Degradation of Polyamide Nanofiltration and Reverse Osmosis Membranes by Hypochlorite

Transcription

1 Supporting Information of Degradation of Polyamide Nanofiltration and Reverse smosis Membranes by Hypochlorite Van Thanh Do 1, huyang Y. Tang 1,2,*, Martin Reinhard 3, James. Leckie 3 School of ivil & Environmental Engineering 1 and Singapore Membrane Technology entre 2 Nanyang Technological University, Singapore, Department of ivil and Environmental Engineering 3 Stanford University, Stanford, alifornia * orresponding author address: Nanyang Technological University; N1-1B-35, 50 Nanyang Avenue; Singapore, ; Tel: (65) ; Fax: (65) ; cytang@ntu.edu.sg Number of Pages: 16 Number of Figures: 8 Number of Tables: 3 Page 2 S1. hlorination mechanisms of fully aromatic polyamide membranes Page 3 S2. Membrane physiochemical properties Page 4 S3. NF/R filtration system and performance evaluation Page 6 S4. Elemental compositions of virgin and chlorinated membranes by XPS Page 7 S5. Surface oxygen content for chlorinated BW30 membrane Page 8 S6. High resolution XPS spectra for virgin and chlorinated BW30 and NF270 membranes Page 10 S7. ATR FTIR spectra at wave number from 2700 to 3800 cm -1 Page 13 S8. Surface charge of virgin and chlorinated BW30 and replicates for virgin membranes. Page 15 S9. Hydrophilicity of virgin and chlorinated membranes

2 S1. hlorination mechanisms of fully aromatic polyamide membranes Three principal chlorination mechanisms of FA PA membranes are summarized in Figure S1 below. H H l H N N A N N B H H N N l Figure S1. hlorination mechanisms of fully aromatic polyamide membranes. (A) N- chlorination; (B) direct ring chlorination; (A) and () ring chlorination by rton rearrangement. 1-3 S2

3 S2. Membrane physiochemical properties Table S1. Membrane physiochemical properties. Data were extracted from Tang et al. 2009, 4 except MWs were from López- Muñoz, et al. 5 Fully aromatic Piperazine based Membrane ompany Type MW (Da) a RMS roughness (nm) ontact angle ( o ) Zeta potential (mv) b Permeability (L/m 2.hr.bar) c Uncoated XLE FilmTec R ± ± ± LE FilmTec R ± ± ± Nal rejection (%) NF90 FilmTec NF ± ± ± ± 1.5 oated SW30HR FilmTec R ± ± BW30 FilmTec R ± ± ± ± 0.4 Uncoated HL GE smonics NF ± ± ± NF270 FilmTec NF ± ± ± ± 3.8 a MW was determined by crossflow filtration of polyethylene glycol (PEG). 5 b Zeta potential was measured at ph 9, with 10 mm Nal as background electrolyte c Permeability was evaluated for MilliQ water, and rejection was performed for a 10 mm Nal solution at ph 7. The applied pressure was 1380 kpa (200 psi). S3

4 S3. NF/R filtration system and performance evaluation Figure S2. Schematic diagram of the NF/R filtration system The laboratory-scale NF/R filtration system used in this study consists of four identical rectangular cross-flow F042 (Delrin Acetal) cells supplied by Sterlitech (Kent, WA, USA). Each cell houses 42 cm 2 (4.6 cm 9.2 cm) of active membrane area and has maximum operating pressure of 1000 psi. Spacers of 1.2 mm thickness from GE smonics (Minnetonka, MN, USA) were used for all filtration tests. The temperature of the feed solution was controlled at about 21 o by a submerged stainless steel heat S4

5 exchange coil connected to a chiller (Polysciene, Niles, IL, USA). Both permeate and concentrate were re-circulated back to the feed tank. Water permeability coefficient, A (m/s.pa) was determined from the water flux (J w ) measurements: 6 J A = w P π where P and π are the applied pressure difference and osmotic pressure difference across the membrane, respectively. Sodium chloride rejection, R was determined from the solute concentrations of the permeate, p and feed, f by: R = 1 p f The solute permeability coefficient, B (m/s) was determined by: 6 B = J w 1 ( 1) R S5

6 S4. Elemental compositions of virgin and chlorinated membranes by XPS Elemental compositions of virgin and chlorinated membranes obtained from XPS survey scans are tabulated in Table S2. In addition, / and /N ratios were calculated. Errors reported for atomic concentration are measurement ranges from at least 2 measurements. Table S2. Elemental compositions of virgin and chlorinated membranes Membrane NF90 XLE BW30 SW30HR NF270 HL [Hl] Soaking Atomic oncentration % Atomic ratios (ppm) time (h) 1s 1s N 1s l 2p S 2p N virgin 12.0 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 0.09 virgin 12.2 ± ± ± ± ± virgin 25.9 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 0.31 virgin virgin 14.2 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± 0.10 virgin S6

7 S5. Surface oxygen content for chlorinated BW30 membrane The oxygen content of BW30 decreased at higher chlorine percentages which is consistent with the assumption that the oxygen-rich PVA coating layer was detached from the PA layer under severe chlorination conditions. Figure S3. Ratio of (a) oxygen to carbon and (b) oxygen to nitrogen as a function of the atomic percent of bound chlorine for BW30 at different chlorination conditions: ph 5; 2000 ppm 24 h, 1000 ppm 24 h, 1000 ppm 1 h, 100 ppm 24 h, 100 ppm 10 h and 10 ppm 100 h. The dotted lines represent the (a) / and (b) /N ratio for virgin membranes. S7

8 S6. High resolution XPS spectra for virgin and chlorinated BW30 and NF270 membranes (a) (b) FIGURE S4. High resolution XPS spectra of (a) 1s, 1s, N 1s for virgin and (b) 1s, 1s, N 1s, l 2p for chlorinated BW30 (2000 ppm 24 h, ph 5) S8

9 (a) (b) FIGURE S5. High resolution XPS spectra of (a) 1s, 1s, N 1s for virgin and (b) 1s, 1s, N 1s, l 2p for chlorinated NF270 (2000 ppm 24 h, ph 5) S9

10 S7. ATR FTIR spectra at wave number from 2700 to 3800 cm -1 FTIR spectra from 2700 to 3800 cm -1 for the 3 membranes are provided in Figure S6 below. For NF90 and BW30 FA membranes, the magnitude of broad peaks centered ~ 3300 cm - 1, which are assigned to N H and/or H stretching 7 depleted as chlorination conditions became more severe. n the other hand, for the NF270 PIP membrane, only a slight reduction in the H stretching peak 7 at 2970 cm -1 was observed Virgin S10

11 Virgin S11

12 Virgin Figure S6. ATR FTIR spectra for (a) NF90, (b) BW30 and (c) NF270: virgin and chlorinated at ph 5; 2000 ppm 24 hr, 1000 ppm 24 hr and 1000 ppm 1 hr. S12

13 S8. Surface charge of virgin and chlorinated BW30 and replicates for virgin membranes. The surface charge of virgin and chlorinated BW30 is presented in the below Figure S7. onsistent surface charge of more severe chlorination conditions could not be obtained, probably due to the detachment of the PVA coating. Figure S7. Zeta potential for virgin and chlorinated BW30 as a function of ph. Background electrolyte was 10 mm Nal. S13

14 A representative zeta potential replicate of virgin coupons is shown as below. Figure S8. Zeta potential of two different virgin coupons for NF90, BW30 and NF270. S14

15 S9. Hydrophilicity of virgin and chlorinated membranes The contact angles of virgin and chlorinated membranes are tabulated in Table S3 below. Error bar indicates the standard deviations of 40 measurements (2 independent membrane coupons and 20 different locations for each sample). Table S3. ontact angles ( o ) for virgin and chlorinated membranes Membrane treatment ontact angle ( o ) [Hl] Soaking (ppm) time (h) NF90 XLE BW30 SW30HR NF270 HL Virgin 66.3 ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± ± S15

16 Literature cited 1. Glater, J.; Hong, S.-k.; Elimelech, M., The search for a chlorine-resistant reverse osmosis membrane. Desalination 1994, 95 (3), Kawaguchi, T.; Tamura, H., hlorine-resistant membrane for reverse osmosis. I. orrelation between chemical structures and chlorine resistance of polyamides. Journal of Applied Polymer Science 1984, 29, (11), Kang, G.-D.; Gao,.-J.; hen, W.-D.; Jie, X.-M.; ao, Y.-M.; Yuan, Q., Study on hypochlorite degradation of aromatic polyamide reverse osmosis membrane. Journal of Membrane Science 2007, 300, (1-2), Tang,. Y.; Kwon, Y.-N.; Leckie, J.., Effect of membrane chemistry and coating layer on physiochemical properties of thin film composite polyamide R and NF membranes: II. Membrane physiochemical properties and their dependence on polyamide and coating layers. Desalination 2009, 242, (1-3), López-Muñoz, M. J.; Sotto, A.; Arsuaga, J. M.; Van der Bruggen, B., Influence of membrane, solute and solution properties on the retention of phenolic compounds in aqueous solution by nanofiltration membranes. Separation and Purification Technology 2009, 66, (1), Mulder, M., Basic principles of membrane technology. 2 nd ed.; Kluwer Academic Publishers: Dordrecht, The Netherlands, Tang,. Y.; Kwon, Y.-N.; Leckie, J.., Effect of membrane chemistry and coating layer on physiochemical properties of thin film composite polyamide R and NF membranes: I. FTIR and XPS characterization of polyamide and coating layer chemistry. Desalination 2009, 242, (1-3), S16