Fractionation and Concentration of High-Salinity ... - ACS Publications

Subscriber access provided by UNIV OF NEWCASTLE

Article

Fractionation and Concentration of High-Salinity Textile Wastewater using an Ultra-Permeable Sulfonated Thin-film Composite Meng Li, Yujian Yao, Wen Zhang, Junfeng Zheng, Xuan Zhang, and Lianjun Wang Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b01795 • Publication Date (Web): 19 Jul 2017 Downloaded from http://pubs.acs.org on July 26, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Environmental Science & Technology is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 32

Environmental Science & Technology

1

Fractionation and Concentration of High-Salinity Textile

2

Wastewater using an Ultra-Permeable Sulfonated Thin-film

3

Composite

4 5

Meng Li, Yujian Yao, Wen Zhang, Junfeng Zheng, Xuan Zhang* and Lianjun Wang*

6

Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of

7

Environmental and Biological Engineering, Nanjing University of Science & Technology,

8

Nanjing 210094, China;

9 10

KEYWORDS: Sulfonated thin-film composite, high salinity textile wastewater, dye/salt

11

fractionation, concentration, anti-fouling property.

12

ABSTRACT

13

A sulfonated thin-film composite (TFC) nanofiltration membrane was fabricated using 2,2'-

14

benzidinedisulfonic acid (BDSA) and trimesoyl chloride (TMC) on a polyether sulfone substrate

15

by conventional interfacial polymerization. Due to a nascent barrier layer with a loose

16

architecture, the obtained TFC-BDSA-0.2 membrane showed an ultra-high pure water

17

permeability of 48.1 ± 2.1 L−1 m−2 h−1 bar−1, and a considerably low NaCl retention ability of

ACS Paragon Plus Environment


Page 2 of 32

18

99%), triethylamine (TEA),

108

and CR were procured from Sinopharm Chemical Reagent Co., Ltd. (Shanghai, China).

109

Trimesoyl chloride (TMC, >99.9%) was purchased from J&K Chemical Reagent Co., Ltd.

110

(Beijing, China). Other reagents and solvents were used as received. Deionized (DI) water with a

111

minimum resistance of 18 MΩ.cm, obtained by purification using a Millipore filter, was used

112

throughout this work.

113

The TFC-BDSA membrane was fabricated by conventional interfacial polymerization (IP) at

114

room temperature (~25 °C), similar to our previous reports.22, 26 In brief, a PES ultrafiltration

115

membrane was immersed in DI water overnight, and then was removed from the water and fixed

116

on a plastic frame. Firstly, 100 mL of an aqueous solution containing a certain amount of BDSA

117

(with a pH initially adjusted by TEA to ca. 10.5) was poured into the frame and allowed to

118

contact the surface of the PES membrane for 3 min before the excess aqueous solution was

119

drained. Residual droplets of the solution were then removed from the membrane surface with a

120

rubber roller. Secondly, the frame and gasket were reassembled and the n-hexane solution

121

containing a certain amount of TMC was poured into the frame. After 30 s, the TMC solution

122

was drained and the membrane surface was rinsed using fresh n-hexane (100 mL) to remove any


Page 6 of 32

Page 7 of 32


123

unreacted reagents. Finally, the membrane was air-dried under ambient conditions for 30 s, and

124

stored wetly prior to the various evaluation studies. The most optimal conditions to obtain the

125

desired membrane were found to be BDSA and TMC concentrations of 0.2% and 0.1%,

126

respectively (see Figure S1), which was designated as TFC-BDSA-0.2.

127

2.2 Membrane Separation Performance

128

Separation tests were conducted at room temperature using a lab-scale cross-flow module

129

with an effective membrane area of 12.56 cm2. The operation details are similar to those in our

130

previous work.22, 26, 27 The flux J was evaluated from the measured volume of the permeate and

131

then calculated by the following equation (1):26, 28

132

J=

133

where V is the volume of the permeate, A is the effective area of the membrane, and ∆t and P are

134

the permeation time and operating pressure, respectively.

V AP∆t

(1)

135

The salt concentration (in the dye-free solution) was calculated by measuring the

136

conductivity of the solution (DDS-307 Conductivity Meter, Shanghai, China), and the dye

137

concentration was measured using a UV/VIS spectrometer (Lambda 25, PerkinElmer, US).

138

Additionally, the salt (NaCl) concentration in the mixed dye/salt solution was measured by ion

139

chromatography (Dionex ICS-2100, USA) in terms of the Cl− ion content. The rejection (R)

140

values for the salt and dye were calculated using equation (2): 26, 27

141

 Cp R = 1 −  C f 

  ×100% 

(2)



142

where Cp and Cf are the concentrations in the permeate and feed, respectively.

143

Prior to the measurements, all membrane samples were subjected to pure water at a pressure

144

of 12 bar for 1 h until they became stable. Each test was performed at least three times and the

145

average values are given.

146

2.2.1 Diafiltration

147

Batch diafiltration was employed to evaluate the dye/salt separation abilities of TFC-BDSA-

148

0.2 and NF270 at a fixed operating pressure of 10 bar. A saline textile wastewater model with an

149

initial volume of 500 mL was used as the feed; the CR:NaCl ratio was 1:20 g L−1. Since a cyclic

150

diafiltration mode was applied in this study, an increased water recovery ratio would inevitably

151

lead to an increased dye concentration in the feed solution. To separate the salt and dye solutes

152

during the diafiltration process in a more efficient way while avoiding unnecessary membrane

153

contamination, the upper concentration factor (CF) limit was set at 2. In other words, the water

154

recovery ratio is equal to 50% (reflected by the decrease in feed volume to 250 mL). Then, the

155

concentrations of NaCl and CR, both in the feed and permeate, were recorded with time.

156

Subsequently, an additional 250 mL of pure water was added to the feed. The above process was

157

repeated until the NaCl concentration in the feed was less than 0.6 g L−1.4

158

2.2.2 Concentration of the Dye Solution

159

The diafiltration process was followed by the concentration process, which was carried out

160

in two stages: the initial pre-concentration and the subsequent deep-concentration steps.

161

Considering the possibility of membrane fouling, which could affect permeability, the

162

membranes were tested without pre-compaction. In this case, the pre-concentration step was


Page 8 of 32

Page 9 of 32


163

performed using a fixed CF (0.5, 1.0, 1.5, …, 3.5) until the value reached 3.5. After that, the

164

filtration continued smoothly and eventually stopped when the water recovery ratio reached

165

90%, which is defined as the deep-concentration process. At this point, the concentrations of

166

NaCl and CR were recorded at regular time intervals (60 min). All the operations were

167

conducted at a pressure of 10 bar at room temperature.

168

2.3 Membrane Cleaning Strategy

169

After the concentration stages, the fouled membranes were washed with various solutions,

170

including pure water and 10%, 20%, and 40% ethanol/water solutions, by back-washing at a

171

fixed pressure (3 bar) for 1 h. The flux recovery ratio (FRR), used for evaluating the effect of

172

cleaning the membrane, was calculated by equation (3):17, 22

173

FRR =

174

where J w ,b and J w , a represent the flux of the CR/NaCl mixed solution at a certain CF before and

175

after cleaning, respectively.

176

2.4 Characterization

J w, a J w ,b

×100%

(3)

177

All membranes were dried using a supercritical drying machine (Leica EM CPD300) before

178

the measurements. Morphologies of the PES substrate and TFC-BDSA samples were directly

179

studied by field emission scanning electron microscopy (FESEM, S-4800, Hitachi, Japan). All

180

membrane samples were dried and sputter coated with gold prior to examination. They were also

181

fractured in liquid nitrogen to allow characterization of their cross-sections. Chemical and

182

elemental compositions of the membrane surfaces were probed using X-ray photoelectron



183

spectroscopy (XPS, PHI Quantera II, Japan). Membrane hydrophilicity was assessed using a

184

contact angle and drop shape analyzer (KRÜSS, DSA30, Germany). At least five measurements

185

were made at different locations for each membrane surface and their averages were recorded.

Page 10 of 32

186

The membrane surface charges were determined by the streaming potential method using an

187

electrokinetic analyzer with a set of AgCl electrodes (SurPASSIII, AntonPaar, Austria). For the

188

streaming potential measurements, an electrolytic solution of 0.01 M KCl (aq.) was used to

189

provide the background ionic strength, and was automatically titrated with 0.05 M HCl (aq.) and

190

0.05 M NaOH (aq.) to investigate the effect of pH on the ζ- potential. The thickness of the

191

selective polyamide layer in the TFC was obtained by ellipsometry (EMPRO-PV, Ellitop

192

Scientific Co., Ltd., China). The sample was simulated as a two-layer composite, consisting of a

193

PES substrate and a top layer of polyamide. The membrane sheets were flattened under vacuum

194

to the stage and measured with a fixed incidence angle of 70°.

195 196

3 RESULTS AND DISCUSSION

197

3.1 Physicochemical Characterization of the TFC-BDSA Membranes

198

The TFCs studied in this paper were prepared from BDSA and TMC by an IP process, and

199

were further optimized by varying the stoichiometries of the amine and carbonyl monomers, as

200

shown in Figure S1. The pure water flux decreased whereas the rejection towards NaCl steadily

201

increased with an increasing BDSA concentration, suggesting the gradual formation of a dense

202

layer. Meanwhile, the TMC content did not notably influence the separation performance, as

203

indicated by the relatively stable rejection to both the salt ions and CR. However, for the purpose


Page 11 of 32


204

of this study, it would be ideal to have a membrane with an exceptionally high dye rejection and

205

simultaneously a low salt retention. Considering the excellent CR rejection of above 99.2 ± 0.1%

206

for all the TFC-BDSA membranes, the initial separation performance was only determined by

207

pure water permeability (PWP) and salt rejection tests using TFC-BDSA-0.2 and TFC-BDSA-

208

0.3 as representative membranes, along with some commercial membranes for comparison. As

209

shown in Figure 2, TFC-BDSA-0.2 showed a rather high PWP of 48.1 ± 2.1 L m−2 h−1 bar−1,

210

which is nearly 3.3 times higher than that of NF270. In addition, it also displayed an extremely

211

low NaCl rejection level of less than 1%, compared to the 7.9 ± 0.6% obtained with NF270.

212

These results suggest the TFC-BDSA-0.2 has significant advantages for use in dye/salt

213

separation.

214

The surface nature of the as-prepared membrane was initially analyzed to determine its

215

chemical composition. As listed in Table S1, the N content dramatically increased to 5.1%,

216

which suggests the formation of a polyamide layer. Calculation of the cross-linking degree

217

(CD,29 described in the Supplementary Information) showed that TFC-BDSA-0.2 had a low CD

218

of 12.8%, in contrast to the CD of 62.0% for NF270. This indicates the former has a less-

219

developed polymeric network. Moreover, the average thickness could also be precisely

220

ascertained by ellipsometry, due to the differences in the refractive indices of the barrier layer

221

and substrate, as shown in Table 1. Consequently, it was determined that the loose architecture

222

and thin nature were largely responsible for the superior permeability of our as-prepared

223

membranes compared to the commercial alternatives.

224

Figure S3 shows the ζ-potentials of the membrane sheets. NF270 was strongly

225

electronegative, particularly under neutral or high pH conditions. In contrast, TFC-BDSA-0.2

226

gave a gentle slope with a curve similar to that of the PES substrate. Interestingly, water contact



227

angle measurements also showed the same trend, as listed in Table 1. Since the BDSA molecule

228

possesses some rigidity due to the presence of the biphenyl unit, it is likely that, after the IP

229

process, most of the sulfonic acid groups were enclosed by the corresponding rigid sulfonated

230

polyamide chains. Such a phenomenon is consistent with our previous study, despite the

231

different amine monomers used.22,

232

molecule is relatively hydrophobic, it can be reasonably stated that the aggregated -SO3− groups

233

inside the barrier layer cavities could still supply an overall strong negative charge, resulting in

234

the significant repulsion of the anionic dye molecules. However, taking into account the hydrated

235

radius of Cl− (0.332 nm),24 the considerably low NaCl rejection with TFC-BDSA-0.2 is

236

predominantly due to its higher MWCO of 836 Da and larger mean pore size of 0.368 nm

237

relative to NF270 (see Figure S4).

23

Therefore, although there are fewer charges and the

238

The morphologies of the membrane surfaces and cross-sections were studied by FESEM.

239

As shown in Figure 3, no apparent discrepancies between the TFC-BDSA-0.2 and PES

240

membranes existed. Due to the large molecular size and existence of highly polar sulfonic acid

241

groups, it is believed that the diffusion rate of BDSA would be much lower than those of the

242

commonly used aliphatic amine monomers, such as piperazine and ethylenediamine, resulting in

243

a relatively flat surface after the IP process. 22, 30


Page 12 of 32

Page 13 of 32


35 [4]

NF 2A [4] NF 6 NF 270 TFC-BDSA-0.2 TFC-BDSA-0.3

Single NaCl Rejection / %

30 25 20 15 10 5 0 -5

5

10 15 20 25 30 35 40 45 50 Pure Water Permeation / L m-2 h-1 bar-1

244 245 246

Figure 2. The pure water permeability (PWP) and rejection of TFC-BDSA and commercial membranes at a NaCl concentration of 20 g L−1.

247

248 249 250

Figure 3. FESEM images of (a) the PES substrate surface; (b) cross-section of the PES substrate; (c) TFCBDSA-0.2 surface; and (d) cross-section of TFC-BDSA-0.2.

251 252



253

254

Page 14 of 32

Table 1. Contact angles and thicknesses of the PES substrate and the NF270 and TFC-BDSA-0.2 membranes. Membrane

Contact angle ( ° )

Thickness ( nm )

MSE a

PES substrate

60.3±0.4

--

--

NF270

30.3±0.8

66.54±2.97

3.721E-10

TFC-BDSA-0.2

65.6±0.7

43.24±3.84

1.653E-10

a) Mean Squared Error.

255

The flux and rejection of the TFC-BDSA-0.2 membrane as functions of salt concentration

256

are displayed in Figure S5. Both parameters decreased with an increase in salt concentration. By

257

increasing the NaCl content, the actual trans-membrane pressure was considerably lowered due

258

to the increased osmotic pressure. This led to the loss of water permeation. On the other hand,

259

the rejection also declined correspondingly, which could be attributed to the significantly

260

weakened Donnan effect brought about by the charge-shielding caused by the enhanced ionic

261

strength.6


Page 15 of 32


262

3.2 Separation Performance for Saline Textile Waster

263

3.2.1 Diafiltration Process

264 265 266

Figure 4. Variations in NaCl concentrations of the feed and permeate and the CR concentration in the feed during diafiltration for (a) (b) NF270 and (c) (d) TFC-BDSA-0.2.

267 268

As discussed above, although a higher salt concentration led to a higher penetration ratio,

269

which is consequently beneficial for the dye/salt separation (see Figure S5), it inevitably made

270

the feed solution more concentrated. Eventually, the operation load increased and caused severe

271

membrane fouling. Therefore, the dye concentration was maintained within an acceptable range

272

during diafiltration by adding a certain amount of pure water to the feed once the water recovery

273

ratio reached 50%. Both membranes showed almost constant CR rejections of over 99%

274

throughout the entire process (Figure 4 (b) and (d)), suggesting negligible dye loss.



Page 16 of 32

275

Moreover, if a membrane could be obtained with a 100% passage of NaCl, the salt

276

concentration should be exactly the same for the feed and permeate. Thus, an equal volume of

277

added water would lead to a two-fold dilution of the solution. As expected, in Figure 4 the NaCl

278

concentration decreased markedly for both the NF270 and TFC-BDSA-0.2 membranes.

279

However, the former showed a more apparent decline at every entry. As a result, an overall water

280

supply of 2000 mL was consumed with NF270 to fulfill the criterion (CNaCl < 0.6 g L−1 in the

281

feed)4. This corresponds to a water consumption of four times that of the feed volume. In

282

contrast, TFC-BDSA-0.2 required only 1500 mL of water (three times the feed volume) to meet

283

the criterion. This could be attributed to its much higher permeability and lower NaCl rejection,

284

as mentioned earlier.

285

At the end of the separation procedure, it was possible to recover about 97.7% and 97.0% of

286

the NaCl from the permeate using the TFC-BDSA-0.2 and NF270 membranes, respectively.

287

Notably, the entire process required about 658 min to complete when using the former

288

membrane, whereas the latter required 1231 min, which is nearly twice as long. Considering the

289

scaled-up applications, shorter operation times and lower water consumptions are crucial for

290

industrial processes as these effectively reduce the production cost. This separation process can

291

be followed by a multiple-effect evaporation or recrystallization method to yield a pure NaCl

292

product.

293 294 295

Table 2. Comparison of the separation performance of TFC-BDSA-0.2 with commercially available and other lab-made membranes. PWP

Rejection/ %

Conditions

Type of membranes

ref L m-2 h-1 bar-1

NaCl

CR


(NaCl + CR)

Page 17 of 32


Modified CA hollow fiber

4.95

61.5

99.8±0.1

0.5+0.1 g L-1

31

PEI/CMCNa/PP

14.1±0.2

36.5

99.4±0.2

0.5+0.05 g L-1

32

PVA/PSSNa

8.4±0.1

56.1

99.7±0.04

0.5+0.05 g L-1

33

Sepro NF 2A

10.5

30

99.96±0.03

20+1 g L-1

4

Sepro NF 6

13.7

10

99.93±0.03

20+1 g L-1

4

Sericin–TMC

12.6±0.06

40.8

99.8

0.5+0.1 g L-1

34

HPAN/PEI

25.1

5

97.1±0.3

1+0.1 g L-1

17

NF270

14.5±1.3

7.9±0.6

99.8±0.1

20+1 g L-1

This work

TFC-BDSA-0.2

48.1±2.1

1.4±0.2

99.1±0.3

20+1 g L-1

This work

296 297

Table 2 summarizes the general separation performance of TFC-BDSA-0.2 along with

298

commercially available and other lab-made membranes, with regards to their PWP and rejections

299

towards CR and NaCl. Regardless of the ionic strength, all the listed membranes exhibited an

300

excellent CR rejection. TFC-BDSA-0.2 also showed the highest permeability for the NaCl

301

solute. It is worth noting that the PWP of our membrane reached a value as high as 48.1 ± 2.1 L

302

m−2 h−1 bar−1, which is in the higher end of the range covering the NF membranes as compared to

303

the data published previously This indicates its outstanding prospects for dye/salt separations.



304

Page 18 of 32

3.2.2 Concentration Process

(a) 3.0

-1

2.0

4.0 3.5 3.0 2.5

1.5

2.0 0.795

0.96

1.0 0.5

1.5 1.0

108.5%

Concentration Factor

2.5 Concentration / g L

4.5

2.78 NaCl Content in Feed NaCl Content in Permeate Actual Dye Content in Feed Calculated Dye Content in Feed Concentration Factor

0.5

0.46

0

50 100 150 200 Operation Time / min

250

0.0

305 4.5

NaCl Content in Feed 2.62 NaCl Content in Permeate Actual Dye Content in Feed Calculated Dye Content in Feed Concentration Factor

2.5 2.0

4.0 3.5 3.0 2.5

1.5 1.0

2.0 0.754

1.5 0.45

26.9 %

0.5

0.5

0.35

0.0

0

1.0

Concentration Factor

NaCl Concentration / g L

-1

(b) 3.0

20

40 60 80 Operation Time / min

100

0.0 120

306 307 308

Figure 5. NaCl concentrations of the feed and permeate, and the dye concentration in the feed at different concentration factors during the pre-concentration process. (a) NF270 and (b) TFC-BDSA-0.2.

309 310

The fractionation of the dye and salt components was followed by the concentration of the

311

CR solution for the TFC-BDSA-0.2 membrane, since this aids dye recovery and reuse under high


Page 19 of 32


312

concentrations (e.g., salting out or recrystallization).35,

36

313

NF270 for comparison, the salt and dye contents were simultaneously monitored at equal CF

314

intervals during the pre-concentration process. Both membranes showed a slight loss of dye over

315

this period, as evidenced by the closed symbols in Figure 5 that lie between the actual and

316

calculated values. In brief, the TFC-BDSA-0.2 membrane showed a CR penetration of merely

317

~0.8% at a CF of 3.5, whereas NF270 gave a value about 0.1%. Apart from the excellent dye

318

rejection abilities of the membranes, the residual salt concentration dramatically increased by

319

108.5%—from the original 0.46 to 0.96 g L−1—with NF270. However, it remained steady at a

320

low percentage (26.9%) in the case using the TFC-BDSA-0.2 membrane. This phenomenon

321

could be explained as follows: Firstly, with the increased concentration in the feed, more CR

322

molecules were likely to adhere to the membrane surface, resulting in the formation of a cake

323

layer.4 Once most of the NaCl is removed from the feed, the charge-shielding at the membrane

324

surface would be reduced due to the significantly weakened ionic strength.6 Based on the fewer

325

negative charges (Figure S3) and larger pores size (Figure S4), the TFC-BDSA-0.2 membrane

326

was expected to have a lower rejection ability than NF270, even to the residual NaCl, deriving

327

from Donnan effect.

Using TFC-BDSA-0.2 along with

328

The comparison of the two membranes in the pre-concentration process is analogous to that

329

for the dye/salt separation. NF270 required ca. 250 min to obtain a CF of 3.5, with a final dye

330

content in the feed of 2.78 g L−1. In contrast, the process using the TFC-BDSA membrane was

331

faster, requiring only 107 min, proving its time efficiency.



Page 20 of 32

332 333 334

Figure 6. Variations in fluxes, dye rejections, and dye concentrations during the deep-concentration process for (a) (b) NF270 and (c) (d) TFC-BDSA-0.2.

335 336

Immediately after the pre-concentration treatment, a deep-concentration process was carried

337

out for the dye solution with a final CF of around 10. In contrast to the nearly constant water flux

338

in the former process, the flux decreased considerably during the deep-concentration process, as

339

shown in Figure 6. In brief, the NF270 water permeation declined to only one fourth (2.0 L m−2

340

h−1 bar−1) of the original (8.2 L m−2 h−1 bar−1). However, TFC-BDSA-0.2 maintained an

341

acceptable level of 6.3 L m−2 h−1 bar−1. Therefore, the time required for the latter membrane was

342

also significantly less, i.e., about 1115 and 782 min, respectively.

343

Notably, the solution became relatively viscous at the end of the test. However, a stable

344

rejection of over 99.4% was continuously observed with both membranes. By comparing the


Page 21 of 32


345

experimental and calculated values, the dye losses were found to be as low as 0.4% and 1.0% for

346

NF270 and TFC-BDSA-0.2, respectively. These again reflect the excellent rejection abilities of

347

both membranes to CR. One advantageous aspect is the negative charges of the membranes that

348

strongly repel the anionic dye molecules, which are responsible for the good rejection observed

349

in the diluted state. Also, it is likely that the gradually generated cake layer played the role of a

350

secondary filtration barrier, providing an enhanced resistance to molecular penetration in the

351

highly concentrated solutions.

352

3.3 Regeneration Performance

353

Although the dye rejection abilities of both membranes were comparable, both the MWCO

354

and mean pore size were greater for TFC-BDSA-0.2 than NF270. Hence, the CR molecules had

355

more opportunities to enter the polyamide layer of the former membrane, which inevitably

356

resulted in a more serious fouling. Therefore, it was necessary to find a proper cleaning method,

357

especially one using organic solvents, to regenerate the separation capability of the TFC

358

membranes. The comparisons in Figure 7 (a) and (b) show that TFC-BDSA-0.2 had a moderate

359

FRR of 84.0% after back-washing with water, which was inferior to the 92.0% obtained with

360

NF270. This result further confirms the more significant fouling that occurred on the surface of

361

TFC-BDSA-0.2. However, after using a 20% ethanol/water solution, its FRR considerably

362

increased to 92.3% and its rejection to CR remained constant. In contrast, although the FRR

363

steadily increased for NF270, its rejection of CR kept decreasing after contact with the alcohol

364

solution. In particular, the CR rejection decreased by about 0.64% when the concentration of

365

ethanol was increased to 40%. This indicates the possibility of damage or degradation of the

366

polyamide layer. Reports have suggested that the typical semi-aromatic poly(piperazine amide)

367

may suffer excessive swelling and/or cracking due to strong solvent–polymer interactions;19, 20



Page 22 of 32

368

these result in the detachment of the barrier layer from the substrate. In contrast, TFC-BDSA-0.2

369

even showed a slight increase in its rejection ability, indicating its excellent stability when

370

exposed to the ethanol solution. Since piperazine is the most commonly used precursor in the

371

fabrication of commercial NF membranes, including NF270, their chemical structures consist of

372

flexible cycloalkyl groups. Therefore, ethanol molecules tend to enter the pores of the polyamide

373

matrix along with diffusing water molecules, leading to the pore expansion and consequent

374

volumetric swelling.20,

375

rigidity—the TFC-BDSA membranes were expected to have strong shape-retention capabilities.

376

In addition, more hydrogen bonds could be generated between the ethanol molecules and the

377

sulfonated polymeric matrix due to the -SO3− groups, which may effectively reduce the

378

membrane swelling and curing compared to that seen with NF270.38, 39

37, 38

Nevertheless, based on the biphenyl unit—which could confer

(a) 110

TFC-BDSA-0.2 NF270

105

FRR /%

100 95 90 85 80

379

PW

10%

20%

40%



(b)

Normalized Dye Rejection Variation /%

Page 23 of 32

0.8

TFC-BDSA-0.2 NF270

0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8

PW

380

95

20%

40% 0.40

FRR Dye Rejection Variation CF:2.5

0.35 0.30

CF:10

CF:5

FRR

0.25 90

0.20 0.15

85

0.10 0.05

80

381 382 383 384

PW

20 %

PW

20 %

PW

20 %

0.00

Normalized Dye Rejection Variation /%

(c) 100

10%

Figure 7. (a) Flux recovery ratio (FRR); (b) normalized dye rejection variations of TFC-BDSA-0.2 and NF270 using different alcohol solutions at a CF of 2.5; (c) FRR and normalized dye rejection variations of TFCBDSA-0.2 at different CFs.

385 386

For the general evaluation of the anti-fouling properties of TFC-BDSA in addition to testing

387

various ethanol contents, a 20% solution was chosen for further tests of the cleaning procedures

388

with different fouling stages (i.e., CFs). As seen in Figure 7(c), the FRRs increased slightly with



Page 24 of 32

389

increasing CF when using either pure water or the ethanol solution. This indicates that the most

390

severe form of fouling occurred in the initial step, that is, as the dye molecules entered the pores

391

or even some dead spaces in the polyamide layer. The formed cake layers were easily removed

392

by back-washing. However, the FRR of the ethanol wash was much higher than that when pure

393

water was used at every CF. For instance, the FRR reached 95.6 ± 0.7% after the alcohol

394

solution treatment at a CF of 10, whereas the FRR in the case of the pure water wash was 88.3 ±

395

0.4%. This indicates the good anti-fouling and solvent-resistant properties of TFC-BDSA-0.2.

396

On the one hand, since CR is more soluble in ethanol than in water, its removal by dissolution

397

was more efficient than relying only on the mechanical hydraulic scouring. On the other hand,

398

the membrane should also retain good dimensional and chemical stabilities in such solvents, to

399

maintain a reasonably high durability.

400

These results were subsequently proved by FESEM, as shown in Figure S6. Significant

401

amounts of cake were deposited on the membrane surface, with thicknesses in the range of 200

402

to 750 nm. Despite this, the fouling situation was suitably resolved after the membrane was

403

washed with the alcohol solution, which again demonstrates the good anti-fouling property and

404

regenerability of TFC-BDSA-0.2.

405 406

ASSOCIATED CONTENT

407

Supporting Information

408

Six supplementary Figures, two Tables and one Scheme. This material is available free of

409

charge via the Internet at http://pubs.acs.org. Optimization experiment of TFC-BDSA membrane

410

(Figure S1); The reaction process of interfacial polymerization between BDSA and TMC


Page 25 of 32


411

(Scheme S1); Polymer structures of TFC-BDSA and NF270 (Figure S2); XPS results for the PA

412

layers of NF270 and TFC-BDSA-0.2 (Table S1); Zeta potential of different membranes as a

413

function of pH (Figure S3); Molecular weight, Stokes radii and rejection of the solutes (Table

414

S2); Pore size distribution of TFC-BDSA-0.2 and NF270 (Figure S4); Separation performances

415

of TFC-BDSA-0.2 as a function of different NaCl concentrations (Figure S5); FESEM images of

416

TFC-BDSA-0.2 before and after back-washing process (Figure S6).

417

AUTHOR INFORMATION

418

Corresponding Author

419

* X. Zhang. E-mail: [email protected], Tel./fax: +86-25-84315916.

420

* L. Wang. E-mail: [email protected].

421

Notes

422

The authors declare no competing financial interest.

423

ACKNOWLEDGMENT

424

This work was financially supported by NSFC (21406117), Natural Science Foundation of

425

Jiangsu Province (BK20140782), Priority Academic Program Development of Jiangsu Higher

426

Education Institutions (PAPD) and State Key Laboratory of Separation Membranes and

427

Membrane Processes (Tianjin Polytechnic University, M2-201604).

428

REFERENCES

429

(1) Werber, J. R.; Deshmukh, A.; Elimelech, M. The Critical Need for Increased Selectivity, Not

430

Increased Water Permeability, for Desalination Membranes. Environ. Sci. Technol. Lett. 2016, 3,

431

112-120.



Page 26 of 32

432

(2) Tufa, R. A.; Curcio, E.; Brauns, E.; Van Baak, W.; Fontananova, E.; Profio, G. D. Membrane

433

Distillation and Reverse Electrodialysis for Near-Zero Liquid Discharge and low energy

434

seawater desalination. J. Membr. Sci. 2015, 496, 325-333.

435

(3) Luo, J.; Wan, Y.; Effect of highly concentrated salt on retention of organic solutes by

436

nanofiltration polymeric membranes. J. Membr. Sci. 2011, 372, 145-153.

437

(4) Lin, J.; Ye, W.; Zeng, H; Yang, J.; Shen.; Darvishmanesh, S.; Luis, P.; Sotto, A.; Van der

438

Bruggen, B. Fractionation of direct dyes and salts in aqueous solution using loose nanofiltration

439

membranes, J. Membr. Sci. 2015, 477, 183-193.

440

(5) De Vreese, I.; Van der Bruggen, B. Cotton and polyester dyeing using nanofiltered

441

wastewater. Dyes Pigm. 2007, 74 (2), 313-319.

442

(6) Shu, L.; Waite, T.; Bliss, P.; Fane, A.; Jegatheesan, V. Nanofiltration for the possible reuse of

443

water and recovery of sodium chloride salt from textile effluent, Desalination, 2005, 172, 235-

444

243.

445

(7) Afkhami, A.; Moosavi, R. Adsorptive removal of Congo red, a carcinogenic textile dye, from

446

aqueous solutions by maghemite nanoparticles. J. Hazard. Mater. 2010, 174, 398-403.

447

(8) Boeniger, M. Carcinogenecity and metabolism of azo dyes, especially those derived from

448

benzidine. DHHS (NIOSH) Tech. Rep. 1980, 80-119.

449

(9) Sakkas, V.A.; Islam, M.A.; Stalikas, C.; Albanis, T.A. Photocatalytic degradation using

450

design of experiments: a review and example of the Congo red degradation. J. Hazard. Mater.

451

2010, 175, 33-44.


Page 27 of 32


452

(10) Han, G.; Liang, C.-Z.; Chung, T.-S.; Weber, M.; Staudt, C.; Maletzko, C. Combination of

453

forward osmosis (FO) process with coagulation/flocculation (CF) for potential treatment of

454

textile wastewater. Water Res. 2016, 91, 361-370.

455

(11) Liang, C.-Z.; Sun, S.-P.; Li, F.-Y.; Ong, Y.-K.; Chung, T.-S. Treatment of highly

456

concentrated wastewater containing multiple synthetic dyes by a combined process of

457

coagulation/flocculation and nanofiltration. J. Membr. Sci. 2014, 469(11), 306-315.

458

(12) Lin, J.; Ye, W.; Huang, J.; Ricard, B.et.al. Toward Resource Recovery from Textile

459

Wastewater: Dye Extraction, Water and Base/Acid Regeneration Using a Hybrid NF-BMED

460

Process. ACS Sustainable Chem. Eng. 2015, 3, 1993-2001.

461

(13) Lin, J. Y.; Ye, W. Y.; Baltaru, M. C.; Tang, Y. P.; Bernstein, N. J.; Gao, P. Tight

462

ultrafiltration membranes for enhanced separation of dyes and Na2SO4 during textile wastewater

463

treatment. J. Membr. Sci. 2016, 514, 217-228.

464

(14) Shao, L.; Cheng, X.Q.; Liu, Y.; Quan, S.; Ma, J.; Zhao, S.Z.; Wang, K.Y. Newly developed

465

nanofiltration (NF) composite membranes by interfacial polymerization for Safranin O and

466

aniline blue removal. J. Membr. Sci. 2013, 430, 96-105.

467

(15) Alicia, K. J. AN.; Guo, J. X.; Lee, E. J.; Jeong, S. H.; Zhao, Y. H.; Wang, Z. K.; Leiknes, T.

468

PDMS/PVDF hybrid electrospun membrane with superhydrophobic property and drop impact

469

dynamics for dyeing wastewater treatment using membrane distillation. J. Membr. Sci. 2017,

470

525, 57-67.



Page 28 of 32

471

(16) Ge, Q. C.; Wang, P.; Wan, C. F.; Chung, T. S. Polyelectrolyte-Promoted Forward

472

Osmosis−Membrane Distillation (FO−MD) Hybrid Process for Dye Wastewater Treatment.

473

Environ. Sci. Technol. 2012, 46, 6236-6243.

474

(17) Zhao, S.; Wang, Z. A loose nanofiltration membrane prepared by coating HPAN UF

475

membrane with modified PEI for dye reuse and desalination. J. Membr. Sci. 2017, 524, 214-224.

476

(18) Yu, S. C.; Chen, Z. W.; Cheng, Q. B.; Lv, Z. H.; Liu, M. L.; Gao, C. J. Application of thin-

477

film composite hollow fiber membrane to submerged nanofiltration of anionic dye aqueous

478

solutions. Sep. Pure. Technol. 2012, 88, 121-129.

479

(19) Lv, L.; Xu, J.; Shan, B.; Gao, C. Concentration performance and cleaning strategy for

480

controlling membrane fouling during forward osmosis concentration of actual oily wastewater. J.

481

Membr. Sci. 2017, 523, 15-23.

482

(20) Kwiatkowski, J.; Cheryan, M. Performance of Nanofiltration Membranes in Ethanol. Sep.

483

Sci. Technol. 2005, 40(13), 2651-2662.

484

(21) Yang, X. J., Livingston, A. G.; Freitas dos Santos, L. Experimental observations of

485

nanofiltration with organic solvents. J. Membr. Sci. 2001. 190(1), 45-55.

486

(22) Hu, J. H.; Lv, Z. W; Xu, Y.; Zhang, X.; Wang, L. J. Fabrication of a high-flux sulfonated

487

polyamide nanofiltration membrane: Experimental and dissipative particle dynamics studies. J.

488

Membr. Sci. 2016, 505, 119-129.

489

(23) Hu, J. H.; Liu, Y.; Cao, X. C.; Zhang, P.; Zheng, J. F; Li, M.; Zhang, X.; Wang, L. J. A

490

comprehensive physico-chemical study on the molecular structure effects of sulfonated


Page 29 of 32


491

polyamide thin-film composites. Mol. Syst. Des. Eng. 2017, 2, 57-66.

492

(24) Richards, L, A.; Vuachère, M.; Schäfer, A. I. Impact of pH on the removal of fluoride,

493

nitrate and boron by nanofiltration/reverse osmosis. Desalination, 2010, 261, 331-337.

494

(25) Pan, Y. Y.; Xu, R. P.; Lv, Z. H.; Yu, S. C.; Liu, M. L.; Gao, C. J. Enhanced both perm-

495

selectivity and fouling resistance of poly(piperazine-amide) nanofiltration membrane by

496

incorporating sericin as a co-reactant of aqueous phase. J. Membr. Sci. 2017, 523, 282-290.

497

(26) Li, M.; Lv, Z. W.; Zheng, J. F.; Hu, J. H.; Jiang, C.; Mitsuru, Ueda.; Zhang, X.; Wang, L. J.

498

Positively Charged Nanofiltration Membrane with Dendritic Surface for Toxic Element

499

Removal. ACS Sustainable Chem. Eng. 2017, 5(1), 784-792.

500

(27) Zheng, J. F; Li, M.; Yu, K.; Hu, J. H.; Zhang, X.; Wang, L. J. Sulfonated multiwall carbon

501

nanotubes assisted thin-film nanocomposite membrane with enhanced water flux and anti-

502

fouling property. J. Membr. Sci. 2017, 524, 344-353.

503

(28) Lv, Z. W.; Hu, J. H.; Zheng, J. F.; Zhang, X.; Wang, L. J. Antifouling and High Flux

504

Sulfonated Polyamide Thin-Film Composite Membrane for Nanofiltration. Ind. Eng. Chem. Res.

505

2016, 55, 4726-4733.

506

(29) Karan, S.; Jiang, Z. W.; Livingston, A. G. Sub-10 nm polyamide nanofilms with ultrafast

507

solvent transport for molecular separation. Science, 2015, 348, 1347-1351.

508

(30) Shaughnessy, B. O.; Sawhney, U. Polymer reaction kinetics at interfaces. Phys. Rev. Lett.

509

1996, 76, 3444-3447.

510

(31) Yu, S.; Cheng, Q.; Huang, C.; Liu, J.; Peng, X. Cellulose acetate hollow fiber nanofiltration



Page 30 of 32

511

membrane with improved permselectivity prepared through hydrolysis followed by

512

carboxymethylation. J. Membr. Sci. 2013, 434(5), 44-54.

513

(32) Chen, Q.; Yu, P.; Huang, W.; Yu, S.; Liu, M. High-flux composite hollow fiber nanofiltration

514

membranes fabricated through layer-by-layer deposition of oppositely charged crosslinked

515

polyelectrolytes for dye removal. J. Membr. Sci. 2015, 492, 312-321.

516

(33) Liu, M.; Zhou, C.; Dong, B.; Wu, Z.; Wang, L. Enhancing the permselectivity of thin-film

517

composite poly(vinylalcohol) (PVA) nanofiltration membrane by incorporating poly(sodium-p-

518

styrene-sulfonate) (PSSNa). J. Membr. Sci. 2014, 463, 173-182.

519

(34) Zhou, C.; Shi, Y.; Sun, C.; Yu, S.; Liu, M. Thin-film composite membranes formed by

520

interfacial polymerization with natural material sericin and trimesoyl chloride for nanofiltration.

521

J. Membr. Sci. 2014, 471(1), 381-391.

522

(35) Han, H. K.; Jung, H. K. Solubility and growth rate of reactive blue49 and black8 dyes in

523

salting-out system. Korean J. Chem. Eng. 2009, 26, 246-249.

524

(36) Cong, H. P.; Yu, S. H. Recrystallization and shape control of crystals of the organic dye

525

acid green 27 in a mixed solvent. Chem. Eur. J. 2007, 13, 1533-1538.

526

(37) Geens, J.; Van der Bruggen, B.; Vandecasteele, C. Characterization of the solvent stability

527

of polymeric nanofiltration membranes by measurement of contact angles and swelling. Chem.

528

Eng. Sci. 2004, 59, 1161-1164.

529

(38) Heffernan, R.; Semião, A. J. C.; Desmond, P.; Cao, H.; Safari, A.; Habimana, O.; Casey, E.

530

Disinfection of a polyamide nanofiltration membrane using ethanol. J. Membr. Sci. 2013, 448,


Page 31 of 32


531

170-179.

532

(39) Lencki, R. W.; Williams, S. Effect of nonaqueous solvents on the flux behavior of

533

ultrafiltration membranes. J. Membr. Sci. 1995, 101, 43-51.



534

For Table of Content Use Only

535

536


Page 32 of 32

Fractionation and Concentration of High-Salinity ... - ACS Publications

Recommend Documents