Bioinspired Polydopamine Sheathed Nanofibers ... - ACS Publications

Research Article pubs.acs.org/journal/ascecg

Bioinspired Polydopamine Sheathed Nanofibers Containing Carboxylate Graphene Oxide Nanosheet for High-Efficient Dyes Scavenger Ruirui Xing,† Wei Wang,† Tifeng Jiao,*,†,‡ Kai Ma,† Qingrui Zhang,*,† Wei Hong,§ Hui Qiu,⊥ Jingxin Zhou,† Lexin Zhang,† and Qiuming Peng‡ †

Hebei Key Laboratory of Applied Chemistry, School of Environmental and Chemical Engineering, Yanshan University, Qinhuangdao 066004, P. R. China ‡ State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004, P. R. China § Qinghuangdao Entry-Exit Inspection & Quarantine Bureau Coal Inspection Technique Center, Qinhuangdao 066003, P. R. China ⊥ Jiangsu Collaborative Innovation Center of Atmospheric Environment and Equipment Technology (CICAEET), School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, P. R. China S Supporting Information *

ABSTRACT: New hierarchical bioinspired nanocomposite materials of poly(vinyl alcohol)/poly(acrylic acid)/carboxylate graphene oxide nanosheet@polydopamine (PVA/PAA/GO-COOH@PDA) were successfully prepared by electrospinning technique, thermal treatment, and polydopamine modification. The obtained composite membranes are composed of polymeric nanofibers with carboxylate graphene oxide nanosheets, which are anchored on the fibers by heat-induced crosslinking reaction. The preparation process demonstrate eco-friendly and controllable manner. These as-formed nanocomposites were characterized by various morphological methods and spectral techniques. Due to the unique polydopamine and graphene oxide containing structures in composites, the as-obtained composite demonstrate well efficient adsorption capacity toward dye removal, which is primarily due to the specific surface area of electrospun membranes and the active polydopamine/graphene oxide components. In addition, the composite membranes reported here are easy to regenerate. In comparison with other composite adsorbents, the preparation process of present new composite materials is highly eco-friendly and facile to operate and regulate, which demonstrates potential large-scale applications in wastewater treatment and dye removal. KEYWORDS: Electrospun nanocomposite, Polydopamine, Dyes removal, Wastewater treatment

■

removing chemical contaminants.11,12 For example, Zhang et al. have reported the preparation of a bilayer biomimetic membrane based on electrospun polyacrylonitrile linked with chitosan and Cibacron Blue F3GA as modifier and surface ligand. The prepared electrospun membranes show good performance to capture bromelain.13 Miao et al. have designed and prepared hierarchical SiO2@γ-AlOOH (Boehmite) core/ shell fiber materials by the combination of electrospinning and hydrothermal treatment for water remediation.14 On the other hand, dopamine demonstrate the properties of self-polymerization under basic systems to form a polydopamine (PDA) film onto various solid substrates.15,16 The obtained PDA films can show a highly stable/active chemically modified surface on the targeted nanostructures and demonstrate novel adhesive capability, suggesting the potential reaction process with

INTRODUCTION In last several decades, various chemical pollutants (e.g., dyes) have drawn wide interests owing to the dangerous effects on public health and living environment.1,2 Thus, efficient and convenient removal of these chemical pollutants from wastewater is becoming an urgent and challenging problem for researchers.3−6 For instance, it is greatly important to design and develop efficient adsorption and catalyst materials for dye removal with high capacity, good compatibility, and long recyclability. It is well-known that electrospinning is a facile method to produce continuous fibers with micro/nanoscale diameters.7 The prepared fibrous materials demonstrate many novel properties, such as large specific surface area, large porosity, and great flexibility. The controllable thickness and diverse architecture of electrospun fibers make them ideal candidates as drug carriers, nanocatalysts, biosensors, protective clothing, and ultrafiltration and separation devices.8−10 In recent reports, functionalized electrospun membranes have been utilized for © 2017 American Chemical Society

Received: February 4, 2017 Revised: March 21, 2017 Published: April 24, 2017 4948

DOI: 10.1021/acssuschemeng.7b00343 ACS Sustainable Chem. Eng. 2017, 5, 4948−4956

Research Article

ACS Sustainable Chemistry & Engineering

Figure 1. Schematic illustration of the fabrication and dye adsorption of PVA/PAA/GO-COOH@PDA nanocomposites by electrospinning and thermal treatment.

designed molecules and possibility for wide applications.17 More importantly, it can readily attach the organic−inorganic compatibility by one-step mixing. The unique nanostructured film along with intrinsic π−π component can further remove organic dyes in wastewaters efficiently. Thus, electrospun fiberbased material provides an excellent platform to host the deposition of PDA films, which can be used as highly effective and long lasting adsorption composites.18−22 And recently, the PDA decorated electrospun nanostructures have also been synthesized and applied for enhanced mechanical properties for nanomaterials, drug delivery vehicles, and secondary lithiumion batteries.23−29 Moreover, due to good specific surface area, easy chemical modification, and excellent mechanical strength of graphene sheet, the graphene oxide could be an ideal component for anchoring various functional nanoparticles for environmental remediation.30−34 Thus, some recent reports demonstrated that GO showed application as novel nanofiller in polymer based composite materials.35−37 However, some practical problems appeared, such as lacking stability and hybridizing difficulty for inorganic GO component with organic fibers. In this work, to solve the above-mentioned challenge, we designed and successfully prepared electrospun poly(vinyl alcohol)/poly(acrylic acid)/carboxylate graphene oxide nanosheets (PVA/PAA/GO-COOH) composite membrane materials, which were next functionalized with PDA coating for organic dyes removal. Water-soluble PVA/PAA and GO system were selected as matrix materials for electrospinning due to the preferred well chemical and mechanical properties as well as large specific surface area.38 At the same time, in comparison with common used organic solvents, pure water is used as the solvent in present preparing electrospun solution, demonstrat-

ing the eco-friendly features and low cost. As compared to the other kinds of composites, some significant advantages for the obtained multicomponent electrospun composites are speculated. First, the PDA coating layer can achieve the well compatibility between the flexible surface of fiber and efficient GO nanosheets. Then, the strong π−π component within PDA and GO materials can attach the powerful adsorption for various dyes in waters. In addition, the fixed carbonyl group within GO nanosheet can construct a strong electrostatic field by its highly negative-charges property, which can promote the target dyes diffusion and enrichment. Moreover, the obtained composited fiber can also be easily separated from the used dye solutions and regenerated for many cycles, demonstrating broad applications in dye removal and wastewater treatment.

■

EXPERIMENTAL SECTION

Materials. The experimental used materials, poly(vinyl alcohol) (PVA, 98−99% hydrolyzed, average M.W. 57 000−66 000), poly(acrylic acid) (PAA, M.W. ∼ 2000), hydroxyphenethylamine hydrochloride (dopamine, 98%), tris(hydroxymethyl)aminomethane (TRIS, 99%), tris(hydroxylmethyl)aminomethane hydrochloride (Tris−HCl, 99%), and chloroacetic acid were purchased from TCI Shanghai Chemicals, Aladdin Chemicals, and Alfa Aesar Chemicals. Graphene oxide was synthesized from graphite powder (8000 mesh, 99.95%, Aladdin Chemicals) according to a modified Hummer’s method.39 Congo red (CR), Rhodamine B (RhB), and methylene blue (MB) were obtained from Tianjin KaiTong Chemical Reagent and Sinopharm Chemical Reagent Co., Ltd. without further purification. Sulfuric acid (H2SO4, 98%), potassium nitrate (KNO3), hydrogen peroxide (H2O2, 30%, w/w), potassium permanganate (KMnO4), and hydrochloric acid (HCl, 37%) were of analytical reagent grade from Sinopharm Chemical Reagent Co., Ltd. and used as received. Deionized (DI) water was used to prepare aqueous solutions in all experiments. 4949


Research Article

ACS Sustainable Chemistry & Engineering Fabrication of the Nanocomposites. First, carboxyl-functionalized graphene oxide (abbreviated as GO-COOH) was prepared according to a reported method,40 and freeze-dried in low temperature (−50 °C). The 10 wt % aqueous solution of PVA was obtained by dissolving PVA in deionized water at 80 °C for 12 h under magnetic stirring. PAA solution (30 wt %) was prepared in deionized water under magnetic stirring at room temperature for 1 h. GO-COOH solid was then supplied to the above PAA solution and stirred at room temperature for another 1 h to prepare solutions with different concentrations (0.3, 0.5, and 0.8 mg/g). The above as-obtained PVA and PAA/GO-COOH solutions were then mixed with a 1:1 volume ratio and next stirred at room temperature for 1 h to achieve a homogeneous solution for subsequent electrospinning.41 For the electrospinning process, a syringe connected to a stainless steel needle with an inner diameter of 0.6 mm was used to load 10 mL of the above PVA/PAA/GO-COOH precursor solution. During electrospinning, a voltage of 20 kV and a flow rate of 0.5 mL h−1 were used for the spinneret. The produced electrospun nanofiber composite were deposited on a flat aluminum collector placed 15 cm away from the needle, and then dried in a vacuum oven at room temperature for 24 h, as demonstrated in Figure 1. After that, the obtained membrane samples were heated at 120 °C for 3 h for heat-induced cross-linking reaction between carboxyl acid groups in PAA/GO-COOH components and hydroxyl groups in PVA molecules. The designed PVA/PAA/GO-COOH@PDA nanocomposites were prepared according to a similar process.42 After annealing treatment at 120 °C and cross-linking reaction, PVA/PAA/GO-COOH membrane materials became insoluble in water due to the chemical esterification reaction between carboxylic acid groups and hydroxyl groups.41 Next, the water insoluble monolithic composite materials were easily separated from aluminum substrate and were immersed into aqueous dopamine solution (2.0 mg mL−1 in 10 mM Tris buffer, pH 8.5) with mild stirring at 50 °C for PDA modification. Thus, the PVA/PAA/ GO-COOH@PDA nanocomposite membranes were prepared by changing the immersed times (5, 15, and 35 h), respectively. The composite membranes were then removed from aqueous PDA suspension, thoroughly washed with deionized water and ethanol for several times to remove completely the free/nonadhered PDA components, and finally dried in a vacuum at 80 °C for 24 h. Batch Adsorption Tests for Dyes Removal. For adsorption experiment, the adsorption properties of present nanocomposite materials were investigated via an absorption spectroscopy. To test the adsorption activity of the PVA/PAA/GO-COOH@PDA nanocomposites at room temperature, 30 mg of freshly prepared PVA/ PAA/GO-COOH@PDA nanocomposite adsorbents was added to a 100 mL dye solutions that contains CR (25 mg/L), RhB (4 mg/L), and MB solution (10 mg/L), respectively. After dispersion of composite materials under magnetic stirring, the mixed solution was stirred under dark condition and the concentrations of the used model dyes in solution were measured and calculated at different time intervals. For the control test of PVA/PAA/GO-COOH nanocomposite, similar experimental procedures were adopted. Upon removal of the solid absorbents samples by centrifugation, the supernatant solutions were measured by 752 UV-vis spectrometer (Sunny Hengping scientific instrument Co., Ltd., Shanghai) at the wavelength of 497 nm (CR), 632 nm (MB), and 554 nm (RhB) with the pre-established calibration curves, respectively. For the recycling experiments, the as-prepared PVA/PAA/GO-COOH@PDA nanocomposite materials (30 mg) were added into 100 mL MB solution (10 mg L−1) under mild stirring. After 4 h of adsorption process, the composite membranes were washed thoroughly with deionized water and ethanol for several times. The whole adsorption processes were repeated for ten consecutive cycles using the same composite membrane materials and initial fresh MB solution. Characterization. The morphologies of all the obtained composite materials were investigated by a field-emission scanning electron microscopy (FE-SEM, SUPRA 55 SAPPHIRE, CARL ZEISS (Shanghai), Co., Ltd.) with the accelerating voltage of 5−15 kV. Raman spectroscopy study was measured using a Horiba Jobin Yvon Xplora PLUS confocal Raman microscope equipped with a motorized

sample stage. The wavelength of the excitation laser was 532 nm and the laser power was kept below 1 mW without noticeable sample heating. X-ray photoelectron spectroscopy (XPS) was measured on the Thermo Scientific ESCALab 250Xi using 200 W monochromated Al Kα radiation. Both survey scan and individual high-resolution scan were recorded. Thermogravimetry-differential scanning calorimetry (TG-DSC) analyses of the samples were obtained in air condition by NETZSCH STA 409 PC Luxxsi multaneous thermal analyzer (Netzsch Instruments Manufacturing Co., Ltd., Germany). FTIR spectra were measured by a Fourier infrared spectroscopy (Thermo Nicolet Corporation) using the conventional KBr disk tablet method. The specific surface areas and pore diameter distribution were determined by the BET measurement (NOVA 4200-P, US).

■

RESULTS AND DISCUSSION Preparation and Characterization of Nanocomposites. First, Figure 1 depicts the experimental procedure through several steps, including the preparation of precursor solutions, electrospinning process of all precursor materials, next thermal treatment and PDA modification for obtained electrospun membranes, and final dye adsorption and recovery capacities of the obtained PDA-modified composites membranes for three model dyes. First, SEM characterization was utilized to investigate the morphologies and nanostructures of all prepared composite materials. The pristine PVA/PAA electrospun membranes from different mixed molar ratios were prepared and characterized (Figure S1). The obtained images clearly demonstrate that the membrane from PVA/PAA with volume ratio of 5:2 show uniform nanostructures with main fiber diameter distribution of 300−500 nm. When different amounts of GO-COOH were added to the mixed electrospinning solution, the formed PVA/PAA/GO-COOH nanocomposite electrospun membranes were also characterized (Figure S2). With increment of the concentrations of GOCOOH in the mixed solutions, the prepared electrospun membranes showed more GO sheets connected with nanofibers in plane and finally form sandwich-like GO layer in the membranes. In consideration of the uniformity and stability of the designed composite materials, the preparation condition of PVA/PAA/GO-COOH composite membrane (PVA/PAA with volume ratio of 5:2, GO-COOH 0.3 mg/g) was preferred to continue next experimental steps. In addition, from the photographs in Figure S3, it can be easily observed the obtained electrospun PVA/PAA/GO-COOH nanocomposite membranes show white monolithic material on aluminum substrate. And the color change to dark brown after modification with PDA layers. Then, SEM images from Figure 2a,a′ shows that the prepared PVA/PAA/GO-COOH nanocomposite membrane by electrospinning and thermal treatment demonstrate porous fibers composed nanostructures with some GO sheet cross-linked with nanofibers in plane. In addition, with the time increment of PDA component modification, as shown in Figure 2b−d, it clearly shows that the surfaces of PVA/PAA/GO-COOH membranes were modified with more PDA nanoparticles stacked onto the fibers surface. This obvious change confirmed the successful preparation of PDA-modified composite materials. It should be noted that the main driving forces for the PDA nanoparticles modification process onto membrane structures could be mainly assigned to the hydrophilic forces, hydrogen bonding, and electronic interactions, as well as the adsorption of GO surface.43−45 It can be estimated that the increased amount of PDA component and their possible aggregation in composite materials could induce 4950


Research Article


to the D band, which originates from a breathing mode of κpoint phonons of A1g symmetry of the defects involved in the sp3-hybridized carbon bonds such as hydroxyl and/or epoxide bonds.47,48 In addition, it is well-known that the D/G peak intensity ratio can serve as a measurement of the sp2 domain size of graphene sheets containing sp3 and sp2 bonds due to the origination of G and D bands.49−51 For research system reported here, the obtained results indicated that the D/G ratio shifted from 0.91 to 0.92 for GO and GO-COOH to the values of 1.66 for the PVA/PAA/GO-COOH (PVA/PAA with volume ratio of 5:2, GO-COOH 0.3 mg/g) and 0.86 for PVA/PAA/GO-COOH@PDA (modified time of 35 h), as shown in Figure 3b. This result confirmed the successful modification of PDA component in the electrospun membrane as well as and the presence of the polymeric alkyl chains linked to GO sheets. Because the obtained PVA/PAA/GO-COOH@PDA nanocomposite membranes were designed and prepared for the adsorption purposes, it is important to perform interfacial analysis and composition analysis using XPS technique. First of all, the survey data of XPS spectra from PVA/PAA/GO-COOH (PVA/PAA with volume ratio of 5:2, GO-COOH 0.3 mg/g) and PVA/PAA/GO-COOH@PDA nanocomposites (modified time of 35 h) in Figure 4A demonstrated the characteristic peaks, such as C(1s), O(1s), and N(1s). And the relative elemental composition and the O/C atomic ratios in both materials have been obtained and calculated (PVA/PAA/GOCOOH, 46.4%; PVA/PAA/GO-COOH@PDA, 27.5%), indicating the decrement of oxygen element after PDA nanoparticles modification. In addition, the deconvolution of C(1s), O(1s), and N(1s) peaks for the PDA modified electrospun nanocomposite materials were analyzed and demonstrated. For the peak deconvolution of C(1s) core levels (Figure 4B), the peak centered at 284.2 eV could be assigned to the CC, CC, and CH bonds. In addition, the other deconvoluted peaks at positions of 285.1, 287.9, and 289.0 eV were attributed to COH and CN, CO, and OCO oxygen-containing bonds, respectively.52−54 Moreover, the O(1s) peak shown in Figure 4C could be deconvoluted into three main Gaussian component peaks after subtraction treatment of Shirley background. The first component peak centered at 532.4 eV could be assigned to the oxygen in water molecules existed in the nanostructure or adsorbed on the membrane material surface. The second peak centered at 531.6 eV could be assigned to the oxygen of CO bond in the

Figure 2. SEM images of the prepared PVA/PAA/GO-COOH nanocomposite (a and a′) by electrospinning and thermal treatment, and next modified with PDA at different time intervals (b and b′, 5 h; c and c′, 15 h; d and d′, 35 h).

the change of adsorption capacities and stability properties of the obtained composite membrane materials. In addition, Raman spectroscopy has been applied to characterize present composite membrane materials.46 The measured Raman data for present composite materials are demonstrated in Figure 3. Two characteristic bands of graphene sheets in Raman spectra appeared. One band at 1601 cm−1 can be attributed to the G band, which comes from the first-order scattering of the E2g phonons of the sp2-hybridized carbon atoms. In addition, another band at 1351 cm−1 can be assigned

Figure 3. Raman spectroscopy (a) and D/G ratios (b) of different prepared composites. 4951


Research Article


Figure 4. Survey XPS spectra of both samples (A): (a) PVA/PAA/GO-COOH nanocomposite; b, PVA/PAA/GO-COOH@PDA nanocomposite modified at time of 35 h. Deconvolution of XPS peaks in spectra b: B, C(1s); C, O(1s); D, N(1s).

nanocomposite, which was helpful to adsorption processes.55,56 The third deconvoluted O(1s) peak centered at 530.5 eV was attributed to the oxygen of CO bond in composites.57 This means that the surface of PVA/PAA/GO-COOH@PDA nanocomposite was still functional and porous, which show an advantage for next adsorption application. Furthermore, in order to characterize the chemical state of nitrogen element, the analysis and deconvolution of N(1s) peak was also finished. As shown in Figure 4D, a strong high-resolution N(1s) spectrum revealed the presence of amine (399.3 eV), CN bond (400.5 eV), and N+ species (401.2 eV), indicating the presence of PDA polymer layers in the composite materials, either in their original amine forms or in grafted forms through the covalent bonding and weak interaction forces with the electrospun membrane and/or GO sheets. In addition, Figure 5 demonstrates the thermograms of PVA/ PAA/GO-COOH and PVA/PAA/GO-COOH@PDA composites with modification time of 35 h. According to TG results, PVA/PAA/GO-COOH@PDA composites showed higher thermal stability in comparison with PVA/PAA/GO-COOH due to the addition of PDA nanoparticles. And it indicated that two mass loss bands between 230 and 550 °C appeared, which could originated from the pyrolysis of various oxygen containing chemical groups, alkyl chains, and GO sheets, respectively.58,59 With increment of temperature up to 550 °C, the qualities retention was not changed with the ratios of 0 and 9.5%, respectively, indicating that abundant PDA components and/or nanoparticles were deposited onto PVA/PAA/GOCOOH membrane with the deposition time. FT-IR spectra of pristine PAA and PVA, the as-obtained PVA/PAA/GO-COOH nanocomposite, and PVA/PAA/GOCOOH@PDA composites with different modification times are

Figure 5. TG curves of electrospun PVA/PAA/GO-COOH nanocomposite and next modified PDA at time of 35 h.

demonstrated in Figure 6. For the spectrum curve of the PVA/ PAA/GO-COOH nanocomposite, the peak corresponding to the −OH vibration stretching appeared at 3430 cm−1, whereas other peaks at 2922, 2850, 1723, and 1461 cm−1 could be attributed to the stretching of CH2 and carboxyl CO, as well as the scissoring vibration of CH2 alkyl chains.60−64 In addition, with the PDA modification, the peak at 3430 cm−1 shifted to new position of 3421 cm−1, and some new characteristic peaks appeared at 1710, 1635, and 1559 cm−1, which could be attributed to the stretching of hydroxyl group, aromatic benzene ring, and amide band in the modified PDA component. The IR data of as-formed PVA/PAA/GOCOOH@PDA composite showed all characteristic peaks, indicating the successful hybrid of PDA component in the electrospun membranes and preparation of objective composite 4952


Research Article


that higher specific surface areas could increase adsorbent activity points and the contact chance between dye molecules and active points. In addition, larger pore diameters and pore volumes give vast channels for dye solutions and reduce the mass transfer resistance, suggesting better absorption performance. Adsorption Performances toward Dye Removal. The adsorption properties of the as-prepared PVA/PAA/GOCOOH@PDA nanocomposite membranes were investigated for the three model dyes solutions (MB, RhB, and CR). The dye removal procedures were characterized by placing the asprepared PVA/PAA/GO-COOH@PDA nanocomposites in different aqueous dye solutions. In addition, the present adsorption experiments were measured and repeated for three times, respectively. The adsorption kinetic experiments of the as-obtained PVA/PAA/GO-COOH@PDA nanocomposites were performed, and the results were shown in Figure 7. In control experiment of PVA/PAA/GO-COOH nanocomposite without PDA modification (Figure S4 and Table S2), the removal performances of the model dyes were significantly reduced. In addition, classical kinetic models were used to demonstrate the mentioned adsorption mechanism as the following formulas: The pseudo-first-order model can be demonstrated by eq 1:

Figure 6. IR spectra of the obtained PVA, PAA, the electrospun PVA/ PAA/GO-COOH nanocomposite, and next modified PDA at time intervals of 5, 15, and 35 h.

materials. In addition, the microstructural characteristics of asprepared composites were further investigated with the N2 adsorption−desorption isotherms. The pore size distribution data were calculated by BJH methods, and the properties of the obtained composite materials were summarized in Table S1. The pore size for PVA/PAA/GO-COOH nanocomposite and PVA/PAA/GO-COOH@PDA nanocomposite modified at time of 35 h were in the range of 14−26 nm. The 3D hierarchical porous structure of PVA/PAA/GO-COOH@PDA nanocomposite could adsorb more nitrogen and demonstrated relatively high BET specific surface area of 54.5571 m2 g−1, which was much larger than that of PVA/PAA/GO-COOH (32.7095 m2 g−1). Furthermore, the pore volume and average pore diameter of PDA-modified membrane material were also larger than that of PVA/PAA/GO-COOH. It can be speculated

log(qe − qt ) = log qe −

k t 2.303

(1)

The pseudo-second-order model can be demonstrated by eq 2: t 1 t = + 2 qt qe kqe

(2)

where qe and qt demonstrate the amount of dye adsorbed (mg/ g) at equilibrium and time t, respectively, and the k1 and k2

Figure 7. Adsorption kinetics curves of as-prepared PVA/PAA/GO-COOH@PDA nanocomposites on MB (a, b), RhB (c, d), and CR (e, f) at 298 K. 4953


Research Article


Table 1. Kinetic Parameters of PVA/PAA/GO-COOH@PDA Nanocomposites for MB, RhB, and CR Adsorption at 298 Ka) pseudo-first-order model

a

pseudo-second-order model

dyes

PDA anchored time

qe (mg/g)

R2

K1 (×102) (min−1)

qe (mg/g)

R2

K2 (×103) (g/min·mg)

MB MB MB RhB CR

5h 15h 35h 5h 5h

25.91 26.92 25.61 6.75 9.62

0.983 0.998 0.992 0.983 0.994

2.37 1.86 1.96 1.64 1.50

31.29 34.05 28.81 8.40 12.94

0.996 0.992 0.996 0.985 0.995

1.13 0.44 0.69 2.32 0.996

Experimental data from Figure 7.

values represent the kinetic rate constants.65,66 The kinetic results (Table 1) can be good characterized by either pseudofirst-order model with a correlation coefficient (R2 > 0.983) or pseudo-second-order model with a correlation coefficient (R2 > 0.985). The present obtained adsorption kinetics curves of synthesized PVA/PAA/GO-COOH@PDA nanocomposites on used three dye solutions indicated present designed functional composite materials can act as excellent adsorbents with pseudo-first-order model or pseudo-second-order model with good correlation coefficient. In addition, it should be noted that the adsorption capacities of the as-obtained PVA/PAA/GOCOOH@PDA nanocomposites on MB show better performance than two other used dyes. The main reason for the difference can be speculated to the matched strong π−π stacking and electrostatic interactions between nanocomposites and MB molecules. At the same time, the abundant amino and hydroxyl groups in PDA surface give more adsorbent activity points for dye molecules, which demonstrate the tailored strategy to improve the absorption performance. On the other hand, good recovery and stability are expected and preferable for the large-scale applications of composite nanomaterials. For examples, in our recent study, the facile preparation and the phosphate sequestration capacity of nanoLa(III) (hydr)oxides or sandwich-like MXene/magnetic iron oxide nanocomposites have been characterized and investigated in details, in which the obtained composite materials can be easily reused and recycled several times, suggesting the longterm stability and application prospect in water purification.67,68 Here, the as-prepared PVA/PAA/GO-COOH@PDA nanocomposite materials were used to investigate the potential application for MB removal. Unlike other reported adsorbents containing nanoparticle, the as-obtained composite materials can be easily separated from the used wastewater solutions. And it should be noted that, after saturated adsorption process, the used composite materials were treated by thoroughly cleaning procedures to remove possible byproducts and to regenerate the materials. The adsorption experiments were repeated for ten consecutive cycles by the same composite material and fresh MB solution, as presented in Figure 8. The results indicated that the adsorbed amount toward MB maintains at about 21.54 mg/g (about 81.4%, compared to 26.45 mg/g in the first adsorption process) for PVA/PAA/GO-COOH@PDA nanocomposite membranes after 10 consecutive cycles, demonstrating an excellent stability and reutilization of the composite materials in this study. In addition, further recycling steps indicated slight decrement of adsorption efficiency, which could be attributed to the byproduct deposition on composite surfaces or slight loss of PDA components from the fibers surface by many washing steps. The above reused data suggested that the prepared composite membrane materials can be potentially applied for wastewater treatment.

Figure 8. Relative adsorption capacity and regeneration studies of asprepared PVA/PAA/GO-COOH@PDA nanocomposite with modified time of 35 h toward MB at room temperature for different consecutive cycles.

■

CONCLUSIONS We have demonstrated the facile preparation and dye adsorption capacities of new composite absorbent materials, i.e., electrospun PVA/PAA/GO-COOH nanofibers modified with PDA component via an eco-friendly and self-assembled process. Because of the characteristic high surface area of electrospun membranes and the high active of PDA nanoparticles, the obtained PVA/PAA/GO-COOH@PDA composite materials showed efficient adsorption capacity toward the three model dyes used in this study. In addition, the composite membranes can be easily separated and regenerated from wastewater dye solution and demonstrated excellent reusability. The present work is expected to open a new avenue for the design and preparation of eco-friendly electrospun composites loaded with functional GO and nanoparticles, which could enhance practical application in wastewater treatment by using functionalized composite nanofibers materials.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.7b00343. SEM images of electrospun fibers with different mixed volume ratios and concentrations, control adsorption kinetics curves, and the photograph of the electrospun composite materials (PDF)

■

AUTHOR INFORMATION

Corresponding Authors

*E-mail: T. Jiao ([email protected]). *E-mail: Q. Zhang ([email protected]). 4954


Research Article

ACS Sustainable Chemistry & Engineering ORCID

(15) Lee, H.; Dellatore, S. M.; Miller, W. M.; Messersmith, P. B. Mussel-inspired surface chemistry for multifunctional coatings. Science 2007, 318, 426−430. (16) Waite, J. H.; Qin, X. Polyphosphoprotein from the adhesive pads of Mytilus edulis. Biochemistry 2001, 40, 2887−2893. (17) Ryu, J. H.; Lee, Y.; Kong, W. H.; Kim, T. G.; Park, T. G.; Lee, H. Catechol-functionalized chitosan/pluronic hydrogels for tissue adhesives and hemostatic materials. Biomacromolecules 2011, 12, 2653− 2659. (18) Kong, J. H.; Yee, W. A.; Wei, Y. F.; Yang, L. P.; Ang, J. M.; Phua, S. L.; Wong, S. Y.; Zhou, R.; Dong, Y. L.; Li, X.; Lu, X. Silicon nanoparticles encapsulated in hollow graphitized carbon nanofibers for lithium ion battery anodes. Nanoscale 2013, 5, 2967−2973. (19) Huang, L. W.; Arena, J. T.; Manickam, S. S.; Jiang, X. Q.; Willis, B. G.; McCutcheon, J. R. Improved mechanical properties and hydrophilicity of electrospun nanofiber membranes for filtration applications by dopamine modification. J. Membr. Sci. 2014, 460, 241−249. (20) Rim, N. G.; Kim, S. J.; Shin, Y. M.; Jun, I.; Lim, D. W.; Park, J. H.; Shin, H. Mussel-inspired surface modification of poly(L-lactide) electrospun fibers for modulation of osteogenic differentiation of human mesenchymal stem cells. Colloids Surf., B 2012, 91, 189−197. (21) Li, D. W.; Luo, L.; Pang, Z. Y.; Ding, L.; Wang, Q. Q.; Ke, H. Z.; Huang, F. L.; Wei, Q. F. Novel phenolic biosensor based on a magnetic polydopamine-laccase-nickel nanoparticle loaded carbon nanofiber composite. ACS Appl. Mater. Interfaces 2014, 6, 5144−5151. (22) Yan, J. J.; Huang, Y. P.; Miao, Y. E.; Tjiu, W. W.; Liu, T. X. Polydopamine-coated electrospun poly (vinyl alcohol)/poly (acrylic acid) membranes as efficient dye adsorbent with good recyclability. J. Hazard. Mater. 2015, 283, 730−739. (23) Luo, C.; Zou, Z. P.; Luo, B. H.; Wen, W.; Li, H. H.; Liu, M. X.; Zhou, C. R. Enhanced mechanical properties and cytocompatibility of electrospun poly (l-lactide) composite fiber membranes assisted by polydopamine-coated halloysite nanotubes. Appl. Surf. Sci. 2016, 369, 82−91. (24) Cheng, L. Y.; Sun, X. M.; Zhao, X.; Wang, L.; Yu, J.; Pan, G. Q.; Li, B.; Yang, H. L.; Zhang, Y. G.; Cui, W. G. Surface biofunctional drug-loaded electrospun fibrous scaffolds for comprehensive repairing hypertrophic scars. Biomaterials 2016, 83, 169−181. (25) Choi, W.; Lee, S.; Kim, S. H.; Jang, J. H. Polydopamine InterFiber Networks: New Strategy for Producing Rigid, Sticky, 3D Fluffy Electrospun Fibrous Polycaprolactone Sponges. Macromol. Biosci. 2016, 16, 824−835. (26) Taskin, M. B.; Xu, R. D.; Gregersen, H.; Nygaard, J. V.; Besenbacher, F.; Chen, M. L. Three-Dimensional Polydopamine Functionalized Coiled Microfibrous Scaffolds Enhance Human Mesenchymal Stem Cells Colonization and Mild Myofibroblastic Differentiation. ACS Appl. Mater. Interfaces 2016, 8, 15864−15873. (27) Zhang, H. F.; Hu, S.; Song, D. D.; Xu, H. Polydopaminesheathed electrospun nanofiber as adsorbent for determination of aldehydes metabolites in human urine. Anal. Chim. Acta 2016, 943, 74−81. (28) Shi, C.; Dai, J. H.; Huang, S. H.; Li, C.; Shen, X.; Zhang, P.; Wu, D. Z.; Sun, D. H.; Zhao, J. B. A simple method to prepare a polydopamine modified core-shell structure composite separator for application in high-safety lithium-ion batteries. J. Membr. Sci. 2016, 518, 168−177. (29) Lin, C. C.; Fu, S. J. Osteogenesis of human adipose-derived stem cells on poly (dopamine)-coated electrospun poly (lactic acid) fiber mats. Mater. Sci. Eng., C 2016, 58, 254−263. (30) Luan, V. H.; Tien, H. N.; Hur, S. H. Fabrication of 3D structured ZnO nanorod/reduced graphene oxide hydrogels and their use for photo-enhanced organic dye removal. J. Colloid Interface Sci. 2015, 437, 181−186. (31) Jiao, T.; Guo, H.; Zhang, Q.; Peng, Q.; Tang, Y.; Yan, X.; Li, B. Reduced graphene oxide-based silver nanoparticle-containing composite hydrogel as highly efficient dye catalysts for wastewater treatment. Sci. Rep. 2015, 5, 11873.

Qingrui Zhang: 0000-0002-2070-2179 Qiuming Peng: 0000-0002-3053-7066 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This work was financially supported by the National Natural Science Foundation of China (Nos. 21473153 and 51578476,21607080), the Support Program for the Top Young Talents of Hebei Province, the China Postdoctoral Science Foundation (No. 2015M580214), the Science & Technology Pillar Program of Hebei Province (Nos. 16211250 and 15273626), and the Scientific and Technological Research and Development Program of Qinhuangdao City (No. 201502A006).

■

REFERENCES

(1) Zhang, Y. R.; Shen, S. L.; Wang, S. Q.; Huang, J.; Su, P.; Wang, Q. R.; Zhao, B. X. A dual function magnetic nanomaterial modified with lysine for removal of organic dyes from water solution. Chem. Eng. J. 2014, 239, 250−256. (2) Ding, Q. W.; Miao, Y. E.; Liu, T. X. Morphology and photocatalytic property of hierarchical polyimide/ZnO fibers prepared via a direct ion-exchange process. ACS Appl. Mater. Interfaces 2013, 5, 5617−5622. (3) Li, D. F.; Wang, F. X.; Zhang, X. Y.; Liang, L.; Sun, J. M. The efficient removal of organic pollutant over magnetic mesoporous polymer. J. Porous Mater. 2014, 21, 811−817. (4) Meidanchi, A.; Akhavan, O. Superparamagnetic zinc ferrite spinel−graphene nanostructures for fast wastewater purification. Carbon 2014, 69, 230−238. (5) Ma, G.; Zhu, Y. M.; Zhang, Z. Q.; Li, L. C. Preparation and characterization of multi-walled carbon nanotube/TiO2 composites: Decontamination organic pollutant in water. Appl. Surf. Sci. 2014, 313, 817−822. (6) Ji, K. M.; Deng, J. G.; Zang, H. J.; Han, J. H.; Arandiyan, H.; Dai, H. X. Fabrication and high photocatalytic performance of noble metal nanoparticles supported on 3DOM InVO4-BiVO4 for the visible-lightdriven degradation of rhodamine B and methylene blue. Appl. Catal., B 2015, 165, 285−295. (7) Reneker, D. H.; Chun, I. Nanometre diameter fibres of polymer, produced by electrospinning. Nanotechnology 1996, 7, 216−223. (8) Li, D.; Xia, Y. N. Electrospinning of nanofibers: reinventing the wheel. Adv. Mater. 2004, 16, 1151−1170. (9) Si, Y.; Wang, X. Q.; Li, Y.; Chen, K.; Wang, J. Q.; Yu, J. Y.; Wang, H. J.; Ding, B. Optimized colorimetric sensor strip for mercury(II) assay using hierarchical nanostructured conjugated polymers. J. Mater. Chem. A 2014, 2, 645−652. (10) Lin, J. Y.; Ding, J. M.; Yang, J. M.; Yu, J. Y.; Sun, G. Subtle regulation of the micro-and nanostructures of electrospun polystyrene fibers and their application in oil absorption. Nanoscale 2012, 4, 176− 182. (11) Bognitzki, M.; Czado, W.; Frese, T.; Schaper, A.; Hellwig, M.; Steinhart, M.; Greiner, A.; Wendorff, J. H. Nanostructured fibers via electrospinning. Adv. Mater. 2001, 13, 70−72. (12) Huang, Z.; Zhang, Y. Z.; Kotaki, M.; Ramakrishna, S. A review on polymer nanofibers by electrospinning and their applications in nanocomposites. Compos. Sci. Technol. 2003, 63, 2223−2253. (13) Zhang, H. T.; Nie, H. L.; Yu, D. G.; Wu, C. Y.; Zhang, Y. L.; White, C. J.; Zhu, L. M. Surface modification of electrospun polyacrylonitrile nanofiber towards developing an affinity membrane for bromelain adsorption. Desalination 2010, 256, 141−147. (14) Miao, Y. E.; Wang, R. Y.; Chen, D.; Liu, Z. Y.; Liu, T. X. Electrospun self-standing membrane of hierarchical SiO2@ γ-AlOOH (Boehmite) core/sheath fibers for water remediation. ACS Appl. Mater. Interfaces 2012, 4, 5353−5359. 4955


Research Article

ACS Sustainable Chemistry & Engineering (32) Zhou, W. W.; Ding, C. Y.; Jia, X. T.; Tian, Y.; Guan, Q. T.; Wen, G. W. Self-assembly of Fe2O3/reduced graphene oxide hydrogel for high Li-storage. Mater. Res. Bull. 2015, 62, 19−23. (33) Sun, Y. M.; Cheng, Y. B.; He, K.; Zhou, A. J.; Duan, H. W. Onestep synthesis of three-dimensional porous ionic liquid-carbon nanotube-graphene gel and MnO2-graphene gel as freestanding electrodes for asymmetric supercapacitors. RSC Adv. 2015, 5, 10178−10186. (34) Jiao, T.; Zhao, H.; Zhou, J.; Zhang, Q.; Luo, X.; Hu, J.; Peng, Q.; Yan, X. Self-Assembly Reduced Graphene Oxide Nanosheet Hydrogel Fabrication by Anchorage of Chitosan/Silver and Its Potential Efficient Application toward Dyes Degradation for Wastewater Treatments. ACS Sustainable Chem. Eng. 2015, 3, 3130−3139. (35) Huang, H. D.; Ren, P. G.; Chen, J.; Zhang, W. Q.; Ji, X.; Li, Z. M. High barrier graphene oxide nanosheets/poly(vinyl alcohol) nanocomposite films. J. Membr. Sci. 2012, 409−410, 156−163. (36) Balandin, A. A.; Ghosh, S.; Bao, W.; Calizo, I.; Teweldebrhan, D.; Miao, F.; Lau, C. N. Superior thermal conductivity of single-layer graphene. Nano Lett. 2008, 8, 902−907. (37) Lee, C.; Wei, X.; Kysar, J. W.; Hone, J. Measurement of the elastic properties and intrinsic strength of monolayer graphene. Science 2008, 321, 385−388. (38) Zeng, J.; Hou, H. Q.; Wendorff, J. H.; Greiner, A. Electrospun poly(vinyl alcohol)/poly(acrylic acid) fibres with excellent waterstability. e-Polym. 2004, 4, 899−906. (39) Li, D.; Muller, M. B.; Gilje, S.; Kaner, R. B.; Wallace, G. G. Processable aqueous dispersions of graphene nanosheets. Nat. Nanotechnol. 2008, 3, 101−105. (40) Orth, E. S.; Fonsaca, J. E.S.; Domingues, S. H.; Mehl, H.; Oliveira, M. M.; Zarbin, A. J.G. Targeted thiolation of graphene oxide and its utilization as precursor for graphene/silver nanoparticles composites. Carbon 2013, 61, 543−550. (41) Baştürk, E.; Demir, S.; Danış, O.; Kahraman, M. V. Covalent immobilization of ş-amylase onto thermally crosslinked electrospun PVA/PAA nanofibrous hybrid membranes. J. Appl. Polym. Sci. 2013, 127, 349−355. (42) Gao, H. C.; Sun, Y. M.; Zhou, J. J.; Xu, R.; Duan, H. W. Musselinspired synthesis of polydopamine-functionalized graphene hydrogel as reusable adsorbents for water purification. ACS Appl. Mater. Interfaces 2013, 5, 425−432. (43) Bao, Q.; Zhang, H.; Yang, J.; Wang, S.; Tang, D. Y.; Jose, R.; Ramakrishna, S.; Lim, C. T.; Loh, K. P. Graphene−polymer nanofiber membrane for ultrafast photonics. Adv. Funct. Mater. 2010, 20, 782− 791. (44) Jiao, T.; Wang, Y.; Zhang, Q.; Yan, X.; Zhao, X.; Zhou, J.; Gao, F. Self-assembly and headgroup effect in nanostructured organogels via cationic amphiphile-graphene oxide composites. PLoS One 2014, 9, e101620. (45) Guo, H.; Jiao, T.; Zhang, Q.; Guo, W.; Peng, Q.; Yan, X. Preparation of graphene oxide-based hydrogels as efficient dye adsorbents for wastewater treatment. Nanoscale Res. Lett. 2015, 10, 272. (46) Du, X.; Guo, P.; Song, H. H.; Chen, X. H. Graphene nanosheets as electrode material for electric double-layer capacitors. Electrochim. Acta 2010, 55, 4812−4819. (47) Ferrari, A. C.; Robertson, J. Interpretation of Raman spectra of disordered and amorphous carbon. Phys. Rev. B: Condens. Matter Mater. Phys. 2000, 61, 14095−14107. (48) Malard, L. M.; Pimenta, M. A.; Dresselhaus, G.; Dresselhaus, M. S. Raman spectroscopy in graphene. Phys. Rep. 2009, 473, 51−87. (49) Kudin, K. N.; Ozbas, B.; Schniepp, H. C.; Prud'homme, R. K.; Aksay, I. A.; Car, R. Raman spectra of graphite oxide and functionalized graphene sheets. Nano Lett. 2008, 8, 36−41. (50) Kim, K. S.; Zhao, Y.; Jang, H.; Lee, S. Y.; Kim, J. M.; Kim, K. S.; Ahn, J. H.; Kim, P.; Choi, J. Y.; Hong, B. H. Large-scale pattern growth of graphene films for stretchable transparent electrodes. Nature 2009, 457, 706−710.

(51) Akhavan, O. Bacteriorhodopsin as a superior substitute for hydrazine in chemical reduction of single-layer graphene oxide sheets. Carbon 2015, 81, 158−166. (52) Akhavan, O.; Ghaderi, E. Self-accumulated Ag nanoparticles on mesoporous TiO2 thin film with high bactericidal activities. Surf. Coat. Technol. 2010, 204, 3676−3683. (53) Hou, C.; Ma, K.; Jiao, T.; Xing, R.; Li, K.; Zhou, J.; Zhang, L. Preparation and dye removal capacities of porous silver nanoparticlecontaining composite hydrogels via poly(acrylic acid) and silver ions. RSC Adv. 2016, 6, 110799−110807. (54) Zhao, X.; Ma, K.; Jiao, T.; Xing, R.; Ma, X.; Hu, J.; Huang, H.; Zhang, L.; Yan, X. Fabrication of hierarchical layer-by-layer assembled diamond based core-shell nanocomposites as highly efficient dye absorbents for wastewater treatment. Sci. Rep. 2017, 7, 44076. (55) Akhavan, O.; Azimirad, R.; Moshfegh, A. Z. Low temperature self-agglomeration of metallic Ag nanoparticles on silica sol-gel thin films. J. Phys. D: Appl. Phys. 2008, 41, 195305. (56) Akhavan, O. Lasting antibacterial activities of Ag-TiO2/Ag/aTiO2 nanocomposite thin film photocatalysts under solar light irradiation. J. Colloid Interface Sci. 2009, 336, 117−124. (57) Rim, N. G.; Kim, S. J.; Shin, Y. M.; Jun, I.; Lim, D. W.; Park, J. H.; Shin, H. Mussel-inspired surface modification of poly(L-lactide) electrospun fibers for modulation of osteogenic differentiation of human mesenchymal stem cells. Colloids Surf., B 2012, 91, 189−197. (58) Konwer, S.; Boruah, R.; Dolui, S. K. Studies on conducting polypyrrole/graphene oxide composites as supercapacitor electrode. J. Electron. Mater. 2011, 40, 2248−2255. (59) Sharma, A.; Kumar, S.; Tripathi, B.; Singh, M.; Vijay, Y. K. Aligned CNT/polymer nanocomposite membranes for hydrogen separation. Int. J. Hydrogen Energy 2009, 34, 3977−3982. (60) Hou, C. Y.; Zhang, Q. H.; Li, Y. G.; Wang, H. Z. Graphene− polymer hydrogels with stimulus-sensitive volume changes. Carbon 2012, 50, 1959−1965. (61) Zhang, R.; Xing, R.; Jiao, T.; Ma, K.; Chen, C.; Ma, G.; Yan, X. Carrier-free, chemo-photodynamic dual nanodrugs via self-assembly for synergistic antitumor therapy. ACS Appl. Mater. Interfaces 2016, 8, 13262−13269. (62) Xing, R.; Liu, K.; Jiao, T. F.; Zhang, N.; Ma, K.; Zhang, R. Y.; Zou, Q. L.; Ma, G. H.; Yan, X. H. An injectable self-assembling collagen-gold hybrid hydrogel for combinatorial antitumor photothermal/photodynamic therapy. Adv. Mater. 2016, 28, 3669−3676. (63) Sui, Z. Y.; Zhang, X. T.; Lei, Y.; Luo, Y. J. Easy and green synthesis of reduced graphite oxide-based hydrogels. Carbon 2011, 49, 4314−4321. (64) Xing, R.; Jiao, T.; Liu, Y.; Ma, K.; Zou, Q.; Ma, G.; Yan, X. Coassembly of graphene oxide and albumin/photosensitizer nanohybrids towards enhanced photodynamic therapy. Polymers 2016, 8, 181. (65) Jiao, T.; Liu, Y.; Wu, Y.; Zhang, Q.; Yan, X.; Gao, F.; Bauer, A.; Liu, J.; Zeng, T.; Li, B. Facile and scalable preparation of graphene oxide-based magnetic hybrids for fast and highly efficient removal of organic dyes. Sci. Rep. 2015, 5, 12451. (66) Wang, W.; Jiao, T.; Zhang, Q.; Luo, X.; Hu, J.; Chen, Y.; Peng, Q.; Yan, X.; Li, B. Hydrothermal synthesis of hierarchical core−shell manganese oxide nanocomposites as efficient dye adsorbents for wastewater treatment. RSC Adv. 2015, 5, 56279−56285. (67) Qiu, H.; Liang, C.; Yu, J.; Zhang, Q.; Song, M.; Chen, F. Preferable phosphate sequestration by nano-La(III) (hydr)oxides modified wheat straw with excellent properties in regeneration. Chem. Eng. J. 2017, 315, 345−354. (68) Zhang, Q.; Teng, J.; Zou, G.; Peng, Q.; Du, Q.; Jiao, T.; Xiang, J. Efficient phosphate sequestration for water purification by unique sandwich-like MXene/magnetic iron oxide nanocomposites. Nanoscale 2016, 8, 7085−7093.

4956


Bioinspired Polydopamine Sheathed Nanofibers ... - ACS Publications

Recommend Documents