Supplementary Material

Recovery of Ammonium from Aqueous Solutions

Using ZSM-5

Michael J. Manto, Pengfei Xie, Mitchell A. Keller, Wilhelm E. Liano, Tiancheng Pu, Chao

Wang*

Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore,

MD 21218, United States. Email: chaowang@jhu.edu; Fax: +410 516 5510; Tel: +410 516 5843

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S1. Indophenol blue assay

The following chemicals were used as-received without any further purification: Ammonium

chloride (NH4Cl, ACS grade, VWR, Radnor, PA, USA), phenol (C6H5OH, > 99.5%, Sigma-

Aldrich, St. Louis, MO, USA), sodium citrate dihydrate (NaC6H7O7-2H2O, > 99%, Aldrich, St.

Louis, MO, USA), sodium hydroxide (NaOH, 99.1%, Fisher Scientific, Hampton, NH, USA),

sodium hypochlorite (NaClO, reagent grade, available chlorine 10–15%, Sigma-Aldrich, St.

Louis, MO, USA), sodium nitroprusside dihydrate (Na2Fe(CN)5NO-2H2O, ACS grade, > 99%,

Sigma-Aldrich, St. Louis, MO, USA) and anhydrous ethanol (C2H5OH, 200 proof, ACS/USP

grade, Pharmco-Aaper, Toronto, Canada). Deionized water (with a resistance of ~18.2 MΩ) was

collected from an ELGA PURELAB flex apparatus (Veolia, Paris, France).

To prepare the indophenol assay for the quantification of dissolved N, the following

solutions were prepared. The phenol solution was prepared by dissolving 0.4 g of C6H5OH in 2

mL of ethanol. The nitroprusside solution was prepared by dissolved 0.01 mg of Na2Fe(CN)5NO-

2H2O in 2 mL of deionized water. The alkaline reagent was prepared by dissolved 2 g of

NaC6H7O7-2H2O and 0.1 g of NaOH into 10 mL of deionized water. The oxidizing solution was

prepared by taking 4 mL of the aforementioned alkaline reagent and adding 1 mL of NaClO.

The alkaline reagent was able to be prepared long in advanced of testing; however the

phenol, nitroprusside and oxidizing solutions were prepared no earlier than 30 min before UV-

Vis characterization.

0.04 mL of the phenol solution, 0.04 mL of the nitroprusside solution and 0.1 mL of the

oxidizing solution were added to 1 mL of samples. The solution was mixed and tested ~2 min

after addition of solutions. Full spectra were collected, with absorbances at 640 nm used to

quantify the amount of N present in solution.

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A calibration curve (Fig. S1) was prepared by dissolving specified amounts of NH4Cl in

deionized water and treating the samples with the indophenol assay.

Fig. S1. Chemical reactions induced by the indophenol assay, sample UV-Vis spectra and

calibration curve for N detection. Synthetic standards were prepared by dissolving NH4Cl in

water. Peaks in the spectra correspond to excess phenol groups (~320 nm) and the indophenol

molecule that forms with dissolved N in the presence of the assay (~640 nm).

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S2. Additional Sorption Data

Fig. S2. (a) Dependence of N capture on the initial solution pH. (b) Dependence of N release (at

initial solution pH of 5.6 ± 0.1) on the concentration of NaCl.

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