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Fabrication of magnetic porous silica submicroparticles for oil removal from water Liuhua Yu, Gazi Hao, Qianqian Liang, and Wei Jiang Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.5b02428 • Publication Date (Web): 09 Sep 2015 Downloaded from http://pubs.acs.org on September 9, 2015

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Industrial & Engineering Chemistry Research

Fabrication of magnetic porous silica submicroparticles for oil removal from water Liuhua Yu, Gazi Hao, Qianqian Liang, Wei Jiang* National Special Superﬁne Powder Engineering Research Center of China, Nanjing University of Science and Technology, Nanjing 210094, PR China Abstract With the development of the world oil production and the increasing of transportation, the oil spillage accidents showed a rising trend, which was not only harmful to the ecological environment, but also a huge threat to people's health. Herein, we reported a novel kind of linear-coated magnetic silica submicron materials with controlled porosity for oil spills clean-up. The result showed that the submicron composite materials with superhydrophobicity, superoleophilicity and good magnetic response, which had a significant effect on oil absorption and was used to absorb different oils up to 11.51 times of its own weight. More importantly, the oil-absorbed material could be recycled in the auxiliary magnetic field and still exhibited an excellent performance after the 20th cycle. With a combination of simple synthesis process, magnetic responsibility, and excellent hydrophobicity, the modified magnetic porous silica submicroparticles as a promising absorbent has broad application prospects. Keywords: Superhydrophobicity and Superoleophilcity, Magnetic field, Recyclable, Porous material, Oil absorption, Environmental protection 1. INTRODUCTION As the rapid development of industry and transportation, there is a growing tendency of pollutant emissions to river and sea with each passing day. According to

*

Corresponding author. Tel.: +86 025-84315042; Fax.: +86 025-84315042 E-mail address: [email protected] (W. Jiang)

ACS Paragon Plus Environment


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the incomplete statistics, the amount of the spilled oil around the world is approximately equal to 400,000 tons through various ways per year.1 Unfortunately, the accidents of offshore oil drilling, production platform and the damaged tanker caused oil pollution on the water surface. These oil extraction accidents led to severe oil pollution on the water surface and threatened ecological environment gravely.2 Once the crude oil leaks out into the water, a certain thickness of oil film formed will isolate water from atmosphere.3 As a result, large amounts of sea life will be damaged severely. Furthermore, the crude oil is persistent environment pollutants and its adverse effect will last for several decades. In order to remove the spilled oil, a variety of traditional measures have been employed, including mechanical collection,4 physical absorption,5 bioremediation,6 combustion method,7 etc.8 Compared with other measures, physical absorption has the advantages of low price, convenient operation and high oil absorption capacity. Therefore, using absorbent materials is considered as one of the most effective degreasing methods. Currently, natural absorption materials such as clay9 and straw10 are applied to the oil-water separation. Due to the low absorption and difficulty to repeated use, they are not suitable for oil removal on large-scale, which limit their application. This situation give the synthetic materials a wide opportunity to develop.11 In recent years, various absorbent materials e.g., cellulose aerogels,12 film,13,14 carbon nanotube,15,16 foam,17 sponge18 and so forth19,20 have been synthesized to absorb oil, owing to their superhydrophobicity and superoleophilicity. In general, an ideal oil absorbing materials should have (i) superhydrophobicity and superoleophilicity (ii) high selectivity of oil-water separation, and (iii) simple preparation process and reutilization after the absorption process. However, the developed absorption materials still have some defects, which do not meet the requirements mentioned


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above. So it is necessary to launch further research on environmental friendly and high oil absorption materials. Recently, much attention has been paid to study porous silica all over the world.21,22 Owing to the large specific surface area, low density and interconnected pore structures, it has been diffusely employed in the fields of medicine,23 catalysis,24 sensing25 and absorption.26,27 Additionally, magnetic separation provides a convenient method for the removal of magnetizable particles by applying an appropriate magnetic field. Therefore, combination of magnetic material and porous silica would be very valuable for oil removal. As is well known, template method is a greatly significant and widely used method for preparation of materials.28-32 High oil absorption materials could be prepared by this method. Here, we reported a simple template approach to fabricate Fe3O4/SiO2 submicron composites with porous and core-shell structure and superhydrophobicity was improved by vinyltriethoxysilane, which had a wide application in the field of superhydrophobic materials.33-35 The as-modified magnetic porous silica submicroparticles could fast and selectively absorb floating oils on the water surface. Moreover, the as-obtained submicron composites exhibited little loss of their absorption capacity and water contact angle after 20 cycles. Because of frequently occurring environment pollution arising from oil spilling, the finding of this article might offer a promising absorbent material for fast and selective removal of oil from water surface 2. EXPERIMENTAL SECTION 2.1 Materials and Chemicals Ferric chloride hexahydrate (FeCl3·6H2O), sodium acetate (NaAc), tetraethyl orthosilicate (TEOS), ammonia water (NH3·H2O) and vinyltriethoxysilane (VTES)



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were bought by Sinopharm Chemical Reagent Co. Ltd., Shanghai, China. Hexadecyl trimethyl ammonium bromide (CTAB) was purchased from Shanghai Lingfeng Chemical Reagent Co. Ltd., Shanghai, China. Ethylene glycol ((CH2OH)2) was received from Shanghai No.4 Reagent & HV Chemical Co. Ltd., Shanghai, China. Polyethylene glycol (PEG4000), sodium hydroxide (NaOH), sodium chloride (NaCl), and ammonium nitrate (NH4NO3) were obtained from Xilong Chemical Reagent Co. Ltd., Shantou, China. Hydrochloric acid (HCl) was obtained from Yonghua chemical technology Co. Ltd., Jiangsu China. Absolute ethanol (C2H5OH) was gained by Nanjing Chemical Reagent Co. Ltd., Nanjing, China. All chemicals were analytic reagent grade and were used without further treatment. Deionized water was used throughout. 2.2 Preparation of Fe3O4 submicroparticles To improve the recyclability, a superparamagnetic Fe3O4 core was incorporated into the center of silica.36,37 Fe3O4 submicroparticles with uniform particle size and good dispersion were prepared through the improved solvent thermal method.38 The specific steps were as follows: first of all, 1.35 g of ferric chloride hexahydrate, 500 mg of PEG4000 and 4 g of sodium acetate were completely dissolved in 40 mL of ethylene glycol and dispersed for 1 h by ultrasonic method, forming a uniform mixed solution of pale yellow. Then, the mixed solution was transferred to a hydrothermal reaction kettle of 100 mL, and maintained at 200 °C for 16 h. After the completion of the reaction, the hydrothermal reaction kettle was cooled to room temperature and the obtained products were washed three times successively with deionized water and absolute ethanol. Subsequently, the as-obtained products were put into the vacuum drying oven at 40 °C for 12 h. Finally, we got the Fe3O4 submicroparticles with uniform particle size and good dispersion.


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2.3 Fabrication of Fe3O4/SiO2 composite submicroparticles We synthetized the magnetic porous silica submicroparticles (MPSS) in the following step. Magnetic silica submicroparticles (MSS) were fabricated by using TEOS as silicon source and CTAB as template at room temperature via template method. Figure 1 illustrates the preparation process in detail. Briefly, 100 mg of Fe3O4 was dispersed into 20 mL of deionized water and 80 mL of absolute ethanol. The black homogeneous precursor solution was produced by ultrasonic dispersion for 10 min. Then 200 mg of CTAB was added into the solution under ultrasonic oscillation for another 10 min. The obtained mixture was transferred to the three-neck flask and then 3 mL of NH3·H2O was added into it, stirred at 30 °C for 10 min. Subsequently, 1.2 mL of TEOS was slowly added dropwise within 1 h, and this reaction lasted 6 h at 30 °C. The as-obtained MSS were dispersed into 100 mL of 6 g/L of ethanol solution of ammonium nitrate at reflux for 10 h to remove CTAB. After that, the rough and porous submicron composites were prepared.

Figure 1. Synthetic procedure of Fe3O4/SiO2 composite submicroparticles. 2.4 Surface modification The MPSS samples were modified with VTES. 150 mg of samples were allowed to react with VTES (2 mL) at room temperature for 2 h.35 After the reaction finished, the obtained magnetic submicroparticles were collected under the magnetic techniques. Furthermore, the coarse products were washed three times with absolute



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ethanol and deionized water in turn, and dried in vacuum at 40 °C for 12 h. Finally, we got the modified MPSS we wanted. 2.5 Characterization Power X-ray diffraction (XRD) patterns were recorded on a Bruker D8 Advanced diffractometer (Bruker D8 Super Speed) with Cu Kα radiation and the scanning angle ranged from 20° to 80° of 2θ at 40 kV. The morphology of the products prepared above was observed by using scanning electron microscopy (SEM, Model-S4800, Hitachi, Japan) under an electron beam with an accelerating voltage of 15 kV. All of the samples were coated with a thin layer of gold for better conductivity. The energy-dispersive X-ray spectroscopy (EDAX) measurements were performed on an OXFORD INCA Energy Dispersive Spectrometer. Brunauer–Emmett–Teller (BET) surface area measurement was carried out using an ASAP 2020 porosimetry system (Micromeritics, USA). Transmission electron microscopy (TEM) images of the synthesized magnetite submicroparticles were taken with Model Tecnai 12 with an acceleration voltage of 200 kV. The sample was prepared by the deposition and drying of a drop of the submicroparticles dispersed in absolute ethanol onto a formal coated 300 mesh copper grid before acquiring the micrographs. Fourier transform infrared (FT-IR) spectra (4000-500 cm-1) in KBr were examined on a Bruker Vector 22 spectrometer by KBr pellet technique. The superhydrophobicity and oleophilicity were estimated on a contact angles measurement apparatus (CAs, SL200B, Solon Tech. Co. Ltd., China) with a 4 µL droplet. Thermal gravimetric analysis (TGA) was utilized by Model TA2100 (TA Instruments, USA). The samples were heated from 50 °C to 800 °C with a heating rate of 10 °C/min under nitrogen atmosphere. The magnetic properties were checked in fields between ±5 kOe at room temperature by a vibrating sample magnetometer (VSM, LakeShore 735).


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2.6 Measurment of absorption capacity Absorption capacities of the modified MPSS for the following oils were measured: lubricating oil, edible oil, salad oil and diesel oil. A few drops of oil were dropped onto the middle on the water surface in the culture dish. Subsequently, a certain amount of the modified MPSS were gently placed on the surface of the oil-water mixture. The total oils were fast and selectively absorbed within several seconds and then the absorbed oils together with the modified MPSS were separated out by a magnet bar for weight measurement. All the absorption experiments were repeated for three times and carried out at room temperature (25 ± 5 °C). We calculated the absorption capacity (Q) of submicroparticles by the formula: Q=(Msat-M0)/M0, where M suggest the weight the modified MPSS before (0) and after (sat) saturation by oils. The purity of the collected oils and the selectively absorption characteristics of the porous materials were investigated by thermal gravimetric analysis (TGA) and water contact angles (WCA). 2.7 Regeneration of absorbent After absorption process, the used materials were washed by absolute ethanol for several times to remove the oil and dried in a vacuum oven at 40 °C for 10 h. We tested the absorption capacity of the recycled submicron composites again. All the experiments were repeated for three times. 3. RESULTS AND DISCUSSION 3.1 The morphology and structure of Fe3O4/SiO2 submicron composites The chemical composition of Fe3O4, unmodified MPSS and modified MPSS were confirmed by XRD analysis. We could see clearly the X-ray diffraction peak positions of these three samples in Figure 2. The diffraction peaks in curve a matched the characteristic peaks in the standard pattern (JCPDS file No. 19-0629) for Fe3O4 at



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30.1° (220), 35.7° (311), 43.1° (400), 57.2° (511) and 62.6° (440). No peak from impurities could be found in the XRD pattern of the as-obtained samples, signifying none of the different crystalline phases were generated. From the patterns, it was evident that the peaks in curve a, curve b and curve c were similar, which indicated the crystal form of Fe3O4 submicroparticles in unmodified MPSS and modified MPSS had not been changed. We also carried out EDAX measurements to prove that no impurity consisted in the samples under the position of coating with a thin layer of gold for better conductivity. It could be obviously seen from the EDAX spectra that the Fe3O4 sample consisted of Fe and O elements, which agreed well with XRD analysis. The EDAX characterization also showed that the main elements of the submicron composites before surface modification were Fe, O, and Si, the additive C element was found in the modified MPSS supporting that the hydrophobic functional groups were grafted to the surface of the submicron composites. (Figure S1, Figure S2 and Figure S3, Supporting Information).

Figure 2. XRD patterns of (a) Fe3O4 submicroparticles, (b) unmodified MPSS, (c)


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modified MPSS. To further characterize the morphology and size of the obtained products, SEM observations were carried out. Continuous structure and well-defined porous structure were distinctly revealed in Figure 3. As was shown in Figure 3(a), it could be observed that Fe3O4 submicroparticles had good dispersion and the particle size was about 200 nm. In accord with SEM observations, it could be concluded that as the coating reaction proceeded, the silica was slowly coated on the surface of Fe3O4 to form a smooth surface and the surface of MSS become rough and porous after removing CTAB, through comparing Figure 3(b) and Figure 3(c). According to SEM images, a large portion of submicroparticles formed intensively porous appearance. The detailed structures of the submicroparticles with the porous submicrospheres became obvious in these images. a

b

c

Figure 3. SEM images of (a) Fe3O4, (b) MSS, (c) MPSS.



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Then the porous structure and textural properties of the submicron composites were further observed by TEM and BET. As we had seen from Figure 4(a), it was evidently certified that Fe3O4 submicroparticles presented good dispersion and welldefined size. Additionally, the outer surface of the Fe3O4 skeleton was coated with SiO2 layer which had a thickness of about 70 nm and then a core-shell submicrostructure was obtained as illustrated in Figure 4(b). Furthermore, no single magnetic particles could be observed in Figure 4(b) and Figure 4(c), suggesting that all of the Fe3O4 submicroparticles had been coated with SiO2 layer. Notably, it had been demonstrated that the formation of silica coating on the surface of Fe3O4 submicroparticles could help prevent their aggregation in liquid. What’s more, silica coating could improve their chemical stability.39 More interestingly, it could be observed that the rough and porous structure became more apparent from Figure 4(c), compared with Figure 4(b), which tallied well with SEM observations. To show the variation clearly, we enlarged magnification of TEM to catch a single particle of MSS and MPSS, as shown in Figure 4(d) and 4(e). Unlike other oil absorbents, the asobtained MPSS possessed porosity and roughness, which could increase their absorption capacities further. The main BET parameters obtained from N2 physisorption experiments were summarized in Table S1 (Supporting Information). The results indicated that specific surface area of the MSS was 2.66 m2/g. Owing to removal of CTAB, the specific surface areas of the unmodified MPSS and modified MPSS were increased to 331.12 m2/g and 306.45 m2/g, respectively. The sufficient large specific surface area could ensure the modified MPSS have potential applications for absorption.


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a

b

c

e

d

Figure 4. TEM images of (a) Fe3O4, (b) MSS, (c) MPSS, (d) a single particle with higher magnification of MSS, (e) a single particle with higher magnification of MPSS. Figure 5 exhibited the FT-IR spectra of Fe3O4, unmodified MPSS and modified MPSS. The characteristic peak around 569.6 cm-1 could be attribute to the stretching vibration of the Fe-O bond of Fe3O4 (curve a). The characteristic peaks at 1110.6 cm-1 could be ascribed to the absorption bands of Si-O-Si (curve b). The strong wellresolved peaks of H2O at 1343.2 cm-1 and 3688.5 cm-1 implied unmodified MPSS possesses hydrophily. However, the peak intensities of H2O significantly diminished and the -CH3 peaks at 3047.8 cm-1 and 841.5 cm-1 were recreated,40 certifying the hydroxyl groups on the surface of unmodified MPSS were replaced by alkoxy (OR) groups. The modified MPSS obtained the property of highly hydrophobicity due to the surface modification of VTES.



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Figure 5. FT-IR spectra of (a) Fe3O4, (b) unmodified MPSS, (c) modified MPSS. In order to measure the coverage degree of alkyl groups on the surface of the modified MPSS, thermogravimetric analysis (TGA) was carried out. As was shown in Figure 6 (curve c), the modified MPSS revealed a 7.6 % weight loss in 150 °C– 600 °C, which was attributed to the decomposition of the ethyl and vinyl groups. Based on the mass loss, the grafted density of alkyls could be calculated. Due to the small quantity of alkyl groups, the modified MPSS exhibited the property of superhydrophobicity. Moreover, we could clearly see that the unmodified MPSS showed a 2.2 % weight loss in the temperature range 65 °C–200 °C and duplicated 1.8 % at 550 °C–600 °C. We could consider that two weight losses were relevant to existing hydroxyl groups on the surface of materials and the difficulty of thermal decomposition of impurities, respectively. As expected, the absorption capacity of the modified MPSS for dyed diesel oil was up to 5.59 times of their own weight, which were closed to the result of TGA (curve d). Interestingly, the mass loss of the modified MPSS after oil absorption was more than the modified MPSS by comparing


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curve c with curve d, which was due to absorbed organic solvents and the pyrolysis of residual organics. Notably, we could clearly see that no weight loss of as-obtained products was seen at 150 °C. So it was concluded that modified MPSS showed excellent stability and only oil was absorbed, which was consist with superhydrophobicity and superoleophilcity of as-obtained materials.

Figure 6. TGA curves of (a) diesel oil, (b) unmodified MPSS, (c) modified MPSS, (d) oil-absorbed modified MPSS. Additionally, we could clearly see the good magnetic property of the modified MPSS (Video S1, Supporting Information). The saturation magnetization of Fe3O4, modified MPSS and oil-absorbed modified MPSS was measured at room temperature and the results were 89.5 emu/g, 24.8 emu/g and 11.1 emu/g, respectively (Figure 7). As expected, curve b showed no remanence or coercivity, proving the superparamagnetic character was essential for the magnetic separation and recycling.



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It was obvious that coating layer became thicker, magnetic property became weaker. Therefore, it was believed that the magnetic submicroparticles had been well coated with SiO2, which affected the magnetism. Even though the as-obtained materials absorbed oils to the largest extent, the submicron composites still remained a certain magnetism which made composite materials recyclable under the magnetic field. Obviously, the modified MPSS would be an environment-friendly material because of its non-pollution and recyclability.

Figure 7. VSM curves of (a) Fe3O4, (b) modified MPSS, (c) oil-absorbed modified MPSS. More importantly, the as-prepared modified MPSS have superhydrophobicity and superoleophilicity. In Figure 8(a), contact angle measurements were carried out and the apparent water contact angle was as high as 148.8° which displayed highly hydrophobic property of the modified MPSS because the vinyl and ethyl groups tend to appear on the surface of the modified MPSS to decrease the surface energy.41 On


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the contrary, the oil contact angle of the modified MPSS were almost 0° in the Figure 8(b). Once droplets of oil was in contact with the surface of the modified MPSS, they spread and penetrated into porous structure in a few seconds. Moreover, the modified MPSS exhibited superior repellency to corrosive liquids such as 1.0 M HCl and 1.0 M NaOH aqueous solutions besides water for 24 h, as shown in Figure 9. The results showed

that the as-obtained

materials

displayed

superhydrophobicity and

superoleophilicity and if they were put into an oil–water mixture, oil would be absorbed immediately nevertheless water would not.

(a )

(b)

Figure 8. Optical image of (a) a drop of water placed on a bed of the modified MPSS, (b) a drop of diesel oil (dyed with Sudan Red) placed on the bed of the modified MPSS.

(a )

(b)

Figure 9. Situation of the modified MPSS floating on (a) 1.0 M HCl aqueous solutions,(b) 1.0 M NaOH aqueous solutions for 24 h. 3.2 The oil absorption capacity of the modified MPSS



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The modified MPSS could be used to absorb floating oils on the water surface. To investigate the oil intake capacity of the modified MPSS, the specific experiment was carried out as shown in Figure 10. A few drops of diesel oil which were dyed by Sudan Red were dropped onto the middle of the water surface, and then a certain amount of the modified MPSS was added. Controlled by a magnet, the modified MPSS could be driven to the water zone and then rapidly absorbed the oils, keeping a balance of absorption. (see Video S2, Supporting Information). To our surprise, the modified MPSS showed unsinkable property when they were put on the both surfaces of the oils and water under vigorous stirring situations (see Video S3, Supporting Information). Four kinds of oils including lubricating oil, edible oil, salad oil and diesel oil were researched in this study. It was reported that the oil absorption capacities increase as density and viscosity of oils went up. The oil-absorption capacity of the modified MPSS was in order of lubricating oil > salad oil > edible oil > diesel oil, which was related to the density and viscosity of the oils.42 Table 1 revealed the physical properties of experimental oils. From Figure 11(b), we could clearly see that the oil absorption capacities of the modified MPSS for the above oil were 11.51, 8.34, 7.14 and 5.59 times of its own weight, respectively. It was satisfactory to use the submicron composites to remove oils from water surface effectively, and the oil-absorption capacity of the modified MPSS was better than many known materials (Table S2, Supporting Information). According to the absorption mechanism, porous absorption materials stored oils in pores and its surface.43 Hence, the more the pores and specific surface area, the larger the absorption capacity.


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a

b

d

c

Figure 10. Removal of diesel oil from water surface by the modified MPSS under magnetic field. ( The diesel oil was dyed by Sudan red for clarity.) Table 1 Comparison among properties of various experimental oils. Density at 25 °C ( g/cm3 )

Viscosity at 25 °C( cP )

Surface tension ( mN/m )

Diesel oil

0.843

6.2

13.0

Edible oil

0.910

10.1

14.3

Salad oil

0.914

13.5

16.4

Lubricating oil

0.923

61.2

31.7

Experimental oil



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a

b


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Figure 11. (a) Water contact angle after different oil-water separation cycles, (b) oilabsorption capacity of the modified MPSS for a selection of different oils in terms of its own weight gain after different oil-water separation cycles. As a kind of promising absorbents, the modified MPSS also had outstanding capability of regeneration, which was extremely important for absorption applications. After absorption, the submicron composite particles could be regenerated by ultrasonic washing in absolute ethanol, then dried in a vacuum oven, and the specific process was exhibited in Figure 12. There was no weight loss and the surface of the modified MPSS was dried after being removed from water surface, indicating its hydrophobic properties. Figure 11 certified the reusability changes in water contact angle and oil-absorption capacity of the modified MPSS for different oils after oilwater separation cycles. As we can see from Figure 11, the sample still kept a high water contact angle of 142.1° after absorbing the lubricating oil and the capacities of sample for four kinds of oils could be up to 9.42, 7.41, 6.51 and 4.68 times of their own weight after the 20th cycles, respectively.



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Figure 12. Illustration of recycle route of the modified MPSS. Interestingly, no particles sank to the water bottom even after ultrasonic treatment. When the particles were put onto the surface of absolute ethanol, all of the particles quickly sank to the bottom. As was shown in Figure 13, the particles were sucked to the right side under the auxiliary magnetic field, which exhibited the property of superoleophilcity. It was again proved that the obtained modified MPSS had excellent selective absorption for oils from water. After one night, the modified MPSS remained highly hydrophobic property after floating on the surface of 0.1 M NaCl solution and we measured the exact water contact angle, as shown in Figure 14 (a). Figure 14 (b) presented the varying water contact angle of the modified MPSS, which was put onto aqueous solution with pH values ranging from 1 to 13 for 24 h.


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Figure 13. Situations of the modified MPSS floating on the water surface by ultrasonication and sinking on the ethanol solution at the bottom of cup. a

b

Figure 14. (a) Optical image of a water droplet on a bed of the modified MPSS after floating on 0.1 M NaCl solution for 24 h, (b) contact angles of the modified MPSS after floating on aqueous solution with pH ranging from 1 to 13 for 24 h. 4.CONCLUSION In summary, we report a simple synthesis process of magnetic porous silica submicroparticles by template method. The modified MPSS shows fast magnetic



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response, superoleophilcity and temperature stability for removal of all kinds of oils from water surface. Furthermore, the porous modified MPSS can absorb different oils up to 11.51 times of its own weight. More importantly, the modified MPSS has high oil absorption capacity and large water contact angle after 20 cycles, implying superior hydrophobicity. Owing to its superhydrophobicity, superoleophilicity, commercial availability, and recyclable capacity, the modified MPSS can selectively collect oils from water surface, which is thought to be a promising candidate for oil absorption application. In a word, the novel strategy is put forward to improve the oil absorption capacity of porous materials, which may pave a new way for researching novel oil absorbents.

ASSOCIATED CONTENT Supporting information Information on EDAX spectra; Tables of BET measurements and comparison of oilabsorption capacity; three videos showing the magnetic property, oil absorption process and unsinkable property of the samples. This material is available free of charge via the Internet at http://pubs.acs.org.

AUTHOR INFORMATION Corresponding Author *Tel.: 86-25-84315042. E-mail: [email protected]; Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT


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This work was financially supported by the National Natural Science Foundation of China (Project No. 41101287), the Scientific and Technical Supporting Programs of Jiangsu province (BE2012758) and Priority Academic Program Development of Jiangsu Higher Education Institutions.

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For Table of Contents Only



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Graphical Abstract: In this article, the modified MPSS present a property called selective absorption. A few drops of oil were dropped onto the middle of the water surface in the culture dish. Subsequently, a certain amount of the modified MPSS were gently placed on the surface of the oil-water mixture. Controlled by a magnet, the modified MPSS could be driven to the water zone and then rapidly absorb the oils, keeping a balance of absorption. After absorption, the submicron composite particles could be regenerated by ultrasonic washing in absolute ethanol, then dried in a vacuum oven, and the specific process was exhibited in the following Figure. Furthermore, the modified MPSS could absorb different oils up to 11.51 times of its own weight. More importantly, the submicron composites have high oil absorption capacity and large water contact angle after 20 cycles.

Figure. Absorption and desorption of the modified MPSS.


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Fabrication of Magnetic Porous Silica ... - ACS Publications

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