Supplemental Materials. Sorption of Tetracycline to Varying-Sized Montmorillonite Fractions

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1 Supplemental Materials Sorption of Tetracycline to Varying-Sized Montmorillonite Fractions Huaizhou Xu, 1, Xiaolei Qu, 1 Hui Li, Cheng Gu 1, and Dongqiang Zhu 1* 1 State Key Laboratory of Pollution Control and Resource Reuse/School of the Environment, Nanjing University, Jiangsu 1009, P.R. China State Key Laboratory Pesticide Risk Assessment and Pollution Control, Nanjing Institution of Environmental Sciences, Ministry of Environmental Protection, Nanjing, 100, China Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, Michigan 88, USA Submitted to Journal of Environmental Quality Prepared on July 09, 01 Number of pages: 1 Number of tables: Number of figures: 7 1

2 Supplemental Table S1. Molecular weight (M W ), water solubility (S W ), and acid dissociation constant (pk a ) of tetracycline. Compound M W (g/mol) S W (mmol/l) pk a Tetracycline..8 a.0(1), 7.68(), 9.69() a a From Mitscher, 1978.

3 Supplemental Table S. Weight percentage, cation exchange capacity (CEC), clay ph, point of zero charge (PZC), H + consumption to reach ph 7.0, and inorganic elemental composition (presented as oxides) for montmorillonite size fractions. Clay size Dry mass CEC H + consumption Elemental composition (%) d ph a PZNPC b fraction (wt %) (cmol/kg) (mmol/g) c SiO AlO MgO CaO FeO NaO TiO KO SrO MnO rpm.17 97± rpm. 9.± rpm ± Rest ± Bulk ± a Measured at 0. g/l clay concentration. b Determined by titration of clay suspension (0. g/l) with 0.1 M HCl. c Measured at 0. g/l clay concentration. 6 d 7 Determined by X-ray fluorescence (XRF).

4 Supplemental Table S. Average volume equivalent diameters of montmorillonite fractions in aqueous solutions measured by laser diffraction. Clay Solution condition Average volume equivalent diameter (μm) deionized water, ph= rpm 0.1M NaCl, ph= M CaCl, ph= deionized water, ph= rpm 0.1M NaCl, ph= M CaCl, ph= deionized water, ph= rpm 0.1M NaCl, ph= M CaCl, ph= deionized water, ph= Rest 0.1M NaCl, ph= M CaCl, ph= deionized water, ph= Bulk 0.1M NaCl, ph= M CaCl, ph=

5 Supplemental Table S. Freundlich sorption model parameters (K F and n ± standard deviation) and solid-to-solution distribution coefficient (K d ) calculated at C e = 0.01mmol/L from tetracycline sorption isotherms. Clay fraction K F (mmol 1-n L n /kg) n R K d (L/kg) rpm 800± ± rpm 0000± ± rpm 0000± ± Rest 1000± ± Bulk 6000± ±

6 Supplemental Table S Release of exchangeable cations from different montmorillonite fractions at ph 7.0. Clay fractions Released divalent cation levels ( 10 - M) rpm rpm rpm 1.08 Rest 0.70 Bulk

7 Supplemental Fig. S1. Chemical structure of tetracycline (TC). The regions framed by dashed lines represent the three functional groups TC 1, TC, and TC + associated with the corresponding acidic dissociation constants (pk a s). (Adopted from Zhao et al., 01) 7

8 Fig. S Mineral compositions of four freeze-dried clay fractions using powder X-ray diffraction (XRD). 8

9 Supplemental Fig. S. -potential of montmorillonite clay fractions in aqueous suspension (0. g/l) versus ph. Error bars represent standard deviations of triplicates. potential (mv) rpm 800rpm 000rpm Rest Bulk ph 9

10 Supplemental Fig. S. Particle size distribution of montmorillonite fractions in aqueous suspension (0. g/l) at ph 7.0. Volume distribution / (%) rpm 800rpm 000rpm Rest Bulk Effective spherical diameter / ( m) 10

$1 Supplemental Fig. S. Atomic force microscopy (AFM) height images and perpendicular section images of selected montmorillonite size fractions. (a) 11000 rpm. (b) Rest.$

11 1 Supplemental Fig. S. Atomic force microscopy (AFM) height images and perpendicular section images of selected montmorillonite size fractions. (a) rpm. (b) Rest. The microscope was operated in ScanAsyst-Air mode. Twenty microliters of montorillonite suspension (0.0 g/l, ph 7.0) were placed on the surface of freshly cleaved mica with a diameter of 10 mm. The samples were dried in clean air at room temperature. Probes with 6 silicon tip on nitride lever were used for measurements, the force constant was 0. Nm 1, and 7 the resonance frequency was 70 khz

12 Supplemental Fig. S6. Schematic diagram for microstructures induced by edge-to-face, edge-to-edge, and face-to-face interactions, respectively. Revised from Saunder et al.,

13 Supplemental Fig. S7. Powder X-ray diffraction (XRD) patterns of freeze-dried clay fractions. (a) Clay fractions only. (b) Clay fractions with sorbed tetracycline (a) clay d 001 = 1.0 nm d 001 = 1. nm d 001 = 1. nm Intensity 11000rpm d 001 = 1. nm 000rpm Rest Bulk (b) clay+tc d 001 = 1.8 nm 11000rpm 16 mmol/kg Intensity 000rpm 19 mmol/kg Rest 1 mmol/kg Bulk 19 mmol/kg

14 6 7 References Mitscher, L. A The chemistry of the tetracycline antibiotics. Marcel Dekker, New York. Saunders, J. M.; J. W., Goodwin; R. M., Richardson; B., Vincent A small-angle X-ray scattering study of the structure of aqueous Laponite dispersions. J. Phys. Chem. B 10: Zhao Y., X. Gu, S. Gao, J. Geng, X. Wang. 01. Adsorption of tetracycline (TC) onto montmorillonite: Cations and humic acid effects. Geoderma 18:

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