1

[Supporting Information]

For the manuscript: REMOVAL OF CALCIUM IONS FROM WATER BY SELECTIVE

ELECTROSORPTION USING TARGET-ION SPECIFIC NANOCOMPOSITE ELECTRODE

Jun Kim1,2, Amit Jain2,3, Kuichang Zuo1,2, Rafael Verduzco2,3, Shane Walker2,4, Menachem

Elimelech2,5, Zhenghua Zhang6, Xihui Zhang6, and Qilin Li1,2,3,*

1Department of Civil and Environmental Engineering, Rice University

6100 Main Street MS 519, Houston, TX 77005, USA

2Nanosystems Engineering Research Center for Nanotechnology-Enabled Water Treatment

6100 Main Street MS 6398, Houston, TX 77005, USA

3Department of Chemical and Biomolecular Engineering, Rice University

6100 Main Street MS 362, Houston, TX 77005, USA

4Department of Civil Engineering, The University of Texas at El Paso

El Paso, TX 79968, U.S.A.

5Department of Chemical and Environmental Engineering, Yale University

New Haven, CT 06520, U.S.A.

6Graduate School of Shenzhen, Tsinghua University

Tsinghua Campus, The University Town, Shenzhen 518055, P. R. China

2

Corresponding Author

*Prof. Qilin Li qilin.li@rice.edu

Department of Civil and Environmental Engineering, Rice University, 6100 Main Street MS

519, Houston, TX 77005, USA.

Mean particle size (nm) 142.5

Standard deviation 44.2

Figure S1. Size distribution of cryo-ground ion-exchange resin particles.

3

Figure S2. Performance of uncoated and CSN electrodes using 10 meq/L NaCl solution. (a) Conductivity and current profiles of the two electrodes; (b) conductivity profile during adsorption stage; (c) conductivity profile during desorption stage.

4

Figure S3 Current and voltage profile of uncoated and CSN coated electrode using 10 meq/L CaCl2 feed solution.

5

Figure S4. Adsorption kinetics of total cation, Ca2+, and Na+ by the CSN electrode at different feed meq ratio. (a) 1:1, (b) 2:1, (c) 5:1, and (d) 10:1. Displaced amount of Na+ (∆𝑞#$) is indicated.

Figure S5. Terminal concentration difference between influent and effluent, at each influent eq ratio.

0.0500.101

0.159

0.259

-0.007 -0.013 -0.015 -0.005

-0.2

0.0

0.2

0.4

Influent Na+:Ca2+ eq ratio

Ca Na

1 -C

eff/C

0 in

1:1 2:1 5:1 10:1

6

Figure S6. Ion-transport rate of Ca2+ and Na+ across the CSN layer. (a) Electrodialysis (ED) cell, (b) the CSN layer, (c) schematic diagram of ED cell, (d) average concentration (normalized) of acceptor and donor chamber.