Facile Preparation of Robust Superhydrophobic Cotton Textile for Self

Subscriber access provided by University of Winnipeg Library

Materials and Interfaces

Facile preparation of robust superhydrophobic cotton textile for self-cleaning and oil-water separation Maiping Yang, Weiqu Liu, Chi Jiang, Chunhua Liu, Sha He, Yankun Xie, and Zhengfang Wang Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b04433 • Publication Date (Web): 06 Dec 2018 Downloaded from http://pubs.acs.org on December 6, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

Facile preparation of robust superhydrophobic cotton textile for self-cleaning and oil-water separation Maiping Yanga,b,c, Weiqu Liua,b,* , Chi Jianga,b,c, Chunhua Liua,b,c, Sha Hea,b,c, Yankun Xiea,b,c, Zhengfang Wanga,b aGuangzhou

Institute of Chemistry, Chinese Academy of Sciences, Guangzhou 510650, China

bKey

Laboratory of Cellulose and Lignocellulosics Chemistry, Chinese Academy of Sciences, Guangzhou 510650, China cUniversity

of Chinese Academy of Sciences, Beijing 100049, China

*Corresponding author: E-mail: [email protected] Postal address: Prof. Weiqu Liu, Guangzhou Institute of Chemistry, Chinese Academy of Sciences, Guangzhou 510650, China Tel.: +86-20-85231269 Fax: +86-20-85231269

1

ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 29

Abstract A facile and mild dip-coating method of fabricating superhydrophobic coating for cotton textiles was proposed. It was treated with TiO2 sols prepared with mild conditions, and subsequently dip-coated by fluoropolymer (PHM). The PHM was synthesized by copolymerization of hexafluorobutyl methacrylate (HFBMA) and 3-methacryloxypropyltrimethoxysilane

(MPS)

to

substitute

the

long

chain

fluoro-alkylsilanes, which are costly and potentially harmful. The coated textile displayed wonderful superhydrophobicity with a water contact angle (WCA) of 153.5o. Additionally, the stability of the coated textile was tested by placing in acidic and alkali solutions, ultrasonic processing and washing, exhibiting desirable durability. Furthermore, the surface showed excellent biomimetic self-cleaning effect of removing both liquid pollutant and solid powder stains. Importantly, the prepared textile exhibited efficient oil-water separation for its superhydrophobicity and superoleophilicity. These advantages make it an ideal material for large-scale industrial applications in various conditions.

2


Page 3 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Keywords: Coatings; Superhydrophobicity; TiO2 sol; Fluoropolymer; oil-water separation.

1. Introduction Super-antiwetting surfaces have acquired enormous interest and research for their wide promising applications, such as self-cleaning materials, anticorrosion devices, anti-icing coatings and water/oil separation substances.1-3 Inspired by amazing creatures in nature, including lotus leaf, rose petal and gecko, superhydrophobic surfaces are generally constructed through the two major methodologies: creating felicitous hierarchical surface roughness and employing low surface energy chemicals.4-5 Among the various of superhydrophobic materials, superhydrophobic textile is commonly considered as a fascinating choice for waterproof applications. Especially cotton fabric, which is in virtue of inexpensive, pliable, ubiquitous and comfortable, is supposed as one of the outstanding candidates.6 On account of low polarizability as well as strong electronegativity, fluoropolymers possess numerous remarkable superiorities including chemical resistance, thermal stability, self-cleaning ability and oil repellence characteristics.7 In consequence, fluoropolymers have been investigated and exploited in abundant domains such as 3



aerospace engineering, electronic, functional coating and fabric finishing.8-9 At present, fluorinated acrylates, especially containing per-fluorooctane groups, are considered as the optimal components to generate hydrophobic surfaces due to the merits of polymerizability and designability.10 However, perfluorooctane sulfonate and perfluorooctanoic acid seriously endanger human health and environment, which cannot be overlooked in practical application.11 Besides, researches have already proved that compounds possessing long perfluoroalkyl chain (>8) are more prone to bioaccumulation and biomagnification than short chains.12 Therefore, it is incontrovertibly significant to seek a less harmful and more efficient method to prepare fluoropolymers with a short fluorinated branched chain. The general strategy to generate superhydrophobic surface is to add micro or nano particles, including TiO2, Fe3O4, SiO2 and ZnO, in materials with low surface energy.13-16 Owing to its impressive physical and chemical properties such as high stability, non-toxicity, and low-cost, TiO2 is an ideal candidate.17 With the fast-growing demands of versatile materials, where substances should not only maintain the inherent properties, but also acquire multi-functions such as superhydrophobicity, anti-bacterial, eco-friendly and anti-stain.18 The sol-gel method is a widely-used approach of fabricating superhydrophobic surfaces due to the efficiency and operability at low temperature.19 According to literatures, sol-gel can be applied to various classes of substrates including plastics, filter paper, fabric, metal and wood.20-22 In sol-gel approach, TiO2 sol is in general acquired by the hydrolysis and condensation of titanium alkoxides.23 However, severe conditions, high 4


Page 4 of 29

Page 5 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


temperature and corrosive chemicals including hydrochloric acid (HCl) and nitric acid (HNO3), are employed in majority of methods on TiO2 preparation.24 Many drawbacks, such as environmental pollution, the damage of strong acid and heat on intrinsic properties of materials, are restricting large-scaled production.25 Regarding the production of TiO2 sols, milder acid and comparably low temperature have preponderance. The optimized preparation technique can not only save cost, but also widen their promising application fields in materials which are vulnerable of chemical and heat, such as paper, cotton and wool.26 To date, many researchers have sought efficient strategies to generate superhydrophobic coatings employed on textiles. For instance, Zhou et al. reported a nature-inspired method of preparing superhydrophobic cotton, which employed phytic acid metal complexes to construct hierarchical roughness and then was modified with PDMS.27 Li et al. studied a simple hydrothermal approach of coating cotton surface with flower-like TiO2 micro/nanoparticles which permitted multi-function of self-cleaning and oil/water separation.28 Panda et al. described a single step strategy to create superhydrophobic coating using trichloro(octadecyl)silane combined with (penta-flurophenyl)triethoxy silane through immersion technique, which is available on industrial application.29 Li et al. presented a facile approach to fabricate a full-thickness coating with modified TiO2 as well as polysiloxane resin, which showed satisfied water-repelling, corrosion resistance and abrasion stability.30 However,

these

approaches

still

possess

some

shortcomings,

such

as

time-consuming process, rigid requirement, complicated operation, which hinder the 5



prospective commercial applications of textile. In this work, a fluoropolymer (PHM) was synthesized by copolymerization with less expensive hexafluorobutyl methacrylate (HFBMA) and 3-methacryloxypropyltrimethoxysilane (MPS) as monomers. TiO2 sols prepared with a simple and mild approach and the PHM were utilized to fabricate the superhydrophobic cotton textiles via a facile and efficient dip-coating method. The chemical stability and durability of ultrasonic processing and washing test were investigated, exhibiting desirable water repellency ability. Meanwhile, the prepared textile shows excellent oil-water separation performance and recyclability in the application of cleaning oil from water. Thus, this facile coating approach provides a new strategy in fabricating functional superhydrophobic materials. 2. Materials and methods 2.1. Materials Tetrabutyl titanate (Ti(OBu)4, ≥99%), (3-Mercaptopropyl)triethoxysilane (MPS), azobisisobutyronitrile (AIBN), anhydrous ethanol, glacial acetic acid, petroleum ether, tetrahydrofuran (THF), dichloromethane, bromobenzene, n-hexane, petroleum, trichloromethane, methyl blue (MB) and oil red O (OR) were provided by Aladdin. Hexafluorobutyl methacrylate (HFBMA) was supplied by Harbin Xuejia Chemical. AIBN needs recrystallization with ethanol before use. Other chemicals were used as supplied. Pristine woven cotton textile (135×70 /inch, 112 g/m2) was obtained from a textile market. Before modification, the textiles were cleaned with ethanol and deionized water, respectively. 6


Page 6 of 29

Page 7 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2.2. Preparation of TiO2 sol TiO2 sol was fabricated with a simple sol-gel approach revised from literature.22 5.0 g of Ti(OBu)4 was added into 22.0 g of ethanol to prepare A-part. B-part was prepared by adding 22.0 g of ethanol, 2.5 g of deionized water and 6.0 g of glacial acetic acid together with strong stir. Next, A-part was dripped dropwise into B-part. The mixed solution was reacted for 20 h at 25 oC. 2.3. Synthesis of PHM The PHM was synthesized by free radical copolymerization. 9.5 g of HFBMA and 0.5 g of MPS were added in 40.0 g of THF with vigorous stirring under nitrogen atmosphere. The copolymerization reaction was initiated with AIBN (0.1 g) and carried out at 65 oC for 12h. The purified copolymer was obtained after reprecipitation, which was achieved by dissolving in THF and reprecipitation in petroleum ether for several times, then dried at 50 oC under vacuum. 2.4 Fabrication of modified cotton textiles (MCTs) The cleaned textiles (4.0 cm × 4.0 cm) were dipped in the TiO2 sol for 15min and washed with anhydrous ethanol 3 times, then dried at 80 oC for 0.5 h. Next, the treated cotton textiles were placed in PHM solutions with 0.4, 0.8, 1.2, 1.6 and 2.4 wt% in ultrasonic bath at 25 oC for 0.5 h. The modified specimens were dried at 110 oC for 0.5 h. Then, the coated textiles were rinsed with THF 3 times to remove unattached fluoropolymer. The achieved textiles were assigned as MCT. 2.6 Characterization The X-ray diffraction (XRD) measurement of powdered TiO2 was performed on a 7



X’Pert-pro MRD X-ray diffractometer (PANalytical B.V.) with Cu-Kα radiation (0.154 nm). The IR spectra of PHM and the fabric specimens were recorded on a TENSOR 27 Fourier transform infrared (FTIR) instrument (Bruker Co., Germany). 1H

NMR spectrum was measured using a Bruker (400 MHz) NMR spectrometer

taking CDCl3 as solvents and tetramethylsilane as internal reference. The molecular mass (Mn, Mw) and polydispersity index (PDI) of PHM were measured with gel permeation chromatography (GPC, a Waters 2410 instrument), taking THF as eluent and polystyrene as standard calibration at 30 oC . Hitachi S-4800 Scanning electron microscope (SEM) was applied to investigate the surface morphology of the fibers. Surface roughness evaluation of fabric was conducted on Atomic force microscopy (AFM, Bruker Dimension edge) The surface compositions of textile specimens were measured using an Horiba EX-250 energy dispersive spectroscope (EDS) attached to SEM and X-ray photoelectron spectra (XPS) instrument ( Escalab 250 Xi spectrometer) with Al Kα X-ray source. A contact angle goniometer (Shanghai Zhong Chen Co., Ltd, China) was employed to determine the water contact angles (WCAs) of textiles. All the data were the average values calculated at five different positions. To test the chemical durability of the MCTs, samples were dipped in solutions of different pH values at 25 oC for 48 h. Some textiles were gone through ultrasonic 8


Page 8 of 29

Page 9 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


processing (40 Hz, 25 oC) for 120 min while immersing in THF. After being washed with deionized water and dried at 80 oC, the WCAs of the MCTs were studied. The laundering test was conducted using a revised approach from literature.31 The MCTs were placed into a mimic washing device which was full of water, 0.4 wt% detergent and 5 balls. The washing behavior repeated for 30 cycles (15 min, 40 oC). The washed textile was rinsed clean completely with deionized water. After dried in oven, the corresponding WCAs were tested. 3. Results and discussion 3.1. Synthesis and characterization of PHM Regarding the expensive price of long chain fluoroalkylsilane (FAS), the copolymer PHM was synthesized through free radical polymerization with cheaper HFBMA (139$/kg) and MPS as monomers to endow cotton superhydrophobicity. The fabrication and structure of PHM are displayed in scheme 1. FTIR spectrum of PHM was shown in Figure 1a. 2852 cm−1 was the representative vibration of C-H (Si-O-CH3) in MPS unit.11, 32 1749 cm−1 was stretching vibration of C=O. 723–686 cm−1 were ascribed to the stretching and wagging vibrations of C-F bonds in HFBMA unit. Besides, the vanished vibration of C=C (1635 cm−1) demonstrated the resoundingly copolymerization of HFM.33 In the 1H NMR spectrum of PHM (Figure 1b), peaks ranging from 0.7–1.2 ppm belonged to the –CH3 (b) and the –SiCH2- (g). Peaks ranging from 1.7–2.1 ppm represented the –CH2- (a,f). The peak at the chemical shift at 3.58 ppm, originated from -Si(OCH3)3 (h) in MPS unit. The peaks observed at 4.40 and 5.15 ppm were assigned to the -O-CH2- (c) and -CHF- (d) of 9



HFBMA unit, respectively.34 At the same time, the characteristic peaks of H2C=C at 5.73 and 6.24 ppm completely disappeared. Moreover, the molecular weight (Mn) and its distribution (PDI) of PHM were 7127 g/mol and 2.47, which were measured by GPC. These results further confirmed the successful synthesis of PHM.

Scheme 1. Synthesis route of PHM.

10


Page 10 of 29

Page 11 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1. FTIR spectrum (a) and 1H NMR spectrum (b) of PHM 3.2. Preparation of superhydrophobic cotton textile The procedure for fabricating superhydrophobic cotton textile via a simple sol-gel method with TiO2 sol and PHM as hydrophobic material is illustrated in scheme 2. During the sol-gel reaction, Ti(OBu)4 was firstly hydrolyzed and condensed to obtain TiO2 sols, which owning rich –Ti-OH groups on the outer surface.35 This method is cost-saving and efficient, and especially suitable for biomaterials, which are vulnerable in high thermal conditions and harsh environments. As shown in Figure 2, the prepared TiO2 was amorphous due to the broad peak appeared at 26.8o.24 Next, PHM endowed the cotton steady superhydrophobicity by dip-coating. 11



Figure 2 XRD pattern of extracted powder of TiO2 sol.

Scheme 2. Preparation route of MCT Figure 3 shows the influence of the concentration of PHM solutions on the WCAs of MCTs. The fabric coated with merely TiO2 sols exhibited hydrophilicity (WCA=0o), due to abundant of -OH on surface

36.

With the increase of PHM

concentration from 0.4 to 1.6 %, the WCA of MCT was improved sharply from 12


Page 12 of 29

Page 13 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


140.4o to 153.5o, exhibiting desirable superhydrophobicity. It was attributed to the cooperation of high fluorine content and multiple-scaled roughness created on surface. However, the WCA was decreased to 144.2o when the concentration of PHM reached 2.4 %. This might be induced by the slightly disappearance of the multi-scaled microstructure, causing the reduction of roughness. Taking the WCA and economy into consideration, the concentration of 1.6 % has been selected in the following experiments.

Figure 3. WCAs of the cotton textiles modified with different concentrations of PHM solutions. 3.3. Surface morphology of superhydrophobic cotton textile Generally, the superhydrophobic property is determined by both the surface roughness and the surface chemical composition. The SEM images of the pristine cotton and MCT are shown in Figure 4. The surface of the pristine cotton textile showed many natural cracks and grooves (Figure 4a), demonstrating inherent 13



roughness at the microscale. As shown in Figure 4b, the TiO2 modified fabric surface presented an even and compact layer of TiO2 nanoparticles. After the cotton textile was coated with TiO2 sols and PHM, it was obvious that the surface was covered with the TiO2 nanoparticles and copolymer (Figure 4c), which provided nano-scaled roughness to complement the inherent micro-scaled roughness of the cotton textile surface. In addition, the surface roughness of the MCT was further probed by AFM observation (Figure 4d). The nanoscaled bumps was obviously discernible on the coated fibers. And the coated cotton textile exhibited excellent superhydrophobic property (WCA=153.4o). Therefore, it can be concluded that this micro/nano hierarchical structure on the coated textile surface is essential for the superhydrophobicity.

14


Page 14 of 29

Page 15 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 4. SEM images of (a) the pristine cotton, (b) TiO2 coated cotton and (c) the MCT surface. Images on the right are at higher magnification. (d) AFM images of the MCT fabric. 3.4. Surface composition of superhydrophobic cotton textile The XPS spectra of pristine and MCT were also analyzed to obtain the chemical composition of the surface of samples. As shown in Figure 5a, only C and O elements were observed on pristine fabric. Meantime, F 1s and Ti 2p elements were obviously checked out on the surface of MCT. According to the peak intensities, the atomic 15



ratios of C: O: Ti: F were determined to be 38.68:19.51:10.71:31.10, respectively. It was proved that the addition of PHM caused the enrichment of F element, which can efficiently lower the surface energy of cotton textile. Moreover, Ti 2p displayed two peaks of Ti 2p1/2 and Ti 2p3/2 at binding energies of 458.68 eV and 464.39 eV (Figure 5b). In Figure 5c, the C 1s curves of pristine cotton were divided into three spectra at 284.61 eV (C-C), 285.74 eV (C-O-C/C-O-H), 288.80 eV (C=O), respectively. Compared with pristine fabric, two new peaks at 291.00 and 293.47 eV were visible in Figure 5d, indicating the C-F2 and C-F3 bonds belonged to MCT. In summary, the combination of low surface energy materials and the hierarchical roughness endows the cotton textile excellent superhydrophobicity.

Figure 5. XPS survey spectra of the pristine textile and MCT (a); Ti 2p high-resolution spectra of MCT (b); C 1s high-resolution spectra of pristine textile (c) 16


Page 16 of 29

Page 17 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and MCT (d). 3.6. Durability of superhydrophobic cotton textile Serving as an imperative consideration, the diversified durability of MCT was measured. TiO2 was acknowledged well affinity with cotton,37 while PHM combines steady with TiO2 by its hydroxyl.30 Figure 6a shows that the WCAs of MCT were around 150o after dipped in solutions of pH values ranging from 1 to 11 for 48h. While the WCA decreased to approximately 140 oC after immersed in solution of pH=13. This phenomenon maybe caused by the partial hydrolysis of the fluoropolymer. In addition, the WCAs of MCT remained around 150o after the coated textiles were treated by ultrasonic for 120 min (Figure 6b). The results manifest positively that the TiO2 nanoparticles and PHM were attached firmly onto textile surface, which rendered cotton super chemical and ultrasonic durability. Meantime, the washing durability of the MCT was also tested (Figure 6c). After washed for 30 cycles, the WCA of MCT decreased from 153.5o to 138.0o, which still kept reasonable hydrophobic performance. The two dominant factors of WCA reduction probably were the disorganization of roughness and slight departure of low surface energy copolymer during washing process. The distinct durability would unquestionably expand its application fields in different harsh and complicated conditions.

17



Figure 6. Influence of solutions of (a) different PH values, (b) ultrasonic treatment and (c) washing test on the WCAs of the MCT. 3.7. Self-cleaning Photographs of the self-cleaning ability of the pristine cotton and MCT were shown in Figure 7. When immersed in liquid pollution, the pristine textile absorbed liquids quickly and was permeated by contaminated solutions. However, the 18


Page 18 of 29

Page 19 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


superhydrophobic specimen maintained clean after dipped in solutions. Meantime, the MCT could float on the liquid surface without additional force. The results demonstrated that the MCT had excellent repellency, which is anticipated in anti-fouling application against daily liquids and other solution pollutants. Thanks to the unique anti-wettability superhydrophobic textile, liquids would readily fall off and incidentally carry off the contaminants on surface, showing the self-cleaning ability. To monitor the self-cleaning performance of tiny particle, the pristine textile and MCT were covered with some fine powders as pollutant (Figure 8). Regarding the MCT, the fluid water could quickly carry off the fine powders, displaying a self-cleaning phenomenon resembled with lotus leaf. Meanwhile, the surface was still clean and absorbed no water for low adhesive force. On the contrary, the pristine textile was immediately wetted and contaminated by powders even rushed with plenty of water. Therefore, the superhydrophobic coating could be adopted in plentiful of daily and industrial occasions, for instance household appliances and outdoor decoration.

19



Figure 7. Self-cleaning ability of (a) the pristine cotton textile and (b) MCT to solution pollution.

Figure 8. Self-cleaning ability of (a) the pristine cotton textiles and (b) MCT to powder contaminant. 3.8. Oil-water separation As shown in Figure 9a, the pristine cotton textile presented a good hydrophilicity and oleophilicity. However, the MCT exhibited excellent superhydrophobicity no matter be contaminated by oil or not (Figure 9b-c). Figure 10a,b show the absorbing 20


Page 20 of 29

Page 21 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


processes of both light and heavy oil with the MCT. When the MCT was utilized to touch oil (dyed with OR) on the surface or the bottom of water, it could absorb the hexane or dichloromethane quickly. These results demonstrated that the MCT acquired the potential of employment in the field of oil-water separation. Furthermore, the representative oil-water separation experiment was performed to verify the separation performance of the MCT (Figure 11). It was clear that the n-hexane could rapidly wet and pass through the MCT, while water was prevented and stopped above the textile. These illustrated that the MCT could separate oil-water mixture efficiently via a simple process. Besides, the separation efficiency of the MCT was also evaluated by the weight ratio of the water before and after separation. As shown in Figure 12a, the separation efficiency of various types of oil was high, up to 99%. N-hexane was chosen as an oil model to test the separation performance of MCT after different separation cycles. The separation efficiency of MCT slightly changed from 99.5% to 98.7% after 20 cycles, indicating good recycling ability. Moreover, the WCA of the MCT still maintained above 145° after 20 cycles, showing satisfied hydrophobicity (Figure 11b). Consequently, the MCT displayed excellent oil-water separation efficiency and recycling ability.

21



Figure 9. (a) Photograph of water (dyed with MB) and n-hexane (dyed with OR) on the pristine textile. (b) Photograph of water droplets on the MCT. (c) Photograph of water droplets and n-hexane on the MCT.

Figure 10. The absorption processes of (a) light oil (n-hexane, dyed with OR) and (b) heavy oil (dichloromethane, dyed with OR) from water by the MCT.

22


Page 22 of 29

Page 23 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 11. Photographs of oil-water separation process with MCT: (a) before and (b) after the separation of oil–water mixture (volume ratio=1:1).

23



Figure 12. (a) The separation efficiency of MCT for various oil-water mixtures. The variation of (b) separation efficiency and (c) WCA of the MCT versus the separation cycles. 4. Conclusions In summary, a facile and mild dip-coating approach with TiO2 sol and PHM to 24


Page 24 of 29

Page 25 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


fabricate superhydrophobic and self-cleaning cotton textile was designed and demonstrated. When the concentration of PHM was 1.6 %, the WCA of MCT was up to 153.5o, owing to the integrated contribution of nano-scaled structures constituted by TiO2 and low surface energy provided by PHM. Besides, the acquired textile was stable enough to withstand acidic aqueous, ultrasonic processing and washing test. Furthermore, the as-prepared coated textile exhibited desirable self-cleaning performance of both liquid and solid powder contaminants. The MCT also showed excellent oil-water separation performance and recycle ability in the cleaning process of oil from water. Therefore, such an easy-operated and mild approach is expected in creating superhydrophobic, self-cleaning and oil-water separated coatings on a large scale, especially for vulnerable materials.

AUTHOR INFORMATION Corresponding Author *Tel.: +86-20-85231269. Fax: +86-20-85231269. E-mail: [email protected] Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS This study is supported by the Key Laboratory of Cellulose and Lignocellulosics, Guangzhou Institute of Chemistry, Chinese Academy of Sciences, and Provincial Science and technology project of Guangdong Province (No. 2015B090925019). REFERENCES 25



1. Cao, W.-T.; Liu, Y.-J.; Ma, M.-G.; Zhu, J.-F., Facile preparation of robust and superhydrophobic materials for self-cleaning and oil/water separation. Colloids. Surfaces A. 2017, 529, 18-25. 2. Cho, E. C.; Chang-Jian, C. W.; Chen, H. C.; Chuang, K. S.; Zheng, J. H.; Hsiao, Y. S.; Lee, K. C.; Huang, J. H., Robust multifunctional superhydrophobic coatings with enhanced water/oil separation, self-cleaning, anti-corrosion, and anti-biological adhesion. Chem. Eng. J. 2017, 314, 347-357. 3. Liu, Q.; Huang, J.; Zhang, J.; Hong, Y.; Wan, Y.; Wang, Q.; Gong, M.; Wu, Z.; Guo, C. F., Thermal, Waterproof, Breathable, and Antibacterial Cloth with a Nanoporous Structure. ACS Appl. Mater. Interfaces. 2018, 10, 2026-2032. 4. Dey, S.; Chatterjee, S.; Singh, B. P.; Bhattacharjee, S.; Rout, T. K.; Sengupta, D. K.; Besra, L., Development of superhydrophobic corrosion resistance coating on mild steel by electrophoretic deposition. Surf. Coat. Tech. 2018, 341,24-30. 5. Caputo, G.; Cortese, B.; Nobile, C.; Salerno, M.; Cingolani, R.; Gigli, G.; Cozzoli, P. D.; Athanassiou, A., Reversibly Light-Switchable Wettability of Hybrid Organic/Inorganic Surfaces With Dual Micro-/Nanoscale Roughness. Adv. Funct. Mater. 2009, 19, 1149-1157. 6. Cai, L.; Dai, L.; Yuan, Y. H.; Liu, A. Q.; Li, Z. X., Synthesis of novel polymethacrylates with siloxyl bridging perfluoroalkyl side-chains for hydrophobic application on cotton fabrics. Appl. Surf. Sci. 2016, 371, 453-467. 7. Xiao, Z.; Guo, P.; Sun, N., Preparation, thermostability, and hydrophobic properties of TiO2/poly(dodecafluoroheptyl methacrylate) nanocomposites. J. Appl. Polym. Sci. 2017, 134. 8. Jiang, J.; Zhang, G.; Wang, Q.; Zhang, Q.; Zhan, X.; Chen, F., Novel Fluorinated Polymers Containing Short Perfluorobutyl Side Chains and Their Super Wetting Performance on Diverse Substrates. ACS Appl. Mater. Interfaces. 2016, 8, 10513-23. 9. Yang, H.; Pi, P.; Yang, Z.-r.; Lu, Z.; Chen, R., Design of a superhydrophobic and superoleophilic film using cured fluoropolymer@silica hybrid. Appl. Surf. Sci. 2016, 388, 268-273. 10. Han, M. S.; Park, Y.; Park, C. H., Development of superhydrophobic polyester fabrics using alkaline hydrolysis and coating with fluorinated polymers. Fiber. Polym. 2016, 17, 241-247. 11. Li, Q.; Yan, Y.; Yu, M.; Song, B.; Shi, S.; Gong, Y., Synthesis of polymeric fluorinated sol–gel precursor for fabrication of superhydrophobic coating. Appl. Surf. Sci. 2016, 367, 101-108. 12. Fang, Y. Q.; Wang, D.; Jing, X.; Xue, B. S., Synthesis and characterization of fluorinated organic-inorganic hybrid coatings on tinplate. J. Appl. Polym. Sci. 2015, 132. 13. Agrawal, N.; Munjal, S.; Ansari, Mohd Z.; Khare, N., Superhydrophobic palmitic acid modified ZnO nanoparticles. Ceram. Int. 2017, 43, 14271-14276. 14. Zhou, Q.; Chen, G.; Xing, T., Facile construction of robust superhydrophobic tea polyphenol/Fe@cotton fabric for self-cleaning and efficient oil–water separation. Cellulose. 2018, 25, 1513-1525. 15. Baba, E. M.; Cansoy, C. E.; Zayim, E. O., Investigation of wettability and optical 26


Page 26 of 29

Page 27 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


properties of superhydrophobic polystyrene-SiO2 composite surfaces. Prog. Org. Coat. 2016, 99, 378-385. 16. Sun, H.; Xu, Y.; Zhou, Y.; Gao, W.; Zhao, H.; Wang, W., Preparation of superhydrophobic nanocomposite fiber membranes by electrospinning poly(vinylidene fluoride)/silane coupling agent modified SiO2 nanoparticles. J. Appl. Polym. Sci. 2017, 134. 17. Banerjee, S.; Dionysiou, D. D.; Pillai, S. C., Self-cleaning applications of TiO2 by photo-induced hydrophilicity and photocatalysis. Appl. Catal. B-Environ. 2015, 176, 396-428. 18. Banerjee, I.; Pangule, R. C.; Kane, R. S., Antifouling coatings: recent developments in the design of surfaces that prevent fouling by proteins, bacteria, and marine organisms. Adv Mater 2011, 23, 690-718. 19. Amiri, S.; Rahimi, A., Hybrid nanocomposite coating by sol-gel method: a review. Iran. Polym. J. 2016, 25, 559-577. 20. Gao, F.; Sheng, Y.; Song, Y.; Zou, H., Sol–gel synthesis of silica composited flower-like microspheres using trivalent europium tartrate as a template. J. Sol-Gel. Sci. Tech. 2017, 85, 470-479. 21. Daoud, W. A.; Leung, S. K.; Tung, W. S.; Xin, J. H.; Cheuk, K.; Qi, K., Self-Cleaning Keratins. Chem. Mater. 2008, 20, 1242-1244. 22. Xue, C. H.; Jia, S. T.; Chen, H. Z.; Wang, M., Superhydrophobic cotton fabrics prepared by sol-gel coating of TiO2 and surface hydrophobization. Sci. Technol. Adv. Mater. 2008, 9, 035001. 23. Macwan, D. P.; Dave, P. N.; Chaturvedi, S., A review on nano-TiO2 sol–gel type syntheses and its applications. Journal of Materials Science 2011, 46, 3669-3686. 24. Daoud, W. A.; Xin, J. H., Synthesis of single-phase anatase nanocrystallites at near room temperatures. Chem. Commun. 2005, 16, 2110-2112. 25. Qi, K.; Xin, J. H., Room-temperature synthesis of single-phase anatase TiO2 by aging and its self-cleaning properties. ACS Appl. Mater. Interfaces 2010, 2, 3479-85. 26. Gao, Z.; Zhai, X.; Liu, F.; Zhang, M.; Zang, D.; Wang, C., Fabrication of TiO2/EP super-hydrophobic thin film on filter paper surface. Carbohydr. Polym. 2015, 128, 24-31. 27. Zhou, C.; Chen, Z.; Yang, H.; Hou, K.; Zeng, X.; Zheng, Y.; Cheng, J., A Nature-Inspired Strategy toward Superhydrophobic Fabrics for Versatile Oil/Water Separation. ACS Appl. Mater. Interfaces 2017, 9, 9184-9194. 28. Li, S. H.; Huang, J. Y.; Ge, M. Z.; Cao, C. Y.; Deng, S.; Zhang, S. N.; Chen, G. Q.; Zhang, K. Q.; Al-Deyab, S. S.; Lai, Y. K., Robust Flower-Like TiO2@Cotton Fabrics with Special Wettability for Effective Self-Cleaning and Versatile Oil/Water Separation. Adv. Mater. Interfaces. 2015, 2. 29. Panda, A.; Varshney, P.; Mohapatra, S. S.; Kumar, A., Development of liquid repellent coating on cotton fabric by simple binary silanization with excellent self-cleaning and oil-water separation properties. Carbohydr. Polym. 2018, 181, 1052-1060. 30. Li, C.; Sun, Y.; Cheng, M.; Sun, S.; Hu, S., Fabrication and characterization of a TiO2 /polysiloxane resin composite coating with full-thickness super-hydrophobicity. 27



Chem. Eng. J. 2018, 333, 361-369. 31. Guo, X.-J.; Xue, C.-H.; Jia, S.-T.; Ma, J.-Z., Mechanically durable superamphiphobic surfaces via synergistic hydrophobization and fluorination. Chem. Eng. J. 2017, 320, 330-341. 32. Wan, S.; Cong, Y.; Jiang, D.; Dong, Z.-H., Weathering barrier enhancement of printed circuit board by fluorinated silica based superhydrophobic coating. Colloids. Surfaces A. 2018, 538, 628-638. 33. Yang, X.; Zhu, L. Q.; Zhang, Y.; Chen, Y. C.; Bao, B. Q.; Xu, J. L.; Zhou, W. W., Surface properties and self-cleaning ability of the fluorinated acrylate coatings modified with dodecafluoroheptyl methacrylate through two adding ways. Appl. Surf. Sci. 2014, 295, 44-49. 34. Li, Y. W.; Zheng, X. W.; Xia, Z. Y.; Lu, M. G., Synthesis of fluorinated block copolymer and superhydrophobic cotton fabrics preparation. Prog. Org. Coat. 2016, 97, 122-132. 35. Li, J.; Lu, Y.; Wu, Z.; Bao, Y.; Xiao, R.; Yu, H.; Chen, Y., Durable, self-cleaning and superhydrophobic bamboo timber surfaces based on TiO2 films combined with fluoroalkylsilane. Ceram. Int. 2016, 42, 9621-9629. 36. Yang, M.; Liu, W.; Jiang, C.; He, S.; Xie, Y.; Wang, Z., Fabrication of superhydrophobic cotton fabric with fluorinated TiO2 sol by a green and one-step sol-gel process. Carbohyd. Poly. 2018, 197, 75-82. 37. Afzal, S.; Daoud, W. A.; Langford, S. J., Superhydrophobic and photocatalytic self-cleaning cotton. J. Mater. Chem. A. 2014, 2, 18005-18011.

28


Page 28 of 29

Page 29 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Graphical Abstract

29


Facile Preparation of Robust Superhydrophobic Cotton Textile for Self

Recommend Documents