Microwell Confined Iron Oxide Nanoparticles in Honeycomblike

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Microwell Confined Iron Oxide Nanoparticles in the Honeycomb-like Carbon Spheres for the Adsorption of Sb (III) and Sequential Utilization as a Catalyst Jingting Wang, Yixin Chen, Ziqing Zhang, Yongjian Ai, Lei Liu, Li Qi, Junjie Zhou, Zenan Hu, Ruihang Jiang, Hongjie Bao, Shucheng Ren, Jiaxing Liang, Hong-bin Sun, Dun Niu, and Qionglin Liang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b02300 • Publication Date (Web): 29 Aug 2018 Downloaded from http://pubs.acs.org on September 1, 2018

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ACS Sustainable Chemistry & Engineering

Microwell Confined Iron Oxide Nanoparticles in the Honeycomb-like Carbon Spheres for the Adsorption of Sb (III) and Sequential Utilization as a Catalyst Jingting Wang†, Yixin Chen†, Ziqing Zhang†, Yongjian Ai‡, Lei Liu†, Li Qi†, Junjie Zhou†, Zenan Hu†, Ruihang Jiang†, Hongjie Bao†, Shucheng Ren†, Jiaxing Liang†, Hong-bin Sun†*, Dun Niu†*, Qionglin Liang‡* †

Department of Chemistry, Northeastern University, Shenyang 110819, P.R. China.

‡

Key Laboratory of Bioorganic Phosphorus Chemistry & Chemical Biology (Ministry of Education), Beijing Key Lab of Microanalytical Methods & Instrumentation, Department of Chemistry, Tsinghua University, Beijing 100084, P.R. China. * Corresponding authors. E-mail address: [email protected]. [email protected]. [email protected]. KEYWORDS adsorption of antimony; mesoporous carbon nanospheres; honeycomb structure; catalytic transfer hydrogenation (CTH); resource utilization; ABSTRACT: The composites of mesoporous carbon nanospheres with iron oxides (mPCS@Fe2O3) was developed for the removal of antimony in water. The good performance of mPCS@Fe2O3 is attributed to honeycomb-like structure, which is the active Fe2O3 particles are dispersedly confined in the micro tunnel of the carbon nanospheres. This adsorbent takes advantages of high adsorption capacity and easiness of preparation. It provides high removal rate for low concentrated Sb (III) and high removal capacity for high concentrated Sb (III). Furthermore, the after-used adsorbent was developed into a catalyst for the transfer hydrogenation of nitroarenes, and the catalyst exhibited good activity, and inherited the magnetic recyclability. This proved a promising way to avoid secondary pollution.

37.

Introduction Antimony contamination in waste water has attracted more and more attention, as antimony compounds are usually mutagenic and oncogenic1-5. The antimony containing water is mainly generated in human activities, so removing antimony before discharge is essential. As a kind of heavy metal, the removal methods of antimony from water are various including adsorption6-7, ion exchange8-9, osmosis membrane10-12, coagulation-flocculation13-14, precipitation15-16 and so on. However, according to the strict restrictions of Sb in drinking water (EU 5 μg/L, US 6 μg/L)17, removal of antimony by adsorption is the most economically efficient way. Thus, quite a few effective adsorbents have been developed such as MOFs18-20, metal (oxyhydro) oxide21-22, gelatum23, graphene oxide and its composites24-26 and other carbon materials27-31. The existence of antimony in environment includes pentavalent and trivalent species. The Sb (III) is mainly exists species in anoxic interstitial waters and underground water6, 32. The toxicity of antimony species is similar to arsenic, whose trivalent compounds are ten times more poisonous than pentavalent species17, 32. Sb (III) has a long biological half-lives1 and shows higher toxicity than Sb (V)33-35. It has been well studied that iron or manganese oxides can adsorb Sb (III) effectively36-

However, the adsorption performance vigorously depends on the tininess of the particle size of the adsorbent. The unsupported metal oxide nanoparticles usually agglomerate to lose its original capacity. Moreover, the Sb (III) can be catalytically oxidized to Sb (V) on the surface of these metal oxides3840, which is more soluble than Sb (III). Therefore, the structural adsorbent for the removal of antimony from waste water is highly desired. Herein, we designed honeycomb structural Sb-adsorbent, which is the mesoporous carbon sphere (mPCS) confined nano-sized iron oxide (mPCS@Fe2O3). The adsorbent showed excellent adsorption capacity towards antimony in water. In our previous research, we discovered that the hydrothermally synthesized carbon nanospheres were multiporous with average pore size of several nanometers, while the iron oxide particles that were synthesized in a water-ethanol mixed solvent have a similar diameter41-42. We realized that confining the iron oxide nanoparticles into the microwell of the carbon sphere would be a promising way to form a wonderful adsorbent for the removal of antimony in water. The fabrication of mPCS@Fe2O3 is presented Scheme 143. At the outset, the mesoporous carbon nanospheres was synthesized by an incomplete hydrothermal carbonization of glycose. Then the Fe2O3 nano particles were deposited in. The freeze-dried particles are used as the adsorbent.

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The Effects of Co-existing Anions The anions salts (0.1 M sulfate, 0.1 M nitrate, 0.1 M carbonate and 0.1 M phosphate) were introduced respectively into the solution with an initial Sb (III) or Sb (V) concentration of 10 mg/L. Portions of 5 mg mPCS@Fe2O3 were added into 25 mL solution, and the samples were taken out after agitating for 24 h at 30 oC. Catalytic Hydrogenation of 4-Nitrophenol

Scheme 1. Schematic illustration of the preparation of the adsorbents. There is still another problem that is seldom mentioned in the research of adsorption. That is treatment of the after-used “dirty” adsorbent, which is a kind of refuse and is not disposable optionally. In our previous study, we discovered that bismuth doping could remarkably improve the catalytic activity of γ-Fe2O3 in the hydrazine mediated reduction of nitrocompound44. This reaction produces the aniline derivatives, that are widely applied in the production of fine chemicals, and their trading value is more than 10 billion dollars per year45. We considered that antimony (III) would possess a similar activity with bismuth (III), because they were in the same column of the periodic table. To our delight, by annealing the after-used adsorbents (mPCS@Fe2O3/Sb (III)) in a muffle furnace at 250 oC in air for 3 hours, the recovered waste adsorbent (mPCS@Fe2O3/Sb2O3) exhibited good catalytic activity in the reduction of nitroarenes Therefore, applying the “dirty” Sb-adsorbents as a catalyst for the reduction of nitro compound could completely solve the secondary pollution issue of waste adsorbent. Experimental Section Adsorption Isotherm The concentrations of the initial Sb (III) solution were from 50 mg/L to 1000 mg/L. A portion of 50 mg of mPCS@Fe2O3 was dispersed in 50 mL of Sb (III) solution with certain concentrations. The mixed solution was vibrated for 24 h at different temperatures (20 oC, 30 oC, 40 oC ).

The collected after-used adsorbent (mPCS@Fe2O3/Sb(III)) was annealed at 250 oC for 3 hours, then it was used as the catalyst named mPCS@Fe2O3/Sb2O3. In a sealed tube, 1 mmol of 4-nitrophenol was dissolved in 2 mL of isopropanol and mixed with 14 mg of mPCS@Fe2O3/Sb2O3. Subsequently, 2.5 mmol of N2H4·H2O was injected into the system and the solution was stirred at 110 oC. The colour fading of the solution indicated the end of the reaction, and the conversion was obtained by HPLC. Results and Discussion Optimization of mPCS@Fe2O3 Inspired by our initial study, we found that the carbon nanospheres manufactured with a freeze-drying procedure showed much better antimony absorbance than the oven-dried carbon spheres (Table S1). This confirmed our speculation that the freeze-dried carbon nanospheres reserved more open microwell, which were like the honeycomb cell and could accommodate more iron oxide nanoparticles. Then we chose the freeze-drying process in the further study. In general, the carbonization degree of mPCS is strongly controlled by hydrothermal conditions. Under the low temperature, the carbonization of the mPCS was relatively low and it had weak adsorption capacity (Table S1). High carbonization degree is also unsuitable, as the over carbonized mPCS trend to close it tunnels then less Fe2O3 particles could be accommodated. Therefore, the fine regulation of carbonization procedure was conducive to effectively control the channels, thus to optimize the adsorption (Table S1). In addition, compared with mPCS@Fe3O4, mPCS@Fe2O3 showed better adsorption performance (Table S1), and the removal efficiency of antimony enhanced gradually with the increasing of the iron content (Figure S1).

Adsorption Kinetics Characterizations Kinetics experiment was performed using 1 mg/L Sb solution. Forty milligrams of the sorbent materials were placed into 400 mL of the solution. Next, the suspension was rapidly wobbled at 150 rpm. A sample of 4 mL of supernate was taken out from the aqueous solution timely. Influence of pH Typically, the adsorption capacity of adsorbent was affected by the pH value of a solution. In our experiments, the pH was altered from 3 to 12 with 0.1 M NaOH and 0.1 M HCl. The batch experiments were carried out with 50 mL of 25 mg/L Sb aqueous solution. Portions of 0.5 g/L adsorbents were added to the solution, then the suspension was shaken at 150 rpm for 24 h and finally was collected after the filtration using 0.45 μm microporous membrane filter.

SEM and TEM Analysis The size and the morphology of the synthesized adsorbents were investigated by SEM and TEM. As can be seen in the Figure 1a and 1b, mPCS and mPCS@Fe2O3 particles exhibit regular spherical morphology with an average diameter of 200 nm. Figure 1c shows the HRTEM image of mPCS@Fe2O3. There are several tiny iron particles (2.7), while antimony (III) exists as H2SbO3- and Sb(OH)4- in a alkaline solution ( pH>10.4)53, Sb(OH)3 is the dominant species when the pH range is from 2 to 1054. So there is little difference in adsorption capacity when the pH value is below 9, but the electrostatic interaction between adsorbent and adsorbate weakens with the increasing of pH value to above 10. The above discovery demonstrates that the fabricated adsorbents possess excellent removal ability for the heavy metals in a wide range of pH, and this advantage is beneficial to practical treatment of acidic wastewater.

Figure 4. XPS survey spectrum (a-d) C 1s of mPCS@Fe2O3, mPCS@Fe2O3/Sb (III) recovered from high concentrated Sb(III), mPCS@Fe2O3/Sb2O3 and mPCS@Fe2O3/Sb (III) recovered from low concentrated Sb(III), (e) O 1s of mPCS@Fe2O3 and (f) O 1s of mPCS@Fe2O3/Sb (III) recovered from high concentrated Sb(III). XPS measurement was carried out to determine the elemental compositions and analyze the metal oxidation states of adsorbents. Figure 4a-d show the C 1s narrow-scan spectra for the samples. The peaks at 284.6 eV, 285.6 eV and 288.2 eV are assigned to C−C bonds, C−O bonds and C=O bonds, respectively49. The C-O peaks appear slight shift before and after Sb (III) adsorption. It appears at 285.6 eV for the as-prepared mPCS@Fe2O3 (4a), and shifts to 285.9 eV after adsorbing Sb (III) (4b and 4d). After annealing at 250 oC, it comes back to 285.6 eV. This indicates a weak interaction between carbon and Sb (III). Two wide peaks of Fe 2p3/2 and Fe 2p1/2 is are 710.7 eV and 724.1 eV (Figure S4). At 718.9 eV, there is a clear characteristic satellite peak. It represents Fe 2p3/2 of Fe3+ in Fe2O350. It is worth to mention that the peak intensity of O 1s weakens and a new peak appears after Sb (III) adsorption in Figure 4e and f. The peak at the binding energy of 530 eV and 539.6 eV are attributed to Sb 3d5/2 and Sb 3d3/2 indicating that Sb (III) are adsorbed in the mPCS@Fe2O351. The partly oxidation of antimony could be observed52, because the transformation of Sb (III) to Sb (V) in air is spontaneous during storage.

Figure 5. Influence of initial pH on the adsorption capacity of Sb on mPCS@Fe2O3 (the inset of the figure is the zeta potential of mPCS@Fe2O3). The initial Sb concentration was 25 mg/L; adsorbent dose was 0.5 g/L; the solution volume was 50 mL. Adsorption Kinetics The kinetic demonstrates the effect of contact time on Sb adsorption and helps to seek out the adsorption rate. As presented in Figure 6a, the adsorption amounts of Sb enhance sharply in the first 40 minutes. Then the adsorption gently reaches the equilibrium within 120 minutes.


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Figure 6. (a) Kinetic curves for the removal of Sb on the mPCS@Fe2O3; (b) pseudo first-order model simulation, and (c) pseudo second-order model simulation. The initial Sb concentration was 1 mg/L; adsorbent dose was 0.1 g/L; the solution volume was 400 mL; the pH was 6.0. The adsorption curves are simulated with the pseudo-first-order or pseudo-second-order kinetic model. They are expressed as eq.1 and eq.2, respectively55.

ln (Qe-Qt) = ln Qe - k1t

eq.1

t/Qt = 1/(k2Qe2) + t/Qe

eq.2

kL (L/mg) is the Langmuir parameter. Kf (mg1−(1/n)L1/ng−1) and n are the Freundlich parameters.

where Qe and Qt (mg/g) represent the amount of adsor ption at equilibrium and at t min, respectively; k1 (min-1) and k2 (g/mg/min) are the rate constants for the pseudo-first-order and pseudo-second-order adsorption; t (min) is the contact time. The kinetic model curves are presented in Figure 6. In contrast, the pseudo-second-order model shows a higher correlation coefficient than the pseudo-first-order model for both Sb(III) and Sb(V). The calculated rate constant k2 was 0.0342 g/mg/min for Sb(III) at 20 oC with the R2=0.995 (detailed in Table S2). This demonstrates that low concentrated antimony adsorption on the mPCS@Fe2O3 is chemisorption56-57. However, with the raising of temperature, the removal efficiency for Sb (III) descends gradually. This implies that the adsorption is not a simply chemical process, and this is coincident with the literature6,26.

Adsorption Isotherms Figure 7 a shows the adsorption isotherms of Sb (III) on mPCS@Fe2O3 at 20, 30 and 40 oC. The equilibrium datas are usually fitted with two models: Langmuir19 (eq.3) and Freundlich19 (eq.4) isotherm models. The models are shown as the following equations: Ce/Qe = Ce/Qmax + 1/(KLQmax)

eq.3

log Qe = (1/n) log Ce+log Kf

eq.4

where Qe is the equilibrium adsorption amount (mg/g); Ce is the equilibrium concentration(mg/L). Qmax represents the theoretical maximum adsorption capacity in Langmuir model;

Figure 7. (a) The factual adsorption isotherm with different temperatures for Sb(III); (b-d) Langmuir adsorption isotherm with different temperatures (20 oC, 30 oC, 40 oC) for removal of Sb (III). Initial Sb (III) concentration was 50−1000 mg/L; adsorbent dose was 1 g/L; the solution volume was 50 mL; and pH was 6. According to Figure 7a, the adsorption amounts of Sb (III) increase gradually with the increasing of initial concentration. Interestingly, the adsorption isotherm exhibits an unusual shape. This can be explained by the unique honeycomb like structure of the adsorbent. In the low concentration range, the highly dispersed Fe2O3 effectively adsorbs the Sb (III) in the water (68 mg/g at 50 mg/L, 90 mg/g at 100 mg/L of antimony), and the adsorption isotherm fits the Langmuir model well. With the increasing of the Sb (III) concentration, the capillary condensation effect emerges. then the experimental data diverges the Langmuir mode. However, it still can be regarded to piecewise fit with the model in high concentration range, as the Langmuir model fitting shows quite higher R2 values (0.977) than the Freundlich model at 20 oC (Table S3 and Table S4). Figure 7b-d show Langmuir adsorption isotherm with different temperatures for removal of Sb (III). Under the high



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initial concentration, mPCS@Fe2O3 shows a prominent adsorption capacity at 20 oC. The theoretical maximum Sb (III) adsorption capacity of mPCS@Fe2O3 is 233.6 mg/g.

1K-1).

The thermodynamic parameters for the Sb (III) adsorption were calculated, including the free energy change, enthalpy change and entropy change. The Go values were -8.1, -10.0 and -11.1 kJ/mol at 20 oC, 30 oC and 40 oC, respectively. The Ho was calculated to be 36.1 kJ/mol, while the So was 152 J/(mol-

Maximum adsorption capacity of the mPCS@Fe2O3 for the removal of Sb (III) was compared with other adsorbents reported in the literatures. As shown in Table 1, mPCS@Fe2O3 nanospheres shows excellent adsorption capacity than other adsorbents, which provide a significant potential for practical removal of aqueous Sb.

These results reveal that the adsorption of Sb (III) is a endothermic and spontaneous process, which is agreed with another porous adsorbent UiO-6619.

Table 1. Adsorption Capacities of Different Adsorbents for Sb (III). Adsorbents

pH

Concentration range (mg/L)

Dose (g/L)

Capacity(mg/g)

Ref.

(ZrO2)-carbon nanofibers

1-13

10-500

1

70.83

58

NU-1000

2.3-9.5

2-500

0.8

136.97

59

UiO-66(NH2)

1.5-12

10-600

1

61.8

19

silica-SH

2-11

100-800

5

108.8

60

Cu(II)-specific metallogels

1-6

20-600

1

102.4

23

RGO/Mn3O4

2-12

10-1000

1

151.84

25

MnO2 nanofibers

1-12

10-500

0.5

111.70

26

Mn-modified expanded perlite

2-8

10-400

4

76.5

61

mPCS@Fe2O3

3-12

50-1000

1

233.6

This study

Effect of Coexisting Anions The influence of different coexisting anions is presented in Figure 8. There is almost no negative effect on the removal of Sb (III) and Sb (V) when NO3- , CO32- or SO42- exists in the Sb containing solution. While PO43− shows a slight inhibition effect on the removal of Sb (III) and Sb (V), which is attributed to similar structure between phosphate ion and antimonate ion 62.

Figure 8. Effect of co-existing anions on Sb adsorption onto mPCS@Fe2O3. Initial Sb concentration was 10 mg/L; anions concentration was 0.1 mol/L; adsorbent dose was 0.2 g/L; the solution volume was 25 mL; and pH was 6.0.

Mechanism According to characterization and adsorption research, we can conclude that the adsorption of Sb on the mPCS@Fe2O3 is a hybrid process of physisorption and chemisorption. This material has a good adsorption capacity because of its honeycomb cell structure. The possible adsorption mechanism of Sb (III) on the mPCS@Fe2O3 nanocomposites can be described as follows: (1) the iron oxides that located in the microwell of the carbon spheres are the initial active site for the immobilization of Sb (III), because we have found that the carbon spheres itself show very low absorbance of Sb (III). The antimony (III) attaches with iron oxide through the hydrogen bond (FeO…H-O-Sb). The incomplete carbonization of the carbon sphere provide plenty of pores, which can act as microwell for the encapsulation of active iron oxide nano particles. Furthermore, this confinement effect can effectively prevent the loss of the adsorbed antimony. (2) We speculate that the pores of the carbon spheres are transformed to ink bottle shape according to the pore distribution comparison of the mPCS and mPCS@Fe2O3 (Figure 2). The crystal growth of Fe2O3 that occurs in the tunnel enlarges some pores, and the filled Fe2O3 nanoparticles narrow the wells of carbon spheres. So there are a lot of micropores and mesopores inside the adsorbents. As mentioned above, antimony is firstly adsorbed in the microwell confined Fe2O3 particles. When the adsorption reaches the saturation of iron oxide’s capacity, the phenomenon of suchlike capillary condensation occurs in the micropores. Then the absorbance increases successively in the mesopores. The harmonic multilayer adsorption effectively improves the adsorption capacity of adsorbent. (3) Due to the presence of a honeycomb like structure, the synthesized iron


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oxide particles reserves small size. The carbonaceous materials with porous structure can provide more active sites for adsorption, which make the antimony completely contact with the adsorbent.

Table 2. Comparison of Different Catalysta.

Reutilization of the after Used Adsorbent: as a Catalyst for CTH Following the successful development of the adsorbent mPCS@Fe2O3 for Sb (III), we extended our sight into the treatment of the after-used adsorbent, which might be a pollutant. The re-dispersion of immobilized pollutant is a severe problem, if it can be recycled in industry, the immobilized antimony content could be well-managed through a series of policy command. In our previous study, we have found that the existence of bismuth could improve the catalytic activity of the iron oxide catalyst in the reduction of nitroaromatics42. Considering that antimony is in the same column with bismuth in the periodic table, we tried to develop the re-utilization of the after-used adsorbent in this field. To our delight, we discovered that a simple annealing treatment will convert the waste to an active catalyst. The catalyst mPCS@Fe2O3/Sb2O3 was characterized with XRD and XPS (Figure 3a, 4c and Figure S4), and the results show that the Fe2O3 remains its original crystal phase even after annealing at 250 oC for 3 hours. Furthermore, the catalyst mPCS@Fe2O3/Sb2O3 has magnetic recyclability and can be reused for several times (presented in Figure S5).

The Exploration of Condition In our study, p-nitrophenol was selected as a model substrate. We can find in Table 2 that mPCS@Fe2O3/Sb2O3 has prior catalytic activity. Neither the single carbon spheres nor Sb2O3 exhibited sufficient activity for this reaction, while Fe2O3 and mPCS@Fe2O3 still showed poor performance. It has been reported that Fe3O4 is a good catalyst for the hydrazine mediated reduction of nitro compound. Our comparison agreed this, as mPCS@Fe2O3 shows lower activity of 34% conversion than mPCS@Fe3O4 in the reduction of 4-nitrophenol to 4amino phenol (Table 2). However, mPCS@Fe3O4 shows poor adsorption performance in comparison with mPCS@Fe2O3 (Table S1), so it is not selected as an adsorbent in the preliminary stage. Interestingly, after the adsorption of antimony, mPCS@Fe2O3 was activated and displayed perfect catalytic performance. It is contributed by the synergy of the doping Sb (III) and mPCS@Fe2O3. For the broad application of the new catalyst, we explored the optimal N2H4·H2O dosage and the catalysis dosage (Table S6, Table S7). The effect of the solvent on the reaction are showed in Table S5. The reaction proceeds smoothly in isopropanol, but other solvent does not work well under the same reaction conditions.

a Reaction conditions: p-nitrophenol (1 mmol), catalyst (14 mg), hydrazine hydrate (2.5 mmol), isopropanol (2 mL), 110 oC, 1 h. b Conversion were determined by HPLC. The Expansion of Substrates Furthermore, Furthermore, a range of functionalized aromatic nitro compounds were studied under the optimal reaction conditions. The reaction results were tested by HPLC. As shown in Table 3, the corresponding substituted anilines are obtained with high selectivity. Various functionalities such as -CH3, -OH, -OCH3 and -CONH2 have no influence on the reduction reaction (entries 1~4). Generally, dehalogenation comes along with the nitro reduction as a side reaction. Therefore, 2-chloro and 4-chloro nitrobenzene were tested. The result shows that they produced the corresponding anilines with >99 % selectivity (entries 5~6). In addition, we turned our interest towards some substrates bearing heterocyclic ring nitro compounds, and we acquired the expected results (entries 7~8). These achievements show that the recovered mPCS@Fe2O3/Sb2O3 has a good catalytic activity and wide functional tolerance towards nitrocompounds.



Table 3. Hydrogenation of Various Nitroarenesa.

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This work was financially supported by the Ministry of Science and Technology (Nos. 2017YFC0906902 and 2017ZX09301032) and National Natural Science Foundation of China (No. 21621003).

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT We gratefully acknowledge the financial support of the NSF of China (No. 21621003) and the Ministry of Science and Technology (Nos. 2017YFC0906902 and 2017ZX09301032).

REFERENCES

a

Reaction conditions: nitroarenes (1 mmol), catalyst (14 mg), hydrazine hydrate (2.5 mmol), isopropanol (2 mL), 110 oC, 1 h. b

Conversion were determined by HPLC.

Conclusions In this study, a honeycomb structural adsorbent was synthesized to remove Sb in water efficiently. The results show that the fabricated adsorbents possess excellent removal ability for the antimony in a wide pH range of 3-10. According to Langmuir model, the maximum adsorption capacities of mPCS@Fe2O3 toward Sb (III) can reach 233.6 mg/g. The adsorption kinetic equilibrium can be reached within 120 minutes, and the adsorption of Sb (III) fits the pseudo-secondorder kinetic model. Furthermore, the after-used waste adsorbent was developed to a catalyst that is active for the transfer hydrogenation of nitro aromatics. This opens a new reasonable vision for the waste reutilization in the antimony immobilization.

ASSOCIATED CONTENT Supporting Information. The Supporting Information is available free of charge on the ACS Publications website at DOI: Figures S1−S5, and Tables S1−S7

AUTHOR INFORMATION Corresponding Author E-mail: [email protected]. Fax: +18624030315. E-mail: [email protected]. E-mail: [email protected].

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Synopsis: Carbon nanospheres confined Fe2O3 are fabricated for adsorbing antimony, and the after-used adsorbents are reutilized as catalyst for transfer hydrogenation.


Microwell Confined Iron Oxide Nanoparticles in Honeycomblike

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