Supporting information

Comprehensive characterization and environmental risk assessment of

End-of-Life automotive catalytic converters to arrange a sustainable

roadmap for future recycling practices

Nazanin Bahaloo-Horeh, Seyyed Mohammad Mousavi

Biotechnology Group, Chemical Engineering Department, Tarbiat Modares University, Tehran, Iran

Corresponding author: Seyyed Mohammad Mousavi

Email address: mousavi_m@modares.ac.ir

Tel.: +98-21-82884917, Fax: +98-21-82884931

Postal address: Iran, Tehran, Jalal Ale Ahmad, Nasr, P.O. Box: 14115-111.

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Text S-1: Chemical digestion procedure

Chemical digestion was done with a mixture of acids, including HCl, HNO3, HClO4, and HF

(HF was applied to digest the metals bounded to silicate materials (Nemati et al., 2011)). In

this regard, 0.25 g of powder was weight, and subjected to an acid mixture in a Teflon

beaker. Then, the sample was heated at 220 °C using a hot box for 4 h for complete digestion.

Next, the digest was filtered and the metal content of the solution was evaluated by ICP-MS.

Besides, the PGMs content was analyzed by the fire assay method.

Concerning the complexity of the SACCs powder, the sampling and measurements were

applied in triplicates to check the accuracy, reliability, and reproducibility of the experiments.

Text S-2: CHNS analysis

For CHNS analysis, 1 mg of the SACCs powder was combusted in a CHNS analyzer under

the O2 stream in a furnace with a temperature of 980 °C. Bypassing the produced combustion

gasses including CO2, H2O, SO2, and NO2 through the column, their concentrations were

calculated. The helium and acetanilide were applied as a carrier gas and standard,

respectively.

Text S-3: BET analysis

Before running BET analysis (Belsorp-mini, BEL Japan Inc.), the SACCs powder was

degassed for 5 h at 150 °C, followed by cooling to room temperature. The BET method in the

relative pressure domain from 0 to 1 was utilized to determine specific surface areas. The

pore size distribution of SACCs powder was specified by the Brunauere-Joynere-Hallenda

(BJH) approach.

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Text S-4: Determination of isoelectric point

The fine SACCs powder (0.1 g) was suspended in 100 mL solution of 0.01 M NaCl as the

base electrolyte, and then, the suspension was agitated to reach chemical equilibrium. NaOH

and HCl were used for adjusting the pH over the range of 2–8 with the concentrations of 1.0

M and 0.1 M in order to change the pH value to a large and small extent, respectively.

Text S-5: TCLP, WET, and SPLP protocol

TCLP protocol

For the TCLP test, two different leaching extraction fluids were applied, based on the

buffering capacity and alkalinity of the waste. To define a proper extraction fluid, the pH of

the sample was determined by adding 5 g of sample to 96.5 mL of deionized water and then

shaking intensely for 5 min. If the pH of the solid waste was<5, the extraction fluid #1 (64.3

mL of 1 N NaOH and 5.7 mL of acetic acid made up to 1 L with deionized water) with a pH

of about 4.93± 0.05 was applied, and if the pH of the solid waste was >5, 3.5 mL of 1 N HCl

was added to the sample and heated to 50 °C for 10 min. After cooling, the pH was measured.

If the pH is <5.0, the extraction fluid #1 was applied, and if the pH is >5.0, the extraction

fluid #2 (5.7 mL of acetic acid made up to 1 L with deionized water) with a pH of about

2.88± 0.05 was adopted.

In the case of SACCs powder, after the addition of 3.5 mL of 1 N HCl, the pH of SACCs

powder in deionized water became under a pH of 5; thus, the proper extraction fluid for the

TCLP test was extraction fluid #1. The SACCs powder was mixed with leaching extraction

fluid at a liquid to solid (L/S) ratio of 20:1 (mL/g) and then agitated for 18 h. Next, the

extract was centrifuged, filtered, and analyzed for metal concentration by ICP-AES.

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It should be noted that acetic acid applied in TCLP demonstrates the organic acids generated

through the biological decomposition of waste in landfills (Priya and Hait, 2019). Albeit

TCLP demonstrates to be very useful, it has been stated that this leaching test is unsuccessful

in predicting the leaching of metals from some waste with alkaline nature (González and

Barnes, 2002; Hira et al., 2018).

WET protocol

For the WET procedure, 0.2 M sodium citrate as an extraction solution at pH 5.0 was used.

The SACCs powder was mixed with leaching extraction solution at an L/S ratio of 10:1

(mL/g) and then agitated for 48 h. The leachates were then centrifuged, filtered, and analyzed

for metal concentration by ICP-AES. Albeit WET exhibits to be very beneficial, it is a

lengthy step in the determination of metals leaching from waste (González and Barnes, 2002;

Hira et al., 2018).

SPLP protocol

For the SPLP, a mix of sulfuric acid/nitric acid (60/40 wt%) as an extraction solution was

used with a proper dilution with deionized water to make pH 4.20 ± 0.05. The SACCs

powder was mixed with leaching extraction solution at an L/S ratio of 20:1 (mL/g) and then

agitated for 18 h. The leachates were then centrifuged, filtered, and analyzed for metal

concentration by ICP-AES (Hira et al., 2018). It should be noted that the SPLP is applied for

the assessment of waste leachability in inert landfills, including no high biodegradable

substance (Jang and Townsend, 2003).

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(a) (b)

(c)

Fig. S1. BSE image and corresponding EDX analysis of the SACCs powder.

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050010001500200025003000350040000

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Wave numbers (cm-1)

Tra

nsm

ittan

ce (%

)

3422.071634.64

958.26909.44

1181.94

675.85

769.58

578.19

448.55

483.40

614.89

Fig. S2. FTIR spectra of SACCs powder.

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Fig. S3. Microphotographs of the SACCs powder surface.

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0.4 4 400

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60

80

100

Particle size (μm)

Cum

ulat

ive

dist

ribu

tion

(%)

Fig. S4. The particle size distribution of the SACCs after crushing and milling.

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Table S1

The water solubility of oxide and hydroxide forms of major metals presented in SACCs (Green and

Perry, 2007).

Name Form Solubility in 100 partsCold water Hot water

Al Al(OH)3 0.000104 InsolubleAl2O3 Insoluble Insoluble

Ba Ba(OH)2 1.67 101.4BaO 1.5 90.8

Ca Ca(OH)2 0.185 0.077CaO Forms Ca(OH)2 -

Fe Fe(OH)3 Insoluble InsolubleFe2O3 Insoluble -Fe(OH)2 0.00067 -FeO Insoluble Insoluble

Mg Mg(OH)2 0.0009 -MgO 0.00062 -

Mn Mn(OH)2 0.002 InsolubleMnO Insoluble InsolubleMn2O3 Insoluble InsolubleMnO2 Insoluble Insoluble

K KOH 97 178K2O Forms KOH Very soluble

Na NaOH 42 347Na2O Forms NaOH -

Sr Sr(OH)2 0.41 21.83SrO Forms Sr(OH)2 -

Zn Zn(OH)2 0.00052 -ZnO 0.00042 -

As As2O3 1.21 2.93Pb PbO 0.0068 -Zr ZrO2 Insoluble InsolubleSi SiO2 Insoluble InsolubleTi TiO2 Insoluble Insoluble

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Table S2

Chemical composition of the SACCs powder using XRF analysis.

Component Al2O3 SiO2 MgO Zr Ce P2O5 MnO Ba Fe2O3 Zn CaO La Pd TiO2 Nd Sr Na2O Hf In K2O SO3 L.O.I

Content (wt

%)40.04

31.6

18.80 4.51

4.1

32.11 1.35 1.29 1.01 0.67 0.66

0.6

20.53 0.46 0.40 0.28 0.26

0.1

60.09 0.08 0.06 0.87

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100

Table S3

The content of typical main elements (wt%) loading in SACCs reported in different studies.

Al Si Zr Ce Nd La Ti Mn Zn Fe Mg Ba Ca K Na Hf Pt Pd Rh Ref.

27.1

4n.a. n.a. n.a. n.a. n.a. n.a. n.a.

0.17

1

0.58

14.18

1.82

4

0.05

7n.a. n.a.

n.a

.

0.200

90.4534 0.0637 (Karim and Ting, 2020)

n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a.n.a

.0.18 0.12 0.016 (Upadhyay et al., 2013)

n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a.n.a

.0.379 0.0582 0.239 (Harjanto et al., 2006)

n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a. n.a.n.a

.

0.081

8

0.0516

7

0.0213

8(Chen and Huang, 2006)

20.2

7n.a.

1.46

7

6.15

3n.a. n.a. n.a. n.a. n.a. n.a

5.89

3

1.15

5n.a. n.a. n.a. n.a

0.230

0n.a 0.0530 (Kim et al., 2000)

28.3 0.133.49

6

7.96

4n.a. n.a.

0.06

3

0.03

1n.a.

1.50

0

0.04

5n.a.

0.04

7

0.00

8

0.15

5

n.a

.

0.067

91.1510 0.0702 (Šebek et al., 2011)

17.6

2

19.2

6

0.00

6

0.00

3n.a. n.a.

0.28

1

0.00

2n.a.

0.33

5

4.79

4n.a.

0.03

20.02

0.09

5

n.a

.

0.397

5- - (Šebek et al., 2011)

23.0

0

15.6

0n.a. 0.61 n.a. n.a. n.a. n.a. n.a. n.a. 5.50 0.50 0.12 n.a. n.a.

n.a

.0.097 <0.001 0.008

(Rumpold and Antrekowitsch,

2012)

16.2

09.00 n.a. 2.50 n.a. n.a. n.a. n.a. n.a. n.a. 6.10 0.49 0.65 n.a. n.a.

n.a

.0.110 <0.001 0.024

(Rumpold and Antrekowitsch,

2012)

n.a n.a n.a n.a n.a n.a n.a n.a0.02

5

0.23

7n.a n.a

0.13

2n.a. n.a. n.a n.a. 0.0441 0.0131 (Nogueira et al., 2014)

30.9 16.6 1.2 3.82 n.a. n.a. n.a. n.a. n.a. n.a. 7.68 n.a. n.a. n.a. n.a. n.a n.a. 0.1698 0.0242 (Chen et al., 2015)

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101

102

7 6 .

17.7

1

30.5

82.74 2.21 n.a. n.a. n.a. n.a. n.a. n.a. 3.12 n.a. n.a. n.a. n.a.

n.a

.

0.070

00.2835 0.0118 (Morcali et al., 2015)

25.7 10.7 10.5 2.7 0.6 0.8 0.7 n.a. n.a. n.a. 4.1 1.7 n.a. n.a. n.a. 0.5 0.010 n.a. 0.010 (Eskina et al., 2016)

22.5 n.a. 15.1 6.03 n.a. 3.37 n.a. n.a. 0.09 0.25 2.61 n.a. n.a. n.a. n.a.n.a

.0.77 1.52 0.34 (Firmansyah et al., 2019)

27.5

88.69 5.74 5.31

0.6

70.33 n.a. 2.82 n.a. n.a. 2.72 n.a. 0.51 n.a. n.a.

n.a

.n.a. n.a. n.a. (Zhao et al., 2019)

16.811.0

02.73 2.23 n.a.

0.23

2

0.31

7n.a.

0.28

1

0.71

35.23 n.a. 0.33 n.a. n.a.

n.a

.

0.095

80.167 0.0318 (Spooren and Atia, 2020)

20.0

0

16.1

61.48 5.53 n.a. n.a. 0.27 n.a. 0.2

0.62

65.55 n.a. 0.57 n.a. n.a.

n.a

.0.069 0.045 0.016 (Shin et al., 2015)

n.a.: not analyzed

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103

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