Application of ceramic membranes in the treatment of oilfield-produced water: Effects of polyacrylamide and inorganic salts

Desalination 309 (2013) 84–90

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Application of ceramic membranes in the treatment of oilfield-produced water: Effects of polyacrylamide and inorganic salts Huiqin Zhang, Zhaoxiang Zhong, Weihong Xing ⁎ Membrane Science & Technology Research Center, State Key Lab of Materials-Oriented Chemical Engineering, Nanjing University of Technology, 5 Xinmofan Road, Nanjing 210009, China

H I G H L I G H T S ► ► ► ►

Ceramic membranes with different membrane pore sizes were studied for their use in produced water treatment. The effects of the NaCl concentrations and the PAM concentrations on the filtration performance were investigated. Interactions between PAM, NaCl and membrane fouling were discussed. The mechanism of membrane fouling and the cleaning methods were also investigated.

a r t i c l e

i n f o

Article history: Received 31 May 2012 Received in revised form 10 September 2012 Accepted 11 September 2012 Available online 11 October 2012 Keywords: Polyacrylamide NaCl solution Ceramic membrane Membrane fouling

a b s t r a c t Polyacrylamide has been widely used for polymer flooding in oil production. Wastewater is produced in the polymer flooding process. In this work, a ceramic membrane system was used to treat the wastewater. The effects of membrane pore size and PAM concentrations on the filtration performance were investigated. With the increase of the membrane pore size, the flux declined severely. When the PAM concentration was lower than the critical micelle concentration (CMC), the pseudo-steady flux decreased with the PAM concentration. When the PAM concentration was close to or higher than the CMC, the PAM concentration had little influence on the PSF. For the ultrafiltration membranes, the average MW of PAM in the permeate changed little with different PAM concentrations. However, for the microfiltration membranes, the average MW of PAM in the permeate decreased with the PAM concentration. The effect of NaCl concentration on the filtration of PAM solutions was studied. As the NaCl concentration increased, the change of PAM morphology caused the PSF to decrease significantly. Membrane fouling mechanisms and membrane cleaning methods were also discussed. Pore blocking and gel layer formation both contributed to the flux decline. The fouled membrane was easily cleaned by a NaOH aqueous solution with pH > 12. © 2012 Elsevier B.V. All rights reserved.

1. Introduction Oilfield-produced water contains different amounts of inorganic salts, suspended solids and oil [1]. Produced-water reinjection and drilling fluid recycling typically require the removal of oil and suspended solids [2]. Microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), membrane distillation and their combined processes are often used to treat the produced water. Most previous reports have focused on the influence of oil on the membrane filtration process. Ebrahimi et al. [3,4] investigated a combined process (UF + NF) for treatment of the produced water. More than 99.5% of the oil and 49% of the total organic carbon (TOC) were removed. The membrane technology used for a produced-water treatment has been reviewed by Ahmadun [5]. Ceramic membranes have been applied to the concentration of aggressive effluents such as black liquor from pulp and paper industries, ⁎ Corresponding author. E-mail address: [email protected] (W. Xing). 0011-9164/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.desal.2012.09.012

to the treatment of acidic effluents from the steel industry, to the treatment of secondary wastewater effluents and so on [6,7]. Due to their extreme stability in harsh environments, ceramic membrane has been reported to be a promising way for produced water purification [2–4]. To improve oil recovery, polymer flooding, alkaline-surfactant polymer flooding and surfactant polymer flooding have been subsequently used in oil production. PAM was the most common flooding agent. When PAM is used for polymer flooding, the produced water contains a considerable amount of residual hydrolyzed PAM [1]. The hydrolyzed PAM residue disperses the suspended solids and oil in the effluent, which makes it difficult to remove [8]. The hydrolyzed PAM significantly influences the membrane performance in the treatment of the produced water. Wang [9] investigated the contribution of the main pollutants to the oilfield polymer-flooding wastewater to the critical flux. The hydrolyzed PAM had a more significant impact on the critical flux than did the oil and the suspended solids. Inorganic salts affect produced water chemistry in terms of buffering capacity, salinity, and scale potential. The salt concentration of the

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produced water may vary from a few parts per million (ppm) to approximately 300,000 mg/L [5]. For high salt concentrations, the pollutant removal efficiencies decrease significantly [10]. The reason was that the size of PAM shrinkage with the salt concentration increased. At quite high ionic strengths, the repulsion between PAM molecules is ‘screened’ by ions in solution so that the coil expansion is not so significant [11]. In summary, the effects of the oil concentration on membrane fouling during produced-water purification have been reported. However, the effect of PAM in high-concentration inorganic salt solutions on membrane fouling has seldom been investigated. Especially, the interactions of NaCl concentration (in particular, 25% (w/w)), PAM and membrane fouling have seldom been investigated. In this study, the interactions of NaCl concentration, PAM and membrane fouling are investigated. The membrane fouling mechanism for different NaCl concentrations is also discussed. 2. Materials and methods 2.1. Materials

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60 °C for 2 h. To obtain the exact morphology of the fouled membrane, the samples were not sputter-coated with Au/Pd. The functional groups of the fouled membrane surface were analyzed by Fourier transform infrared spectroscopy (FT-IR, Tensor 27 FT-IR spectrometer, Bruker Optics, Germany), using spectroscopic purity (SP) KBr (Sinopharm Chemical Reagent Co., Ltd., China). The FT-IR equipment was operated with a resolution of 4 cm−1 and a scanning range of 4000 cm−1 to 400 cm−1. The average MW of the PAM in the permeate was determined by the intrinsic viscosity, which has been described in the ChinaNational Standard [12]. The particle size of PAM was determined by a dynamic laser light-scattering measurement, which was performed at room temperature. The average size of PAM was 71.5 nm (Fig. 1a), which was measured according to the report by Barari [13]. The morphology of PAM was also analyzed by FESEM (Fig. 1b). The structure of PAM was comb-shaped. The morphology of the PAM also confirmed that the PAM molecular was extended in the NaCl dilute solution.

2.3. Experimental procedures

Ceramic membranes with 19 channels were used. The pure water fluxes (PWF) of membranes with average pore sizes of 20, 50, 200 and 500 nm were measured to be 227.5, 956.8, 1074.2 and 1330.4 L m −2 h −1 (0.1 MPa, 25 °C), respectively. For the membranes with pore sizes of 20 and 50 nm, the membrane material was ZrO2/ α-Al2O3. For the membranes with pore sizes of 200 and 500 nm, the membrane material was α-Al2O3/α-Al2O3. All of these membranes had an external diameter of 31 mm, a channel diameter of 4 mm, a length of 500 mm and a membrane area of 0.1 m 2. The membranes were supplied by Jiangsu Jiuwu Hitech Co., Ltd. (China). Nonionic PAM used in this work was supplied by the SNF group of France. The average molecular weight (MW) was 1.0 × 10 4 kDa, a value that was provided by the suppliers. NaCl was analytically pure from Shanghai Lingfeng Chemical Reagent Co., Ltd. 2.2. Analysis methods The surface morphology and the cross-section morphology of the membranes before and after the filtration were investigated by field-emission scanning electron microscopy (FESEM, S-4800, Hitachi, Japan). The fouled membranes (fouled membranes were defined as the membranes which filtered PAM solutions for 3 h) were dried at

a

The NaCl solutions were prepared by dissolving preweighed quantities of NaCl in deionized water. Different concentrations of PAM were added to the NaCl solutions. The mixing process continued for 30 min at a stirring speed of 150 rpm. The concentrations of PAM were 5, 15, 30 and 50 mg/L, and the concentrations of NaCl were 0.1%, 3% and 25% (w/w). The critical micelle concentration (CMC) of the PAM aqueous solution was determined by the surface tension method (KSV-Sigma70, Finland) at 20 °C [14,15]. Aqueous solutions with different PAM concentrations were used to determine the CMC of the PAM aqueous solution. The membrane setup of a cross-flow filtration was described in detail previously [16]. In this work, a parallel operation with four membrane modules was used. Permeate and retentate were returned to the feed tank to ensure the equilibrium of the feed water. The transmembrane pressure (TMP) was 0.1 MPa, and the cross-flow velocity (CFV) was 2 m/s. The temperature of the feed was 25 ± 2 °C. Flux curves were monitored during the course of the experiments. After each run, the system was thoroughly rinsed with deionized water to remove a residual process solution. The membrane was cleaned by circulating NaOH (Shanghai Chemical Reagents Co. Ltd.,

b 50

Intensity/%

40

30

20

10

0 0

50

100

150

200

Size/nm Fig. 1. Molecular size distribution and SEM morphology of PAM (a — molecular size distribution of PAM, b — FESEM-morphology of PAM (NaCl concentration was 0.1 wt.% and PAM concentration was 100 mg/L.)).

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800

70

Flux/L/(m2·h)

600

400

20nm

300

Interfacial tension / mN/m

PSF/L/(m2· h)

400

50nm 200nm

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500nm 100

0

0

100

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Membrane pore size/nm

200

68

66

64

60 0

0

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120

160

CMC=25mg/L

62

0

10

20

30

40

50

PAM concentration/mg/L

200

Time/min

Fig. 4. Effect of PAM concentration on the interfacial tension.

Fig. 2. Effect of membrane pore size on the flux (PAM — 5 mg/L, NaCl — 3% (w/w), TMP — 0.1 MPa, CFV — 2 m/s, t — 25 °C).

PR China) solution (pH > 12) at 40 °C for 2 h. The apparatus was then rinsed with deionized water until the pH returned to 7. To ensure that the experiments had a good reproducibility, the PWF was measured using deionized water after every cleaning operation.

3. Results and discussion 3.1. Effect of the membrane pore size on the filtration process Fig. 2 shows typical experimental data for the filtrate flux as a function of time during constant TMP cross-flow filtration for different membranes. The ratios of Jp/J0 (Jp — PSF, J0 — PWF) were 0.75, 0.20, 0.17 and 0.19 for the membranes with pore sizes of 20, 50, 200 and 500 nm, respectively. The flux decline was caused by the viscosity increase and membrane fouling. The viscosity of a pure NaCl solution was calculated by Eq. (1) [17] (the error between the calculated value and experiment value (measured by Ubbelohde capillary viscometer) was less than 4.4%. Where C was the molar concentration of the brine solution, μc was the viscosity of the brine solution when the NaCl concentration was C mol L −1 at 25 °C and μ0 was the viscosity of pure water at 25 °C). When the NaCl concentration increased from 0 to 3% (w/w), the viscosity of the solutions increased by 5%. The flux changed by less than 5% as a result of the viscosity change. In other words, most of the flux decline was due to the membrane fouling by PAM.

As shown in Fig. 2, the flux of the membranes with large pore sizes decreased rapidly from the initial water flux values compared with the membranes with small pore sizes. According to the critical flux theory, this might be due to the quick deposition of PAM on the membrane with large pores caused by the high initial flux [18]. These conclusions were also reported for humic acid and disinfection by-product fouling of UF and MF membranes [19–21]. pffiffiffi 2 μ c =μ 0 ¼ 1 þ 0:0062 C þ 0:0793C þ 0:008C :

ð1Þ

3.2. Effect of PAM concentration on the membrane performance The PSF values for the filtration of PAM solutions with different concentrations are shown in Fig. 3. The PSF decreased quickly at PAM concentrations from 5 to 15 mg/L. When the PAM concentration was greater than 15 mg/L, the PAM concentration had little influence on the PSF. Fig. 4 shows the interfacial tension of the aqueous solution for different PAM concentrations. The CMC of the PAM aqueous solution was 25 mg/L. The concentration polarization resistance decreased when the PAM concentration was close to or higher than the CMC of the PAM solution. As the PAM concentration increased, the resistance caused by pore blocking and the gel layer increased. The PSF did not decrease with the PAM concentration. This result was also reported for sodium dodecyl benzene sulfonate filtration with hydrophilic polyethersulfone (PES) membranes [22].

300

PSF/L(m2·h)

200 150 100 50 0

15

Average MW / ×105

20nm 50nm 200nm 500nm

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5mg/L 30mg/L

12

9 UF

MF

6

3

0

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PAM concentration/ mg/L

0

0

100

200

300

400

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Membrane pore size/nm Fig. 3. Effect of PAM concentration on PSF of the membrane with different pore sizes (NaCl — 3%, CFV — 2 m/s, TMP — 0.1 MPa, t — 25 °C).

Fig. 5. Average MW of the permeate with different membrane pore sizes.

H. Zhang et al. / Desalination 309 (2013) 84–90

250

200

PSF/ L·m-2·h-1

Jc ¼

20nm 50nm 200nm 500nm

150

100

50

0

0.1%

3%

25%

Salt concentrations/ %(w/w) Fig. 6. Effect of NaCl concentration on PSF of the membrane with different pore sizes (CFV — 2 m/s, TMP — 0.1 MPa, cPAM — 5 mg/L).

Intrinsic viscosity was used to determine the average MW of the PAM. The average MW of the permeate is shown in Fig. 5. As the pore size of the membranes increased, the average MW of the permeate increased. For the UF (20 and 50 nm) membranes, the average MW of PAM in the permeate changed little with different PAM concentrations. However, for the MF (200 and 500 nm) membranes, the average MW of PAM in the permeate decreased with the increasing PAM concentration. The reason was that with the increase of the PAM concentration, the pore blocking was more severe and the effective membrane pore size became small for the MF membranes. As the effective membrane pore size decreased, PAM molecules with large MWs were rejected.

3.3. Effect of NaCl concentration on flux To examine the interactions between the PAM, membranes, and NaCl, the filtration characteristics during the filtration of feed solution with different concentrations of NaCl were studied. The PSF for the filtration is shown in Fig. 6. It can be seen that the PSF decreased as the NaCl concentration increased. The PSF decline ratios of these membranes were 51%, 57%, 51% and 41% when the NaCl concentration increased from 0.1% (w/w) to 25% (w/w), respectively. Combining the Darcy's law (Eq. (2)) with Eq. (1), a formula (Eq. (3)) is then derived for calculating the PSF of pure NaCl solution. The results showed that increasing the concentration of the NaCl solution from 0.1% (w/w) to 25% (w/w) resulted in a 27% decline of PSF. Therefore, for the PAM–NaCl solution, the decrease in the flux showed that the interactions between NaCl and PAM were significant and not negligible.

J¼

ΔP μR

ð2Þ

ΔP   : pffiffiffi μ 0 1 þ 0:0062 C þ 0:0793C þ 0:008C 2 Rm

87

ð3Þ

Possible mechanisms of membrane fouling for interactions between NaCl and PAM with different concentrations of NaCl in the feed are shown in Fig. 7. Fig. 7 also illustrates the three morphologies of PAM for increasing NaCl concentrations. We inferred that when the filtration of the PAM solution with 0.1% (w/w) NaCl was performed (Fig. 7a), a porous gel layer was formed, and a slight pore blocking occurred. When the filtration of the PAM solution with 3% (w/w) NaCl was performed, the PAM morphologies change from comb-shaped (Fig. 1b) to spherical (Figs. 7b and 8b). In this situation, the pore blocking became severe, and the gel layer became dense. The reason for the change of the PAM morphologies was that as the salt concentration was reduced, PAM adopted a more expanded configuration. At quite high ionic strengths, the PAM expansion is not so significant [11]. When the filtration of the PAM solution with 25% (w/w) NaCl was performed, the size of the PAM became smaller than the 3% (w/w) NaCl used as the feed (Fig. 7c). The pore blocking became more severe, and the gel layer resistance increased. The PAM molecules had a more compact geometry that allowed them to pass through the membrane. These types of interactions have also been observed in many synthetic polymers [11,23] and in humic acid [24]. 3.4. Membrane fouling mechanism SEM micrographs of the surface and cross-sections of fouled membranes (PAM concentration was 50 mg/L, NaCl concentration was 3% (w/w)) are shown in Fig. 8. The figure shows the particles, which are approximately 0.1 μm in size, and their aggregates depositing on the membrane surface. The thickness of the fouled layer was 2–3 μm, as shown in Fig. 8d. Compared to the new membrane, the surface of the fouled membrane was compact, thus leading to an increase in membrane filtration resistance. This is the reason why the PSF was much lower than the pure water flux. The FT-IR spectrum of the fouled membrane surface (Fig. 9) was analyzed qualitatively. The analysis showed that the fouled membrane surface contains N\H, C\H from the methylene group and C_O. All of these groups were functional groups of PAM [25–27]. Other transmittance peaks in Fig. 9 correspond to membrane materials, as reported by He and Gao [28,29]. Therefore, the FT-IR spectra clearly support the conclusion that the membrane surface was covered by PAM. The fouled surface seemed dense in dry conditions, while under hygrometric conditions, the fouled surface became more compact. Therefore, this graph shows that the gel layer was one of the reasons for membrane fouling. To determine the fouling mechanism of the membrane, the filtration resistance of the membrane pore size of 50 nm was analyzed. The methods were described in detail previously [30]. The value of the RT was 2.6 × 10 12 m −1. The Rm, Rp and Rc accounted for 25.8%, 35.1% and 39.1%, respectively, of the total resistance (RT); Rm was the intrinsic resistance of the new membrane. Rp was a pore blocking

Fig. 7. Schematic diagrams of fouling mechanism for the membrane with different concentrations of NaCl (a — 0.1 wt.%, b — 3 wt.%, c — 25 wt.%).

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Fig. 8. FESEM-micrograph of new ceramic membrane and fouled membrane (a — surface morphology of new membrane, b — surface morphology of fouled membrane, c — cross-section morphology of new membrane, d — cross-section morphology of fouled membrane).

resistance of the fouled membrane and Rc was the cake filtration resistance of the fouled membrane. RT was the total resistance of the fouled membrane. Rp and Rm comprised similar proportions of RT. In summary, both the pore blocking and gel layer formation had significant effects on the performance of the PAM solution filtration processes. We inferred that the membrane fouling processes were divided into two stages. First, a permeate drag force caused PAM molecule extrusion deformation, and pore blocking occurred. Second, PAM molecules formed a dense gel layer on the surface of the filtration membrane. As the filtration time increased, the thickness of the gel layer increased. This type of fouling mechanism has been reported in many colloidal particle systems [31,32]. A comprehensive analysis of filtration resistance, FT-IR spectra of the fouled membrane and SEM micrographs of the surface and

1.0 1632

1080

Transmittance/%

C=O 3437

C-H

N-H

0.6

461 655 610

0.4

4000

3200

2400

1600

Wavenumber/cm-1 Fig. 9. FT-IR spectra for fouled membrane.

800

3.5. Membrane cleaning methods The investigation of the membrane fouling indicated that the main foulant in this process was PAM. According to the chemical properties of foulants, a NaOH solution, which can dissolve the foulants, was chosen to clean the fouled membranes [33,34]. Before the chemical cleaning, deionized water was used to clean the fouled membrane. The results showed that the membrane was covered with a dense gel layer (Fig. 10a) and was blocked with PAM (Fig. 10b). Therefore, the flux was not restored (Fig. 11). Fig. 11 also showed that the membrane was restored to 90% of the original PWF after chemical cleaning. For each experiment, the PWF was measured using deionized water after the cleaning operations. The cleaning method showed a good reproducibility and was used to reverse the membrane fouled by PAM. 4. Conclusions

2858

0.8

cross-sections of the membrane indicated that pore blocking and gel layer formation both contributed significantly to the flux decline during the PAM filtration process.

PAM was the main reason for membrane fouling during the treatment of the produced water. Meanwhile, the interactions between NaCl and PAM were significant and not negligible. In this study, the following conclusions can be drawn: As the membrane pore size increased, the flux decreased more severely. The average molecular weight of PAM in the permeate also increased with the membrane pore size. When the PAM concentration was below the CMC, the PSF decreased as the PAM concentration increased. When the PAM concentration was close to or higher or greater than CMC, the PAM concentration had little influence on the PSF. For UF membranes, the average MW of PAM in the permeate changed little with different PAM concentrations. However, for the MF membranes, the average MW of PAM in the permeate decreased as the PAM concentration increased. As the NaCl concentration

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Fig. 10. The surface and cross-section of fouled membrane washed by deionized water (a — surface morphology of membrane, b — cross-section morphology of membrane).

1600 20nm 50nm 200nm 500nm

PSF/ L/(m2·h)

1200

800

400

0

a

b

c

The types of the membrane Fig. 11. Flux recovery after various cleaning methods a — fouled membrane; b — fouled membrane cleaned by deionized water; c — fouled membrane after chemical cleaning.

increased, the PSF of the membrane decreased because the increased viscosity of the feed water and the change in the PAM morphology caused more severe membrane fouling. The membrane fouling process was divided into two stages. First, the permeate drag force caused an extrusion deformation, and the large PAM molecules entered and blocked the membrane pores. Second, the PAM molecules were deposited, and dense gel layers were formed on the membrane surface. PAM was easily hydrolyzed and degraded in an alkali solution; thus, the membrane was easily cleaned by aqueous NaOH solutions (pH > 12).

Acknowledgments Financial support was provided by the National Basic Research Program (2009CB623406), the National Natural Science Foundation of China (No. 21125629, 21076102), the Research Project of Natural Science for Universities Affiliated to Jiangsu Province (10KJB530002), Key Projects in the National Science & Technology Pillar Program (2011BAE07B09-3) and the Jiangsu Provincial Science and Technology Support Program (BE2011831).

References [1] Y. Zhang, B. Gao, L. Lu, Q. Yue, Q. Wang, Y. Jia, Treatment of produced water from polymer flooding in oil production by the combined method of hydrolysis acidification-dynamic membrane bioreactor–coagulation process, J. Petrol. Sci. Eng. 74 (2010) 14–19.

[2] L. Li, R. Lee, Purification of produced water by ceramic membranes: material screening, process design and economics, Sep. Sci. Technol. 44 (2009) 3455–3484. [3] M. Ebrahimi, D. Willershausen, K.S. Ashaghi, L. Engel, L. Placido, P. Mund, P. Bolduan, P. Czermak, Investigations on the use of different ceramic membranes for efficient oil-field produced water treatment, Desalination 250 (2010) 991–996. [4] M. Ebrahimi, K.S. Ashaghi, L. Engel, D. Willershausen, P. Mund, P. Bolduan, P. Czermak, Characterization and application of different ceramic membranes for the oil-field produced water treatment, Desalination 245 (2009) 533–540. [5] A. Fakhru'l-Razi, A. Pendashteh, L.C. Abdullah, D.R. Biak, S.S. Madaeni, Z.Z. Abidin, Review of technologies for oil and gas produced water treatment, J. Hazard. Mater. 170 (2009) 530–551. [6] S. Vercauteren, K. Keizer, E.F. Vansant, J. Luyten, R. Leysen, Porous ceramic membranes: preparation, transport properties and applications, J. Porous Mater. 5 (1998) 241–258. [7] J. Llanos, P.M. Williams, S. Cheng, D. Rogers, C. Wright, A. Perez, P. Canizares, Characterization of a ceramic ultrafiltration membrane in different operational states after its use in a heavy-metal ion removal process, Water Res. 44 (2010) 3522–3530. [8] X.F. Zhao, L.X. Liu, Y.C. Wang, H.X. Dai, D. Wang, H. Cai, Influences of partially hydrolyzed polyacrylamide (HPAM) residue on the flocculation behavior of oily wastewater produced from polymer flooding, Sep. Purif. Technol. 62 (2008) 199–204. [9] X.Y. Wang, Z. Wang, Y.N. Zhou, X.J. Xi, W.J. Li, L.Y. Yang, Study of the contribution of the main pollutants in the oilfield polymer-flooding wastewater to the critical flux, Desalination 273 (2011) 375–385. [10] A. Fakhru'l-Razi, A. Pendashteh, Z.Z. Abidin, L.C. Abdullah, D.R. Biak, S.S. Madaeni, Application of membrane-coupled sequencing batch reactor for oilfield produced water recycle and beneficial re-use, Bioresour. Technol. 101 (2010) 6942–6949. [11] B. Bolto, J. Gregory, Organic polyelectrolytes in water treatment, Water Res. 41 (2007) 2301–2324. [12] Determination for limiting viscosity number of polyacrylamide, China NationalStandard, GB12005.1-1989. [13] M. Barari, M. Abdollahi, M. Hemmati, Synthesis and characterization of high molecular weight polyacrylamide nanoparticles by inverse-emulsion polymerization, Iran. Polym. J. 20 (2011) 65–76. [14] S.Y. Lin, Y.Y. Lin, E.M. Chen, C.T. Hsu, C.C. Kwan, A study of the equilibrium surface tension and the critical micelle concentration of mixed surfactant solutions, Langmuir 15 (1999) 4370–4376. [15] E. Calvo, R. Bravo, A. Amigo, J. Gracia-Fadrique, Dynamic surface tension, critical micelle concentration, and activity coefficients of aqueous solutions of nonyl phenol ethoxylates, Fluid Phase Equilib. 282 (2009) 14–19. [16] Z.X. Zhong, W.H. Xing, X. Liu, W.Q. Jin, N.P. Xu, Fouling and regeneration of ceramic membranes used in recovering titanium silicalite-1 catalysts, J. Membr. Sci. 301 (2007) 67–75. [17] J. Shi, J.D. Wang, G.Z. Yu, M.H. Chen, in: Handbook of Chemical Engineering, 1, Chemical Industry Press, Beijing, 2002, pp. 1–141. [18] Y.J. Zhao, Y. Zhang, W.H. Xing, N.P. Xu, Treatment of titanium white waste acid using ceramic microfiltration membrane, Chem. Eng. J. 111 (2005) 31–38. [19] A.R. Costa, M.N. de Pinho, Effect of membrane pore size and solution chemistry on the ultrafiltration of humic substances solutions, J. Membr. Sci. 255 (2005) 49–56. [20] W. Yuan, A.L. Zydney, Humic acid fouling during ultrafiltration, Environ. Sci. Technol. 34 (2000) 5043–5050. [21] B.I. Harman, H. Koseoglu, N.O. Yigit, E. Sayilgan, M. Beyhan, M. Kitis, The removal of disinfection by-product precursors from water with ceramic membranes, Water Sci. Technol. 62 (2010) 547–555. [22] Z. Tu, L. Ding, M. Frappart, M.Y. Jaffrin, Studies on treatment of sodium dodecyl benzene sulfonate solution by high shear ultrafiltration system, Desalination 240 (2009) 251–256.

90

H. Zhang et al. / Desalination 309 (2013) 84–90

[23] B.L. Rivas, E.D. Pereira, M. Palencia, J. Sanchez, Water-soluble functional polymers in conjunction with membranes to remove pollutant ions from aqueous solutions, Prog. Polym. Sci. 36 (2011) 294–322. [24] I. Sentana, M.A.D.L. Rubi, E. Sentanaa Rodrigueza, D. Pratsa, Removal of natural organic matter by cationic and anionic polyacrylonitrile membranes. The effect of pressure, ionic strength and pH, Sep. Purif. Technol. 68 (2009) 305–311. [25] H. Shirota, E. Castner, Ultrafast dynamics in aqueous polyacrylamide solutions, J. Am. Chem. Soc. 123 (2001) 12877–12885. [26] H.L. Wang, J.Y. Cui, W.F. Jiang, Synthesis, characterization and flocculation activity of novel Fe(OH)3-polyacrylamide hybrid polymer, Mater. Chem. Phys. 130 (2011) 993–999. [27] Y. Zhao, Y. Chen, M. Li, S. Zhou, A. Xue, W. Xing, Adsorption of Hg2+ from aqueous solution onto polyacrylamide/attapulgite, J. Hazard. Mater. 171 (2009) 640–646. [28] N. Gao, M. Li, W. Jing, Y. Fan, N. Xu, Improving the filtration performance of ZrO2 membrane in non-polar organic solvents by surface hydrophobic modification, J. Membr. Sci. 375 (2011) 276–283.

[29] H. He, W. Jing, W. Xing, Y. Fan, Improving protein resistance of α-Al2O3 membranes by modification with POEGMA brushes, Appl. Surf. Sci. 258 (2011) 1038–1044. [30] M. Li, Y. Zhao, S. Zhou, W. Xing, F.S. Wong, Resistance analysis for ceramic membrane microfiltration of raw soy sauce, J. Membr. Sci. 299 (2007) 122–129. [31] X.L. Qiao, Z.J. Zhang, N.C. Wang, V. Wee, M. Low, C.S. Loh, N.T. Hing, Coagulation pretreatment for a large-scale ultrafiltration process treating water from the Taihu River, Desalination 230 (2008) 305–313. [32] M.H. Al-Malack, A.A. Bukhari, N.S. Abuzaid, Crossflow microfiltration of electrocoagulated kaolin suspension: fouling mechanism, J. Membr. Sci. 243 (2004) 143–153. [33] D.B. Levin, G.A. Pope, S. Jouenne, Chemical degradation of polyacrylamide polymers under alkaline conditions, SPE Reserv. Eval. Eng. 14 (2011) 281–286. [34] J.J. Sheng, Modern chemical enhanced oil recovery, in: Chapter 11: Alkaline-Polymer Flooding, 2010, pp. 461–472.