ars.els-cdn.com · Web viewHydrochloric acid (35.0%, Daejung Chemicals & Metals, South Korea), methyl isobutyl ketone (MIBK) (≥ 98.5%, Sigma-Aldrich, USA), NaBH 4 (≥ 99%, Sigma-Aldrich,

Supporting Information

Novel synthesis of nanoscale zerovalent iron

from coal fly ash and its application in oxidative

degradation of methyl orange by Fenton

reaction

Sunho Yoon and Sungjun Bae*

Department of Civil and Environmental Engineering, Konkuk University, 120 Neungdong-

ro, Gwangjin-gu, Seoul 05029, Republic of Korea

*Corresponding author: phone: 82-42-450-3904

E-mail: [email protected]

A revised manuscript submitted to Journal of Hazardous Materials

Details for materials and experimental methods, 16 pages, 2 Table and 10 Figures

Materials and Chemicals

1


Hydrochloric acid (35.0%, Daejung Chemicals & Metals, South Korea), methyl isobutyl

ketone (MIBK) (≥98.5%, Sigma-Aldrich, USA), NaBH4 (≥99%, Sigma-Aldrich, USA),

ferric(III) chloride hexahydrate (≥98.5%, Sigma-Aldrich, USA), and ethyl alcohol anhydrous

(99.9%, Daejung Chemicals & Metals, South Korea) were used for synthesis of NZVI-CFA.

Methyl orange (C14H14N3NaO3S, Samchun chemical, South Korea), hydrogen peroxide (H2O2,

30−¿35%, Samchun Chemical, South Korea), and iron(II) chloride tetra hydrate (≥98%,

Sigma-Aldrich, USA) were used for oxidation of MO by Fenton reaction. All other chemicals

used in the experiments were of analytical grade, and all solutions were prepared using

deionized water (DIW, 18.2 MΩ) which was purified by ultrapure filtration system (HUMAN

POWER I+ Water purification system).

Characterization of NZVI-CFA

The chemical composition of CFA was determined by X-ray fluorescence (XRF, PANalytical,

epsilon3-XL), showing that our target element (i.e., Fe oxides) was almost 14.5% in total

(Table S1). The specific surface area of NZVI-CFA was determined by the BET N2

adsorption/desorption method at 77K using a surface area analyzer (ASAP 2000,

Micrometrics). The structure of NZVI-CFA was identified by XRD using Rigaku automated

diffractometer (JP/MAX-3C) with Cu Kα radiation. The NZVI-CFA containing in ethanol

was used for XRD analysis. The NZVI-CFA suspensions were transferred to XRD holder and

dried in the anaerobic chamber. Then, the dried samples were coated with 1:1 (v:v) glycerol

solution to avoid the oxidation of NZVI-CFA during XRD analysis [1,2]. The scan range was

0–90° 2θ with a scan speed of 2° min-1. To investigate the morphological information of

NZVI-CFA, SEM (TESCAN VEGA3, TESCAN) and TEM (JEM-2010, JEOL) analysis were

conducted. A droplet of diluted NZVI-CFA suspension was put on aluminum foil and on 300

mesh carbon-Cu TEM grids for SEM and TEM analysis, respectively. The EDS analysis was

2


also conducted to investigate the elemental distribution of NZVI-CFA. The spectra of FTIR

were recorded using a Nicolet iS10 FT-IR spectrometer system (Thermo). The solid samples

were recorded between 4000 and 400 cm-1 with KBr disks, while liquid samples were

recorded between 4000 and 650 cm-1 on Attenuated total reflectance (ATR) accessory. Spectra

were recorded at room temperature at a 4 cm-1 resolution by averaging 100 scans.

Optimal condition for synthesis of NZVI-CFA

To find out the optimal condition for NZVI-CFA synthesis, we firstly investigated the kinetics

of Fe dissolution from CFA in 7N HCl for 46 h. At each sampling time, suspension was

withdrawn and filtered with 0.2 μm membrane filter (Whatman) for measurement of Fe(II)

concentration by ferrozine method [1–6]. Total Fe concentration was also measured by

adding 10% hydroxylamine solution [2,3,6]. Fe(III) concentration was calculated by

subtracting Fe(II) concentration from total Fe concentration. The concentration effect of HCl

(3, 4, 5, 6, 7, 8, 9 and 10 N) for Fe dissolution of CFA was investigated in this study. The

efficiency of Fe-chelation from HCl to MIBK phases was calculated by measuring the Fe

concentration in HCl layer after solvent extraction by MIBK. Lastly, the effect of NaBH 4

concentration (0.1, 0.25, 0.5, 0.75 and 1 M) on the formation of NZVI-CFA was investigated.

For determining the amount of NZVI-CFA formed by NaBH4 addition, we collected NZVI-

CFA by a magnet and fully dissolved NZVI-CFA in 7 N HCl solution for 3 h. The total Fe

concentration was measured as described above and calculated its concentration as total

amount of NZVI-CFA.

Analytical methods used for Fenton reaction

The concentrations of MO, aqueous Fe(II) and Fe(III), and H2O2 were measured using a UV-

visible spectrophotometer (GENESYS 10S, Thermo) after filtering the NZVI-CFA-H2O2

3


suspension with 0.2μm membrane filter. The concentration of MO, aqueous Fe, and H2O2

were quantified by measuring the absorbance at 465 [7], 562, and 405 nm [3,4] respectively.

The concentration of HCl was determined using ion chromatography (IC) (Metrohm, 883

Basic IC plus) equipped with a compact auto-sampler (Metrohm, 863 Compact IC), and

anion column (Shodex IC Anion Sep No.82504A). Mixture of Na2CO3 (3.5 mM) and

NaHCO3 (3.5 mM) was prepared for IC eluent. For the MO measurement, we quenched the

Fenton reaction by adding 1M NaOH right after each sampling to avoid further degradation

of MO by Fenton oxidation. H2O2 concentration was analyzed using titanium sulfate method

[3,4]. Finally, the concentration of total organic carbon (TOC) was measured using a multi

N/C 3100 TOC analyzer (Analytic Jena) operated in TOC mode.

Table S1.

Chemical composition of coal fly ash determined by XRF

4


Contents CFA (%)

SiO2 50.2

Al2O3 15.8

Fe2O3 14.5

CaO 11.0

K2O 3.3

Ti 1.5

SO3 1.3

Table S2.

Cost analysis for synthesis of NZVI-CFA and NZVI-Bare

Materials Reagents Manufacture Cat.No Amount Prices

5


NZVI-CFAMIBK Sigma-Aldrich 360511 2.5 L 134 USD

HCl Daejung 4090-4405 20 L 22.1 USD

NZVI-Bare

Iron(III)

chloride

hexahydrate

Sigma-Aldrich 236489 500 g 105 USD

* The required chemicals (e.g., NaBH4 and ethanol) during both NZVI synthesis are not

considered in the calculation. Based on the typical synthesis method for NZVI-Bare, we can obtain

almost 103 g of dried NZVI-Bare using 500 g of iron(III) chloride hexahydrate, and the price per

gram can be calculated as 1.02 USD/g NZVI-Bare. In contrast, we can synthesize 3–30 g of NZVI-

CFA using 1L of MIBK and HCl using the CFA derived dissolved Fe concentration (3000–30000

mg L-1, Fig. S1), and the price per gram without recycling process can be calculated as 1.82–18.23

USD/g NZVI-CFA. Because we confirmed that 3 times recycling of liquids is possible, resulting in

the cost of 0.61 – 6.08 USD/g NZVI-CFA when we consider the recycling processes.

6


Fig. S1. Fe(III) chelation by MIBK in different concentration of initial Fe(III) dissolved in 7

N HCl.

‘

7


Fig. S2. Synthesis percentage of (a) NZVI-CFA and (b) NZVI-Bare by addition of different

NaBH4 concentration. Experimental conditions: CFA : HCl = 1 g : 10 mL for NZVI-CFA,

Fe(III) chloride hexahydrate as Fe sources (3500 mg L-1) for NZVI-Bare, Mixing time = 24 h,

[HCl] = 7 N

8


Fig. S3. (a) SEM image and (b) XRD diffraction pattern of raw CFA

9


Fig. S4. TEM images of NZVI-Bare at different magnifications.

10


Fig. S5. XRD diffraction patterns of NZVI-Bare and NZVI-CFA

\

11


Number of cycles

1 2 3 4

Dis

solv

ed C

l - conc

entr

atio

n (m

ol L

-1)

0

2

4

6

8

(a) (b)

Fig. S6. (a) Changes in dissolved Fe concentration in CFA-7 N HCl suspension with respect

to different volume ratio of MIBK:HCl and (b) variation of dissolved Cl- concentration after

finishing four recycling test.

12


Fig. S7. Variation of pH during the synthesis of NZVI-CFA. The pH increased immediately

from 5.08 to 6.65 by addition of 2 mg of NZVI-CFA within 0.5 min, then decreased to 5.97 in

2.5 min. After 5 min, the pH was adjusted to 3.0 by using HCl and NaOH. MO stock solution

was spiked at 10 min. After 1 min mixing, H2O2 was injected to initiate the Fenton reaction.

The dissolved Fe(II) in the NZVI-CFA suspension (i.e., before the addition of H2O2) was 5.3

mg L-1 (=0.095 mM). The pH during the Fenton reaction was maintained well around 3.

13


Fig. S8. Variation of UV-vis spectra of MO during the NZVI-CFA Fenton reaction.

Experimental conditions: [MO]0 = 20 mg L-1, [H2O2]0 = 5.0 mM, [NZVI-CFA]0 = 10 mg L-1

and initial pH=3.0.

14


Fig. S9. TOC concentration (a) during NZVI-CFA Fenton reaction and (b) in different

reaction conditions after 60 min reaction time Experimental conditions: [MO]0 = 20 mg L-1,

[H2O2]0 = 5.0 mM, [NZVI-CFA]0 = 10 mg L-1 and initial pH=3.0.

15


Fig. S10. Degradation kinetics of MO by classic Fenton and NZVI-CFA Fenton reactions.

Experimental conditions: [MO]0 = 20 mg L-1, [H2O2]0 = 5.0 mM, [NZVI-CFA]0 = 10 mg L-1,

[aqueous Fe(II) in classic Fenton]0 = 0.095 mM and initial pH=3.0.

References16


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17

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ars.els-cdn.com · Web viewHydrochloric acid (35.0%, Daejung Chemicals & Metals, South Korea), methyl isobutyl ketone (MIBK) (≥ 98.5%, Sigma-Aldrich, USA), NaBH 4 (≥ 99%, Sigma-Aldrich,