Novel dendrimer-like magnetic bio-sorbent based on modified orange peel. waste: adsorption-reduction behavior of arsenic

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1 Supplementary Information: Novel dendrimer-like magnetic bio-sorbent based on modified orange peel waste: adsorption-reduction behavior of arsenic Fanqing Meng1, Bowen Yang1, Baodong Wang 2, Shibo Duan1, Zhen Chen1, Wei Ma1* Fig. S1. Low-magnification TEM images of (a) 5 wt% HF-D, (c) 10 wt% HF-D and (e) 15 wt% HF-D. High-magnification TEM images of (b) 5 wt% HF-D, (d) 10 wt% HF-D and (f) 15 wt% HF-D. Fig. S2. Adsorption/desorption isotherm of 10 wt% HF-D. S1

2 Fig. S3. ATR-FTIR spectra of aqueous arsenic and arsenic adsorbed onto the surface of 10wt% HF-D at different ph. Fig. S4. Zeta potential of As-free and As-loaded 10 wt% HF-D and OP-R dispersed in 0.01 mm NaNO 3 solution. Fig. S5. Effects of different cations on the adsorption of 25 mg/l As (V) at 298 K. S2

3 Fig. S6. Arrhenius plots of the apparent rate constants for arsenic removal by a suspension of 10 wt% HF-D. Fig. S7. Magnetic hysteresis loops of 5 wt% and 10 wt% HF-D (insert of figure shows the used particles of HF-D can be separated easily under an external magnetic field) Fig. S8. Variation of the adsorption capacity of the 10 wt% HF-D as a function of regeneration cycle. S3

4 Fig. S9. The released total iron ions from 10 wt% HF-D at the tested ph in 500 min. Table S1. Chemical composition of the OP-R and three HF-D. Elements OP-R 5 wt% HF-D 10 wt% HF-D 15 wt% HF-D Fe 0.02 wt% 7.48 wt% wt% wt% C(organic) wt% wt% wt% wt% C(inorganic) wt% wt% wt% wt% Table S2. The BET analysis of the OP and three HF-D. Fe/biomas ration S BET (m 2 /g) S ext (m 2 /g) V midr (cm 3 /g) V me (cm 3 /g) W(nm) OP-R wt% HF-D wt% HF-D wt% HF-D Table S3. Thermodynamic parameters of arsenic adsorption on 10% HF-D. Concentration As(V) (mg/l) 20 mg/l Temperature (K) K L G θ H θ S θ (L mg -1 ) (kj mol -1 ) (kj mol -1 ) (kj mol -1 K -1 ) S4

5 Table S4. Values of the Mössbauer hyperfine parameters, derived from fitting of the Mössbauer spectra of As (V) free 10 wt% HF-D and As (V) loaded 10 wt% HF-D. T is the temperature of the measurement, δ is the isomer shift, E Q is the quadrupole splitting, B hf is the hyper-fine magnetic field, and R A is the spectral area of individual spectral components identified during spectra processing. Sample Component δ (mm/s) As (V) free HF-D As (V) loaded HF-D E Q (mm/s) B hf (T) R A % Assignment Sextet Fe 3 O 4 - O-sites (Fe 2+ ) Mixed Fe 3 O 4 - O-sites (Fe 3+ ) Doublet Amorphous-Fe(II) hydrate Doublet Amorphous-Fe(III) hydrate Sextet Fe 3 O 4 - O-sites (Fe 2+ ) Mixed Fe 3 O 4 - O-sites (Fe 3+ ) Doublet Amorphous-Fe(II) hydrate Doublet Amorphous-Fe(III) hydrate Arsenic analysis method: In the arsenic analysis process, the filtrate was analyzed by ICP-OES using an external calibration method. The whole analytical procedure has been commonly suggested in the literature (31) which consists of three steps: i) the pre-treatment for arsenic filtrate, ii) the generation of the hydrides and iii) the measurement with ICP-OES. Blank, standard solutions and samples went through the same procedure. Firstly, the arsenic filtrate was pre-reduced to As (III) with 1% KI (in 0.2% ascorbic acid) and 3 mol L -1 HCl. Accordingly, an aliquot of 2.5 ml of each sample solution was transferred to a 5 ml volumetric flask, then 0.5 ml of 10 wt% (m/v) KI in 2% (m/v) ascorbic acid and 1.25 ml of concentrated HCl were added and left to react for about 20 min. After this time flask was diluted to the volume with deionised water. Secondly, Hydride generation was made based on the reaction of As form with NaBH 4 S5

6 in HCl medium. Typical concentration of NaBH 4 was used (1% (m/v)). Finally, the arsenic concentration was performed using an inductively coupled plasma optical emission spectrometry (ICP, PerkinElmer Optima2000DV, Waltham, MA, USA). Desorption and regeneration analysis method: To evaluate the reusability of the HF-D, three cycles of sorption and desorption tests were performed. For the sorption test, 1 g HF-D was added into a bottle containing 2 L 50 mg/l arsenic solution. After stirring for 24 h at about ph 6.0 ± 0.1, the HF-D was separated and collected from the solution. For the desorption test, the arsenic-containing HF-D was added into 100 ml 0.5 M NaOH solution, the mixture was stirred for 10 h and then regenerated HF-D was separated from the NaOH solution. After washing and drying, it was used in the next sorption desorption cycle. Thermodynamic calculation: Thermodynamic parameters are important indicators of the adsorbing process, including Gibbs free energy ( G), enthalpy change ( H), and entropy change ( S). G= RTK d (1) S H ln k d = (2) R RT q e k d = (3) ce G= H T S (4) Where R is the universal gas constant (8.314 J/(molK)), T is the adsorption temperature (K), and k d is the equilibrium constant. The k d was calculated according to Eq. (3), H and S were calculated from the slope and intercept of the Eq. (2) of lnk d versus 1/T, respectively. At any given q e, C e was computed using the Langmuir S6

7 parameters obtained at different temperatures. REFERENCES Zhang, Y.Z., Li, J., Zhao, J., Bian, W., Li, Y., Wang, X.J., Adsorption behavior of modified Iron stick yam skin with Polyethyleneimine as a potential biosorbent for the removal of anionic dyes in single and ternary systems at low temperature. Bioresour. Technol. 222, S7

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