Additional file 1 of Immobilization of Cr(VI) by sulphate green rust and sulphidized nanoscale zerovalent iron in sand media: batch and column studies
Creators: name: Digiacomo, Flavia
name: Tobler, Dominique J.
name: Held, Thomas
name: Neumann, Thomas
Publisher: name: figshare
Year: 2020
Subjects: subject: Biochemistry
subject: Medicine
subject: Biotechnology
subject: Environmental Sciences not elsewhere classified
subject: Chemical Sciences not elsewhere classified
subject: Ecology
subject: FOS: Biological sciences
subject: Biological Sciences not elsewhere classified

description: Additional file 1: Text S1. Synthesis and characterization of GRSO4 and S-nZVI. Figure S1. XRD patterns (Cu-Kα) of freshly synthesized and glycerol-coated a) GRSO4 (PDF# 13-0092) and (b) S-nZVI (Fe0 PDF# 06-0696 and FeS PDF# 89-6268). Figure S2. XRD patterns (Cu-Kα) of oxidation products after reaction with Cr(VI) solution (pH 7) of a) GRSO4: goethite (α-FeOOH, PDF# 29-0713) and GRSO4, and (b) S-nZVI: Fe0, FeS, lepidocrocite (PDF# 44-1415) and magnetite (PDF# 19-0629). Text S2. Calculation of the iron content, mass and volume of GRSO4 and S-nZVI. Figure S3. Control batch experiment with sand and Cr(VI) only (no added GRSO4 or S-nZVI) showed that Cr(VI) sorption to grain surfaces was negligible over 48 h (note that x-axis is not linear). Text S3. NaNO3, Cr(VI) and total Cr measurements. Figure S4. (a) Effect of Cr(VI) solution pH (4.5, 7.0 and 9.5) on UV–Vis absorption spectra; (b) UV–Vis spectra of Cr(VI) solutions of varying concentration (0.125 and 2 mM; at pH 7) used to make the calibration curves shown in (c) and (d) where adsorption readings were taken at 274.3 (R2 = 0.999) and 371.3 nm (R2 = 0.998), respectively. Figure S5. (a) BTCs (as a function of time) obtained by injecting 0.4 M NaNO3 at 0.25, 1 and 3 ml/min. (b) Comparison of BTCs (as a function of pore volume) obtained by injecting 0.5 mM Cr(VI) solution (control) at 0.25, 1 and 3 ml/min and 0.4 M NaNO3 solution (tracer) at 1 ml/min. All BTCs show no delay in breakthrough, i.e., are typical of non-reactive solutes. Figure S6. Comparison of BTCs obtained by measuring effluent Cr(VI) concentrations using the on-line UV–Vis set-up (black symbols) and by determining total Cr concentrations via ICP-OES in manually collected samples (red symbols). The test conditions were identical with [Cr(VI)0] = 0.5 mM, pH = 7 and flow rate = 1 ml/min. The fact that the two BTCs overlap demonstrates that Cr(VI) is the only Cr species detected in the effluent. Thus, any Cr(III) forming due to reduction is immobilised within the sand column. Figure S7. Eh–pH diagram for chromium based on experimental chromium concentration (10−3 M). Dashed line is based on lower concentrations (10−6 M). Calculations were made using PHREEQC (USGS). Figure S8. Prior to each Cr(VI) injection, columns were pre-flushed with 5 PVs of MilliQ water to remove aqueous Fe2+ present in the GR slurry that was mixed with the sand. Manually collected samples were analysed via ICP-OES to determine loss in total Fe as a function of flushed MilliQ pore volumes, which is depicted here. The plotted data show average values of 6 columns (3 columns run at 1 ml/min and 3 run at 3 ml/min). Figure S9. Cr(VI) breakthrough curves in S-nZVI amended packed sand columns as a function of inlet solution pH: 4.5 and 7.0 ([(Cr(VI)0] = 0.25 mM, flow rate = 0.25 ml/min). The dashed lines help to identify the breakthrough (C/C0 = 0.05) and exhaustion (C/C0 = 0.9) points on each curve. Table S1. Breakthrough (C/C0 = 0.05) and exhaustion (C/C0 = 0.9) points expressed in terms of pore volumes (PV) for GRSO4 and S-nZVI sand column experiments performed at different [Cr(VI)0], flow rates and solution pHs (data taken from Fig. 4a, 5 and 6b).