencher, and thecorresponding contribution sulfate and reduce the activation energy. This result was -1 -1 rate. Conditions: [Biochar] = 0.2 g L , [PMS] = 0.5 g L ,[NTP] = 40 mg verified by the DFT calculation. Hence, this system could -1 L , [temperature] =25°C, [initial pH] = 5.87. Fig. S6 The apparent rate remove 89.5% NTP in 60 min under neutral and acidic constants (k )of NTP degradation in the SFB900-0/PMS system with app -1 different proportions of Fe O .Conditions: [Biochar] = 0.2 g L , [PMS]= conditions. Then, the quenching experiment and EPR 2 3 -1 -1 0.5 g L , [NTP] = 40 mg L , [temperature] = 25°C, [initial pH]= 5.87. Fig. detection proved that the non-radical way ( O ) played S7 The apparent rate constants (k ) of NTPdegradation in the SFB900-0/ app an important role in the SFB900-3/PMS/NTP system. Xiong et al. Biochar (2023) 5:19 Page 16 of 18 References PMS system with different proportions of Fe C.Conditions: [Biochar] = 0.2 3 Cai S, Zuo XX, Zhao HY, Yang SJ, Chen RZ, Chen LW, Zhang RH, Ding DH, Cai TM -1 -1 -1 g L , [PMS]= 0.5 g L , [NTP] = 40 mg L , [temperature] = 25°C, [initial (2022) Evaluation of N-doped carbon for the peroxymonosulfate activa- pH]= 5.87. Fig. S8 The apparent rate constants (k ) of NTPdegradation in app tion and removal of organic contaminants from livestock wastewater and the SFB900-0/PMS system with different proportions of calcinedFe(acac) . 3 groundwater. J Mater Chem A 10:9171–9183. https:// doi. org/ 10. 1039/ -1 -1 -1 Conditions: [Biochar] = 0.2 g L ,[PMS] = 0.5 g L ,[NTP] = 40 mg L , d2ta0 0153e [temperature] =25°C, [initial pH] = 5.87. Fig. S9 The TOC removal rate Cui P, Yang Q, Liu C, Wang Y, Fang G, Dionysiou DD, Wu T, Zhou Y, Ren J, of NTP on SFB900-3 withoutor with PMS within 60 mins. Conditions: Hou H, Wang Y (2021) An N, S-anchored single-atom catalyst derived -1 -1 -1 [Biochar] = 0.2 g L ,[NTP] = 40 mg L , [PMS] = 0.5 g L , [temperature] from domestic waste for environmental remediation. ACS ES&T Eng = 25°C, [initial pH] =5.87. Fig. S10 The apparent rate constants (k ) of app 1:1460–1469. https:// doi. org/ 10. 1021/ acses tengg. 1c002 55 NTPdegradation in the SFB900-0/PMS system under different pH value. Fang LP, Liu K, Li FB, Zeng WB, Hong ZB, Xu L, Shi QT, Ma YB (2021) New -1 -1 -1 Conditions: [Biochar]= 0.2 g L , [NTP] = 40 mg L , [PMS] = 0.5 g L , insights into stoichiometric efficiency and synergistic mechanism of [temperature] = 25°C. Fig. S11 Theapparent rate constants (k ) of NTP app persulfate activation by zero-valent bimetal (iron/copper) for organic pol- degradation in the SFB900-0/PMSsystem with different proportions of lutant degradation. J Hazard Mater 403:123669. https:// doi. org/ 10. 1016/j. -1 -1 calcined Fe(acac) . Conditions:[Biochar] = 0.2 g L , [NTP] = 40 mg L , 3jhazm at. 2020. 123669 -1 [PMS] = 0.5 g L , [temperature] = 25°C, [initial pH] = 5.87, [ions]= 2 mM. Feng K, Xu Z, Gao B, Xu X, Zhao L, Qiu H, Cao X (2021) Mesoporous ball-milling Fig. S12 Iron leaching concentration of SFB900/PMS system duringNTP iron-loaded biochar for enhanced sorption of reactive red: performance -1 -1 degradation process. Conditions: [Biochar] = 0.2 g L ,[NTP] = 40 mg L , and mechanisms. Environ Pollut 290:117992. https:// doi. org/ 10. 1016/j. -1 [PMS] = 0.5 g L , [temperature] = 25°C, [initial pH] =5.87. Fig. S13 (a) Pos- envpol. 2021. 117992 sible pathways proposed for NTP degradation by theSFB900/PMS system. Fu HC, Ma SL, Zhao P, Xu SJ, Zhan SH (2019) Activation of peroxymonosulfate The Two potential degradation pathways of (b) Route 1 and(c) Route 2. by graphitized hierarchical porous biochar and M nFe O magnetic nano- 2 4 -1 Fig. S14 LC/MS spectrogram of initial NTP solution with 40 mgL . Fig. S15 architecture for organic pollutants degradation: structure dependence LC/MS spectrum ofSFB900/PMS/NTP system after 10 min reaction. Fig. and mechanism. Chem Eng J 360:157–170. https:// doi. org/ 10. 1016/j. cej. S16 LC/MS spectrum ofSFB900/PMS/NTP system after 20 min reaction. 2018. 11. 207 Fig. S17 LC/MS spectrum ofSFB900/PMS/NTP system after 30 min reac- Gao Y, Zhu Y, Li T, Chen Z, Jiang Q, Zhao Z, Liang X, Hu C (2021) Unraveling tion. Fig. S18 LC/MS spectrum ofSFB900/PMS/NTP system after 40 min the high-activity origin of single-atom iron catalysts for organic pol- reaction. Fig. S19 LC/MS spectrum ofSFB900/PMS/NTP system after 50 lutant oxidation via peroxymonosulfate activation. Environ Sci Technol min reaction. Fig. S20 LC/MS spectrum ofSFB900/PMS/NTP system after 55:8318–8328. https:// doi. org/ 10. 1021/ acs. est. 1c011 31 60 min reaction. Table S1.Bader charge of different component in the Han Y, Li QK, Ye K, Luo Y, Jiang J, Zhang G (2020) Impact of active site density structures. For the Bader charge in this table, the negativevalues indicate on oxygen reduction reactions using monodispersed Fe-N-C single-atom negative charge while positive values indicate positive charge.Table S2. catalysts. ACS Appl Mater Interfaces 12:15271–15278. https:// doi. org/ 10. Bond length,adsorption energy and energy barrier of PMS dissociation 1021/ acsami. 0c012 06 processes over thedifferent systems. Table S3. Characteristics of the real Jiang SF, Ling LL, Chen WJ, Liu WJ, Li DC, Jiang H (2019) High efficient removal water samples. of bisphenol A in a peroxymonosulfate/iron functionalized biochar system: mechanistic elucidation and quantification of the contributors. Chem Eng J 359:572–583. https:// doi. org/ 10. 1016/j. cej. 2018. 11. 124 Acknowledgements Lawrinenko M, Jing DP, Banik C, Laird DA (2017) Aluminum and iron biomass Not applicable. pretreatment impacts on biochar anion exchange capacity. Carbon 118:422–430. https:// doi. org/ 10. 1016/j. carbon. 2017. 03. 056 Author’s contributions Li SP, Jiang YY, Cao XH, Dong YW, Dong M, Xu J (2013) Degradation of nitenp- SX: Formal analysis, Investigation, Writing -Original Draft. HZ: Investigation. yram pesticide in aqueous solution by low-temperature plasma. Environ YD*: Conceptualization, Writing—Review and Editing, Funding acquisition, Technol 34:1609–1616. https:// doi. org/ 10. 1080/ 09593 330. 2013. 765914 Supervision. RT: Investigation. JW: Validation. LL: Validation. ZZ: Validation. DG*: Li JK, Ghoshal S, Liang WT, Sougrati MT, Jaouen F, Halevi B, McKinney S, McCool Writing—Review and Editing, Supervision. All authors read and approved the G, Ma CR, Yuan XX, Ma ZF, Mukerjee S, Jia QY (2016) Structural and final manuscript. mechanistic basis for the high activity of Fe-N-C catalysts toward oxygen reduction. Energ Environ Sci 9:2418–2432. https:// doi. org/ 10. 1039/ c6ee0 Funding 1160h The study was financially supported by the National Natural Science Founda- Li H, Chen S, Ren LY, Zhou LY, Tan XJ, Zhu Y, Belver C, Bedia J, Yang J (2019) tion of China (Grant No.52270156, 51909089), Natural Science Foundation of Biochar mediates activation of aged nanoscale ZVI by Shewanella putre- Hunan Province, China (Grant No. 2020JJ5252), Training Program for Excellent faciens CN to enhance the degradation of Pentachlorophenol. Chem Young Innovators of Changsha (Grant No. kq2209015). Eng J 368:148–156. https:// doi. org/ 10. 1016/j. cej. 2019. 02. 099 Li JQ, Li MT, Sun HQ, Ao ZM, Wang SB, Liu SM (2020) Understanding of the Availability of data and materials oxidation behavior of benzyl alcohol by peroxymonosulfate via carbon All data generated or analysed during this study are included in this article. nanotubes activation. 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Journal
Biochar – Springer Journals
Published: Apr 6, 2023
Keywords: Biochar; Fe-single-atom; Fe3C; Nitenpyram; Degradation