Magnetically Enhanced Superhydrophobic Functionalized Polystyrene Foam for the High Efficient Cleaning of Oil Spillage

    Magnetically Enhanced Superhydrophobic Functionalized Polystyrene Foam for the High Efficient Cleaning of Oil Spillage Liuhua Yu, Hanfei Yang, Yujiao Wang, Wei Jiang PII: DOI: Reference:

S0032-5910(17)30103-1 doi:10.1016/j.powtec.2017.01.084 PTEC 12326

To appear in:

Powder Technology

Received date: Revised date: Accepted date:

8 November 2016 7 January 2017 29 January 2017

Please cite this article as: Liuhua Yu, Hanfei Yang, Yujiao Wang, Wei Jiang, Magnetically Enhanced Superhydrophobic Functionalized Polystyrene Foam for the High Efficient Cleaning of Oil Spillage, Powder Technology (2017), doi:10.1016/j.powtec.2017.01.084

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ACCEPTED MANUSCRIPT Magnetically

Enhanced

Superhydrophobic

Functionalized

Polystyrene Foam for the High Efficient Cleaning of Oil Spillage

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Liuhua Yu1,2, Hanfei Yang1,2, Yujiao Wang1, Wei Jiang1*

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1 National Special Superfine Powder Engineering Research Center of China, Nanjing University of Science and Technology, Guanghua Road, Xuanwu Strict, Nanjing 210094, PR China.

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2 These two authors contributed equally to this work

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Abstract

Pollution of oils and organic solvents is a great harm to water environment,

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therefore, the design to develop high efficient material to absorb the sudden accidents

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of oil leakage is increasing instantly. A series of highly efficient absorption materials,

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which had been cross-linked into the three dimensional structure, such as foam and sponge were applied to extract oil from water. In this study, we for the first time,

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introduce Fe3O4 and polystyrene (PS) to produce the efficient absorption of functionalized

magnetic

polystyrene

foam

(FMPF).

The

superhydrophobic

functionalized magnetic polystyrene foam (SFMPF) was synthesized via an environmentally friendly low surface energy modification, and the thicknesses effect on the oil absorption efficiency of the as-prepared foam was studied. Our SFMPF could separate numerous oils and organic solvents from their mixtures with water, and the maximum absorption capacity could reach up to 56.8 times of its own weight. The absorbed oils and organic solvents could be recycled by a simple mechanical *

Corresponding author. Tel.: +86-25-84315042; Fax.: +86-25-84315042 E-mail address: [email protected] (W. Jiang)

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ACCEPTED MANUSCRIPT extrusion. Moreover, SFMPF remained a high absorption capacity and water contact angle under magnetic field even after 60 times regeneration, certifying their good

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durability. The superhydrophobic functionalized foam prepared by the facile method

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could be used to deal with large scale oil spills, which makes it very promising for practical applications.

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Keywords: Absorption, Function, Superhydrophobicity, Thickness, Selectivity,

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CE P

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Environmentally friendly

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1. Introduction

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With the development of marine resources, the sea has been seriously polluted.

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Among numerous pollution, the oil pollution is particularly serious, especially the oil spills which has great harm and is also difficult to be cleaned up [1-3]. The crisis of oil spills depends on the characteristics of oils. Once the oil leak into the water body,

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it starts to spread, and be oxidated. As a result, oil spills cause injure to the organism

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itself. Moreover, the toxicity of oils eventually enriches and causes severe harm to human body through the food chain [4-7]. Various methods including classified

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physical, chemical, and biological approaches have been applied to solve the pollution

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from oil leakage [8-16]. To date, as a result of the possibility to remove and collect

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oils/organic solvents, the physical treatment method via absorbents is considered to be the most promising method. Various traditional absorbents were investigated for

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removal of oil spillage, such as sawdust, straw and activated carbon [17-19]. However, those traditional materials had a number of defects such as low absorption capacity, poor selectivity and inconvenient to use, which was not suitable to deal with the large-scale oil spillages. The superabsorbents for oil spillage cleanup with low cost and simple preparation process were highly desired [20,21]. The porous materials with interconnected 3D network structure were considered to be a new type of material to clean up the oil contamination because of their absorption capacity higher than other absorbents [22-25]. Recently, many researchers have made many new types of highly efficient absorption materials through the modification of sponges or foams, 3

ACCEPTED MANUSCRIPT but these materials still have some problems which hinder their scalable application [26-29]. For instance, these reported materials had poor mechanical properties and

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chemical stability. The absorption capacity of oils or organic solvents with large

complex process and expensive raw materials.

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viscosity was low. Furthermore, these developed materials were fabricated through

Surface wettability is critical for absorption materials. Researchers have focused

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on preparing artificial superhydrophobic surfaces, which inspired by nature objects,

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e.g., water strider legs and lotus leaves [30,31]. For a superhydrophobic surface, the water contact angle should achieve above 150 °, which would lead to a promising oil

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absorbents [32-34]. Both the geometrical structure and the surface chemical

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composition control the wettability of a surface [35-38]. Hence, we prepared

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superhydrophobic absorbents for selective absorption by introducing appropriate hydrophobic groups to decrease surface energy and changing the smooth surface

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topography to be very rough. Herein, superhydrophobic functionalized magnetic polystyrene foam (SFMPF) was fabricated through a facile and low-cost immersion approach. We also studied the effects of different thicknesses of the functional foam on absorption capacity of various types of oils and organic solvents. Owning to excellent magnetic performance, simplicity of the approach and excellent absorption capacity, SFMPF has great potential applications for practical oils/organic solvents-water separation.

2. Experimental 4

ACCEPTED MANUSCRIPT 2.1 Materials Polyethylene (PE) ordinary shock absorption foam (Figure S1), trimethylchlorosilane

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(TMCS) and methyltrimethoxysilane (MTMS) were gained from Aladdin. Absolute

China.

Azobisisobutyronitrile

(AIBN),

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ethanol (C2H5OH) was bought from Nanjing Chemical Reagent Co. Ltd., Nanjing, iron

(II)

ammonium

sulfate

(FeSO4·(NH4)2SO4·6H2O) and acetone (C3H6O) were obtained from Shanghai No.4

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Reagent & HV Chemical Co. Ltd., Shanghai, China. Polyethylene glycol (PEG4000)

Ltd.,

Shantou,

China.

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and sodium hydroxide (NaOH) were purchased from Xilong Chemical Reagent Co. Hydrochloric

acid

(HCl),

oleic

acid

(C18H34O2),

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vinyltriethoxysilane (VTES), and vinyltrimethoxysilane (VTMS) were received by

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Sinopharm Chemical Reagent Co. Ltd., Shanghai, China. All chemicals were used as

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received without further purification, and deionized water was used for all the

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experiments and tests.

2.2 Preparation of OA-Fe3O4 particles OA-Fe3O4 particles were synthesized through the improved solvent thermal method [39]. In a typical reaction, 1.56 g of FeSO4·(NH4)2SO4·6H2O was dissolved in the 40 mL of the deionized water to form the precursor solution. Then, 500 mg of PEG4000 and 2 g of NaOH were dispersed in the mixture of 20 mL absolute enthanol and 20 mL oleic acid until a homogeneous solution was obtained. The precursor solution was quickly poured into the above-mentioned homogeneous solution and stirred vigorously to form a pale yellow solution. The as-prepared mixture solution 5

ACCEPTED MANUSCRIPT was transferred into a hydrothermal reaction kettle at 180 °C for 24 h. The original products were washed by absolute enthanol and deionized water for several times

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after the reaction. Finally, the products were obtained after drying at 45 °C for 3 h.

2.3 Fabrication of superhydrophobic functionalized magnetic polystyrene foam PS microspheres were prepared by dispersion polymerization in absolute

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enthanol/isopropanol media by using polyacrylic acid as steric stabilizer [40]. The

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fabrications of FMPF and SFMPF are shown in Scheme 1. Briefly, shock absorption foams with different thicknesses were cleaned ultrasonically with acetone and

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deionized water successively at 65 °C for 2 h to remove possible impurities. After

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cleaning, the pure foam was dried in a vacuum oven and then immersed in absolute

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enthanol containing OA-Fe3O4 particles under the ultrasonication along with mechanical vibration at 50 °C for 1.5 h. Then, PS microspheres were added into the

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solution and the reaction was kept for 2.5 h in the presence of AIBN as initiator at 55 °C to obtain the functionalized magnetic polystyrene foam. Subsequently, FMPF was immersed in enthanol solution with four kinds of silane coupling agents for 3 h. Finally, SFMPF was obtained after drying at 60 °C in a vacuum oven for 2 h. The different thicknesses of shock absorption foams researched in the study were listed in Table 1.

2.4 Characterization X-ray diffraction (XRD) analysis was performed by using a D8 advance (Bruker D8 6

ACCEPTED MANUSCRIPT Super Speed) X-ray diffractometer with Kα radiation at 40 kV and 40 mA. Transmission electron microscopy (TEM) images were investigated with Model

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Tecnai 12. The morphology and cross-section of the as-prepared foams were

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examined by field-emission scanning electron microscope (FESEM) (Model-S4800, Hitachi, Japan). Before observation, the samples were fixed on a layer of gold to obtain electrical conductivity. The energy- dispersive X-ray spectroscopy (EDS) was

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done using an attachment to the field-emission scanning electron microscope. Fourier

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transform infrared (FT-IR) spectra was taken on a Bruker Vector 22 spectrometer and the scan range was 4000-500 cm-1. Thermogravimetric analyses (TGA, Model TA

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Instruments, USA) was utilized with a heating rate of 10 °C/min from 30 to 650 C

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under nitrogen atmosphere. Magnetic measurements of the as-obtained samples were

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recorded by using a magnetometer (VSM, Lake Shore 735). Contact angle measurement (SL200B, Solon Tech. Co. Ltd., China) was carried out to investigate

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the hydrophobicity and oleophilicity through using a droplet of deionized water and lubricating oil as indicators at ambient temperature.

2.5 Oil absorption capacity tests. All the oil absorption measurements were investigated at ambient temperature through the following steps. A piece of sample was immersed in four kinds of oils/organic solvents mixed with deionized water, and then removed from the mixture until saturation under the magnetic field or a simple external force. The oil absorption capacity F (g/g) of the sample was determined by weighing the sample before and 7

ACCEPTED MANUSCRIPT after oils/organic solvents absorption and calculated according to the formula: F=(wo-ws)/ws, where wo is the total mass of the saturated sample with oils and organic

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three times and the average values were calculated.

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solvents (g), and ws is the mass of the dry sample (g). Each sample was measured

2.6 Reusability of the superhydrophobic functionalized magnetic polystyrene

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foam.

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The absorbed oils and organic solvents were collected by simple mechanical squeezing and washed by absolute enthanol to completely remove the residue oils or

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organic solvents. Then, the sample was dried under vacuum oven at 60 °C for 2 h

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before next cyclic operation. The absorption-desorption procedure was repeated 60

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each cycle.

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times and its water contact angle along with absorption capacity were measured after

3. Results and discussion OA-Fe3O4 particles on the surface of the as-prepared foam were confirmed by XRD measurements. As shown in curve a of Figure 1, five peaks (2θ = 30.1°, 35.6°, 43.1°, 57.2°, and 62.8°) were found in the case of OA-Fe3O4 particles, corresponding to the diffractions from the (220), (311), (400), (511), and (440) planes of the magnetite, respectively. As expected, all of the five characteristic peaks appeared in curve b, demonstrating that the crystal form of OA-Fe3O4 particles in FMPF had not been changed. We also conducted Energy-dispersive X-ray (EDS) measurement to test the 8

ACCEPTED MANUSCRIPT existing elements of the as-prepared samples. The results demonstrated that the elements of magnetic foam and FMPF were Fe, O and C. (Figure S2).

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To further characterize the morphology of the as-obtained samples, SEM

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observations were carried out and shown in Figure 2. Additionally, the inset observation of TEM (Figure 2a) evidently illustrated that the successful preparation of OA-Fe3O4 particles with well-defined size and the particle size was about 400 nm,

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which agreed with SEM indication. As shown in Figure 2b, it could be clearly

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observed that pure foam with interconnected 3D network structure had a smooth surface. Figure 2c and 2d exhibited the SEM observations of surface morphologies of

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magnetic foam at 100× and 10000× magnification, respectively. Compared to

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Figure 2b, micro sized hierarchical spheres were seen on the surface and the surface

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became rougher after introducing OA-Fe3O4 particles. Although the pure foam was uniformly coated by OA-Fe3O4 particles, the interaction between them was very weak.

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When the magnetic foam immersed in deionized water and absolute enthanol, a lot of OA-Fe3O4 particles fell off the magnetic foam (Figure S3a and S3b). Thus, the PS coating was applied to bond the Fe3O4 particles on the foam surface. According to SEM images of Figure 2e and 2f, FMPF also had micro scaled hierarchical structures in 100× magnification and such structures were much more complex than those on surface of the magnetic foam, which could improve the property of hydrophobicity. Moreover, we could also found that all of OA-Fe3O4 particles were coated by PS layer and firmly attached in the surface of the foam with the coated reaction conducting, as shown in Figure 2f. No falling of OA-Fe3O4 particles and PS layer were observed 9

ACCEPTED MANUSCRIPT after repeated ultrasonication of FMPF in deionized water and absolute enthanol (Figure S3c, S3d and Figure S4).

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The mechanical properties of pure foam and FMPF-3 were evaluated by

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compressing-releasing cycles. The height of the pure foam decreased from 100% to 75% after the 50th cycle, as exhibited in Figure 3a. In contrast, Figure 3b showed that FMPF-3 (taking FMPF-3 for example) could be compressed to large strains (80%)

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due to its high elasticity and porosity (Table S1 and Figure S5). After being

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extensively pressed, FMPF-3 could almost recover about 95% of its initial height even after 50 cycles. The results suggested that FMPF possessed good mechanical strength

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and reusability which would greatly facilitate oils and organic solvents recovery. As

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illustrated in the inset of the Figure 3c and Movie S1, the as-prepared FMPF could be

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controlled by a magnetic bar, showing excellent magnetic properties. The saturation magnetization of the as-prepared six samples were examined and compared with each

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other. All samples exhibited standard paramagnetic curves without hysteresis behavior, which was essential for the magnetic separation and recycling. The saturation magnetization of six samples were 21.1, 29.1, 32.8, 36.3, 39.9 and 40.1 emu/g, respectively (Figure 3c). Interestingly, compared to the saturation magnetization of OA-Fe3O4 (Figure S6), all the magnetization values decreased because of the existence of a large fraction of foam and PS layer in FMPF. In addition, as the thicknesses of the six samples increased, the magnetization values of the six samples decreased. The possible reason for this phenomenon was proposed as follows: Under ultrasonic oscillation and mechanical vibration, OA-Fe3O4 particles dissolved 10

ACCEPTED MANUSCRIPT uniformly in absolute enthanol and high energy induced by ultrasonication treatment push OA-Fe3O4 particles to the pure foam surface to form a rough 3D interconnected

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network structure rapidly. Through the actions mentioned above, the magnetic foam

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was finally formed. However, OA-Fe3O4 particles only attached on the outer surface. The interaction between molecules in the foam which was larger than the adhesion between OA-Fe3O4 particles and the contact surface of pure foam prevent OA-Fe3O4

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particles from entering the interior of the foam. Due to the strong intermolecular

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forces and no OA-Fe3O4 particles attached on the interior surface of the foam, PS microspheres only bind OA-Fe3O4 particles on the outer surface of the foam tightly

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instead of the interior surface of the foam. The interior of the foam seemed to be

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forming a huge protection net and none of OA-Fe3O4 particles and PS layer could

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attach on the inner surface. To further prove this theory, we cut off FMPF-3 and found that the interior color of the foam was white, indicating neither OA-Fe3O4 particles

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nor PS layer exist inside (see Supporting Information Figure S7). Thus, the thicknesses of the foam affected the saturation magnetization of the samples. It was obvious that the thickness became larger, while the magnetic property became weaker. In addition, the magnetization values of FMPF-5 and FMPF-6 was almost approximate and unchangeable, as shown in curve e and f of Figure 3c. That was because the thickness of the both samples were thin, OA-Fe3O4 particles and PS layer could uniformly attached onto the inside and outside surface of the pure foam. In order to confirm the accurate oil absorption efficiency and selectivity of FMPF by the weight measurement (FMPF-3 as an example), a series of organic 11

ACCEPTED MANUSCRIPT solvents/oils absorption experiments were carried out, as shown in Figure 4 and Movie S2. When a piece of FMPF-3 was placed in a water-p-xylene mixture labeled

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by Sudan Red for clear observation, it could selectively absorbed p-xylene quickly

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rather than water. The organic solvent-filled foam could float on the water surface without organic solvent release. After absorption, FMPF-3 could be magnetically driven to the polluted water zone by using a magnet, as shown in Figure 4a. The

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magnetic responsivity of absorption materials was an important property for recycling

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the oil/organic solvent-absorbed materials. Additionally, the as-prepared FMPF-3 could also absorb oils and the oil-absorption process was exhibited in Figure 4b by

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taking lubricating oil labeled by Sudan I as an example. When a piece of FMPF-3 was

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brought into contact with lubricating oil on water surface, it could selectively absorb

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lubricating oil from water surface in a short time and no water droplet was observed during the absorption process. FMPF-3 could float on the water surface after

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absorbing lubricating oil and could be easily collected through a simple external force, as shown in Figure 4b. It was clear that no dripping of the absorbed oil was observed in handing process, indicating the material not only absorbed oil but also retained oil. The oil absorption capacities of different FMPF were investigated, and the results were shown in Figure 5a. Four kinds of oils and organic solvents were prepared as the absorbing targets, including lubricating oil, salad oil, trichloromethane and p-xylene. The absorption capacity of FMPF could up to 40.4 g/g for lubricating oil, 39.1 g/g for salad oil, 54.1 g/g for trichloromethane and 42.4 g/g for p-xylene, respectively. The high absorption value was attributed to the 3D interconnected 12

ACCEPTED MANUSCRIPT network structure of the foam and PS coating layer. Moreover, with decreasing thickness from 3.0 cm to 0.2 cm, absorption capacities of the oils and organic solvents

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mentioned above increased significantly. The interesting phenomena could be

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explained by the theory proposed above, which also explained the increasing magnetic property along with the decreasing thickness. OA-Fe3O4 particles could only attach on the outer surface foam with a larger thickness. Similarly, PS layer only

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coated on the outside surface of the magnetic foam and we finally obtained the

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absorption material with asymmetrical coating. When thickness of the foam decreased the extent of the corresponding, OA-Fe3O4 particles and PS coating layer could

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uniformly attach onto the inner and outer surface of the pure foam. Hence, the

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absorption capacity reflected the tendency of geometric multiply with the decreasing

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thickness of FMPF. However, we could observe in Figure 5a, the absorption values of FMPF-5 and FMPF-6 were similar. The reasons for this phenomenon was OA-Fe3O4

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particles and PS coating layer could uniformly attach into the surface of the foam, of which the thickness was not affected by the coating rates of magnetic particles and polymer layer.

The application of superhydrophobic materials for selective oil absorption was encouraged, owing to their excellent different wettability by water and oils/organic solvents. As a parameter crucial to hydrophobicity, contact angle depended on the surface energy and morphology, including surface roughness, functional group and fraction of air trapped on a surface. Although there were 3D interconnected network structure and roughness of the foam, it did not possess excellent hydrophobicity 13

ACCEPTED MANUSCRIPT (WCA=129° << 150°)[12,16,23,30]. In our paper, we compared four kinds of silane coupling agents for surface hydrophobic modification in order to graft functional

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groups which could obtain hydrophobic material, as shown in Table 2. In addition, the

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relatively larger absorption capacity of FMPF-5 between as-prepared samples was used as raw materials for modification. Chemical immersion method was used to fabricate a superhydrophobic functionalized foam to separate oil/organic solvent from

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water surface. The surface energy was directly bound up with kinds of surface

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function groups.

The elements of modification groups and enhanced surface function groups of

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SFMPF-5b were identified by EDS and FT-IR spectrum (Figure S8 and Figure 5b).

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The EDS showed a sharp peak of silicon after modification, confirming the successful

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silanization. The high concentration of C and Si elements led to low surface energy on coated foam. The low surface energy, combined with the rough surface morphology,

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resulted in a hydrophobic surface of the as-prepared SFMPF-5. Figure 5b present the compared FT-IR of FMPF and SFMPF-5b, the absorption peak at 571.6 cm-1 could be ascribed to the stretching vibration of the Fe-O bond. The bands at 3480.4, 2747.8 and 2688.7 cm-1 were assigned to the presence of oleic acid [41], and the characteristic peaks at 1291.8, 907.6 and 719.3 cm-1 corresponded to the typical absorption peaks of polystyrene [42], as shown in curve a of Figure 5b. All of the characteristic peaks appeared in curve b indicated the unchangeable functional group of FMPF after chemical surface hydrophobic modification. After modification by VTES, the newly additive absorption bands at 2806.9 and 789.3cm-1 were assigned to the stretching 14

ACCEPTED MANUSCRIPT vibration of -CH3 and vibrations were observed at 1238.9 cm-1 corresponding to Si-O-Si chemical bond in curve b, which agreed well with the EDS analysis. The

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newly generated groups made SFMPF-5b have the property of high hydrophobicity.

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In order to estimate the coverage degree of functioned alkyl groups on the modified surface of SFMPF-5b, thermogravimetric analysis (TGA) was utilized and exhibited in Figure 5c. Compared with curve b and curve c, about 12.3% weight loss was

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attributed to functioned alkyl groups on the surface of SFMPF-5b. Noted that no

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weight loss was seen at 200 °C, indicating the chemical stability of the as-prepared foams for practical application in extreme environment.

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To understand the ideal selectivity of SFMPF to separate oils and organic

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solvents, the contact angles were tested to examine the surface wettability of the

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as-prepared materials. After modification, the water contact angle of SFMPF-5b increased up to 154° (Figure 5d). In contrast, the contact angle of the lubricating oil

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droplet was approximate to 0°. Similarly, the water contact angle of FMPF-5 was 129°, indicating its intrinsical hydrophobicity. The contact angles of SFMPF-5(a-d) after modified by TMCS, VTES, MTMS and VTMS further increased up to 142°, 154°, 150°, and 136°, respectively. It can be concluded that VTES was a better functional reagent to enhance the hydrophobic property, due to its long-chain alkyls with lower surface energy than other silane coupling agents. We have successfully used SFMPF-5b absorbing oils and organic solvents, including lubricating oil, salad oil, trichloromethane and p-xylene. When SFMPF-5b was placed on the mixture, it could selectively absorb oils and organic solvents 15

ACCEPTED MANUSCRIPT without water. The absorption capacity F could be calculated through weight measurement. The as-modified SFMPF-5b could absorb a series of oils and organic

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solvents, the absorption intake capacities for the four absorption target agents were

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42.5, 41.3, 56.8 and 44.3 g/g, respectively, as shown in Figure 6a. Obviously, the absorption of SFMPF-5b increased after surface chemical modification via comparing the absorption capacity of FMPF-5. Moreover, the superabsorbent could be reused for

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more than 60 cycles and the absorbed oils/organic solvents could be easily collected

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by simple mechanical squeezing, which was the most facile method through comparing with other reused methods for absorbents. The absorption and reuse

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process exhibited in Figure 7. After absorption, the oils and organic solvents could be

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recovered through squeezing and washed by absolute enthanol to remove residual

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oils/organic solvents. Indeed, no water droplet could be observed after the absorption of SFMPF-5b in the beaker and water droplets were clearly seen in the oil collected

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from the original foam, suggesting the high selectivity and efficiency of the as-prepared functioned foam for oil/organic solvents-water separation, which shown in Figure S9. Moreover, the absorption capacity and water contact angle after 60 absorption-desorption cycles were shown in Figure 6. The absorption capacity of SFMPF-5b for four kinds of oils and organic solvents all remained over 75% of their original uptake capacity after the 60th cycle. (Figure 6a) Additionally, the water contact angle decreased slightly by 10 degrees after 60 squeezing-absorption cycles, indicating the regenerated SFMPF still remained high hydrophobicity (Figure 6b). Moreover, SFMPF-5b still kept a highly water contact angle after immersing in 16

ACCEPTED MANUSCRIPT lubricating oil, p-xylene and 0.1 M NaCl solution for 7 days. Afterwards, the sample was washed with absolute enthanol and dried in a vacuum oven at 60 °C before WCA

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measurement, as shown in Figure 8(a, b, and c). The as-prepared sample also

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displayed a stable highly hydrophobicity even floating on the aqueous solutions with pH values ranging from 1 to 13 for 168 h. (Figure 8d). As a cost-effective, highly recyclable and large absorption capacity absorbent, SFMPF could be considered to be

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a promising absorbent for the removal of oil spills and organic solvents.

4. Conclusion

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In summary, a superhydrophobic functionalized magnetic polystyrene foam was

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fabricated by an environmentally friendly surface chemical modification. The

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superhydrophobic material showed excellent selectivity, mechanical and chemical stability as well as the magnetic property. Consequently, the functionalized foam

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could be easily driven to the polluted water zone under the magnetic field and the absorbed oils/organic solvents could be collected by a simple mechanical extrusion, due to its excellent elasticity. Importantly, the as-obtained absorption material still remained a high absorption capacity and water contact angle after the 60 cycles of absorption-desorption. The low-cost, simple and environmentally friendly process made the functionalized magnetic polystyrene foam become a very promising absorption material for large scale of oil-water separation.

Acknowledgements 17

ACCEPTED MANUSCRIPT This work was financially supported by the National Natural Science Foundation of China (Project No. 41101287), the Scientific and Technical Supporting Programs of

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Jiangsu province (BE2012758) and Priority Academic Program Development of

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Jiangsu Higher Education Institutions.

Notes and references:

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[1] J.W. Farrington, Oil Pollution in the Marine Environment Inputs, Big Spills, Small Spills, and Dribbles, Environ. Sci. Policy. 55 (2013) 3–13.

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[2] S.J. Yang, J.H. Kang, H. Jung, T. Kim, C.R. Park, Preparation of a freestanding, macroporous reduced graphene oxide film as an efficient and recyclable sorbent

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for oils and organic solvents, J. Mater. Chem. A 1 (2013) 9427–9432.

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[3] J. Schaum, M. Cohen, S. Perry, R. Artz, R. Draxler, J.B. Frithsen, D. Heist, M. Lorber, L. Philips, Screening level assessment of risks due to dioxin emissions

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from burning oil from the BP deepwater horizon Gulf of Mexico spill, Environ. Sci. Technol. 44 (2010) 9383–9389. [4] M. Montgomery, M. Elimelech, Water and Sanitation in Developing Countries:

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Including Health in the Equation, Environ. Sci. Technol. 41 (2007) 17–24. [5] E. Kintisch, Gulf Oil Spill an Audacious Decision in Crisis Gets Cautious Praise, Science, 329 (2010) 735–736. [6] E.B. Kujawinski, M. C. Kido Soule, D.L. Valentine, A.K. Boysen, K. Longnecker, M.C. Redmond, Fate of dispersants associated with the deepwater horizon oil spill, Environ. Sci. Technol. 45 (2011) 1298–1306. [7] M.A. Shannon, P.W. Bohn, M. Elimelech, J.G. Georgiadis, B.J. Marinas, A.M. Mayes, Science and Technology for Water Purification in the Coming Decades, Nature 452 (2008) 301–310. [8] X.Y. Li, D. Hu, K. Huang, C.F. Yang, Hierarchical rough surfaces formed by LBL self-assembly for oil-water separation, J. Mater. Chem. A 2 (2014) 11830–11838. 18

ACCEPTED MANUSCRIPT [9] J. Howarter, J. Youngblood, Amphiphile Grafted Membranes for the Separation of Oil-in-Water Dispersions, J. Colloid Interface Sci. 329 (2009) 127–132.

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of Oil−Water Mixtures, Adv. Mater. 24 (2012) 3666–3671

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[10] G. Kwon, A. Kota, Y. Li, A. Sohani, J. Mabry, A. Tuteja, On-Demand Separation

[11] A. Raza, B. Ding, G. Zainab, M. El-Newehy, S.S. Al-Deyab, J.Y. Yu, In situ

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cross-linked superwetting nanofibrous membranes for ultrafast oil-water separation, J. Mater. Chem. A 2 (2014) 10137–10145.

[12] D. Deng, D.P. Prendergast, J. Macfarlane, R. Bagatin, F. Stellacci, P.M.

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Gschwend, Hydrophobic meshs for oil spill recovery devices, ACS Appl. Mater. Interfaces 5 (2013) 774–781.

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[13] K. Agne, V. Sigitas, Evaluation of forming mixture composition impact on properties of water blown rigid polyurethane (PUR) foam from rapeseed oil

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polyol, Ind. Crop. Prod. 66 (2015) 210–215.

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[14] S.D. Yang, L. Chen, L. Mu, P.C. Ma, Magnetic graphene foam for efficient adsorption of oil and organic solvents, J. Colloid Interf. Sci. 430 (2014) 337–344.

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[15] P. Jing, X.H. Fang, J.L. Yan, J. Guo, Y. Fang, Ultra-low density porous polystyrene monolith: facile preparation and superior application, J. Mater. Chem. A 1 (2013) 10135–10141.

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[16] C.F. Wang, S.J. Lin. Robust Superhydrophobic/Superoleophilic Sponge for Effective Continuous Absorption and Expulsion of Oil Pollutants from Water, ACS Appl. Mater. Interfaces 5 (2013) 8861−8864. [17] N.A. Klymenko, E.A. Samsoni-Todorova, L.K. Patiuk, Restoration of activated carbon adsorption capacity after a long-term use of filters for add-on treatment of tap water, J. Water. Chem. Techno. 35 (2013) 159–164 [18] H.M. Choi, R.M. Cloud, Natural sorbents in oil spill cleanup, Environ. Sci. Technol. 26 (1992) 772–776. [19] S.S. Banerjee, JM. V.oshi, R.V. Jayaram, Treatment of oil spill by sorption technique using fatty acid grafted sawdust, Chemosphere 64 (2006) 1026–1031 [20] H.C. Bi, X. Xie, K.B. Yin, Y.L. Zhou, S. Wan, L.B. He, F. Xu, F. Banhart, L.T. 19

ACCEPTED MANUSCRIPT Sun, R.S. Ruoff, Spongy Graphene as a Highly Efficient and Recyclable Sorbent for Oils and Organic Solvents, Adv. Funct. Mater. 22 (2012) 4421–4425. [21] Y.Q. Li, Y.A. Samad, K. Polychronopoulou, S.M. Alhassan, K. Liao, Carbon

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Aerogel from Winter Melon for Highly Efficient and Recyclable Oils and Organic Solvents Absorption, ACS Sustainable Chem.Eng. 2 (2014) 1492–1497.

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[22] Y. Gao, Y.S. Zhou, W. Xiong, M.M. Wang, L.S. Fan, H. Rabiee-Golgir, L.J. Jiang, W.J. Hou, X. Huang, L. Jiang, J.F. Silvain, Y.F. Lu, Highly Efficient and Recyclable Carbon Soot Sponge for Oil Cleanup, ACS Appl. Mater. Interfaces 6

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(2014) 5924−5929.

[23] Z.X. Xue, Z.X. Sun, Y.Z. Cao, Y. Chen, L. Tao, K. Li, L. Feng, Q. Fu, Y. Wei,

MA

Superoleophilic and superhydrophobic biodegradable material with porous structures for oil absorption and oil–water separation, RSC Adv. 3 (2013)

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23432–23437.

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[24] L. M. Xu, G.Y. Xiao, C.B. Chen, R. Li, Y.Y. Mai, G.M. Sun, D.Y. Yan, Superhydrophobic and superoleophilic grapheme aerogel prepared by facile

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chemical reduction, J. Mater. Chem. A 3 (2015) 7498–7504. [25] N. Cervin, C. Aulin, P. Larsson, L. Wagberg, Ultra Porous Nanocellulose Aerogels as Separation Medium for Mixtures of Oil/Water Liquids, Cellulose 19

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(2012) 401–410.

[26] S.Y. Tao, Y.C. Wang, Y.L. An, Superwetting monolithic SiO2 with hierarchical structure for oil removal, J. Mater. Chem. A 21 (2011) 11901–11907. [27] C. Liu, J. Yang, Y.C. Tang, L.T. Yin, H. Tang, C.S. Li, Versatile fabrication of the magnetic polymer-based graphene foamand applications for oil–water separation, Colloids Surf. A: Phy. Eng. Aspects 468 (2015) 10–16. [28] L. X. Li, B.C. Li, L. Wu, X. Zhao, J.P, Zhang, Magnetic, superhydrophobic and durable silicone sponges and their applications in removal of organic pollutants from water, Chem. Commun. 50 (2014) 7831–7833. [29] B. Ge, X.T. Zhu, Y. Li, X.H. Men, P.L. Li, Z.Z. Zhang, Versatile fabrication of magnetic superhydrophobic foams andapplication for oil-water separation, 20

ACCEPTED MANUSCRIPT Colloids Surf. A: Phy. Eng. Aspects 482 (2015) 687-692. [30] X.T. Zhang, M. Jin, Z.Y. Liu, D.A. Tryk, S. Nishimoto, T. Murakami, A. Fujishima,

Superhydrophobic

TiO2

surfaces:

preparation,

photocatalytic

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wettability conversion, and superhydrophobic-superhydrophilic patterning, J. Phys. Chem. C 111 (2007) 14521–14529.

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[31] J. Drelich, E. Chibowski, D.D. Meng, K. Terpilowski, Hydrophilic and Superhydrophilic Surfaces and Materials, Soft Matter 21 (2011) 9804−9828 [32] M. Abraham, Superhydrophobic and Superhygrophobic Surfaces: from

NU

Understanding Non-Wettability to Design Considerations, Soft Matter 9 (2013) 7900–7904.

MA

[33] M. Jarn, M. Heikkila, M. Linden, Bioinspired synthesis of superhydrophobic coatings, Langmuir 24 (2008) 10625–10628.

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[34] R. Rioboo, M. Voue, A. Vaillant, D. Seveno, J. Conti, A.I. Bondar, D.A. Ivanov,

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J.D. Coninck, Superhydrophobic surfaces from various polypropylenes, Langmuir 24 (2008) 9508–9514.

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[35] K.E. Tettey, M.I. Dafinone, D. Lee, Progress in Superhydrophilic Surface Development, Mater. Express 2 (2011) 89–104. [36] C.X. Wang, T.J. Yao, J. Wu, C. Ma, Z.X. Fan, Z.Y. Wang, Y.R. Cheng, Q. Lin, B.

AC

Yang, Facile approach in fabricating superhydrophobic and superoleophilic surface for water and oil mixture separation, ACS Appl. Mater. Interfaces 1 (2009) 2613–2617. [37] S. Nishimoto, B. Bhushan, Bioinspired Self-Cleaning Surfaces with Superhydrophobicity, Superoleophobicity, and Superhydrophilicity, RSC Adv. 3 (2013) 671–690. [38] T. Darmanin, F. Guittard, Wettability of Conducting Polymers: From Superhydrophilicity to Superoleophobicity, Prog. Polym. Sci., 4 (2014) 656–682. [39] L.H. Yu, G.Z. Hao, Q.Q. Liang, W. Jiang Fabrication of Magnetic Porous Silica Submicroparticles for Oil Removal from Water, Ind. Eng. Chem. Res. 54 (2015) 21

ACCEPTED MANUSCRIPT 9440–9449. [40]

C.W.

Chen,

C.Y.

Chen,

C.L.

Lin,

Preparation

of

monodisperse

poly(methylmethacrylate) microspheres: effect of reaction parameters on particle

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formation, and optical performances of its diffusive agent application, J. Polym. Res. 18 (2011) 587–594.

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[41] L. Zhang, R. He, H.C. Gu, Oleic acid coating on the monodisperse magnetite nanoparticles, Appl. Surf. Sci. 253 (2006) 2611–2617.

[42] D. Z. Wu, X.W. Ge, Z.C. Zhang, M.Z. Wang, S.L. Zhang, Novel One-Step Route

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ACCEPTED MANUSCRIPT Figures caption:

functionalized magnetic polystyrene foam.

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Fig. 1. XRD patterns for (a) OA-Fe3O4 and (b) FMPF.

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Scheme 1. Illustration of the fabrication process of the superhydrophobic

Fig. 2. SEM images of (a) OA-Fe3O4, (b)pure foam, (c, d) magnetic foam and (e, f) FMPF at different magnification. The inset in a is a TEM image of OA-Fe3O4.

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Fig. 3. Height recovery of (a) pure foam and (b) FMPF-3 as a function of recycle number at 80% compression strain. The inset illustrated the compressing-release

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processes of pure foam and FMPF-3, respectively. (c) Room-temperature magnetization curves of as-prepared six samples. The inset are two images showing the magnetic property of FMPF-3.

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Fig. 5. (a) Absorption capacity for four kinds of oils and organic solvents of as-prepared samples. (b) FT-IR spectra for FMPF and SFMPF-5b. (c) TGA curves of

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OA-Fe3O4, FMPF-5, SFMPF-5b and pure foam. (d) Water contact angles and the images taken by the contact-angle goniometer corresponding to the data. The materials include FMPF-5, SFMPF-5a, SFMPF-5b, SFMPF-5c and SFMPF-5d modified by different silane coupling agents. Fig. 6. (a) Absorption capacity and (b) water contact angle of SFMPF-5b after 60 cycles. Fig. 7. High efficiency in oil recovery and absorbent reusability of SFMPF-5b. Fig. 8. Photograph of water droplets on the surface of SFMPF-5b after immersing in (a) lubricating oil (b) p-xylene and (c) 0.1 M NaCl solution for 7 days. (d) Contact angles after floating on aqueous solutions with pH values ranging from 1 to 13 for 168 h.

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Scheme 1. Illustration of the fabrication process of the superhydrophobic

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Figure 1. XRD patterns for (a) OA-Fe3O4 and (b) FMPF.

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Figure 2. SEM images of (a) OA-Fe3O4, (b)pure foam, (c, d) magnetic foam and (e, f)

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FMPF at different magnification. The inset in a is a TEM image of OA-Fe3O4.

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Figure 3. Height recovery of (a) pure foam and (b) FMPF-3 as a function of recycle number at 80% compression strain. The inset illustrated the compressing-release processes of pure foam and FMPF-3, respectively. (c) Room-temperature

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Figure 4. Selective absorption of (a) organic solvent under magnetic field and (b) oil

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Figure 5. (a) Absorption capacity for four kinds of oils and organic solvents of

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Figure 6. (a) Absorption capacity and (b) water contact angle of SFMPF-5b after 60

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Figure 7. High efficiency in oil recovery and absorbent reusability of SFMPF-5b.

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Figure 8. Photograph of water droplets on the surface of SFMPF-5b after immersing in (a) lubricating oil (b) p-xylene and (c) 0.1 M NaCl solution for 7 days. (d) Contact

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Length (cm)

Width (cm)

FMPF-1

3

1

FMPF-2

3

FMPF-3

3

FMPF-4

3

FMPF-5

3

FMPF-6

3

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1.5

1

1.0

1

0.75

1

0.4

1

0.2

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Table 2. Different modifiers of FMPF-5. Modifier

Dosage of modifier (v/v %)

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SFMPF-5b

Vinyltriethoxysilane (VTES)

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SFMPF-5c

Methyltrimethoxysila (MTMS)

8

SFMPF-5d

Vinyltrimethoxysilane (VTMS)

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SFMPF-5a

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Graphical Abstract:

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NO.2 SFMPF showed excellent selectivity, mechanical stability as well as magnetic

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NO.3 The absorbed oils could be collected by a simple mechanical extrusion.

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NO.4 SFMPF remain about 80.1% absorption ability and a high WCA after 60 cycles.

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