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Graphene oxide membranes supported on the ceramic hollow fiber for efficientH2 recovery

Kang Huang, Jianwei Yuan, Guoshun Shen, Gongping Liu, WanqinJin

PII: S1004-9541(16)30677-2DOI: doi:10.1016/j.cjche.2016.11.010Reference: CJCHE 717

To appear in:

Received date: 15 July 2016Accepted date: 22 November 2016

Please cite this article as: Kang Huang, Jianwei Yuan, Guoshun Shen, Gongping Liu,Wanqin Jin, Graphene oxide membranes supported on the ceramic hollow fiber for effi-cient H2 recovery, (2016), doi:10.1016/j.cjche.2016.11.010

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Graphene oxide membranes supported on the ceramic

hollow fiber for efficient H2 recovery

Kang Huang, Jianwei Yuan, Guoshun Shen, Gongping Liu, Wanqin Jin*

State Key Laboratory of Materials-Oriented Chemical Engineering, College of

Chemical Engineering, Jiangsu National Synergetic Innovation Center for

Advanced Materials, Nanjing Tech University, 5 Xinmofan Road, Nanjing 210009,

PR China

*Corresponding author

Tel.: +86-25-83172266;

Fax: +86-25-83172292;

E-mail: wqjin@njtech.edu.cn

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Separation Science and Engineering

Graphene oxide membranes supported on the ceramic

hollow fiber for efficient H2 recovery#

Kang Huang, Jianwei Yuan, Guoshun Shen, Gongping Liu, Wanqin Jin*

State Key Laboratory of Materials-Oriented Chemical Engineering, College of

Chemical Engineering, Jiangsu National Synergetic Innovation Center for

Advanced Materials, Nanjing Tech University, Nanjing 210009, China

*Corresponding author

Tel.: +86-25-83172266;

Fax: +86-25-83172292;

E-mail: wqjin@njtech.edu.cn( W.Q. Jin)

#Supported by the National Natural Science Foundation of China (Grant Nos.

21476107, 21490585, 21406107), the Innovative Research Team Program by the

Ministry of Education of China (Grant No. IRT13070) and the Topnotch Academic

Programs Project of Jiangsu Higher Education Institutions (TAPP).

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Abstract

The special channels and intrinsic defects within GO laminates make it a very

potential candidate for gas separation in recent years. Herein, the gas separation

performance of GO membranes prepared on the surface of ceramic α-Al2O3 hollow

fiber were investigated systematically. The microstructures of ceramic hollow fiber

supported GO membranes were optimized by adjusting operation conditions. And, the

GO membrane fabricated at 30 min exhibited great promising H2 recovery ability

from H2/CO2 mixture. At room temperature, the H2 permeance was over 1.00 ×10-7

mol·(m2·s·Pa)

-1 for both single gas and binary mixture. The corresponding ideal

selectivity and mixture separation factor reached around 15 and 10, respectively. In

addition, humility, operation temperature, H2 concentration in the feed and the

reproducibility were also studied in this work.

Keywords: Graphene oxide; ceramic hollow fiber; gas separation; hydrogen recovery

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1. Introduction

Gas separation membranes are increasingly becoming an important and convenient

technology for the recovery of hydrogen from gas mixtures (H2/N2, H2/CO2,

H2/hydrocarbons and so on), oxygen-nitrogen separation, natural gas separation, CO2

capture, vapour-vapour separation and air dehydration. [1] The attractive and

significant reason is that the membrane technology can effectively separate gas

mixtures under low pressure, obviously reduce required industry area and minimize

necessary energy consumption with relatively low contamination, compared with

traditional separation technologies. [2, 3] Up to now, numerous creative works about

gas separation membranes are focused on achieving high flux and surprising

selectivity. [4-7] In order to obtain this target, three main routes are employed: 1)

designing and synthesizing new materials with special and excellent properties; 2)

improving current gas separation membrane materials by modification; 3) developing

novel and high-effective membrane processes based on current materials. The

intrinsic excellent properties of the membrane materials are the precondition to

achieve high separation performance. Beyond their outstanding properties, the

membrane materials should also satisfy other necessary practical application

conditions, such as low production cost, simple preparation process and easy scale-up.

Recently, considerable interest has been aroused by the emerging two-dimensional

structural materials, such as MoS2, [8, 9] phosphorene, [10] ZIF-7 [11] and graphene,

[12] due to their ultra-thin thickness and unique physicochemical property. Utilizing

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two-dimensional intriguing materials to fabricate thin membranes has been considered

as a useful and effective way to overcome the current permeability/selectivity

trade-off, [13, 14] which often occurred in traditional polymer membranes. [14, 15]

Among them, there is no doubt that graphene, a two-dimensional monolayer of sp2

hybridized carbon atoms arrayed in a honeycomb pattern, exhibits the most

imaginative and outstanding prospect, because of a series of unique properties, such

as good chemical stability, excellent thermal conductance and strong mechanical

strength. [12, 16-19] For example, Nair et al. found that graphene oxidce (GO, the

oxygen-containing analogue of graphene) membrane allowed unimpeded permeation

of water while other molecules were blocked, because of the low-friction flow of

water molecules through 2D capillaries between graphene sheets. [20] Subsequently,

based on this interesting discovery, significant amount of researches about GO

membranes for water treatment, [21-26] liquid organic separation [27-30] and ion

sieve [31, 32] were investigated and showed great attractive performance.

GO’s precise transport channels and atomic-scale pores also make it a potential

candidate in gas separation. Up to now, some exciting and encouraging works have

been achieved. [33, 34] However, because of the complicated membrane preparation

process, [34-36] it is very hard to transfer their membrane to the practical application.

On the other hand, the attractive ultrathin flat membrane structure brings another

critical issue: how to bear complex and harsh long-term operation environments in the

real industry (such as high pressure and unstable gas flow). Usually, extremely careful

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manipulations are needed for these few-layers GO membranes. [33, 34] Therefore, it

is still necessary to design GO membranes which can satisfy the practical

requirements and explore their gas separation.

In order to make up above shortages, we are apt to prepare porous ceramic supported

GO membranes, because porous ceramic substrates not only can decrease thickness of

membranes to realize high flux obviously, but also can offer a good mechanical

strength for composite membranes. [37, 38] In this study, the porous ceramic hollow

fiber was selected as the substrates due to its characteristic configuration (low mass

transfer resistance and high-packing density) and good chemical and thermal stability.

[39] Previously, we have proposed a convenient and rapid vacuum suction method to

prepare GO membranes on the ceramic hollow fiber, which exhibited excellent

pervaporation separation performance. [27] The special configuration makes GO

membranes very easy to be scale-up. In addition, GO nanosheets stacked to form a

cylinder shell around the ceramic hollow fiber, keeping it more stable than flat GO

membranes. Herein, we will deeply study the gas separation performance of the

ceramic hollow fiber supported GO membranes by: 1) optimizing microstructures of

GO membranes; 2) exploring gas separation ability systemically, including single gas

and binary mixture; 3) investigating stability of GO membranes in the gas system.

Small gas molecules (H2, CO2, N2, O2 and CH4) will be employed to investigate the

potential separation in the whole study.

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2. Experimental

2.1 Materials

GO powder prepared by modified hummer’s method [40] was purchased from

Nanjing JCNANO Tech Co., Ltd, China. The ceramic -Al2O3 hollow fiber support

was prepared as our previous method. [7] 99.999% H2, H2, CO2, N2, O2 and CH4 were

used as the gas sources, which were brought from Nanjing Special Gas Co., LTD,

China. Deionized water were also employed in the whole experiment.

2.2 Preparation of GO membrane

A typical process to prepare GO membranes is described as follow: Firstly,

preparation of GO aqueous solution. GO powder was dissolved into deionized water,

and at the same time the mixture solution was treated by ultrasound equipment for 1

hour to form a high concentration GO aqueous solution. In this step, GO powder was

exfoliated to nanosheets. Then, above GO solution was centrifuged at 3000 r·min-1

for

10 min in order to remove agglomerated powder and impurity. After this, the

as-prepared solution was diluted 1000 times to form a very low concentration solution

(about 0.001 mg·ml-1

). Secondly, fabrication of GO membranes. The GO

membrane was prepared by our previous reported method (i.e., Vacuum Suction

method). [27] The detailed steps are listed as below. One side of the ceramic hollow

fiber was sealed and the other side was connected to a vacuum pump. Then, the whole

hollow fiber was immersed in the GO aqueous solution. With the pressure driving,

GO flakes were stacked on the surface in order. Through changing the operation time,

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different thickness GO membranes were fabricated. Finally, the as-prepared GO

membrane was dried in a vacuum oven at 45 oC over 48 h. The quality of as-prepared

GO membranes were examined by testing the H2 and CH4 single gas permeation.

2.3 Characterization

The morphologies of the GO membranes and the ceramic hollow fiber were

characterized by field emission scanning electron microscope (FESEM S4800,

Hitachi, Japan). The working parameters were a voltage (HV) of 5 kV and a work

distance (WD) of 8 mm. Fourier transform infrared spectroscopy were recorded by

using a FTIR spectrophotometer (AVATAR-FT-IR-360, Thermo Nicolet, USA) over

the range of 4000-500 cm-1

. The X-ray photoelectron spectroscopy (XPS) was carried

out through an X-ray photoelectron spectrometer (Thermo ESCALAB 250, USA)

with monochromatized Al K radiation. Atomic force microscopy (AFM, XE-100,

Park Systems, Korea) was used to detect the size of GO flakes and the surface

morphologies of the GO membrane.

2.4 Gas permeation test

Gas permeation experiments were performed by small gas molecules (H2, CO2, N2, O2

and CH4) on the permeation setup. Fig. 1 shows the schematic of the gas separation

setup. All the measurements were performed using the Wicke–Kallenbach technique

with an on-line gas chromatography (Agilent Technologies 7820A) at room

temperature. Before test, the membrane was activated at 45 oC. And, all the results

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were tested three times, making sure that the results were reliable.

For the single gas measurement, the feed flow rate was set to 30 ml·min-1

. When

studying the influence of humidity, the dried gas flow would go through a water bottle.

For the binary mixture, the feed side was fed at a total volumetric flow rate of 60

mL/min with each gas of 30 ml·min-1

. When investigating the influence of H2 fraction

in the feed, the total flow kept at 60 ml·min-1

. In all measurements, helium was used

as sweep gas at a flow rate of 30 ml·min-1

. Atmosphere pressure was applied to both

sides of the permeation cell. The temperature was controlled by a circulation oven.

The membrane permeance (Fi) is defined as:

AP

NF

i

ii

Where iN is the permeate rate of component i (mol·s

-1),

iP is the

transmembrane pressure difference of i (Pa), and A is the effective membrane area

(m2).

The ideal selectivity is calculated by the ratio of single gas permeances.

The separation factor was calculated as:

ji

ji

jixx

yy

/

/,

Where x and y are the molar fraction of the one component in the feed and

permeate, respectively.

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Fig. 1. Schematic diagram of the gas separation setup. “MFC” and “GC” are mass flow controller

and gas chromatography (Agilent Technologies 7820A), respectively. “F” and “P” are the flow

rate and pressure, respectively.

3. Results and Discussion

3.1 Basic characterization of GO materials and hollow fiber support

As we know, the properties of membrane materials have great effect on the eventual

separation performance. Before experiments, we first characterized the basic

properties of GO materials, including AFM, FTIR, XPS and Raman spectrum. Fig.

2(a) shows the AFM image of GO flakes deposited on the mica substrate. The size of

GO flake is about 1 m size. The depth profile indicates that the GO sheet is

approximately 1 nm in thickness. The FTIR spectrum (Fig. 2(b)) proves the presences

of O–H stretching vibrations (3415 cm-1

), C=O stretching vibrations from carbonyl

and carboxylic groups (1733 cm-1

), unoxidized sp2 C=C bonds in the carbon lattice

(1624 cm-1

), and C–O stretching vibrations from epoxy groups (1051 cm-1

). These

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functional groups were further confirmed by the XPS measurement. As shown in Fig.

2(c), the XPS C1s spectrum of GO clearly indicates four kinds of C atoms in different

functional groups: C–C (~284.8 eV), C–O (~286.8 eV), C=O (~287.8 eV), and C(O)O

(~289.0 eV). The C–O groups (representing hydroxyl and epoxide groups) comprise

approximately 45.3% of the total C1s peak area, whereas C=O and C(O)O are 11.07%

and 5.4%, respectively. The results show that the ratio of O/C in GO is approximately

0.6, which is relatively high as compared to the reported values. [41] XPS and FTIR

results are well in agreement with the Lerf-Klinowski Model of the GO sheet. [42, 43]

When the Hummer method produced amount of oxygen-containing groups, some

intrinsic defects were also created at the same time. The present of defects can be

supported by the Raman spectrum. As shown in Fig. 2(d), the ID/IG ratio of the GO

powder is about 1.05, which be assigned to higher defects/disorders in the GO flake.

[33] The diverse carbon functional groups and intrinsic defects on the GO structure

will be beneficial for the gas separation through the molecular interaction and sieving.

The structure of the ceramic hollow fiber was also investigated. Fig. 2(e) gives an

optical picture of the hollow fiber and the traditional ceramic tube support. Compared

with tube, the hollow fiber owns a slender shape with smaller diameter (about 1.5

mm), implying a higher packing density. Fig. 2(f) shows the detail features of the

hollow fiber by FESEM. Its asymmetric structure (i.e., a thin separation dense layer

integrated with finger-like porous layers on both sides in Fig. 2(f-i) reduces the mass

transfer resistance of supports. The relatively smooth surface makes (Fig. 2(f-ii)) GO

sheets easy to stack and reduces the formation of big holes.

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Fig. 2. (a) AFM image of GO flakes deposited on the mica substrate; (b) FTIR, (c) XPS and (d)

Raman spectrum characterization of GO; (e) Optical picture of the ceramic tube and hollow fiber;

(f) FESEM images of the ceramic hollow fiber (insert i: cross-section; insert ii: surface).

3.2 Optimizing structures of GO membranes

In order to obtain high flux and selectivity, the microstructures of the hollow fiber

supported GO membranes were optimized systematically. By adjusting the

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preparation time, GO membranes with different thickness were achieved. Fig. 3

shows that the thickness of the GO membranes increases with the operation time

increasing. However, there is a nonlinearity between the membrane thickness and

operation time. The reason is that the resistance was reinforced with increasing the

membrane thickness, which inhibited more GO sheets to stack on the surface. The

insert in Fig. 3 presents two typical GO membranes prepared at 10 and 120 min,

respectively. Obviously, the membrane colour becomes darker when the thickness

increases. Additional, both of them show a continuous and uniformly layer, indicating

that the vacuum suction method is very effectively to fabricate tubular GO

membranes.

Fig. 3. The thickness of the ceramic hollow fiber supported GO membrane as a function of the

membrane preparation time.

Fig. 4 shows the microstructures of three typical GO membrane which were prepared

at 5, 30 and 120 min, respectively (the corresponding membranes are marked as T5,

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T30 and T120, respectively). When the time is too short, there are some pin holes on

the surface of GO membrane (Fig. 4(a)). The insert of Fig. 4(a) gives a clearer and

enlarged image. From Fig. 4(b) and Fig. 4(c), continuous and complete membranes

can be observed. And, the surface becomes smoother with the growth of thickness.

Fig. 4(d), 4(e) and 4(f) exhibit the corresponding cross-section images of T5, T30 and

T120 membranes, respectively. All of them attach well with the ceramic hollow fiber,

which may be attributed to the hydrogen bond between the oxygen containing

functional groups of the GO membrane and the hydroxy group on the surface of the

ceramic hollow fiber.

Fig. 4. FESEM images of the GO membrane prepared under different operation time: (a-c) the

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surface images; (e-f) the cross-section images.

Gas separation measurements of single H2 and CH4 were utilized to examine the

membranes’ quality. As shown in Fig. 5, the gas permeances of H2 and CH4 decline

together, when the membrane thickness increases. But the H2/CH4 selectivity of T30

GO membrane gets a peak and meanwhile the membrane still has a good H2

permeance. Obviously, with increasing the membrane thickness, the H2 permeance

declines quickly. This is why Nair et al. found the thick GO membrane was

impermeable to gases because of the higher membrane thickness. [20] Considering

permeance and selectivity, we selected the 30 min operation time as the most

optimized condition to prepare the ceramic hollow fiber supported GO membranes.

Fig. 6 shows the FESEM image of T30 GO membrane after rotating 45° and the

corresponding AFM image, indicating that the membrane is very intact with lots of

ripples and the membrane thickness is about 300 nm. The corresponding XRD result

(the inset in Fig. 6(a)) shows the d-spacing size of the GO membranes is ~ 0.81 nm.

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Fig. 5. The H2 and CH4 permeance and corresponding H2/CH4 selectivity of GO membrane as a

function of the membrane preparation time.

Fig. 6. (a) FESEM image and (b) AFM image of T30 GO membrane. The inset of (a) is the XRD

result.

3.3 Single gas separation performance

Single gas permeations of T30 GO membrane, including H2, CO2, O2, N2 and CH4,

were tested in detail. From Fig. 7, the permeances of these small gas molecules

decreases in the order H2 > CH4 > N2 > O2 > CO2, with increasing the molecular

weight. The corresponding ideal selectivity (Fig. 8) of H2/CO2, H2/O2, H2/N2 and

H2/CH4 are 15.0, 7.5, 7.2 and 6.4, respectively. In contrast to other gases, CO2 shows

a sharp down in the permeance and the highest hydrogen selectivity, which can be

attributed to the chemical nature of GO material. As we know, there are numerous

carboxylic acid groups distributed at the edge of GO flakes. Strong interplay between

these polar groups and C-O bonds in the nonpolar CO2 molecules would happen. For

CO2 transfer, CO2 as a Lewis acid or a Lewis base participates in hydrogen bonding,

which inhibits it from transferring within the stacked GO structure. [34] The similar

phenomenon was also found in the porous metal-organic framework (MOF) ZIF-78

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membrane. [44] The two polar functional groups –NO2 in ZIF-78 structure made it

exhibit the highest affinity for CO2, which blocked the diffusion of CO2 molecules

through the ZIF-78 channels.

Fig. 7. Single gas permeance (H2, CO2, O2, N2 and CH4) with dry feed or hydrated feed as a

function of the molecular kinetic diameter.

Then, we investigated the influence of humidity for the gas transfer. As shown in Fig.

7, most gas permeances (except CO2) decreases when the humid steam is added in the

feed, because the water molecules in the GO channels limits the gas transfer.

However, a slight increase of CO2 is observed. Kim et al. [34] found the same trend

when GO membrane was used to separate humid gas. This result further confirms that

CO2 molecules have special interaction with the carboxylic acid groups in GO.

Because of the growth of CO2 permeance, the corresponding H2/CO2 ideal selectivity

declines obviously under the wet condition (Fig. 8), indicating that wet gas has

disadvantages for hydrogen recovery from H2/CO2 mixture.

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Fig. 8. Selectivity of H2/CH4, H2/N2, H2/O2 and H2/CO2 with dry feed or hydrated feed

3.4 Binary gas separation performance

Single gas measurements only can give the ideal selectivity, because the gas

molecular transfer in this process is relatively independent. However, interplays

between different gases are generally not negligible, which may result in a prominent

deviation of the mixture separation factor from the ideal selectivity. Table 1 lists all

the single gases and binary mixtures separation performances. Like single gas test, the

ceramic hollow fiber supported GO membrane shows a same regular for mixtures.

But the corresponding permeance and separation factor has a bit of decrease because

of the competitive adsorption and diffusion between different gas molecules. This

phenomenon was often observed in zeolite membranes. For example, a CVD

modified ZSM-5 membrane exhibited a higher H2/CO2 ideal selectivity (17.5) than

the mixture separation factor (10.8). [45] Another AlPO4 membrane also showed a

lower separation factor (9.7) in H2/CO2 binary system than the ideal selectivity of

23.9. [46] Generally speaking, although the H2/CO2 separation factor drops, it still

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reveals a useful separation ability (10.2) for practical hydrogen recovery application.

The Robeson plot for H2-CO2 selectivities versus CO2 permeabilities of polymer

membranes has been widely used to compare the performance of membranes.[47] As

shown in Fig. 9, our GO hollow fiber membranes exhibit superior properties.

Table 1. Single gases and binary mixtures separation performances under dry state.

Permeance×107

/ mol ·m-2

·s-1

·Pa-1

H2 ideal selectivity H2 separation factor

Single gas

H2 1.34 —

CO2 0.09 14.98

O2 0.18 7.48

N2 0.19 7.21

CH4 0.21 6.37

Mixed gas

H2 (50 vol% in CO2) 1.20 10.22

CO2 (50 vol% in H2) 0.11

H2 (50 vol% in O2) 1.04 4.69

O2 (50 vol% in H2) 0.20

H2 (50 vol% in N2) 1.03 4.43

N2 (50 vol% in H2) 0.21

H2 (50 vol% in CH4) 1.24 4.67

CH4 (50 vol% in H2) 0.24

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Fig. 9. Comparison of H2/CO2 gas separation performances of GO hollow fiber membranes with

Robeson upper bound[47].

3.5 Effect of the H2 concentration in the feed for H2/CO2 mixture

In general, the H2/CO2 rate in the real mixture is very complicated and cannot be one

to one. In order to assess the influence of the feed composition on the hydrogen

recovery, the separation of H2/CO2 binary mixture was explored under different H2

concentrations in the feed. As shown in Fig. 10, with increasing the H2 concentration,

the H2 permeance has a slight growth because of the enhanced driving force. In

contrast, an imperceptible downtrend exists in the CO2 permeance line. As a result,

the H2/CO2 separation factor is almost unchanged and almost keeps a constant (about

10), which is independent of H2 fraction in the feed.

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Fig. 10. Effect of the H2 concentration in the feed for H2/CO2 mixture separation performance.

Fig. 11 presents the corresponding H2 and CO2 fraction in the permeate as a function

of H2 concentration in the feed. Obviously, a high H2 concentration mixture over 90%

in volume will be obtained, when the feed is equimolar. According to Fig. 11, for 20%

H2 concentration of H2/CO2 mixture, the finally H2 concentration mixture will be

more than 95% only after twice purification in theory.

Fig. 11. H2 and CO2 fraction in the permeate as a function of H2 concentration in the feed

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3.6 Effect of temperature on H2/CO2 separation

Fig. 12 represents the variation of the H2 and CO2 permeances and their

corresponding separation factors from their equimolar binary mixture in the

temperature of 50-200 oC. Both the permeances of H2 and CO2 increase quickly with

increasing operation temperature because of an activated diffusion process. The

corresponding separation factor shows a down trend, indicating that some inevitable

pores were formed in the GO laminates by heating. On the other hand, these pores

would also contribute to improving the permeance. X-ray photoelectron spectroscopy

(Fig. 13) shows that most of the oxygen containing functional groups have

disappeared after heating treatment, implying that this process is irreversible.

Therefore, low temperature (room temperature) is very suitable for GO membrane

used in gas separation industry field.

Fig. 12. Effect of temperature on H2/CO2 separation

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Fig. 13. X-ray photoelectron spectroscopy result of the GO membrane after heating treatment.

3.7 Repeatability and Stability of GO hollow fiber membranes

As shown in Table 2, the ceramic hollow fiber supported T30 GO membranes exhibit

very good repeatability on the separation of equalmolar H2/CO2 binary mixture at

room temperature. All the membranes were prepared under the same conditions. The

single permeaces of H2 and CO2 are around 1.3×10-7

and 0.09 ×10-7

mol·m-2

·s-1

·Pa-1,

respectively, and the corresponding ideal selectivity is around 15. For binary mixture,

the as-prepared GO membranes show similar results as listed in Table 2. This well

reproducibility will benefit to the practical application. What’s more, we also

summarize the H2-CO2 separation performance of one of the as-prepared GO hollow

fiber membranes during the whole test process. As shown in Fig. 14, the GO hollow

fiber membrane showed a very good stability under different test conditions.

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Table 2. Repeatability of GO membranes

No.

Single gas Mixed gas

Permeance×107

/mol·m-2

·s-1

·Pa-1

H2/CO2 ideal

selectivity

Permeance×107

/mol·m-2

·s-1

·Pa-1

H2/CO2

separation factor

H2 CO2 H2 CO2

M04 1.34 0.09 14.98 1.20 0.11 10.22

M02 1.23 0.07 16.68 1.09 0.10 10.01

M03 1.47 0.11 13.82 1.30 0.12 9.73

M01 1.41 0.09 15.74 1.21 0.12 9.30

M05 1.34 0.09 14.50 1.26 0.10 10.85

Fig. 14. The long term stability of GO hollow fiber membrane under different test conditions.

4. Conclusions

The ceramic hollow fiber supported GO membranes were studied systematically in

the present work. The optimized GO membranes possess a good balance between H2

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permeance and selectivity. Considering the uncomplicated fabrication process and

high packing density, the gas separation ability of ceramic hollow fiber supported GO

membranes will create a great amount of brilliance in the gas separation field. The

high specific surface area of GO material also makes GO membranes very attractive,

due to the resource saving and cost-effective. In addition, because of their special

oxygen containing functional groups, it may further handle the chemical nature of GO

membranes by modifying surface or channels, the gas separation ability of GO

membranes could become adjustable and various.

References

[1] P. Bernardo, E. Drioli, G. Golemme, Membrane gas separation: A review/state of

the art, Ind. Eng. Chem. Res. 48 (2009) 4638-4663.

[2] R.W. Baker, Future directions of membrane gas separation technology, Ind. Eng.

Chem. Res. 41 (2002) 1393-1411.

[3] X.-L. Li, S. Tao, K.-D. Li, Y.-S. Wang, P. Wang, Z.-J. Tian, In situ synthesis of

ZIF-8 membranes with gas separation performance in a deep eutectic solvent, Acta

Phys.-Chim. Sin. 32 (2016) 1495-1500.

[4] A.J. Brown, N.A. Brunelli, K. Eum, F. Rashidi, J.R. Johnson, W.J. Koros, C.W.

Jones, S. Nair, Interfacial microfluidic processing of metal-organic framework hollow

fiber membranes, Science 345 (2014) 72-75.

[5] Y. Hu, J. Wei, Y. Liang, H. Zhang, X. Zhang, W. Shen, H. Wang, Zeolitic

imidazolate framework/graphene oxide hybrid nanosheets as seeds for the growth of

ultrathin molecular sieving membranes, Angew. Chem. Int. Ed. 55 (2016) 2048-2052.

[6] J. Shen, G. Liu, K. Huang, Z. Chu, W. Jin, N. Xu, Subnanometer two-dimensional

graphene oxide channels for ultrafast gas sieving, ACS Nano 10 (2016) 3398-3409.

[7] K. Huang, Z. Dong, Q. Li, W. Jin, Growth of a ZIF-8 membrane on the

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

inner-surface of a ceramic hollow fiber via cycling precursors, Chem. Commun. 49

(2013) 10326-10328.

[8] RadisavljevicB, RadenovicA, BrivioJ, GiacomettiV, KisA, Single-layer MoS2

transistors, Nat Nano 6 (2011) 147-150.

[9] K.G. Zhou, N.N. Mao, H.X. Wang, Y. Peng, H.L. Zhang, A mixed-solvent strategy

for efficient exfoliation of inorganic graphene analogues, Angew. Chem. Int. Ed. 50

(2011) 10839-10842.

[10] H. Liu, A.T. Neal, Z. Zhu, Z. Luo, X. Xu, D. Tománek, P.D. Ye, Phosphorene: An

unexplored 2D semiconductor with a high hole mobility, ACS Nano 8 (2014)

4033-4041.

[11] Y. Peng, Y. Li, Y. Ban, H. Jin, W. Jiao, X. Liu, W. Yang, Metal-organic

framework nanosheets as building blocks for molecular sieving membranes, Science

346 (2014) 1356-1359.

[12] A.K. Geim, Graphene: Status and Prospects, Science 324 (2009) 1530-1534.

[13] Z. Zheng, R. Grunker, X. Feng, Synthetic Two-dimensional materials: a new

paradigm of membranes for ultimate separation, Adv. Mater. (2016).

[14] Z.P. Smith, B.D. Freeman, Graphene oxide: a new platform for high-performance

gas- and liquid-separation membranes, Angew. Chem. Int. Ed. 53 (2014)

10286-10288.

[15] T.-S. Chung, L.Y. Jiang, Y. Li, S. Kulprathipanja, Mixed matrix membranes

(MMMs) comprising organic polymers with dispersed inorganic fillers for gas

separation, Prog. Polym. Sci. 32 (2007) 483-507.

[16] C. Sun, B. Wen, B. Bai, Recent advances in nanoporous graphene membrane for

gas separation and water purification, Sci. Bull. 60 (2015) 1807-1823.

[17] J. Kim, L.J. Cote, J. Huang, Two dimensional soft material: new faces of

graphene oxide, Acc. Chem. Res. 45 (2012) 1356-1364.

[18] G. Liu, W. Jin, N. Xu, Two-dimensional-material membranes: a new family of

high-performance separation membranes, Angew. Chem. Int. Ed. 5 (2016) 2-16.

[19] X. Yang, X. Yang, S. Liu, Molecular dynamics simulation of water transport

through graphene-based nanopores: Flow behavior and structure characteristics,

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

Chinese. J. Chem. Eng. 23 (2015) 1587-1592.

[20] R.R. Nair, H.A. Wu, P.N. Jayaram, I.V. Grigorieva, A.K. Geim, Unimpeded

permeation of water through helium-leak–tight graphene-based membranes, Science

335 (2012) 442-444.

[21] Y. Han, Z. Xu, C. Gao, Ultrathin graphene nanofiltration membrane for water

purification, Adv. Funct. Mater. 23 (2013) 3693-3700.

[22] M. Hu, B. Mi, Enabling graphene oxide nanosheets as water separation

membranes, Environ. Sci. Technol. 47 (2013) 3715-3723.

[23] K. Xu, B. Feng, C. Zhou, A. Huang, Synthesis of highly stable graphene oxide

membranes on polydopamine functionalized supports for seawater desalination, Chem.

Eng. Sci. 146 (2016) 159-165.

[24] N.F.D. Aba, J.Y. Chong, B. Wang, C. Mattevi, K. Li, Graphene oxide membranes

on ceramic hollow fibers – Microstructural stability and nanofiltration performance, J.

Membr. Sci. 484 (2015) 87-94.

[25] X. Chen, G. Liu, H. Zhang, Y. Fan, Fabrication of graphene oxide composite

membranes and their application for pervaporation dehydration of butanol, Chinese. J.

Chem. Eng. 23 (2015) 1102-1109.

[26] H. Huang, Z. Song, N. Wei, L. Shi, Y. Mao, Y. Ying, L. Sun, Z. Xu, X. Peng,

Ultrafast viscous water flow through nanostrand-channelled graphene oxide

membranes, Nat. Commun. 4 (2013) 2979.

[27] K. Huang, G. Liu, Y. Lou, Z. Dong, J. Shen, W. Jin, A graphene oxide membrane

with highly selective molecular separation of aqueous organic solution, Angew. Chem.

Int. Ed. 53 (2014) 6929-6932.

[28] Y.P. Tang, D.R. Paul, T.S. Chung, Free-standing graphene oxide thin films

assembled by a pressurized ultrafiltration method for dehydration of ethanol, J.

Membr. Sci. 458 (2014) 199-208.

[29] G. Li, L. Shi, G. Zeng, Y. Zhang, Y. Sun, Efficient dehydration of the organic

solvents through graphene oxide (GO)/ceramic composite membranes, RSC Adv. 4

(2014) 52012-52015.

[30] W.-S. Hung, Q.-F. An, M. De Guzman, H.-Y. Lin, S.-H. Huang, W.-R. Liu, C.-C.

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

Hu, K.-R. Lee, J.-Y. Lai, Pressure-assisted self-assembly technique for fabricating

composite membranes consisting of highly ordered selective laminate layers of

amphiphilic graphene oxide, Carbon 68 (2014) 670-677.

[31] R.K. Joshi, P. Carbone, F.C. Wang, V.G. Kravets, Y. Su, I.V. Grigorieva, H.A. Wu,

A.K. Geim, R.R. Nair, Precise and ultrafast molecular sieving through graphene oxide

membranes, Science 343 (2014) 752-754.

[32] S.C. O'Hern, M.S. Boutilier, J.C. Idrobo, Y. Song, J. Kong, T. Laoui, M. Atieh, R.

Karnik, Selective ionic transport through tunable subnanometer pores in single-layer

graphene membranes, Nano Lett. 14 (2014) 1234-1241.

[33] H. Li, Z. Song, X. Zhang, Y. Huang, S. Li, Y. Mao, H.J. Ploehn, Y. Bao, M. Yu,

Ultrathin, molecular-sieving graphene oxide membranes for selective hydrogen

separation, Science 342 (2013) 95-98.

[34] H.W. Kim, H.W. Yoon, S.-M. Yoon, B.M. Yoo, B.K. Ahn, Y.H. Cho, H.J. Shin, H.

Yang, U. Paik, S. Kwon, Selective gas transport through few-layered graphene and

graphene oxide membranes, Science 342 (2013) 91-95.

[35] S.P. Koenig, L. Wang, J. Pellegrino, J.S. Bunch, Selective molecular sieving

through porous graphene, Nat. Nanotechnol. 7 (2012) 728-732.

[36] S.C. O’Hern, M.S. Boutilier, J.-C. Idrobo, Y. Song, J. Kong, T. Laoui, M. Atieh,

R. Karnik, Selective ionic transport through tunable subnanometer pores in

single-layer graphene membranes, Nano Lett. 14 (2014) 1234-1241.

[37] H. Kaur, V.K. Bulasara, R.K. Gupta, Preparation of kaolin-based low-cost porous

ceramic supports using different amounts of carbonates, Desalin. Water. Treat. 57

(2016) 15154-15163.

[38] A. Kaiser, S.P. Foghmoes, G. Pećanac, J. Malzbender, C. Chatzichristodoulou,

J.A. Glasscock, D. Ramachandran, D.W. Ni, V. Esposito, M. Søgaard, P.V. Hendriksen,

Design and optimization of porous ceramic supports for asymmetric ceria-based

oxygen transport membranes, J. Membr. Sci. 513 (2016) 85-94.

[39] R. Faiz, M. Fallanza, I. Ortiz, K. Li, Separation of olefin/paraffin gas mixtures

using ceramic hollow fiber membrane contactors, Ind. Eng. Chem. Res. 52 (2013)

7918-7929.

ACC

EPTE

D M

ANU

SCR

IPT

ACCEPTED MANUSCRIPT

[40] Y. Xu, H. Bai, G. Lu, C. Li, G. Shi, Flexible graphene films via the filtration of

water-soluble noncovalent functionalized graphene sheets, J. Am. Chem. Soc. 130

(2008) 5856-5857.

[41] S. Pei, H.-M. Cheng, The reduction of graphene oxide, Carbon 50 (2012)

3210-3228.

[42] A. Lerf, H. He, M. Forster, J. Klinowski, Structure of graphite oxide revisited, J.

Phys. Chem. B 102 (1998) 4477-4482.

[43] H. He, J. Klinowski, M. Forster, A. Lerf, A new structural model for graphite

oxide, Chem. Phys. Lett. 287 (1998) 53-56.

[44] X. Dong, K. Huang, S. Liu, R. Ren, W. Jin, Y.S. Lin, Synthesis of zeolitic

imidazolate framework-78 molecular-sieve membrane: defect formation and

elimination, J. Mater. Chem. 22 (2012) 19222.

[45] X. Gu, Z. Tang, J. Dong, On-stream modification of MFI zeolite membranes for

enhancing hydrogen separation at high temperature, Micropor. Mesopor. Mat 111

(2008) 441-448.

[46] G. Guan, T. Tanaka, K. Kusakabe, K.-I. Sotowa, S. Morooka, Characterization of

AlPO 4-type molecular sieving membranes formed on a porous α-alumina tube, J.

Membr. Sci. 214 (2003) 191-198.

[47] L.M. Robeson, The upper bound revisited, J. Membr. Sci. 320 (2008) 390-400.

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EPTE

D M

ANU

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IPT

ACCEPTED MANUSCRIPT

Highlights

1. Integrated and stable GO membranes were prepared on the ceramic hollow fiber.

2. Gas separation performance of GO membranes was investigated systematically.

3. GO membranes exhibit efficient hydrogen recovery.