Feasible One-Pot Sequential Synthesis of Aminopyridine

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Feasible one-pot sequential synthesis of aminopyridine functionalized magnetic Fe3O4 hybrids for robust capture of aqueous Hg(II) and Ag(I) Zaixin Zhang, Yuzhong Niu, Hou Chen, Zheng-Long Yang, Liangjiu bai, Zhongxin Xue, and Huawei Yang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.9b00471 • Publication Date (Web): 03 Mar 2019 Downloaded from http://pubs.acs.org on March 4, 2019

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ACS Sustainable Chemistry & Engineering

Feasible one-pot sequential synthesis of aminopyridine functionalized magnetic Fe3O4 hybrids for robust capture of aqueous Hg(Ⅱ) and Ag(Ⅰ) Zaixin Zhang, Yuzhong Niu*, Hou Chen, Zhenglong Yang, Liangjiu Bai, Zhongxin Xue, Huawei Yang School of Chemistry and Materials Science, Ludong University, No.186 Hong Qi Zhong Lu, Yantai 264025, PR China

Abstract Heavy metal pollution to aqueous media is an important issue for environmental sustainability. Simple strategy for the synthesis of efficient adsorbent is strongly desired for water remediation. Herein, aminopyridine functionalized magnetic Fe3O4 (HO-Fe3O4@ SiO2-AP) with excellent adsorption capacity and selectivity was synthesized by feasible one-pot sequential reaction. As a comparison, the same adsorbent was also prepared by the general step-by-step surface modification method. The structure characterization and adsorption performance prove the efficiency of this strategy. The factors that affect the adsorption were determined. XPS, FTIR, and DFT calculation were used to demonstrate the adsorption mechanism. As HO-Fe3O4@SiO2-AP exhibits competitive adsorption capacity and excellent adsorption selectivity, it can be used potentially for robust removal, preconcentration and recovery of aqueous Hg(Ⅱ) and Ag(Ⅰ).

Key words: One-pot sequential synthesis method; Magnetic Fe3O4; Aminopyridine; Adsorption selectivity; Mechanism

Introduction *

Corresponding author. Tel.: +86 535 6696162 E-mail address: [email protected] 1

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Heavy metal ions contamination to aqueous media has attracted lasting attention.1 These ions would accumulate in living organisms due to the non-biodegradable property, and exert deleterious effect to human health and environmental safety.2,3 Hg(Ⅱ) and Ag(Ⅰ) are among the most toxic metal ions which usually discharged from the battery manufacture, electronic industry, metal smelting, etc.4-6 The uptake of Hg( Ⅱ ) can exert harmful effect to nervous system, digestive system, lung, and kidney.4,7 And the intake of Ag( Ⅰ ) would bring about damage to liver, kidney, and trophic chain.5,8 Therefore, the decontamination of Hg(Ⅱ) and Ag(Ⅰ) pollution is very important. Adsorption is extensively used metal ion pollution remediation as it is convenient, efficient, low energy requirement, and cost-effective.9,10 Magnetic Fe3O4 based adsorbent has captured special attention as it exhibits excellent properties such as good biocompatibility, high efficiency, and easy to be separated under external magnetic field.11-13 However, the stability, adsorption capacity and selectivity of bare magnetic Fe3O4 are relative low, which hinders its application for metal ion adsorption and separation.9,14 In order to overcome these drawbacks, surface coating or functionalization is considered to be an effective method.14,15 Different coating agents and functional groups including silica, carbon, graphene oxide, and polymers have been employed to enhance the stability and promote the adsorption capacity and selectivity of magnetic Fe3O4.12,16-19 Coating Fe3O4 by silica (Fe3O4@SiO2) is widely adopted as silica shell not only protects the inner magnetite core, but also provides a compatible surface that facilitates further functionalization to meet different demand.20 One feasible approach is to introduce active binding sites by the condensation reaction with silane coupling agents for direct adsorption or further modification. For example, Zhang synthesized

2


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thiol functionalized Fe3O4@SiO2 to remove Hg(Ⅱ).21 Li prepared amidoxime-functionalized Fe3O4@SiO2 to remove aqueous U(Ⅵ).22 Pylypchuk employed diethylenetriamine pentaacetic acid to modified amino-containing Fe3O4@SiO2 to adsorb Cd( Ⅱ).23 Aminopyridine ligands contain abundant nitrogen atoms which exhibit remarkable binding ability and selectively for Hg( Ⅱ ) and Ag( Ⅰ ).24,25 Therefore, it can be assumed the functionalization of Fe3O4@SiO2 with aminopyridine functional groups onto would significantly improve the adsorption efficiency and achieve the selective adsorption of Hg(Ⅱ) and Ag(Ⅰ). In general, the construction strategy based on silane coupling agent as bridging unit involves at least two step solid-liquid surface reactions between Fe3O4@SiO2 and the functional group. The relative low reaction efficiency of multistep solid-liquid reactions usually reduces the functional group content.26,27 Hence, simplification of synthetic procedure and improvement of reaction efficiency are the key points for the application of the adsorbent. As an alternative, the functionalization of silane coupling agent first in the liquid phase and then attached onto Fe3O4@SiO2 is supposed to be more efficient. This strategy not only reduces the solid-liquid surface reaction steps and simplifies the purification procedure, but also provides versatile silane coupling agent for the modification of various substrates such as silica, clay, carbon, etc. In this study, magnetic Fe3O4 was functionalized by aminopyridine with feasible one-pot sequential reaction method (HO-Fe3O4@SiO2-AP) and traditional method (HE-Fe3O4@ SiO2-AP) as described in Scheme 1. The adsorbents were used to remove Hg(Ⅱ) and Ag(Ⅰ) from aqueous solution. The factors that affect the adsorption were determined and the adsorption mechanism was demonstrated. The detail experimental section is provided in

3



Supporting Information.

Scheme 1 Synthesis route for HO-Fe3O4@SiO2-AP and HE-Fe3O4@SiO2-AP

Results and Discussion Characterization of HO-Fe3O4@SiO2-AP and HE-Fe3O4@SiO2-AP. FTIR spectra, XRD patterns, and hysteresis loops for the adsorbents are dispalyed in Fig. 1. Fe3O4 exhibits the characteristic Fe-O adsorption at 592 cm-1. After coating with silica, Fe3O4@SiO2 exhibits the Si-O-Si stretching vibration at 1090 cm-1.9,28 Compared with Fe3O4@SiO2, the vibration of -CH2- band appear at 2920 and 2850 cm-1, and the absorption of pyridyl ring presents at 1460 cm-1 in the spectra of HO-Fe3O4@SiO2-AP and HE-Fe3O4@ SiO2-AP.24,30 Moreover, the intensity of Si-O-Si peak decreases after functionalization, further suggesting the successful synthesis of HO-Fe3O4@SiO2-AP and HE-Fe3O4@SiO2-AP. Elemental analysis indicates the nitrogen content of HO-Fe3O4@SiO2-AP and HE-Fe3O4@SiO2-AP are 1.24% and 0.35% (0.89 and 0.25 mmol/g), not only demonstrates

4


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Fig. 1 (a) FTIR spectra, (b) XRD patterns and (c) magnetic property of the adsorbent and its derivatives the successful synthesis of the adsorbents, but also proves one-pot sequential synthesis strategy is more efficient. The crystal structure of HO-Fe3O4@SiO2-AP and its derivatives are presented in Fig.1 (b). Fe3O4 exhibits the characteristic diffraction peaks of (220), (311), (400), (422), (511), and (440) planes at 30.8°, 35.8°, 43.4°, 53.5°, 57.4°, and 62.9°, which is consistent with previous reports.9,31 These peaks also appear in the XRD patterns of HO-Fe3O4@ SiO2-AP and HE-Fe3O4@SiO2-AP, indicating the structure of Fe3O4 is not changed after modification. However, the intensity of the diffraction peaks becomes stronger as the crystal size change. A relative low peak which attributes to silica amorphous diffraction appears at about 22°, further indicating the successful synthesis of the products.32 The magnetic property of the adsorbents is illustrated in Fig.1(c). The magnetic curves 5



exhibit no remanence and coercivity, suggesting the superparamagnetic nature of Fe3O4 and the as-synthesized adsorbents.14 Fe3O4, HO-Fe3O4@SiO2-AP, and HE-Fe3O4@SiO2-AP exhibit the saturation magnetization of 41.3, 11.59, and 15.70 emu·g-1, respectively. The decrease of saturation magnetization is ascribed to the segregation effect of silica shell and the functional groups. Kumar et al. have demonstrated 8 emu·g-1 is sufficient for magnetic recovery from the solution.19 Therefore, HO-Fe3O4@SiO2-AP and HE-Fe3O4@SiO2-AP can be manipulated easily or recovered rapidly from aqueous solution with a magnetic field. The composition of HO-Fe3O4@SiO2-AP is further validated by XPS analysis. As illustrated by Fig.2 (a), O, Fe, N, C, Si can be identified by the XPS of HO-Fe3O4@SiO2-AP. The C 1s spectrum is divided into five peaks at 283.24, 284.21, 286.04, 286.44, and 286.53 eV, which can be assigned to C–C, C–N, C–O–C, C–O, and C=N of carbon atom.33,34 The N

Fig. 2

XPS spectrum of (a) HO-Fe3O4@SiO2-AP, (b) C 1s, (c) N 1s, and (d) O 1s 6


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1s spectrum exhibits the =N– and –NH– peaks of aminopyridine group at 398.14 and 399.23 eV.30,35 For O 1s spectrum (Fig. 2 (d)), the C–OH and C–O–C peaks appear at 530.53 and 531.55 eV. 36 The thermal behavior of HO-Fe3O4@SiO2-AP and its derivatives are demonstrated in Fig. 3(a). Fe3O4 exhibits the evaporation of surface adsorbed H2O molecules from100℃to 800℃ with a weight loss of 2.84%.37 The evaporation of physical adsorbed water molecules also accounts for the weight loss of HO-Fe3O4@SiO2-AP and HE-Fe3O4@SiO2-AP from 25 to 110 ℃. Moreover, the weight loss of Fe3O4@SiO2 in the range of 110 to 800℃ is attributed to the loss of water caused by surface silanol group condensation. Similar decomposition are also be observed in the curves of HO-Fe3O4@SiO2-AP and HE-Fe3O4@SiO2-AP from 110 to 280℃. For HO-Fe3O4@ SiO2-AP and HE-Fe3O4@SiO2-AP, a sharp decrease around 280 ℃ is ascribed to surface functional group decomposition and residual silanol groups condensation. The final weight loss of HO-Fe3O4@SiO2-AP is higher than HE-Fe3O4@SiO2-AP by 4.0%, further demonstrating the one-pot sequential synthesis strategy is more efficient. The porous structure and surface area of HO-Fe3O4@SiO2-AP and its derivatives are presented in Fig. 2(b) and Table 1. According to the classification of IUPAC, all the three curves belong to type IV isotherm.38 Compared with Fe3O4@SiO2, the BET surface area of HO-Fe3O4@SiO2-AP decreases from 42.02 to 23.34 m2·g-1, and BJH desorption cumulative volume reduces from 0.17 to 0.11 cm3·g-1. Similar phenomenon can also be observed for HE-Fe3O4@SiO2-AP. It can be observed the pore radius, volume, and surface area of HO-Fe3O4@SiO2-AP are lower than HE-Fe3O4@SiO2-AP, demonstrating Fe3O4@SiO2 contains more functional groups. The result is consistent with the results of TGA and

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elemental analysis.

Fig. 3 (a) TGA and (b) nitrogen adsorption–desorption isotherm curves Table 1 The porous structure parameters BET surface area

Adsorbents

BJH desorption cumulative

·

(m2

g-1)

pore volume

·

(cm3

g-1)

BJH desorption pore radius (nm)

Fe3O4@SiO2

42.02

0.17

104.22

HO-Fe3O4@SiO2-AP

23.34

0.11

71.87

HE-Fe3O4@SiO2-AP

32.31

0.15

83.50

The morphology of HO-Fe3O4@SiO2-AP is revealed by TEM as shown in Fig.4. It is clear that HO-Fe3O4@SiO2-AP exhibits relatively uniform core-shell spherical morphology with the thickness of outer coating shell in the range of 2-3 nm. The lattice fringes of

Fig. 4 TEM images of the HO-Fe3O4@SiO2-AP HO-Fe3O4@SiO2-AP is shown in Fig.4 (b) and the lattice fringes belong to (111) planes and 8


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(002) planes are 0.681 and 0.297 nm, respectively.39,40 Influence of pH to the adsorption. Fig. 5 shows the influence of pH to the adsorption. It shows solution pH has dramatically effect on the adsorption and pH 6 is the optimum. The variation of adsorption capacity can be interpreted by the variation of functional group existing form at varying solution pH.41 The functional groups of nitrogen and oxygen are existed in the protonated form at low pH, the positive charge prevent the contact of metal ion with functional groups, description the adsorption amount. The protonation would be alleviated and more functional group is accessible for the adsorption when the pH increase, resulting adsorption capacity increase. Therefore, the pH 6 is selected for the following experiments.

The

adsorption

capacity

of

HO-Fe3O4@SiO2-AP

is

larger

than

HE-Fe3O4@SiO2-AP, which due to more functional groups are achieved by one-pot sequential reaction. It is also found that HO-Fe3O4@SiO2-AP and HE-Fe3O4@SiO2- AP display similar adsorption capacity for Ag(Ⅰ) at pH 6, while for Hg(Ⅱ) is quite different. The reason mainly attribute to the higher binding ability of aminopyridine toward Hg(Ⅱ) as compared to Ag(Ⅰ).

Fig. 5 The influence of pH (t: 12 h; T: 25 °C; C: 0.002 mol·L-1) Adsorption kinetic. Fig. 6 shows the profiles of adsorption kinetic for Hg(Ⅱ) and Ag(Ⅰ) under different concentration. It is obvious the uptake of metal ions is fast during the first 120 9



and 100 min, respectively. After that, the rate gradually decreases and adsorption equilibrium is reached at 220 and 180 min, respectively. The rapid adsorption during the initial stage may be associated with the abundant binding sites and high concentration of metal ion, which facilitates the diffusion of ions and chelates with the active binding site.29 The metal ion concentration and binding site would decrease with the adsorption proceeding, which reduces the adsorption rate gradually. The final adsorption capacity of HO-Fe3O4@SiO2-AP is higher than HE-Fe3O4@SiO2-AP, which is consistent with the previous obtained results.

Fig. 6 Profiles of adsorption kinetic (T: 25 °C; pH: 6; C: 0.002 and 0.004 mol·L-1) Pseudo-first- and pseudo-second-order kinetic models are utilized to analyze the adsorption kinetic mechanism.29,42,43 The detail information of the models is provided in the Supporting Information. Table 2 summarizes the fitting parameters and indicates pseudosecond-order kinetic model is more suitable to interpret the adsorption kinetic as the values of

10


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R22 are higher than R12. Moreover, the closeness of calculated adsorption capacity (qe,cal) to the experimental data (qe,exp) also demonstrate pseudo-second-order model is more suitable. Boyed film diffusion model is used to confirm whether the rate-controlling step is film or interparticle diffusion.44 The detail information for the model is provided in the Supporting Information and Table 3 summarizes the relative parameters. Results suggests film diffusion dominates the adsorption kinetic as the fitting lines show satisfactory linearity without passing through the origin.45 Table 2 The adsorption kinetic parameters

Ions

Hg(II)

Ag(II)

C(mol· L-1)

qe,exp (mmol·g-1 )

HO-Fe3O4 @SiO2-AP

0.002

0.58

0.004

HE-Fe3O4 @SiO2-AP

Adsorbents

Pseudo-first-order model

Pseudo-second-order model

qe, cal

qe,cal

k1 (min-1)

R12

0.26

0.01

0.9829

0.73

0.24

0.01

0.002

0.15

0.21

0.004

0.36

HO-Fe3O4 @SiO2-AP

0.002

HE-Fe3O4 @SiO2-AP

(mmol· )

(mmol· )

k2 (mmol·g-1 ·min-1)

R22

0.60

0.10

0.9983

0.8971

0.75

0.13

0.9994

0.01

0.9711

0.19

0.03

0.9990

0.44

0.01

0.9508

0.37

0.02

0.9991

0.26

0.15

0.01

0.9691

0.28

0.14

0.9980

0.004

0.35

0.27

0.01

0.9300

0.39

0.07

0.9985

0.002

0.18

0.16

0.01

0.9939

0.22

0.07

0.9993

0.004

0.24

0.17

0.01

0.9772

0.26

0.08

0.9993

g-1

g-1

Table 3 The parameters of Boyed film diffusion model Ions

Adsorbents

C(mol·L-1)

Equation of line

Intercept errors

R2

Hg(Ⅱ)

HO-Fe3O4@SiO2-AP

0.002

Bt=0.0115t+0.4018

0.0745

0.9831

0.004

Bt=0.0171t+0.6162

0.1591

0.9624

0.002

Bt=0.0110t-0.6602

0.1130

0.9640

0.004

Bt=0.0124t-0.6327

0.0341

0.9972

0.002

Bt=0.0125t+0.0982

0.0340

0.9965

0.004

Bt=0.0174t-0.3538

0.0764

0.9759

0.002

Bt=0.0101t-0.2323

0.1109

0.9424

0.004

Bt=0.0102t-0.1011

0.0439

0.9818

HE-Fe3O4@SiO2-AP

Ag(Ⅰ)

HO-Fe3O4@SiO2-AP

HE-Fe3O4@SiO2-AP

11



Adsorption isotherm. Fig. 7 shows the curves of adsorption isotherm. The adsorption for Hg( Ⅱ ) and Ag( Ⅰ ) is promoted with temperature and concentration increase. The high driving force under high concentration is responsible for the increase of adsorption capacity associates with concentration. The promotion of adsorption capacity with high temperature indicates the endothermic nature of the adsorption.

Fig. 7 Adsorption isotherm curves (C: 0.0005-0.05 mol·L-1; T: 15, 25, and 35 °C; t: 12 h) The adsorption isotherm mechanism is analyzed by Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherm models.41,46,47 The detail information of the models is provided in the Supporting Information. The fitting parameters are tabulated in Table 4 and 5. Table 4 shows the adsorption isotherm can be described better by Langmuir model as RL2 values are higher than RF2, suggesting the adsorption of Hg(Ⅱ) and Ag(Ⅰ) is proceeded by monolayer behavior. The D-R model fitting parameters in Table 6 suggest the nature of the adsorption is chemical as the E values of HO-Fe3O4@SiO2-AP for Hg(Ⅱ) and Ag(Ⅰ) range from 8 to 16 kJ·mol-1.47 12


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Table 4 The Langmuir and Freundlich fitting parameters Langmuir model Metal ions

T

Absorbents

(oC)

HO-Fe3O4@SiO2- AP

Hg(Ⅱ)

HE-Fe3O4@SiO2-AP

Ag(I)

HO-Fe3O4@SiO2-AP

HE-Fe3O4@SiO2-AP

qm

KF

KL

(mmol· )

g-1

Freundlich model

(mL·mmol-1)

RL

2

(mmol·g-1 )

n

RF2

15

0.92

1004.18

0.9879

5.49

2.80

0.9718

25

0.97

1013.22

0.9882

6.35

2.67

0.9606

35

1.11

1061.49

0.9839

9.47

2.39

0.8591

15

0.24

194.89

0.9757

2.36

2.15

0.8878

25

0.46

257.23

0.9920

8.83

1.53

0.9838

35

0.64

657.38

0.9967

14.41

1.41

0.9911

15

0.49

604.99

0.9853

3.15

2.61

0.9785

25

0.63

620.28

0.9989

6.01

2.14

0.9852

35

0.64

844.69

0.9976

5.92

2.17

0.9797

15

0.57

376.63

0.9901

8.76

1.72

0.9884

25

0.58

503.97

0.9728

8.92

1.78

0.9118

35

0.65

551.49

0.9897

7.65

1.96

0.9821

Table 5 The D-R model fitting parameters Ions

Adsorbents

HO-Fe3O4 @SiO2-AP Hg(Ⅱ) HE-Fe3O4@ SiO2-AP HO-Fe3O4 @SiO2-AP Ag(Ⅰ) HE-Fe3O4@ SiO2-AP

qm

k

E

T (oC)

Linear equation

15

y=-4.84×10-9x+0.57

1.77

4.84·10-9

10.16

0.9818

25

y=-4.76×10-9x+0.66

1.94

4.76·10-9

10.25

0.9735

35

y=-5.03×10-9x+0.94

2.56

5.03·10-9

9.97

0.8912

15

y=-6.63×10-9x-0.55

0.58

6.63·10-9

8.68

0.9173

25

y=-8.66×10-9x+0.18

1.20

8.66·10-8

7.60

0.9927

35

y=-8.75×10-9x+0.49

1.62

8.75·10-9

7.56

0.9981

15

y=-5.19×10-9x-0.06

0.94

5.19·10-9

9.82

0.9833

25

y=-5.92×10-9x+0.31

1.37

5.92·10-9

9.19

0.9985

35

y=-5.45×10-9x+0.31

1.37

5.45·10-9

9.58

0.9971

15

y=-8.01×10-9x+0.35

1.42

8.01·10-9

7.90

0.9962

25

y=-7.25×10-9x+0.45

1.56

7.25·10-9

8.30

0.9368

35

y=-6.09×10-9x+0.43

1.53

6.09·10-9

9.06

0.9911

(mmol·

g-1)

·

(mol2

J-2)

(kJ·mol-1)

R2

Table 6 shows the comparison of qm and adsorption kinetic equilibrium time (te) with 13



Page 14 of 33

other adsorbents. It is evident the qm of HO-Fe3O4@SiO2-AP is larger than most of the alternative adsorbents, indicating the one-pot sequential synthesis strategy is credible for efficient adsorbent synthesis. Moreover, the te of HO-Fe3O4@SiO2-AP for Hg(Ⅱ) and Ag(Ⅰ) adsorption of is comparable and shorter than some of the alternative adsorbents. Therefore, HO-Fe3O4@SiO2-AP could be potential used for robust remove aqueous Hg(Ⅱ) and Ag(Ⅰ). Table 6 Comparison of qm with alternative adsorbents te (min)

Ref

0.97

220

This study

HE-Fe3O4@SiO2-AP

0.46

220

This study

Magnetic carbon nanotube

1.19

60

48

Nanoplates of cobalt phosphonate

0.78

-

49

Silica coated Fe3O4 nanoparticle

0.74

360

21

Thiol functionalized Fe3O4

0.66

400

50

Magnetic graphene oxide

0.58

240

51

Thiolated carbon nanotube

0.53

180

52

Humic acid coated Fe3O4

0.49

15

53

Magnetic β-cyclodextrin composite

0.32

30

54

HO-Fe3O4@SiO2-AP

0.63

180

This study

HE-Fe3O4@SiO2-AP

0.58

180

This study

Tripolyphosphate crosslinked chitosan

0.77

50

55

Thiourea modified poly(vinyl alcohol)

0.62

170

56

Diethylenetriamine modified silica

0.10

480

27

Expanded perlite

0.08

120

57

Hydrolyzed plant biomass

0.06

15

58

Metal ions

Adsorbent

Hg(Ⅱ)

HO-Fe3O4@SiO2-AP

Ag(Ⅰ)

qm (mmol·

g-1)

Thermodynamic parameters of ΔG, ΔH and ΔS are obtained based on Eqs. (1) and (2):47

G   RT ln K L

(1)

S H  R RT

(2)

ln K L 

where R (8.314 J·mol−1·K−1) is gas constant and T donates temperature (K). Table 7 lists the 14


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obtained thermodynamic parameters and it indicates the adsorption is spontaneous by the negative ΔG values. The positive ΔH and ΔS values imply the endothermic and enthalpy increase nature of the adsorption. Table 7 Thermodynamic parameters Mental ions Hg(Ⅱ)

Adsorbents HO-Fe3O4@SiO2-AP

HE-Fe3O4@SiO2-AP

Ag(Ⅰ)

HO-Fe3O4@SiO2-AP

HE-Fe3O4@SiO2-AP

T(℃)

△G(kJ·mol-1)

15

-16.56

25

-17.16

35

-17.85

15

-12.63

25

-13.76

35

-16.62

15

-15.34

25

-15.94

35

-17.26

15

-14.21

25

-15.42

35

-16.17

△H(kJ·mol-1)

△S(J·mol-1·K-1)

2.03

64.47

44.59

197.64

12.20

95.19

14.15

98.69

Adsorption selectivity. Adsorption selectivity for Hg( Ⅱ ) by HO-Fe3O4@SiO2-AP was investigated as representative and presented in Table 8. HO-Fe3O4@SiO2-AP can 100% selective adsorb Hg(Ⅱ) with the coexistence of Cd(Ⅱ), Ni(Ⅱ), Ag(Ⅰ), Cu(Ⅱ), and Zn(Ⅱ), which indicates it can be potentially used for efficient preconcentration, separation and recovery of aqueous Hg(Ⅱ). The excellent adsorption selectivity of HO-Fe3O4@SiO2-AP for Hg( Ⅱ ) indicates aminopyridine group dominates the adsorption of metal ion, as previous report demonstrates the binding ability of pyridine-containing functional group for metal ion follows the order of Hg(Ⅱ) > Cu(Ⅱ) > Ni(Ⅱ) > Cd(Ⅱ) > Pb(Ⅱ).59 The adsorption mechanism and selectivity is further demonstrated. The FTIR and XPS spectra were conducted preliminarily to explore the adsorption mechanism. Fig. 8 shows the 15



Page 16 of 33

FTIR and XPS spectra of HO-Fe3O4@SiO2-AP before and after adsorption. the characteristic System Hg(II)-Cd(II)

Hg(II)-Cu(II)

Hg(II)-Ag(I)

Hg(II)-Zn(II)

Hg(II)-Ni(II)

Hg(II)-Pb(II)

q (mmol·g-1)

Ions Hg(Ⅱ)

0.55

Cd(II)

0.00

Hg(Ⅱ)

0.57

Cu(II)

0.00

Hg(Ⅱ)

0.57

Ag(Ⅰ)

0.00

Hg(Ⅱ)

0.56

Zn(II)

0.00

Hg(Ⅱ)

0.57

Ni(II)

0.00

Hg(Ⅱ)

0.48

Pb(II)

0.09

Selective coefficient ∞

∞

∞

∞

∞

5.33

Absorption peak of pyridyl ring at 1460 cm-1 nearly disappears in the spectra of HO-Fe3O4@SiO2-AP-Hg and HO-Fe3O4@ SiO2-AP-Ag after adsorption, indicating the participation of pyridyl group during the adsorption. However, due to the overlap of the absorption peaks of N-H, O-H and silanol groups, FTIR cannot reflect whether -NH- and -OH involve in the adsorption. In the spectrum of HO-Fe3O4@SiO2-AP-Ag, the peak at 1385 cm−1 belongs to the characteristic absorption of NO3- as AgNO3 is adopted in the adsorption experiment, further demonstrating the adsorption mechanism is chemical in nature.41 The new peak assigned to Hg 4f and Cl 2p, Ag 3d3/2 and Ag 3d5/2 appear in the XPS spectrum of HO-Fe3O4@SiO2-AP after adsorption in Fig.8(b), which confirms the successful capture of metal ions.51,60 Fig.8 (c) and (e) show the peaks that ascribed to =N– and –NH– shift from 398.14 and 399.23 eV to 399.03 and 401.16 eV after adsorption Hg(Ⅱ), while these peaks shift to 398.93 and 399.76 eV after adsorption Ag(Ⅰ). The result suggests the participation of aminopyridine group during the adsorption, which also supports the result of FTIR analysis. 16


Page 17 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The variation of the spectra is due to the coordination of metal ion with –NH– and =N–

Fig. 8 (a) FTIR spectra, (b) XPS spectrum, (c and e) N 1s, and (d and f) O 1s high resolution spectra of HO-Fe3O4@SiO2-AP after adsorption groups, which decreases the electron density of N atoms. Similar phenomenon is also observed in O 1s spectra (Fig.8 (d) and (f)) for C–OH and C–O–C peaks, suggesting the oxygen atoms of –OH and C–O–C also take part in the adsorption.

17



Page 18 of 33

DFT calculation is further explored to reveal the adsorption selectivity and adsorption behavior difference between Hg(Ⅱ) and Ag(Ⅰ). As the functional group of HO-Fe3O4@ SiO2-AP is mainly responsible for the binding ability of metal ion, the surface functional group is selected as computational model in order to enhance the computational efficiency. Fig.9 displays the optimized structures and Table 9 summarizes the computational parameters. It can be seen the surface functional group mainly binds metal ions in tri- and tetra-coordinated modes. For M-complex-1(M=Hg(Ⅱ), Ag(Ⅰ)) , the functional group coordinates with metal ion by aminopyridine nitrogen atoms and hydroxyl oxygen atom.

Fig. 9 The optimized structures of the complexes Table 9 The computational parameters of the complexes NBO partial charge

Complexs

Binding energy (kcal/mol)

Ligand

Ion

Electron configuration of metal ion

Hg(Ⅱ)-Complex-1

-208.22

0.51

1.49

6s0.505d9.996p0.01

Hg(Ⅱ)-Complex-2

-215.64

0.50

1.50

6s0.505d9.996p0.017p0.01

Hg(Ⅱ)-Complex-3

-230.04

0.43

1.57

6s0.435d9.986p0.017p0.01

Ag(Ⅰ)-Complex-1

-63.57

0.14

0.86

5s0.144d9.976p0.02

Ag(Ⅰ)-Complex-2

-63.92

0.18

0.82

5s0.214d9.956p0.02

18


Page 19 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Ag(Ⅰ)-Complex-3

-68.07

0.15

0.85

5s0.184d9.966p0.02

Similarly, the functional group can also interact with metal ion to form Hg(Ⅱ)-complex-2 and Ag(Ⅰ)-complex-2 by replacing hydroxyl oxygen atom with the oxygen atom of ether linkage. For M-complex-1(M=Hg( Ⅱ ), Ag( Ⅰ )), the functional interact with metal ion by tetracoordinated manner involving the participation of all the donor atoms. It can be observed that the bond lengths between metal ion and pyridyl ring nitrogen atom are shorter than the bond lengths of amino nitrogen atom, suggesting pyridyl nitrogen atom exhibits higher binding than the nitrogen atom of amino group. Similar phenomenon is also observed for the oxygen atom of ether linkage, indicating the preference of binding metal ion with ether linkage oxygen as compared with hydroxyl oxygen atom. The binding energy follows the order of M-Complex-3 > M-Complex-2 > M-Complex-1 (M=Hg( Ⅱ ), Ag( Ⅰ )), indicating M-Complex-3 is the dominant mode during the adsorption, which supports the XPS results. As illustrated by elemental analysis, the nitrogen content of HO-Fe3O4@SiO2-AP is 0.89 mmol/g and the adsorption amount for Hg( Ⅱ ) is 0.80 mmol/g at the optimum pH 6, indicating the functional group and Hg(Ⅱ) tend to interact with each other by the ratio of 1:1. Moreover, the binding energy of the functional group for Hg( Ⅱ ) is higher, indicating the functional group is preferred to bind Hg(Ⅱ) than Ag(II). The result is well agreement with the adsorption selectivity phenomenon as HO-Fe3O4@SiO2-AP can 100% selectively adsorb Hg(Ⅱ) with Ag(I) as interfering ion. As can be seen from Table 9, the NBO partial charges of Hg(Ⅱ) and Ag(Ⅰ) are lower than 2 and 1 in the complexes, respectively. The result indicates charge transfer from functional group to metal ion takes place along with the adsorption. The charge mainly

19



transferrs to the 6s and 5s empty orbital of Hg(Ⅱ) and Ag(Ⅰ). The lowest unoccupied orbital (LUMO) and highest occupied molecular orbital (HOMO) contour plots are described in Fig.10 by selecting the functional group, Hg( Ⅱ )-Complex-3 and Ag( Ⅰ )-Complex-3 as models. The LUMO of functional group is mainly locate on the pyridine ring, and the HOMO spreads dominantly on aminopyridine and the adjacent hydroxyl groups. After coordination, the LUMO of the complexes are dominated by the location of charge density on the metal ion, while a little portion spreads over the pyridine ring and donor atoms. The charge density of HOMO for Hg( Ⅱ )-Complex-3 is similar to that of the functional, while that for Ag( Ⅰ )-Complex-3 spreads over the metal ion, aminopyridine, oxygen atoms, and the neighbor carbon atoms.

Fig. 10 HOMO and LUMO contour plots of the functional group and the complexes Second order perturbation theory analysis equipped in NBO analysis is further used to estimate the adsorption mechanism and adsorption behavior difference between Hg(Ⅱ) and Ag(Ⅰ).47,61 For M-complex-1(M=Hg(Ⅱ), Ag(Ⅰ)), the functional group mainly interacts with metal ion by the σ donation of electron from nitrogen and oxygen to the empty orbital of metal ions. The LP(N)→LP*(Hg) stabilization energy (E(2)) are 24.28 and 29.68 kcal/mol for

20


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Page 21 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


amino and pyridyl nitrogen atoms, which are higher than LP(N)→LP*(Ag) by 9.62 and 21.44 kcal/mol. Moreover, the LP(O)→LP*(Hg) and LP(O)→LP*(Ag) E(2) energy are 15.34 and 14.34 kcal/mol. These results suggest the nitrogen atoms of aminopyridine are the dominant contributors for the adsorption. Furthermore, the difference between LP(N)→LP*(Hg) and LP(N)→LP*(Ag) E(2) energy is mainly responsible for the adsorption behavior difference of Hg( Ⅱ ) and Ag( Ⅰ ). HO-Fe3O4@SiO2-AP exhibits remarkable adsorption selectivity and capacity for Hg( Ⅱ ) than Ag( Ⅰ ) due to the LP(N)→LP*(Hg) E(2) energy is higher than LP(N)→LP*(Ag),. With respect to Hg(Ⅱ)-complex-2 and Ag(Ⅰ)-complex-2, the adsorption is also characterized by the donor atom-metal ion σ donation. The LP(N)→LP*(Hg) E(2) values are 20.30 and 34.46 kcal/mol, and those for LP(N)→LP*(Ag) are 6.33 and 19.76 kcal/mol. Moreover, the LP(O)→LP*(Hg) and LP(O)→LP*(Ag) E(2) values are 16.23 and 8.01 kcal/mol. Similarly, the E(2) energies of LP(N)→LP*(Hg) for Hg( Ⅱ )-complex-3 are 14.70 and 32.73 kcal/mol, and for LP(O)→LP*(Ag) are 7.85 and 16.13 kcal/mol. The LP(N)→ LP*(Hg) energy are higher than the corresponding LP(N)→LP*(Ag) by 10.75 and 15.38 kcal/mol, while that of LP(O)→LP*(Hg) are larger than the corresponding LP(O)→LP*(Ag) by 5.02 and 9.81 kcal/mol. These results also suggest aminopyridine group is mainly contributed to the adsorption process and the functional group prefers to bind Hg(Ⅱ) than Ag(Ⅰ), which is reasonable for the adsorption difference between Ag(Ⅰ) and Hg(Ⅱ), and is in well consistent with the adsorption selectivity results. The coordination mode and interaction mechanism of Cd(II) and Cu(II) were also calculated as representatives to further interpret the adsorption selectively. The complexes formed by Cd(II) and Cu(II) with the functional group are presented in Fig. S1 and the

21



Page 22 of 33

corresponding E(2) values are presented in Table S1. The structure of Cd(II) and Cu(II) complexes are similar to those of Hg( Ⅱ ) and Ag( Ⅰ ). Moreover, the LP(N)→ LP*(M) (M=Cd and Cu) E(2) values are lower than the corresponding LP(N)→LP*(Hg), which further indicates the binding ability of aminopyridine group for Hg(Ⅱ) is superior to Cd(II) and

Cu(II).

The

result

is

consistent

with

the

selective

adsorption

result

as

HO-Fe3O4@SiO2-AP can adsorb Hg(Ⅱ) selectively with the coexistence of Cd(II) and Cu(II). The regeneration of the adsorbent. The regeneration is important to evaluate the practical application property of adsorbent. Therefore, the regeneration property of HO-Fe3O4@SiO2-AP was evaluated by employing 5% thiourea-0.2 mol·L-1 HCl solution as eluent. Fig. 11 shows that the adsorbed ions can be facilely desorbed by the eluent. The desorption rate for Hg(Ⅱ) and Ag(Ⅰ) is 95.9% and 96.2% for the first cycle. Even after 3 adsorption-desorption cycles, the desorption rate can also achieve 91.6% and 92.0%. The good regeneration property indicates HO-Fe3O4@ SiO2-AP can be reused in the practical water treatment.

Fig.11 The regeneration for HO-Fe3O4@SiO2-AP (eluent: 5% thiourea-0.2 mol·L-1 HCl)

Conclusion 22


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In this study, HO-Fe3O4@SiO2-AP and HE-Fe3O4@SiO2-AP were synthesized by feasible one-pot sequential reaction and general step-by-step surface modification method. The as-prepared adsorbents were used to remove aqueous Hg( Ⅱ ) and Ag( Ⅰ ). Results indicate the one-pot sequential reaction is more efficient than the general step-by-step surface modification method. HO-Fe3O4@SiO2-AP exhibits higher adsorption capacity. The optimum pH for Hg( Ⅱ ) and Ag( Ⅰ ) adsorption the is 6.0. Pseudo-second-order model is suitable to describe the adsorption kinetic and film diffusion process is the rate-controlling step. Adsorption isotherm process is fitted well by Langmuir model. Thermodynamic parameters indicate the adsorption is endothermic, spontaneous, and enthalpy increase process. Adsorption selectivity reveals HO-Fe3O4@SiO2-AP can 100% selective adsorb Hg(Ⅱ) with the coexistence of Cd( Ⅱ ), Ni( Ⅱ ), Ag( Ⅰ ), Cu( Ⅱ ), and Zn( Ⅱ ). Adsorption mechanism indicates the adsorption is dominated by the formation tetra-coordinated complex involves all oxygen and nitrogen atoms. The interaction between nitrogen atoms of aminopyridine group and metal ions are mainly contributed to the adsorption. As HO-Fe3O4@SiO2-AP displays relative high adsorption selectivity and capacity, it would be potentially used for the robust removal, preconcentration and recovery of aqueous Hg(Ⅱ) and Ag(Ⅰ).

Supporting Information The experimental section, optimized structure of the complexes for Cd(II) and Cu(II), the E(2) values of LP(N)→LP*(M) (M=Cd and Cu).

Acknowledgements National Natural Science Foundation of China (21307053 and 51673090), Natural Science Foundation of Shandong Province (ZR2018MB039), Science and Technology

23



Page 24 of 33

Research Program of Yantai (2017ZH060), and The Key Program for Basic Research of Natural Science Foundation

of

Shandong

Province

(ZR2018ZC0946)

are

grateful

acknowledged.

References (1) Aguila, B.; Sun, Q.; Perman, J.; Earl, L.; Abney, C.; Elzein, R.; Schlaf, R.; Ma, S. Efficient Mercury Capture Using Functionalized Porous Organic Polymer. Adv. Mater. 2017, 29, 1700665. (2) Cohen, E.; Weissman, H.; Shimoni, E.; Kaplan-Ashiri, I.; Werle, K.; Wohlleben, W.; Rybtchinski, B. Robust Aqua Material: A Pressure-Resistant Self-Assembled Membrane for Water Purification.Angew. Chem.Int. Edit. 2017, 56, 2203-2207. (3) Francis, A.; Dodge, C.; Gillow, J. Biodegradation of Netal Citrate Complexes and Implications for Toxie-metal Mobility. Nature 1992, 356, 140-142. (4) Mon, M.; Lloret, F.; Ferrando-Soria, J.; Marti-Gastaldo, C.; Armentano, D.; Pardo, E. Selective and Efficient Removal of Mercury from Aqueous Media with the Highly Flexible Arms of a BioMOF.Angew. Chem.Int. Edit. 2016, 55, 11167-11172. (5) Liu, X.; Yang, L.; Luo, X.; Pei, J.; Xi, Y.; Liu, C.; Liu, L. A novel non-imprinted adsorbent with superior selectivity towards high-performance capture of Ag(Ⅰ). Chem. Eng. J. 2018, 348, 224-231. (6) Xie, L.; Yu, Z.; Islam, S.; Shi, K.; Cheng, Y.; Yuan, M.; Zhao, J.; Sun, G.; Li, H.; Ma, S.; Kanatzidis, M. Remarkable Acid Stability of Polypyrrole-MoS4: A Highly Selective and Efficient Scavenger of Heavy Metals Over a Wide pH Range.Adv. Funct. Mater. 2018, 28, 1800502.

24


Page 25 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(7) Ding, S.; Dong, M.; Wang, Y.; Chen, Y.; Wang, H..; Su, C.; Wang, W. ThioetherBased Fluorescent Covalent Organic Framework for Selective Detection and Facile Removal of Mercury(II). J. Am. Chem. Soc. 2016, 138, 3031-3037. (8) Fard, Z.; Malliakas, C.; Mertz, J.; Kanatzidis, M. Direct Extraction of Ag+ and Hg2+ from Cyanide Complexes and Mode of Binding by the Layered K2MgSn2S6 (KMS-2). Chem. Mater. 2015, 27, 1925-1928. (9) Zhao, J.; Niu, Y.; Ren, B.; Chen, H.; Zhang, S.; Jin, J.; Zhang, Y. Synthesis of Schiff Base Functionalized Superparamagnetic Fe3O4 Composites for Effective Removal of Pb(II) and Cd(II) from Aqueous Solution.Chem. Eng. J. 2018, 347, 574-584. (10)Ma, L.; Islam, S.; Xiao, C.; Zhao, J.; Liu, H.; Yuan, M.; Sun, G.; Li, H.; Ma, S.; Kanatzidis, M. G. Rapid Simultaneous Removal of Toxic Anions [HSeO3]−, [SeO3]2–, and [SeO4]2–, and Metals Hg2+, Cu2+, and Cd2+ by MoS42– Intercalated Layered Double Hydroxide. J. Am. Chem. Soc. 2017, 139, 12745-12757. (11)Cal, E.; Qi, J.; Preedy, O.; Chen, S.; Boldrin, D.; Branford, W.; Vandeperre, L.; Ryan, M. Functionalised Nagnetic Nanoparticles for Uranium Adsorption with Ultra-high Capacity and Selectivity.J. Mater. Chem. A 2018, 6, 3063-3073. (12)Shao, M.; Ning, F.; Zhao, J.; Wei, M.; Evans, D.; Duan, X. Preparation of Fe3O4@SiO2@Layered Double Hydroxide Core-Shell Microspheres for Magnetic Separation of Proteins. J. Am. Chem. Soc. 2012, 134, 1071-1077. (13)Du, Z.; Deng, S.; Zhang, S.; Wang, W.; Wang, B.; Huang, J.; Wang, Y.; Yu, G.; Xing, B. Selective and Fast Adsorption of Perfluorooctanesulfonate from Wastewater by Magnetic Fluorinated Vermiculite. Environ. Sci. Technol. 2017, 51, 8027-8035.

25



(14)Zhang, J.; Han, J.; Wang, M.; Guo, R. Fe3O4/PANI/MnO2 core-shell hybrids as advanced adsorbents for heavy metal ions. J. Mater. Chem. A 2017, 5, 4058-4066. (15)Yue, Q.; Li, J.; Luo, W.; Zhang, Y.; Elzatahry, A.; Wang, X.; Wang, C.; Li, W.; Cheng, X.; Alghamdi, A.; Abdullah, A.; Deng, Y.; Zhao, D. An Interface Coassembly in Biliquid Phase: Toward Core-Shell Magnetic Mesoporous Silica Microspheres with Tunable Pore Size. J. Am. Chem. Soc. 2015, 137, 13282-13289. (16)Yang, J.; Zhao, Y.; Ma, S.; Zhu, B.; Zhang, J.; Zheng, C. Mercury Removal by Magnetic Biochar Derived from Simultaneous Activation and Magnetization of Sawdust. Environ. Sci. Technol. 2016, 50, 12040-12047. (17)Jiang, W.; Cai, Q.; Xu, W.; Yang, M.; Cai, Y.; Dionysiou, D.; O'Shea, K. Cr(VI) Adsorption and Reduction by Humic Acid Coated on Magnetite. Environ. Sci. Technol. 2014, 48, 8078-8085. (18)Wang, L.; Hu, D.; Kong, X.; Liu, J.; Li, X.; Zhou, K.; Zhao, H.; Zhou, C. Anionic Polypeptide Poly(gamma-glutamic acid)-functionalized Magnetic Fe3O4-GO-(o-MWCNTs) Hybrid Nanocomposite for High-efficiency Removal of Cd (II), Cu(II) and Ni(II) Heavy Metal Ions. Chem. Eng. J. 2018, 346, 38-49. (19)Kumar, A.; Khan, M.; Zeng, X.; Lo I. Development of g-C3N4/TiO2/Fe3O4@SiO2 Heterojunction via Sol-gel Route: A Nagnetically Recyclable Direct Contact Z-scheme Nanophotocatalyst for Enhanced Photocatalytic Removal of Ibuprofen from Real Sewage Effluent Under Visible Light, Chem. Eng. J. 2018, 353, 645-656. (20)Shan, C.; Ma, Z.; Tong, M.; Ni, J. Removal of Hg(Ⅱ) by poly(1-vinylimidazole) -grafted Fe3O4@SiO2 magnetic nanoparticles.Water Res. 2015, 69, 252-260.

26


Page 26 of 33

Page 27 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(21)Zhang, S.; Zhang, Y.; Liu, J.; Xu, Q.; Xiao, H.; Wang, X.; Xu, H.; Zhou, J. Thiol modified Fe3O4@SiO2 as a robust, high effective, and recycling magnetic sorbent for mercury removal. Chem. Eng. J. 2013, 226, 30-38. (22)Zhao, Y.; Li, J.; Zhao, L.; Zhang, S.; Huang, Y.; Wu, X.; Wang, X. Synthesis of Amidoxime-functionalized Fe3O4@SiO2 Core–shell Magnetic Microspheres for Highly Efficient Sorption of U(VI). Chem. Eng. J. 2014, 235, 275-283. (23)Pylypchuk,

I.;

Kessler,

V.;

Seisenbaeva,

G.

Simultaneous

Removal

of

Acetaminophen, Diclofenac, and Cd(II) by Trametes versicolor Laccase Immobilized on Fe3O4/SiO2-DTPA Hybrid Nanocomposites.Acs Sustain. Chem. Eng. 2018, 6, 9979-9989. (24)Ji, C.; Song, S.; Wang, C.; Sun, C.; Qu, R.; Wang, C.; Chen, H. Preparation and Adsorption Properties of Chelating Resins Containing 3-aminopyridine and Hydrophilic Spacer Arm for Hg(Ⅱ). Chem. Eng. J. 2010, 165, 573-580. (25)Song, S.; Ji, C.; Wang, M.; Wang, C.; Sun, C.; Qu, R.; Wang, C.; Chen, H. Adsorption of Silver(I) from Aqueous Solution by Chelating Resins with 3-Aminopyridine and Hydrophilic Spacer Arms: Equilibrium, Kinetic, Thermodynamic, and Mechanism Studies.J.Chem. Eng. Data 2011, 56, 1001-1008. (26)Pérez-Quintanilla, D.; Hierro, I.; Fajardo, M.; Sierra, I. 2-Mercaptothiazoline Modified Mesoporous Silica for Mercury Removal from Aqueous Media. J. Hazard. Mater. 2006, 134, 245-256. (27)Zhang, Y.; Qu, R.; Sun, C.; Chen, H.; Wang, C.; Ji, C.; Yin, P.; Sun, Y.; Zhang, H.; Niu, Y. Comparison of Synthesis of Chelating Resin Silica-gel-supported Diethylenetriamine and Its Removal Properties for Transition Metal Ions. J. Hazard. Mater. 2009, 163, 127-135.

27



Page 28 of 33

(28)Zhu, M.; Zhang, W.; Li, Y.; Gai, L.; Zhou, J.; Ma, W. Multishell Structured Magnetic Nanocomposites Carrying a Copolymer of Pyrrole-thiophene for Highly Selective Au(III) Recovery.J. Mater. Chem. A 2016, 4, 19060-19069. (29)Song, X.; Niu, Y.; Qiu, Z.; Zhang, Z.; Zhou, Y.; Zhao, J.; Chen, H. Adsorption of Hg(Ⅱ) and Ag(Ⅰ) from Fuel Ethanol by Silica Gel Supported Sulfur-containing PAMAM Dendrimers: Kinetics, Equilibrium and Thermodynamics.Fuel 2017, 206, 80-88. (30)Zhang, Y.; Chen, Y.; Wang, C.; Wei, Y. Immobilization of 5-aminopyridine-2tetrazole on Cross-linked Polystyrene for the Preparation of a New Adsorbent to Remove Heavy Metal Ions from Aqueous Solution. J. Hazard. Mater. 2014, 276, 129-137. (31)Wu, X.; Wang, L.; Chen, C.; Xu, A.; Wang, X. Water-dispersible Magnetitegraphene-LDH Composites for Efficient Arsenate Removal. J. Mater. Chem. 2011, 21, 17353-17359. (32)Niu, Y.; Qu, R.; Chen, H.; Mu, L.; Liu, X.; Wang, T.; Zhang, Y.; Sun, C. Synthesis of Silica Gel Supported Salicylaldehyde Modified PAMAM Dendrimers for the Effective Removal of Hg(Ⅱ) from Aqueous Solution. J. Hazard. Mater. 2014, 278, 267-278. (33)Circu, M.; Radu, T.; Porav, A.; Turcu, R. Surface Functionalization of Fe3O4@SiO2 Core-shell

Nanoparticles

with

Vinylimidazole-rare

Earth

Complexes:

Synthesis,

Physico-chemical Properties and Protein Interaction Effects.Appl. Surf. Sci. 2018, 453, 457463. (34)Kang, D.; Yu, X.; Ge, M.; Lin, M.; Yang, X.; Jing, Y. Insights into Adsorption Mechanism for Fluoride on Cactus-like Amorphous Alumina Oxide Microspheres. Chem. Eng. J. 2018, 345, 252-259.

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Page 29 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(35)Senthilnathan, J.; Yoshimura, M. Low Energy Liquid Plasma for Direct Reduction and Formation of rGO-aminopyridine Hybrid for Electrical and Environmental Applications. J. Hazard. Mater. 2017, 340, 26-35. (36)Singha, N.; Mahapatra, M.; Karmakar, M.; Dutta, A.; Mondal, H.; Chattopadhyay, P. K. Synthesis of Guar Gum-g-(acrylic acid-co-acrylamide-co-3-acrylamido propanoic acid) IPN

via

in

Situ

Attachment

of

Acrylamido

Propanoic

Acid

for

Analyzing

Superadsorption ,echanism of Pb(II)/Cd(II)/Cu(II)/MB/MV.Polym. Chem. 2017, 8, 67506777. (37)Fan, H.; Zhou, S.; Jiao, W.; Qi, G.; Liu, Y. Removal of Heavy Metal Ions by Magnetic Chitosan Nanoparticles Prepared Continuously via High-gravity Reactive Precipitation Method.Carbohydr. Polym. 2017, 174, 1192-1200. (38)Qiao, M.; Lei, X.; Ma, Y.; Tian, L.; Su, K.; Zhang, Q. Dependency of Tunable Nicrowave Absorption Performance on Morphology-controlled Hierarchical Shells for Core-shell Fe3O4@MnO2 Composite Microspheres.Chem. Eng. J. 2016, 304, 552-562. (39)Zhai, Y.; Han, L.; Wang, P.; Li, G.; Ren, W.; Liu, L.; Wang, E.; Dong, S. Superparamagnetic Plasmonic Nanohybrids: Shape-Controlled Synthesis, TEM-Induced Structure Evolution, and Efficient Sunlight-Driven Inactivation of Bacteria.Acs Nano 2011, 5, 8562-8570. (40)Li, C.; Wei, Y.; Liivat, A.; Zhu, Y.; Zhu, J. Microwave-solvothermal Synthesis of Fe3O4 magnetic nanoparticles.Mater. Lett. 2013, 107, 23-26. (41)Niu, Y.; Qu, R.; Sun, C.; Wang, C.; Chen, H.; Ji, C.; Zhang, Y.; Shao, X.; Bu, F. Adsorption of Pb(II) from Aqueous Solution by Silica-gel Supported Hyperbranched

29



Polyamidoamine Dendrimers. J. Hazard. Mater. 2013, 244–245, 276-286. (42)Ho, Y.; McKay, G. Kinetic Models for the Sorption of Dye from Aqueous Solution by Wood.Process Saf. Environ. 1998, 76, 183-191. (43)Ho, Y. Second-order Kinetic Model for the Sorption of Cadmium onto Tree Fern: A Comparison of Linear and Non-linear Methods.Water Res. 2006, 40, 119-125. (44)Boyd, G.; Adamson, A.; Myers, L. The Exchange Adsorption of Ions from Aqueous Solutions by Organic Zeolites. II. Kinetics1. J. Am. Chem. Soc. 1947, 69, 2836-2848. (45)Reichenberg, D. Properties of Ion-Exchange Resins in Relation to their Structure. III. Kinetics of Exchange. J. Am. Chem. Soc. 1953, 75, 589-597. (46)Ma, L.; Wang, Q.; Islam, S.; Liu, Y.; Ma, S.; Kanatzidis, M. Highly Selective and Efficient Removal of Heavy Metals by Layered Double Hydroxide Intercalated with the MoS42– Ion. J. Am. Chem. Soc. 2016, 138, 2858-2866. (47)Song, X.; Niu, Y.; Zhang, P.; Zhang, C.; Zhang, Z.; Zhu, Y.; Qu, R. Removal of Co(II) from Fuel Ethanol by Silica-gel Supported PAMAM Dendrimers: Combined Experimental and Theoretical study.Fuel 2017, 199, 91-101. (48)Sadegh, H.; Ali, G.; Makhlouf, A.; Chong, K.; Alharbi, N.; Agarwal, S.; Gupta, V. MWCNTs-Fe3O4 nanocomposite for Hg(Ⅱ) high adsorption efficiency.J. Mol. Liq. 2018, 258, 345-353. (49)Cao, F.; Yin, P.; Zhang, J.; Chen, H.; Qu, R. Nanoplates of Cobalt phosphonate with Two-dimensional Structure and Its Competitive Adsorption of Pb(II) and Hg(Ⅱ) Ions from Aqueous Solutions.J. Ind. Eng. Chem. 2014, 20, 2568-2573. (50)Wang, Z.; Xu, J.; Hu, Y.; Zhao, H.; Zhou, J.; Liu, Y.; Lou, Z.; Xu, X. Functional

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Page 30 of 33

Page 31 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Nanomaterials: Study on Aqueous Hg(Ⅱ) Adsorption by Magnetic Fe3O4@SiO2-SH nanoparticles.J. Taiwan Inst. Chem. E. 2016, 60, 394-402. (51)Ma, Y.; Xing, D.; Shao, W.; Du, X.; La, P. Preparation of Polyamidoamine Dendrimers Functionalized Magnetic Graphene Oxide for the Adsorption of Hg(Ⅱ) in Aqueous Solution.J. Colloid Inter. Sci. 2017, 505, 352-363. (52)Hadavifar, M.; Bahramifar, N.; Younesi, H.; Li, Q. Adsorption of Mercury Ions from Synthetic and Real Wastewater Aqueous Solution by Functionalized Multi-walled Carbon Nanotube with Both Amino and Thiolated Groups. Chem. Eng. J. 2014, 237, 217-228. (53)Liu, J.; Zhao, Z.; Jiang, G.. Coating Fe3O4 Magnetic Nanoparticles with Humic Acid for High Efficient Removal of Heavy Metals in Water. Environ. Sci. Technol. 2008, 42, 69496954. (54)Cui, L.; Wang, Y.; Gao, L.; Hu, L.; Wei, Q.; Du, B. Removal of Hg(Ⅱ) from Aqueous Solution by Resin Loaded Magnetic β-cyclodextrin Bead and Graphene Oxide Sheet: Synthesis, Adsorption Mechanism and Separation Properties. J. Colloid Inter. Sci. 2015, 456, 42-49. (55)Mao, C.; Imtiaz, S.; Zhang, Y. Competitive Adsorption of Ag (I) and Cu (II) by Tripolyphosphate Crosslinked Chitosan Beads.J. Appl. Polym. Sci. 2015, 132, 42717. (56)Yang, T.; Zhang, L.; Zhong, L.; Han, X.; Dong, S.; Li, Y. Selective Adsorption of Ag(Ⅰ) ions with Poly(vinyl alcohol) Modified with Thiourea (TU–PVA). Hydrometallurgy 2018, 175, 179-186. (57)Ghassabzadeh, H.; Mohadespour, A.; Torab-Mostaedi, M.; Zaheri, P.; Maragheh, M. G.; Taheri, H. Adsorption of Ag, Cu and Hg from Aqueous Solutions using Expanded Perlite.

31



J. Hazard. Mater. 2010, 177, 950-955. (58)Vassileva, P.; Radoykova, T.; Detcheva, A.; Avramova, I.; Aleksieva, K.; Nenkova, S.; Valchev, I.; Mehandjiev, D. Adsorption of Ag+ Ions on Hydrolyzed Lignocellulosic Materials Based on Willow, Paulownia, Wheat Straw and Maize Stalks.Int. J. Environ. Sci. Technol. 2016, 13, 1319-1328. (59)Norkus, E.; Stalnioniene, I.; Crans, D. Interaction of Pyridine- and 4hydroxypyridine-2,6-dicarboxylic Acids with Heavy Metal Ions in Aqueous Solutions, Heteroatom Chem., 2003,14,625-632. (60)Tian, G.; Wang, W.; Mu, B.; Kang, Y.; Wang A. Ag(Ⅰ)-triggered One-pot Synthesis of Ag Nanoparticles onto Natural Nanorods as a Multifunctional Nanocomposite for Efficient Catalysis and Adsorption, J. Colloid Inter. Sci. 473 (2016) 84-92. (61)Schweinfurth, D.; Sommer, M. G.; Atanasov, M.; Demeshko, S.; Hohloch, S.; Meyer, F.; Neese, F.; Sarkar, B. The Ligand Field of the Azido Ligand: Insights into Bonding Parameters and Magnetic Anisotropy in a Co(II)-Azido Complex.J. Am. Chem. Soc. 2015, 137, 1993.

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For Table of Contents Use Only

Aminopyridine functionalized magnetic Fe3O4 was synthesized and used for the robust removal of Hg(II) and Ag(I) from aqueous solution.

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Feasible One-Pot Sequential Synthesis of Aminopyridine

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