Preparation of Superhydrophilic and Underwater Superoleophobic PVDF-g-PAA Porous Membranes and Their Oil-water Separation Performance†

doi:10.7503/cjcu20150961

Abstract

Abstract:

Traditional polymer membranes used for treating emulsified oil/water mixtures always suffer from low flux, membrane damage and separation efficiency decline, which limit its further application. Here we fabricated a superhydrophilic and underwater superoleophobic poly(vinylidene fluoride)-grafed-poly(acrylic acid)[PVDF-g-PAA] membrane by salt-induced phase inversion method, the saturated sodium chloride solution was used as coagulation bath. In order to improve membrane performance polyvinylprrolidone(PVP) was added as porogen to improve internal structure of the membrane. The result showed that when the content of PVP was 5% the PVDF-g-PAA membrane could be used to separate both simple oil/water mixture and oil in water emulsion, the separation efficiency of oil in water emulsion still reaches 91% after several times and the flux maintained at 444 L/(m² · h) or more. Also the membrane exhibits an excellent antifouling property and is easily recycled for long-term use. The outstanding performance of the membrane and the efficient, energy and cost-effective preparation process highlight its potential for practical applications.

Key words: Superhydrophilic and underwater superoleophobic, Poly(vinylidene fluoride)-grafed-poly(acry-lic acid) membrane, Oil-water separation

CLC Number:

O632.51

TrendMD:

GAO Hong, DUAN Yueqin, YUAN Zhihao. Preparation of Superhydrophilic and Underwater Superoleophobic PVDF-g-PAA Porous Membranes and Their Oil-water Separation Performance^†[J]. Chem. J. Chinese Universities, 2016, 37(6): 1208.

Figures/Tables 11

Scheme 1 Surface modification of PVDF membrane(A) and surface grafting of PVDF membrane(B)

Fig.1 SEM image(A) and contact angle(B) of cross section of original PVDF membrane

Fig.2 Change of contact angle after the water droplet contact with the surface of PVDF-g-PAA membraneTime/s: (A) 0; (B) 7.5; (C) 15; (D) 22.5; (E) 30; (F) 37.5; (G) 45.Contact angle/(°): (A) 41.4; (B) 32.5; (C) 25.9; (D) 24.6; (E) 23.8; (F) 16.1; (G) 0.

Fig.3 SEM images of PVDF(A, B) and PVDF-g-PAA membranes(C, D)(A) Top surface of PVDF membrane; (B) bottom surface of PVDF membrane; (C) top surface of PVDF-g-PAA membrane;(D) bottom surface of PVDF-g-PAA membrane.

Fig.4 SEM images of top surface of PVDF-g-PAA membrane with different component contents of PVPw(PVP)(%): (A) 0; (B) 2; (C) 5; (D) 10; (E) 15; (F) 20.

Fig.5 SEM images of cross section of PVDF-g-PAA membrane with different component contents of PVPw(PVP)(%): (A) 0; (B) 2; (C) 5; (D) 10; (E) 15; (F) 20.

Table 1 Separation efficiency of oil-water emulsion

w(PVP)(%)	Separation efficiency(%)
w(PVP)(%)	First time	Second time	Third time	Forth time	Fifth time
0	98	96	87	83	77
2	96	96	89	81	78
5	95	93	92	91	91
10	84	81	80	77	75
15	77	76	75	74	72
20	72	71	69	67	66

Fig.6 Photoimage of particle size of oil/water emulsion system

Scheme 2 Possible mechanism of O/W emulsion separation by PVDF-g-PAA membrane

Fig.7 Flux of PVDF-g-PAA membrane with different component of PVP

Fig.8 Mechanical property of PVDF-g-PAA membrane with different component of PVP

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