Supporting information

Rethinking anaerobic As(III) oxidation in filters: Effect of indigenous nitrate respirers

Jinli Cuia, Jingjing Dua, b, Haixia Tiana, Tingshan Chanc, *,

Chuanyong Jinga, b, *

aState Key Laboratory of Environmental Chemistry and Ecotoxicology, Research

Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing,

100085, P. R. ChinabUniversity of Chinese Academy of Sciences, Beijing 100049, ChinacNational Synchrotron Radiation Research Center, HsinChu, 300, Taiwan

*Corresponding author: Chuanyong Jing

Tel: +86 10 6284 9523

Fax: +86 10 6284 9523

E-mail: cyjing@rcees.ac.cn

*Co-corresponding author: Tingshan Chan

Tel: +886 3 578 0281 Ext. 7304

Fax: +886 3 578 3805

E-mail: chan.ts@nsrrc.org.tw

Arsenic and Fe speciation analysis on spent GTiO2 using XANES

The spent GTiO2 samples were ground into powder and loaded on Scotch tape

for analysis. The As (11,867 eV) and Fe (7112 eV) K-edge XANES spectra were

collected at beamline 01C1 at the National Synchrotron Radiation Research Center

(NSRRC), Taiwan. Spectra were acquired at cryogenic temperature (77 K) using a

cryostat to prevent the oxidation of As(III) by X-rays. The fluorescence signals were

collected using a Lytle detector. Two to three scans were collected for each sample

and averaged to improve the signal/noise ratio. The XANES analysis was performed

with the Athena program in the IFEFFIT computer package for linear combination fit

(LCF) (Ravel and Newville, 2005).

Amorphorous FeAsO4 (poorly crystalline ferric arsenate) was synthesized by

mixing 0.02 M As(V) (Na2HAsO4·7H2O) and 0.02 M Fe(III) (Fe2(SO4)3·5H2O) (Jia, et

al., 2006). The mixture pH was adjusted from initial pH 1.3 to 1.8 using NaOH

solution and agitated for another 1 h vigorously. The solid product was separated by

filtration, washed with HNO3 acidified water (pH 2), and vacuum-dried at 60 oC.

Goethite was synthesized according to our previous study (Yang et al., 2012).

First, 48.5 g Fe(NO3)3·9H2O and 24.6 g KOH were dissolved in 200 ml and 100 ml

deionized (DI) water, respectively. Then, the KOH solution was added drop by drop

into 200 ml Fe(NO3)3 solution in a plastic beaker under vigorous stirring. The above

suspension was diluted to 400 ml with DI water. The suspension was then incubated

in a water bath at 70 °C for 60 h and repeatedly washed with DI water. Finally, the

solids were washed with absolute ethyl alcohol twice, filtered, and dried for 2 h at 60 oC.

Ferrihydrite was synthesized from Fe2(SO4)35H2O (Jia, et al., 2006). Generally,

Fe2(SO4)35H2O was prepared in deionized water, and the solution pH was raised to ∼7.5 in about 5 min using NaOH solution. The suspension was maintained at pH ~7.5

for 1 h under vigorous agitation. Finally, the precipitated solid was washed four times

with deionized water and freeze-dried in vacuum.

Table S1 Average concentrations of As, coexisting ions (mg/L), and water chemistry

for geogenic groundwater (GGW) and synthetic groundwater (SGW).

Parameters GGW SGW

As(III) 0.642 ± 0.028 0.667

As(V) 0.089 ± 0.099

Si 8.9 ± 0.3 5.0

Ca 39.1 ± 2.1 35.2

Mg 104.3 ± 4.2 24.6

Na 329.4 ± 18.6 13.2

Cl- 614.3 ± 39.2 71.6

PO43- <0.02

SO42- 117.6 ± 3.7 98.4

NO3- 3.4 ± 1.6 3.8

F- 1.2 ± 0.1

Br- 2.3 ± 3.0

S2- 0.011 ± 0.004

K 1.4 ± 0.2 10.1

Al 0.06 ± 0.03

Fe(II) 0.47 ± 0.19

Mn 0.12 ± 0.04

Alk (mg CaCO3 /L) 629 ± 20 86.3

T (oC) 11.6 ± 0.3

pH 8.20 ± 0.06 8.20

DO (mg/L) 0.42 ± 0.61

ORP -40 ± 22

TDS (g/L) 1.75 ± 0.02

Conductivity (mS/cm) 2.66 ± 0.18

Fig. S1 Effluent As(III) (I) and As(V) (II) concentrations (in red squares) after sand

column filtration using geogenic groundwater. The circles show the As(III/V)

concentrations in groundwater.

Table S2 LCF analysis (%) of the Fe K-edge XANES spectra of the spent GTiO2 in columns during anaerobic landfilling. The other Fe standards showed no detection during the XANES fitting and was not listed.

SampleFerrihydrite

GoethiteamFeAsO4

R-factor χ2

Groundwater -0 day 26 5 69 0.00060.0520

Groundwater -4 day 26 5 69 0.00040.0393

Groundwater -10 day 25 8 67 0.00050.0442

Groundwater with nitrate-0 day 26 6 68 0.00050.0476

Groundwater with nitrate-4 day 25 6 69 0.00050.0444

Groundwater with nitrate-10 day

24 8 68 0.00050.0501R factor, goodness-of-fit parameter, Σ(χdata – χfit)2/Σ(χdata)2; χ2

represents the fitting quality of the XANES data.

Fig. S2. Bacterial community structure (29 OTUS) of the indigenous microorganisms

from the spent GTiO2 in groundwater based on 16S rRNA genes (44 sequences).

Fig. S3 Rarefaction curve of the 16S rRNA sequences.

ReferencesJia, Y.F., Xu, L.Y., Fang, Z., Demopoulos, G.P., 2006. Observation of surface precipitation of arsenate

on ferrihydrite, Environ. Sci. Technol 40, 3248-3253.Ravel, B., Newville, M., 2005. ATHENA, ARTEMIS, HEPHAESTUS: Data analysis for X-ray

absorption spectroscopy using IFEFFIT. J Synchrotron Radiat 12, 537-541.Yang, Y.L., Yan, W., Jing, C.Y., 2012. Dynamic adsorption of catechol at the goethite/aqueous

solution interface: A molecular-scale study, Langmuir, 28 (41), 14588–14597.