Preparation and Characterization of NaA Zeolite Membranes on Inner-surface of Four-channel Ceramic Hollow Fibers

doi:10.15541/jim20170174

Abstract

Abstract:

High-performance NaA zeolite membranes were prepared on inner-surface of four-channel ceramic hollow fibers by combined counter-diffusion vacuum seeding and dynamic hydrothermal synthesis method. The as-prepared membranes were adopted to the pervaporation dehydration of 90wt% ethanol/water mixture at 75℃. Effects of seeding and synthesis conditions on morphology and separation performance of the membranes were extensively investigated in terms of flow rate of seed suspension, seeding time and synthesis temperature. These results showed that dense and uniform NaA zeolite membrane was obtained when the flow rate of seed suspension was 100 mL/h and the seeding time was 5 s. Over slow flow rate of seed suspension or too long seeding time increased the membrane thickness but generated defects on membrane surface simultaneously. When the NaA zeolite membrane was hydrothermally synthesized at 100℃ for twice, the membrane achieved the best water/ethanol separation factor of 1585 while the permeation flux was 8.8 kg/(m²·h) in the pervaporation dehydration. Lower synthesis temperature led to incomplete membrane crystallization and some defects were observed on the membrane surface. With excessive synthesis temperature defects were also detected in the cross-section of the membrane due to the over rapid crystallite rate, which resulted in poor separation performance of the membrane.

Key words: four-channel hollow fiber, NaA zeolite membrane, inner membrane, pervaporation

CLC Number:

TQ028

WANG Xiao-Lei, ZHANG Yu-Ting, GAO Bing, ZHANG Chun, GU Xue-Hong. Preparation and Characterization of NaA Zeolite Membranes on Inner-surface of Four-channel Ceramic Hollow Fibers[J]. Journal of Inorganic Materials, 2018, 33(3): 339-344.

Figures/Tables 10

Fig. 1 Schematic diagram of counter-diffusion vacuum seeding

Fig. 2 Schematic diagram of dynamic hydrothermal synthesis method

Fig. 3 SEM images of four-channel ceramic hollow fiber(a) Cross-section; (b) Inner-surface

Fig. 4 XRD patterns of NaA zeolite and zeolite membrane(a) Four-channel ceramic hollow fiber; (b) NaA zeolite; (c) NaA zeolite membrane

Fig. 5 Surface and cross-sectional SEM images of NaA zeolite membranes prepared at different seeds suspension flow rates(a-b) 500 mL/h; (c-d) 300 mL/h; (e-f) 100 mL/h; (g-h) 50 mL/h

Table 1 Pervaporation performance of NaA zeolite membrane prepared at different seeds suspension flow rate

Seeds suspension flow rate/(mL·h^-1)	J/(kg∙m^-2∙h^-1)	α_{water/ethanol}
500	12.5	780
300	10.17	1061
100	8.8	1585
50	12.3	446

Fig. 6 Surface and cross-sectional SEM images of NaA zeolite membrane prepared for different coating periods(a-b) 3 s; (c-d) 5 s; (e-f) 10 s; (g-h) 15 s

Table 2 Pervaporation performance of NaA zeolite membrane prepared for different coating poriod

Coating period/s	J/(kg∙m^-2∙h^-1)	α_{water/ethanol}
3	9.5	133
5	8.8	1585
10	10.4	178
15	9.1	70

Fig.7 Surface and cross-sectional SEM images of NaA zeolite membrane prepared at different temperatures(a-b) 95℃; (c-d) 100℃; (e-f) 105℃; (g-h) 110℃

Table 3 Pervaporation performance of NaA zeolite membrane prepared at different temperatures

Temperature/℃	J/(kg∙m^-2∙h^-1)	α_{water/ethanol}
95	8.3	273
100	8.8	1585
105	8.0	433
110	9.0	217

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