A R T I C L E
Fabrication of polyamide thin film nanocomposite reverse osmosis membrane incorporated with a novel graphite-based carbon material for desalination
Han Zhang | Yanyi Wang | Yulin Wei | Congjie Gao | Guiru Zhu
Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao, China
Correspondence
Guiru Zhu, Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao, 266100, China.
Email: zhugr@ouc.edu.cn
Funding information
Fundamental Research Funds for the Central Universities, Grant/Award Number: 201964020; National Natural Science Foundation of China, Grant/
Award Number: U1607124
Abstract
The properties of polyamide (PA) thin film composite (TFC) membranes are affected by many variables, especially the additives in the process of interfacial polymerization that play an important role in the properties of membranes. In this study, a new type graphite carbon was added into organic phase con- taining trimesoyl chloride for interfacial polymerization with aqueous phase containing m-phenylenediamine to prepare modified polyamide thin film nanocomposite (TFN) membranes for reverse osmosis (RO) adhibition. Poly- sulfone ultrafiltration membranes were used as the carrier of the interfacial polymerization. The concentration of graphite carbon was selected from 0.002 to 0.01 wt%. The polyamide nanocomposite membrane prepared with the con- centration of 0.004 wt% graphite carbon showed the best RO desalination per- formance, which the water flux of this TFN membrane is over 2.3 times as much as pristine TFC membrane, and the salt rejection is over 99%. This arti- cle provides a well-performing polyamide thin film nanocomposite membrane modified by a new-type carbon nanoparticles consequently.
K E Y W O R D S
desalination, Graphite carbon nanoparticles, Thin film nanocomposite RO membrane
1
|I N T R O D U C T I O N
Over the past three centuries, the amount of fresh water extracted by humans has increased 35-fold as population growth and economic development have increased the amount of water used per person.[1]Desalination is widely recognized as an important way to provide fresh water to humans by removing salt and other impurities.[2–4]
The RO technology has become diffusely used with many advantages over other desalination methods such as low energy consumption, environment-friendly, sim- ple operation and simple process for water treatment.[5,6]
RO water desalination has developed to be the superior technology for water treatment after decades of rapid pro- gress.[7] On that basis, brackish water reverse osmosis
(BWRO) and seawater reverse osmosis (SWRO) are seen as the most hopeful solutions to the world water resource crisis.[8–10] Among the process of RO desalination, effi- cient semi-permeable membrane plays a crucial role, which determine the water quality, and affect the energy consumption.[11]Therefore, a type of efficient RO mem- branes with increasing productivity and high salt rejec- tion are sufficiently anticipated.
The polyamide (PA) thin film composite (TFC) mem- brane fabricated by interfacial polymerization between trimesoyl chloride (TMC) andm-phenylenediamine (MPD) has become a leader in the field of RO desalination because of the distinctive structure containing an active layer on the top, an porous polymer support in middle and a nonwoven polyester fibers as backing.[12,13] The resulting TFC
DOI: 10.1002/app.49030
J Appl Polym Sci.2020;e49030. wileyonlinelibrary.com/journal/app © 2020 Wiley Periodicals, Inc. 1 of 10
https://doi.org/10.1002/app.49030
membrane has a very dense layer due to its active layer being enriched by hydrogen bonds, which has a controlla- ble degree of crosslinking by the presence of multifunctional monomers. It makes TFC membrane has a better hydrophilicity and salt rejection performance.[11]It is worth mentioning that the dense active layer and the porous support layer of polyamide membrane can be inde- pendently optimized and modified.[14]The polyamide active layer provides excellent selectivity and permeability while the porous support layer providing commendable mechani- cal strength. Jeong et al.[15] provided a novel method to ameliorate the performance of the TFC membranes by incorporating polyamide layer with NaA zeolite which is inorganic porous nanoparticles, leading to the actuality of TFN membranes. The TFN membrane in this study can sig- nificantly improve the water flux, which is primarily due to the favorable flow of water through the micropores of NaA zeolite. Up to present, many nanomaterials such as zeolite,[16–18] silica-based materials,[19–21] carbon-based materials,[22–25]and MOFs,[26]have been used as nanofillers for TFN membranes. By adding nanomaterials with differ- ent functional properties into the process of interfacial poly- merization for fabricating of TFN membrane,[27–29]effective water molecular channels can be added to produce the TFN membranes with enhanced properties than TFC mem- branes.[30] Nanomaterials have become the key to amelio- rate the TFN membranes performance.
In this article, carbon nanoparticles with nano-flake graphite structure, high-specific surface area, and good hydrophilicity were used as a nanofiller to prepare the PA- TFN reverse osmosis membrane. Different contents of the carbon nanoparticles were added in the polyamide layer by interfacial polymerization to inspect the effects of mem- brane desalination performance and antifouling perfor- mance. The scanning electron microscope (SEM), contact angle analyzer, and atomic force microscope (AFM) were used to characterize surface morphology of the membrane and the hydrophilicity of TFN membrane. A lab-scale cross-flow RO test unit was debuged to characterize TFN membranes separation performance by evaluating the
rejection and water flux. The stability and antifouling per- formance of TFN membrane were investigated under brackish water testing condition. The separation perfor- mance of TFN membrane was also studied under seawater testing condition.
2
|E X P E R I M E N T A L 2.1
|Materials
Triethylamine (TEA, >99.5%), m-phenylenediamine (MPD, >99%), trimesoyl chloride (TMC, >98%) and sodium dodecyl sulfate (SDS) were obtained from Alad- din Co. Ltd. (China). n-Hexane was purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). All the chemicals are analytical grade and used as received without further purification. The polysulfone (PSF) support membrane was purchased from Pureach Technology Co. Ltd. (Beijing, China). The novel graphite- based carbon nanoparticles were provided by JiaTan Technology Co. Ltd. (Hangzhou, China) with graphite structure and nano-flake, higher hydrophilicity.
2.2
|Membrane preparation
The TFN membranes incorporated carbon nanoparticles were fabricated via the interfacial polymerization of TMC with MPD on the substrate of PSF ultrafiltration membrane (Figure 1). First, PSF substrate was fixed with a frame and the excess water was removed out of the surface. Then, the top surface of PSF membrane was immersed by the MPD aqueous solution contained 0.15 wt% SDS and 2.0 wt%
MPD for 2 min. The excess MPD solution was drained off and dried for 8 min in air. Further, the surface of MPD-soaked PSF support was covered by the TMC hexane solution (0.1 wt% TMC and 0–0.01 wt% carbon nanoparticles) for 2 min to form the polyamide layer via interfacial polymerization. Then, removing the excess
F I G U R E 1 Schematic diagram of interfacial polymerization [Color figure can be viewed at wileyonlinelibrary.com]
TMC solution and air-drying the membrane for 1 min at 25 ± 2C, the formed membrane was heat treatment in oven at 80C for 5 min for further cross linking reaction of the PA layer. Finally, the resultant membrane was tested after soaked in deionized water for performance.[31,32]
2.3
|Characterization of membranes
The surface morphology of membrane was visualized by scanning electron microscope (SEM, XL-30 ESEM). The samples were deposited on the sample holder with an adhesive carbon foil and sprayed with gold before SEM measurement. The atomic force microscope (AFM, Agilent 5,400) was used to quantify the roughness of the samples surface by means of a probe that travels across the surface. The hydrophilicity of membranes was tested by contact angle analyzer (KRüSSDSA100, Germany).The data for each set of contact angle was obtained from the average of several points.
The desalination performance of membranes was assessed using a lab-scale cross-flow RO test unit with an valid membrane area of 24 cm2. The 2,000 ppm NaCl aqueous solution was prepared as feed solution simulat- ing brackish water. The membranes were pre-pressurized at 1.8 MPa operation pressure for 30 min to make the membrane to steady state permeation. After the mem- branes had been compacted, the water flux and salt rejec- tion were measured at 1.6 MPa and 25 ± 2C. The RO membranes were tested under seawater testing condition
(32,000 ppm NaCl feed, 5.5 MPa pressure and 25
± 2C).[33] A thermostatic bath was used through the whole process of experiment to maintain operating tem- perature at 25 ± 2C. The water flux (F, L m−2h−1) and salt rejection (R, %) were calculated as follows:
F= V
AΔt ð1Þ
R= 1−Cp Cf
×100% ð2Þ
whereV(L) is the volume of the permeated water;A(m2) is the effective membrane area; Δt (h) is the infiltration time;Cp(mg L−1) andCf(mg L−1) are the salt concentra- tion of the penetrating solution and feed solution, respec- tively, which are confirmed by an electric conductivity meter (DDS-307A, Shanghai INESA Scientific Instrument Company). The data of each sample membrane was repeated more than three times to ensure its accuracy, and the error bar revealed the standard deviation.
3
|R E S U L T S A N D D I S C U S S I O N 3.1
|Carbon nanoparticles
characterization
The SEM image of graphite carbon nanoparticles is shown in Figure 2a. It can be seen that the graphite
F I G U R E 2 (a) SEM image, (b) XRD pattern, (c) N2adsorption– desorption isotherms, and (d) pore size distribution curve of the graphite carbon material
carbon has nano-flake shape with uniform particle size.
The crystal structure of nanoparticles was characterized by XRD shown in Figure 2b. The XRD pattern displays an obvious broad diffraction peaks at 26.5, corresponding to the characteristic (002) lattice planes of the graphite carbon material,[34] which proves that the carbon material has a graphite structure. The nitrogen adsorption–desorption isotherms (Figure 2c) show that the carbon nanoparticles exhibit a type IV isotherm, dem- onstrating that it has mesoporous structures. The BJH pore size distribution curve (Figure 2d) indicates that the carbon nanoparticles have mesoporous sizes mainly cen- tered at 3.8 nm.
3.2
|Characterization of the TFC and TFN membranes
3.2.1
|The influence of carbon nanoparticles on the morphology of membrane surface
With the increasing content of carbon nanomaterials, the color of the TFN membrane surface gradually deepens.
Obviously, a thin layer of carbon nanoparticles begins to be seen clearly on the surface of the TFN membranes by naked eye when the content of addition increases to 0.004 wt%. Thus, it's proved that carbon nanomaterials have been effectively added into the polyamide active layer.
The surface morphology structure of TFC and TFN membranes with diverse content of carbon material are shown in Figure 3. The surface morphology of TFC mem- brane clearly shows a typical ridge-and-valley structure of the polyamide active layer prepared by interfacial poly- merization of TMC and MPD (Figure 3a). In comparison to the surface of TFC membrane, the surface of the TFN membranes exhibit a type of “leaf-like” morphological structures, and the size of the “leaf-like” structure increases with the rise of the content of carbon materials (Figure 3b–f). When the content of carbon nanoparticles is >0.004 wt%, the polyamide membrane surface morphol- ogy presents a large leaf-like structure which may lead to a decrease in the specific surface area of the TFN mem- brane. As can be seen from the SEM images of the cross- section of TFN membrane containing 0.004 wt% carbon material in Figure 3g–h, the graphite carbon material has been doped into the active layer of polyamide. What's more, the TFN membrane surface prepared by graphite carbon nanoparticles in moderation presents a more extended ridge-and-valley structure compared with TFC membrane, which may affect the crosslinking degree of the TFN membrane surface. It has been reported that the
addition of hydrophilic nanofiller[1,28,35] to the organic phase can affect the interfacial polymerization reaction and possibly lead to the“leaf-like”structure. The presence of the hydrophilic nanofiller in organic phase can improve the miscibility of aqueous phase and organic phases, thus increasing the additional width of the reaction zone that could generate the“leaf-like”structure.
3.2.2
|Membrane interfacial properties
The contact angle was measured when the water drop reached equilibrium on the surface of the sample. The contact angle of membrane was determined by the trans- formation of the wetting tension on the membrane sur- face. Usually, the smaller the contact angle, the better hydrophilicity of membrane. In Figure 4a, the contact angle first gradually decreases, and reaches the lowest value at the content of 0.004 wt%, at which the TFN membrane has the best hydrophilicity. Then, the contact angle gradually increases as the content of carbon nanoparticles increases. After the addition of carbon nanoparticles rises >0.006 wt%, its water contact angles begin to increase gradually, which may be because of the agglomeration of carbon materials on the membrane sur- face. The PA layer of TFC film is formed of two mono- mers within organic phase and aqueous phase by interfacial polymerization reaction. Specifically, TMC in organic phase and MPD in aqueous phase diffuse to the reaction interface and form a thin film polyamide layer.The existence of graphite carbon nanoparticles may impede MPD diffusion and have an influence of the reac- tion between the –NH2 group and the –COCl group, resulting in correspondingly loose structure of polyamide layer.[18] As a result, there are more –NH2and –COOH hydrophilic groups exposed to the surface resulting in enhanced hydrophilicity of the membrane.
The surface charge properties of TFC and TFN mem- branes were measured by zeta potential. As shown in Figure 4b, zeta potential of the membranes begin to decrease gradually with the increase of PH value. Gener- ally, membranes keep a high negative surface charge den- sity due to the carboxyl groups formed by hydrolysis of acyl chloride groups.[10]It is determined by the balance of carboxyl and amino groups. When PH > 3.2, the mem- brane surface begins to show electronegativity. As PH increases, more carboxyl and amino groups are produced.
When the PH value reaches 10, the charge electronegativ- ity of the TFN membrane surface reaches the highest, and the hydrophilicity of the membrane surface is the strongest.
The introduction of carbon nanoparticles in interfa- cial polymerization also affect the roughness of TFN
membrane surface, which is analyzed by the AFM (Figure 5). The surface roughness parameters (Sq,Sa) of the TFC and TFN membranes are shown in Table 1. As the surface roughness increases, the contact angle decreases and the surface of membrane becomes more hydrophilic according to Wenzel equation,[36]that is why the roughness of TFN membrane surface is higher than TFC membrane surface, and the contact angle of TFN membrane is lower than TFC membrane.[27,36,37] In this
study, when the graphite carbon material was within the effective addition amount, the change in contact angle and surface roughness conformed to the Wenzel equa- tion. After exceeding the optimal addition amount, the effective addition amount of the graphite carbon material reaches the highest value, and the material starts to agglomerate on the membrane surface, which causes the hydrophilicity of the membrane surface to decrease and the roughness to increase.
F I G U R E 3 SEM images of surface morphology of (a) TFC and (b–f) TFN membranes prepared with different contents of carbon
nanoparticles (wt%): (b) 0.002, (c) 0.004, (d) 0.006, (e) 0.008, and (f) 0.010, (g, h) cross-section SEM images of TFN membrane with 0.004 wt% carbon nanoparticles [Color figure can be viewed at wileyonlinelibrary.com]
F I G U R E 4 Interfacial properties of TFC and TFN membranes: (a) contact angles of TFC and TFN membranes prepared with different contents of carbon nanoparticles; (b) zeta potential [Color figure can be viewed at wileyonlinelibrary.com]
F I G U R E 5 AFM images for the surfaces of (a) TFC and (b–f) TFN membranes prepared with different contents of carbon nanoparticles (wt%): (b) 0.002, (c) 0.004, (d) 0.006, (e) 0.008, and (f) 0.010 [Color figure can be viewed at wileyonlinelibrary.com]
3.3
|Performance of TFC and TFN membranes in RO process
The desalination performance of RO membrane depends on the density of the desalination layer on membrane surface. In Figure 6, the water flux starts to increase as the content of graphite carbon nanomaterial increases gradually. When the content of carbon nanoparticles is of 0.004 wt%, the water flux of TFN membrane attains 73.36 L m−2 h−1, and the salt rejection is also
significantly ameliorated, effectively improving the mem- brane desalination performance. When the content exceeds 0.006 wt%, a kind of underperformed larger leaf- like structure who affects the properties of the mem- branes starts to appear (Figure 3). The water flux began to flatten after it dropped to 51.89 L m−2 h−1. The salt rejection of which is still better than TFC membrane is barely changed during the whole process. There are two reasons for the phenomenon that the water flux of TFN membrane begin to decrease when the content of the graphite carbon nanomaterials exceeds 0.006 wt%. First, it might be due to the increase of the nanoparticles load- ing, which leads to the blockage of a small number of water channels on the substrate.[18]Second, the aggrega- tion of high-content carbon nanoparticles tends to form large leaf structures in the selective layer of PA-TFN (Figure 3), decreasing the specific surface area of mem- brane and leading to a decline of the water flux.
Compared with pure polyamide TFC membrane in Figure 6, the TFN membrane prepared by adding 0.004 wt
% carbon nanoparticle into the organic phase could signifi- cantly increase the water flux from 31.4 to 73.36 L m−2h−1, and the salt rejection rate is as high as 99.04%. The optimal adding amount of carbon nanoparticles (0.004 wt%) was used to test the membranes in the following experiments.
Table 2 shows the desalination performance of the pristine TFC and graphite carbon materials-TFN membranes pre- pared in this study compared with other reported high per- formance TFN membranes. All membranes were tested using 2,000 ppm NaCl feed. Carbon material modified TFN film with 0.004 wt% showed better desalination per- formance compared with TFC membrane and other TFN membranes. The comparison between different membrane properties may lead to some misunderstandings due to dif- ferent experimental formulations and IP processes.
3.4
|Stability of RO membranes
As shown in the Figure 7, under the condition of 1.6 MPa, the stability experiment was conducted in the 2,000 ppm T A B L E 1 Surface roughness parameters of TFC and TFN
membranes
Membrane
Surface roughness parameters Sq(nm) Sa(nm)
TFC 78.9 60.6
TFN-0.002 90.7 71.5
TFN-0.004 119 95.8
TFN-0.006 115 80.6
TFN-0.008 132 94.1
TFN-0.010 144 115
T A B L E 2 Desalination performance comparison of pristine TFC, graphite carbon materials-TFN membranes, and other high performance TFN RO membranes
Membranesa Loading concentration Water flux (L m−2h−1bar) Salt rejection (%) References
Pristine TFC – 1.96 97.82 This study
Graphite carbon materials-TFN 0.004 wt% 4.585 99.04 This study
TFN-GO 0.0038 w/v% 1.07 98.0 [38]
TFN-NaY zeolite 0.15 wt% 4.78 98.8 [18]
TFN-ZIF-8 0.4 w/v% 3.35 ± 0.08 98.5 ± 0.5 [39]
aPristine TFC and graphite carbon materials-TFN membranes were tested under 16.0 bar pressure, other membranes were tested under 15.5 bar pressure with 2,000 ppm NaCl in the feed.
0.000 0.002 0.004 0.006 0.008 0.010 20
30 40 50 60 70 80 90
Concentration of carbon nanoparticles (wt%) Water flux (L/m2 h)
50 60 70 80 90 100
Salt rejection (%)
F I G U R E 6 Effects of carbon nanoparticles content on water flux and salt rejection (2,000 ppm NaCl solution, 1.6 MPa) [Color figure can be viewed at wileyonlinelibrary.com]
NaCl solution for 48 h with TFC membrane and 0.004 wt%
carbon nanoparticles in the TFN membrane. The water flux of TFC membrane decreased by about 3%, and that of the modified polyamide membrane decreased by about 4%
in the first 10 h. This result shows that the TFN membrane can be more compacted than TFC membrane, indicating that the active layer of modified TFN membrane is looser than TFC membrane. It is confirmed that the addition of nanofiller into the PA layer can reduce the degree cross- linking of it.[40] The larger ridge-and-valley structure and leaf-like morphology (Figure 3) combining the lower cross- linking could cause the looser structure of polyamide active layer of TFN membranes. Figure 7 shows that the water flux of TFN membrane stayed in a stable range and did not decrease continuously after 10 h. After desalination opera- tion for 48 h, the water flux of TFN membrane (71.23 L m−2 h−1) is still far higher than TFC membrane (31.36 L m−2h−1), and the salt rejection remained 98.59%.
Although the resultant TFN reverse osmosis membrane has loose polyamide active layer, it could still maintain rel- atively stable and enhanced desalination performance under the long-term operation. The graphite carbon struc- ture, the hydrophilic and small nanoparticle diameter, which decrease the PA layer density and effectively improve the desalination performance. In addition, the incorporated carbon nanoparticles make the modified poly- amide membrane have a certain compressive resistance, improve the mechanical properties of the membrane.
3.5
|Membrane fouling with natural organic matter
Natural organic matter is an important factor causing membrane pollution. In the process of membrane
separation, the adsorption of organic pollutants on mem- brane surface and in the pores often leads to membrane blockage, which is an important factor affecting the ser- vice life of the membrane. The membrane fouling should be reduced as much as possible during the process of using reverse osmosis membranes in order to enhance the service life of them. Humus acid exists as a typical representative organic pollutant in this experiment was used to research the anti-fouling properties of TFC and TFN membranes who were tested for 48 h under the con- ditions of 2,000 ppm NaCl and 5 ppm of humic acid aqueous solution, 1.6 MPa pressure and 25 ± 2C. Three samples are calculated to get an average value.
The change of the relative flux (the ratio of actual flux to the initial flux) results was adopted to evaluate the membrane pollution for eliminating the influence of membrane conditions on the water flux variation in the experiment. As seen in Figure 8, the water fluxes of TFC and TFN membranes show a downward trend due to the presence of humic acid. In the first 5 h, the water flux of TFC membrane drops sharply to 85% of the original
0 10 20 30 40 50
10 20 30 40 50 60 70 80 90 100 110 120
TFN TFC
Time (h) Water flux(L/m2 h)
70 80 90 100
Salt rejection (%)
F I G U R E 7 Stability of the TFC membrane and the TFN membrane prepared with 0.004 wt% carbon nanoparticles [Color figure can be viewed at wileyonlinelibrary.com]
0 10 20 30 40 50
0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05
TFNTFC
Relative flux
Time (h)
0 10 20 30 40 50
96 97 98 99 100
TFCTFN
Rejection (%)
Time (h) (b)
(a)
F I G U R E 8 Organic fouling characteristics of pure polyamide TFC and carbon incorporated TFN membranes. (a) Changes in normalized flux and (b) Changes of salt rejection. The condition of fouling resistance experiment: operating pressure is 1.6 MPa, operating temperature is 25 ± 2C, feed solution is 2,000 ppm of NaCl, and 5 ppm of humic acid aqueous solution
membrane, while that of TFN membrane only drops to 99%, indicating that TFN membrane has stronger anti- fouling capacity than TFC membrane. And the water flux of TFC membrane drops sharply that maintained a con- tinuous state of decline for 48 h with increasing the cross-membrane resistance of water molecules by the col- lected fouling on membrane surface. In contrast, the water flux of TFN membrane contained with carbon nanoparticles correspondingly shows a trend of slow decrease and gradually levels off during the test. The water flux of TFN membrane only decreases to 96% of the original value after 48 h of operation compared the decline 68% of TFC membrane. It is attributed to the addition of graphite carbon materials, which increases the electronegativity and hydrophilicity of membrane surface. It indicates that the TFN membrane with graph- ite carbon nanoparticles has better anti-fouling perfor- mance than the TFC membrane.
3.6
|RO membrane performances for seawater
Seawater, compared with brackish water, has higher salt content and stronger pressure requirements for membrane performance. Therefore, the TFC membrane and the TFN membrane added with graphite carbon nanoparticles pre- pared under the same conditions were tested under high pressure with simulated seawater. We selected the TFN membrane with the best performance of adding amount at 0.004 wt% and the TFC membrane which were prepared under the same conditions, and evaluated the seawater desalination performance of the two.
As shown in Figure 9, TFC membrane kept higher water flux and lower salt rejection for seawater at higher pressure than brackish water at lower pressure. The results were similar with the reported reference [31, 33]. How- ever, the water flux of the TFN membrane for seawater at 5.5 MPa only slightly increased than brackish water at 1.6 MPa. It is exactly caused by that the TFN membrane has a much looser active layer than the TFC membrane.
Under the action of high pressure, the PA layer of TFN membrane is easier to be compacted than that of TFC membrane. Although TFN membrane was compacted at higher pressure, it still had improved properties with water flux of 73.60 L m−2 h−1 and the salt rejection of 98.45%
than TFC membrane with water flux of 50.12 L m−2h−1 and salt rejection of 96.65%. The results demonstrate that the polyamide reverse osmosis nanocomposite membrane with graphite carbon nanomaterials has great potential in seawater desalination similarly.
4
|C O N C L U S I O N S
A novel graphite carbon nanoparticles added into the polyamide layer were used to synthetic a kind of modified polyamide TFN membrane by interfacial polymerization to enhance the desalination performance of RO mem- brane. Using 2,000 ppm NaCl solution to simulate brack- ish water at a pressure of 1.6 MPa and 32,000 ppm NaCl feed for seawater testing under the condition of 5.5 MPa pressure, the polyamide membrane added with carbon nanoparticles was confirmed that the hydrophilic and separation properties have been significantly improved. A series of studies were conducted on the concentration of carbon nanoparticles, the stability of the membrane, and the anti-fouling property. The water flux for brackish water increased from 31.4 to 73.36 L m−2h−1by treated with graphite carbon nanoparticles, and the salt rejection was as high as 99.04%. The water flux increased to 73.60 L m−2 h−1 for seawater desalination simulation.
The optimal addition of the carbon nanomaterials was 0.004 wt%. It was indicated that the addition of the novel graphite carbon nanoparticles had effectively improved performance of the brackish water and seawater desalination.
A C K N O W L E D G M E N T S
This study was supported by the National Natural Sci- ence Foundation of China (U1607124) and the Funda- mental Research Funds for the Central Universities (201964020).
O R C I D
Guiru Zhu https://orcid.org/0000-0002-4749-5229
0 10 20 30 40 50 60 70 80 90
TFN-5.5 TFN-1.6
TFC-5.5
Flux Rejection
Water flux (L/m2 h)
TFC-1.6 0
20 40 60 80 100
Salt rejection (%)
F I G U R E 9 The TFC and TFN membranes RO desalination performance for simulated brackish water and seawater. The testing condition: 1.6 MPa with 2,000 ppm NaCl solution as simulated brackish water and 5.5 MPa pressure with 32,000 ppm NaCl solution as simulated seawater, and 25 ± 2C
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How to cite this article:Zhang H, Wang Y, Wei Y, Gao C, Zhu G. Fabrication of polyamide thin film nanocomposite reverse osmosis membrane incorporated with a novel graphite- based carbon material for desalination.J Appl Polym Sci. 2020;e49030.https://doi.org/10.1002/
app.49030
