Does Hydrophilic Polydopamine Coating Enhance Membrane Rejection of

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1 1 Supporting Information Does Hydrophilic Polydopamine Coating Enhance Membrane Rejection of Hydrophobic Endocrine Disrupting Compounds? Hao Guo, Yu Deng, Zhijia Tao, Zhikan Yao, Jianqiang Wang, Chuner Lin, Tong Zhang, Baoku Zhu, Chuyang Y. Tang* Department of Civil Engineering, The University of Hong Kong, Pokfulam, Hong Kong, ERC Membrane and Water Treatment Technology (MOE), Department of Polymer Science and Engineering, Zhejiang University, Hangzhou , PR China These authors contributed equally *Corresponding Author: Chuyang Y. Tang, tangc@hku.hk, Number of pages (including the cover page): 11 Number of figures: 5 Number of tables: 2 1

2 Page 3 Page 4 Page 5 Page 6 Page 8 Page 9 Page 10 S1. Preparation of PDA coated membranes S2. Procedures of surface energy determination S3. Laboratory cross-flow filtration setup S4. UPLC-MS/MS operational conditions S5. Effect of PDA coating on the passage of BPA S6. Effect of filtration time on EDCs rejection S7. Extraction of EDCs

3 32 S1. Preparation of PDA coated membranes Pristine membrane coupons of suitable size (around 23.5 cm 12.0 cm) were thoroughly rinsed with deionized water to remove any impurities and were soaked in deionized water for 35 at least 24 h before coating. A membrane coupon was placed in a custom-designed container 36 (Figure S2) which only exposes the rejection layer side of the membrane. PDA coating was 37 performed by adding 300 ml 0.2 wt.% dopamine hydrochloride in 10 mm tris solution at ph The container was shaken at 60 rpm and coated for 0.5, 1, 2, and 4 h at room temperature 39 (~ 25 C) Figure S1. Illustration of custom-designed container for single-side PDA coating. 3

4 S2. Procedures of surface energy determination Three probing liquids, water (H 2 O, surface tension γ = mn/m), di-iodomethane (CH 2 I 2, γ = mn/m), and glycerol (C 3 H 8 O 3, γ = mn/m), were used to determine contact angles of various membranes using a contact angle goniometer (OCA20, Dataphysics, Germany) at 25 C. The measured contact angle values were corrected for the roughness effect by applying Wenzel equation: 1 cos = (1) where θ m is the measured contact angle, θ Y is the corrected contact angle, and r is membrane surface roughness ratio. The surface roughness ratio was determined by atomic force microscopy and calculated by the Nanoscope Software (Bruker, Camarillo, CA). Membrane surface energy was then calculated on the basis of corrected contact angle results of mentioned three liquid by the SCA software from DataPhysics (using Owens Wendt Kaelble approach)

5 57 S3. Laboratory cross-flow filtration setup Figure S2. Illustration of laboratory cross-flow filtration setup. Figure S2 illustrates the laboratory cross-flow filtration setup used in this study. The setup consists of three parallel cross-flow cells (CF042, Sterlitech, Kent, WA). Solution was placed in a stainless steel tank with an overhead mixer and a refrigerated cooling coils (JP Selecta, Barcelona, Spain). A high pressure pump (Wanner Engineering Inc., Minneapolis, MN) was used to recirculate and pressurize the water solution. A relief valve was set at the output tube of the pump to adjust the outlet pressure. Each cell was connected to a separate cross-flow tubing system equipped with a needle valve and a pressure relief valve to allow independent pressure setting for each cell. The solution temperature was maintained at 25 C during the 68 operation. 5

6 S4. UPLC-MS/MS operational conditions The four selected EDCs in this study were analyzed by UPLC-MS/MS. LC operational conditions were: Eluent A consisted of 95% water, 5% methanol, and 0.1 mm ammonium acetate; Eluent B contained 95% methanol, 5% water, and 0.1 mm ammonium acetate. The gradient eluting conditions were: initial hold at 20% A and 80% B, followed by a 1.5min gradient to 5% A and 95% B. Flow rate was 0.4 ml/min, sample injection volume was 10 ul, and sample room temperature was 10 C. MS detector operational mode was negative ion mode (ES-). Desolvation temperature was 400 C and source temperature was 120 C, observed capillary voltage was 2.5kV. Nitrogen was used as cone and desolvation gas, with the flow rate of 50 L/h and 600 L/h, separately. The pressure for collision gas (Argon) was set at mbar. The MS detector parameters are summarized in table S1. In order to prevent unexpected loss of EDCs, all the samples were directly taken from feed solution and permeate without further filtration. 5 Table S1. MS detector parameters. Compound Parent (m/z) Daughter (m/z) Dwell (s) Cone (V) Collision (V) Retention time (min) Ethylparaben Propylparaben Benzylparaben BPA In this study, serial calibration points ( µg/l) were used to calibrate the concentration of each compound. All the lowest calibration concentration of each analyte gave a 6

7 86 signal-to-noise (S/N) ratio above 10:1 (Figure S3), which is a critical value of instrumental 87 quantification limit (IQL). 6 The linearity of the tested dynamic range (i.e. the lowest 88 calibration concentration of each compound to the highest concentration used) also showed 89 good fit with linearity over 0.99 (Figure S3) Figure S3. Chromatograms of detected compounds (a) ethylparaben; (b) propylparaben; (c) benzylparaben; and (d) BPA at instrumental quantification limits within dynamic ranges. 7

8 95 S5. Effect of PDA coating on the passage of BPA Figure S4. Effect of PDA coating on the passage of BPA. Figure S4 gives the passage of BPA through membrane for original and PDA coated membranes. Significantly reduced passage was observed on PDA coated membrane compared with uncoated NF90. The hydrophilic PDA coating may weaken the hydrophobic interaction between BPA and membrane surface so that it can reduce the sorption, thus further decreases the passage

9 104 S6. Effect of filtration time on EDCs rejection 105 The rejection of EDCs was monitored at different filtration time (Figure S5). The rejection of 106 EDCs became stable within 12 h Figure S5. Effect of filtration time on EDCs rejection. 9

10 S7. Extraction of EDCs An EDC extraction experiment was conducted to evaluate the recovery ratio using 50% methanol as the extract solution. Briefly, a membrane coupon of 1 cm 2 cm (both uncoated NF90 or 4 h PDA coated NF90-C4) was immersed into 10 ml solution (200 ppb EDCs, 10 mm NaCl, and ph 6.6) and was shaken at 120 rpm for 12 h. A blank text without membrane coupon was also conducted to evaluate the sorption on container wall. After 12 h shaking, the membrane was taken out, gently rinsed with DI water, and put in 5 ml 50% methanol solution for EDC extraction (12 h, shaking at 120 rpm). Bulk solution samples were taken at beginning and end of the sorption tests and extraction tests. All the tests were triplicated. The results showed that the sorption of four EDCs on container wall was less than 7%. The recovery ratio for ethylparaben, propylparaben, benzylparaben, and BPA by NF90 and NF90-C4 were consistently high (Table S2). The results indicate that 50% methanol was effective to extract EDCs from the membranes Table S2. Recovery ratio (%) of four EDCs by using 50% methanol extraction Ethylparaben Propylparaben Benzylparaben BPA NF ± ± ± ± 3.2 NF90-C ± ± ± ±

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