Carbon Nanotube Modified Sepiolite Porous Ceramics for High-efficient Oil/Water Separation

doi:10.15541/jim20190382

Abstract

Abstract:

To efficiently recovery oil from oil/water mixed liquid, fibrous sepiolite, polyethylene powder and nickel nitrate was respectively used as raw mateials, carbon source and pore-forming agents, and catalyst precursor to prepare carbon nanotubes (CNTs) modified sepiolite porous ceramics by freeze-drying/catalytic pyrolysis method, and the effects of solid content and pyrolysing temperature on the morphology of the modified porous ceramics were studied. The water contact angle and oil-water separation performance in severly environment such as acid (pH=1), alkali (pH=14), and high (373 K) and low temperature (77 K) were also characterized. The results showed that when the concentration of catalyst precursor solution was 0.5 mol/L, the solid content of sepiolite was 15wt%, the catalytic pyrolysis temperature was 973 K, and the soaking time was 2 h, the as-prepared CNTs modified porous ceramics possessed superhydrophobic/superlipophilic nature, and their maximum adsorption capacity for diesel, paraffin oil, vegetable oil, and vacuum pump oil is respectively 15.7, 20.8, 23 and 25 times of their own weight. The oil flux during the continuous separation process is up to 250 kg·s ^-1·m ^-2, and the separation efficiency and selectivity can be maintained without significant decreasing within 5 h.

Key words: sepiolite porous ceramics, freeze drying, carbon nanotubes, superhydrophobic/superlipophilic, oil/water separation

CLC Number:

TQ174

DONG Longhao,ZHANG Haijun,ZHANG Jun,WU Wenhao,JIA Quanli. Carbon Nanotube Modified Sepiolite Porous Ceramics for High-efficient Oil/Water Separation[J]. Journal of Inorganic Materials, 2020, 35(6): 689-696.

Figures/Tables 13

Fig. 1 SEM micrographs of the as-prepand sepiolite porous ceramics (a-b) Before CNTs modification; (c-d) Modified with CNTs

Fig. 2 SEM micrographs and carbon content change of CNTs modified sepiolite porous ceramics with various solid contents (a) 10wt%; (b) 15wt%; (c) 20wt%; (d) Carbon content change

Fig. 3 The static water contact angle of CNTs modified sepiolite porous ceramics with various solid contents (a) 10wt%; (b) 15wt%; (c) 20wt%

Fig. 4 SEM micrographs and carbon content change of CNTs modified sepiolite porous ceramics prepared at various pyrolysis temperatures (a) 923 K; (b) 973 K; (c) 1023 K; (d) Carbon content change

Fig. 5 TEM and HRTEM images of CNTs resultant from pyrolysis of polyethylene at 973 K for 2 h under the optimal condition (a) Low transmission electron microscopy; (b) Tip of CNTs; (c) HRTEM images of the walls of CNTs

Fig. 6 Static adsorption capacities of CNTs modified sepiolite porous ceramics for different oils

Table 1 Comparison of adsorption capacity values of various adsorbent materials developed to date

Adsorbent material	Adsorbate	Modified substance	Adsorption capacity (g?g^-1)	Ref.
Sepiolite powders	Motor oil	-	0.174-0.184	[29]
Modified silica powders	Motor oil	1, 7-octadiene	0.330	[30]
Diatomite/silicalite-Ⅰcomposite powders	Benzene	Silicalite-Ⅰ	0.095-0.246	[31]
Modified diatomite porous ceramics	Toluene	Graphene/carbon nanobelts	1.090	[19]
Modified diatomite porous ceramics	Vacuum pump oil	Graphene/carbon nanobelts	1.025	[19]
Boron nitride aerogel	Salad oil	-	5	[32]
Modified alumina porous ceramics	Hexane	Polydimethylsiloxane	2	[33]
Modified rock wool	Diesel oil	Polydimethylsiloxane/silica	7	[34]
Polymethylsilsesquioxane aerogel	Hexane	-	6.2	[35]
Modified sepiolite porous ceramics	Hiesel oil	CNTs	15.7	This work
Modified sepiolite porous ceramics	Haraffin oil	CNTs	20.8	This work
Modified sepiolite porous ceramics	Vegetable oil	CNTs	23	This work
Modified sepiolite porous ceramics	Vacuum pump oil	CNTs	25	This work

Fig. 7 Pore size distribution of CNTs modified sepiolite porous ceramics

Fig. 8 Schematic illustration (a) and images (b-c) of the continuously oil recovery instrument

Fig. 9 The oil flux of CNTs modified sepiolite porous ceramics for paraffin oil/water mixture within 5 h

Fig. 10 The static water contact angles of CNTs modified sepiolite porous ceramics in various environments (a) As-synthesized ceramic; (b) pH=1; (c) pH=13; (d) 373 K; (e) 77 K

Fig. 11 Oil/water separation selectiviies of CNTs modified porous ceramics in various environments (1) As-synthesized ceramic; (2) pH =1; (3) pH=13; (4) Heating at 373 K for 4 h; (5) Freezing at 77 K for 4 h

Fig. 12 Static water/oil contact angle of porous ceramics without CNTs (a) Water contact angle; (b) Oil contact angle

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