Sustainable Synthesis of High-Surface-Area Graphite Oxide via Dry

Research Article Cite This: ACS Sustainable Chem. Eng. 2018, 6, 6358−6369

pubs.acs.org/journal/ascecg

Sustainable Synthesis of High-Surface-Area Graphite Oxide via Dry Ball Milling Alaa El Din Mahmoud,*,†,‡ Achim Stolle,† and Michael Stelter†,§ †

Downloaded via DURHAM UNIV on July 9, 2018 at 09:18:30 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

Institute for Technical Chemistry and Environmental Chemistry, Center for Energy and Environmental Chemistry, Friedrich-Schiller University Jena, Philosophenweg 7a, 07743 Jena, Germany ‡ Environmental Sciences Department, Faculty of Science, Alexandria University, 21511 Alexandria, Egypt § Fraunhofer IKTS, Fraunhofer Institute for Ceramic Technologies and Systems, 07629 Hermsdorf, Germany S Supporting Information *

ABSTRACT: A sustainable route to produce graphite oxide (GO) is presented using dry ball milling. The production method was based on pristine graphite flakes in a planetary ball mill. The prepared GO was characterized using UV−vis spectroscopy, BET surface area analysis, thermal analysis, SEM-EDX, TEM, XPS, elemental analysis, and Raman spectroscopy. The degree of graphite oxidation was controllable by the milling time and milling material, and the carbon-based yields ranged from 86 to 97%. The maximum oxygen/carbon ratios of the produced GOs were 0.16 and 0.15 after 24 h of ball milling with steel and zirconia balls, respectively. The BET surface area increased with increasing milling time from 1 m2 g−1 for pristine graphite up to 730 m2 g−1 for the ball-milled samples. Furthermore, the intensity ratios of the D and G bands (ID/IG) from the Raman spectra were 0.84 and 0.77 for GO produced with the steel and zirconia balls, respectively. The in-plane sp2 crystallite sizes (La) of graphite (168 nm) decreased to 20 (steel balls) and 22 nm (zirconia balls). Additionally, the produced GO was tested as an adsorbent for methylene blue dye removal. KEYWORDS: Mechanochemistry, Graphene, Oxidation, Methylene blue, Treatment, Adsorption

■

INTRODUCTION Graphene is a type of carbon nanomaterial that has gained rapidly expanded research attention since single-layer graphene was first prepared from the isolation of graphene from graphite in 2004.1,2 This isolation was accomplished by micromechanical cleavage, which earned Novoselov and Geim the Nobel Prize in 2010.1 This procedure is a suitable method for research applications but is not suited for large-scale graphene production or the production of related materials. Blake et al.3 and Marcano et al.4 concluded that no industrial technology could rely on the micromechanical cleavage technique because only low quantities of graphene can be obtained. Other routes to graphene/graphite oxide (cf. Supporting Information (SI)) suffer from high investment or operative costs or are not sustainable due to the consumption of hazardous chemicals or the existence of impurities originating from wet chemical oxidation.5 Therefore, a scalable and low cost approach to obtain large quantities of graphene oxide/graphene is needed.6 The synthesis of such nanomaterials requires interdisciplinary green chemistry principles that utilize nontoxic chemicals or environmentally benign solvents.7,8 Recently, AmbrosioMartin et al.9 reported ball milling as an efficient and sustainable strategy to synthesize different composites. The mechanochemical method was identified as a sustainable © 2018 American Chemical Society

technique to synthesize graphene materials with less structural defects.10 Utilization of mechanical stress can be realized in ball mills. During operation, the milling balls roll down the surface of the jar in a series of parallel layers and transfer energy to the powder.11 Furthermore, the high speed of the planetary rotation and collisions of the jars and balls generate sufficient kinetic energy for bond cleavages in the aromatic graphite structure. This process introduces functional groups on the edges, surfaces, and basal planes of graphene materials during the milling process.10 Consequently, comminution using ball mills not only reduces the particle size but also refines the grains into nanoscale sizes and increases the surface area of the solids. Ball milling is expected to increase the proportion of highly active regions on the material surface.12 The large-scale production of graphite oxide (GO)/graphene may be achieved using ball milling. As the moving balls apply their kinetic energy to the milled material, strong bonding interactions will break, producing fresh surfaces.13 In this process, the milling jar is not supposed to be filled completely by the balls and powder to allow the milling process Received: January 11, 2018 Revised: March 8, 2018 Published: March 26, 2018 6358

DOI: 10.1021/acssuschemeng.8b00147 ACS Sustainable Chem. Eng. 2018, 6, 6358−6369

Research Article

ACS Sustainable Chemistry & Engineering to occur. Thus, air (or another gas) is present after closing the jar. The presence of air reduces the cold welding to a favorable level.14 Therefore, process control agents are generally not required. Once graphene/GO is prepared, these materials can be dispersed in water or organic solvents to form stable suspensions to use for various purposes.15 Previous reports have stated that graphene sheets can be prepared from wet ball milling and active precursors. For instance, Zhao et al.16 conducted a wet ball milling experiment for graphite with N,Ndimethylformamide (DMF) solvent for 30 h at 300 rpm in order to exfoliate it into graphene sheets. However, Coleman17 reported that the liquid exfoliation of graphite in a majority of solvents requires their subsequent removal that hinders the preparation process. Other researchers used various active precursors with the starting graphite material. For example, melamine,18,19 ammonia borane,20 cellulose,21 and dry ice13 have been applied to weaken the van der Waals interactions between graphite layers. In general, molecular adsorption on the graphite surface effectively weakens those interactions, facilitating the exfoliation of graphite particles.20 The previous methods required tedious multistep washing processes or freeze-drying to get the final desired product. In addition to applications in materials science, graphene/ GO materials have potential environmental applications, such as attractive adsorbents for wastewater treatment, due to their high surface areas and sorption capacities as well as nontoxicity.22,23 For instance, several authors demonstrated the adsorption capability of graphene oxide for heavy metals, such as As, Cd, Cr, or Pb.24,25 Dyes, as examples of colored organic pollutants, exist in the effluents of textile, paper, polymer, and food production. Moreover, dye wastewater affects the environment and human health because of its color depth and high content of organic pollutants with poor biodegradability.26,27 The annual production of dyes has been calculated to be more than 700,000 ton with a high variability in their chemical nature.28 In this study, methylene blue (MB) was applied as an example of a cationic dye with positively charged sulfur groups, which can have strong electrostatic attractions with the negative oxygen-containing functional groups on carbon materials.29 Here, we report a sustainable synthesis of GO using a dry ball milling technique. We investigated the effects of two different milling materials and the ball milling conditions on the produced GO. In addition, the adsorption efficiency of the produced GO for MB as a model contaminant was demonstrated.

■

Table 1. Experimental Conditions of the Ball Milling Experiments ball-to-powder ratio rotation frequency [min−1] ball size [mm] milling tool material beaker volume [cm3] graphite weight [g] Φtotal 1-Φtotal milling atmosphere [cm3] milling time [h] sample notation

7:1 600 5 stainless steel 80 1.49 0.049 0.951 76.1 6, 16, 24 A-6h, B-16h, C-24h

zirconia 80 1.40 0.049 0.951 75.9 6, 16, 24 D-6h, E-16h, F-24h

temperatures and pressures inside the milling beakers were monitored using an Easy-GTM system (Fritsch GmbH, Germany). Characterization. The suspensions were created by adding 50 mg of carbon material to 10 mL of deionized water followed by ultrasonication for 30 min. Each suspension (0.5 mg mL−1) was made transparent by diluting by a factor of 10 prior to UV−vis measurements (PerkinElmer Lambda 35; scan range, 800−200 nm; resolution, 1 nm; scan rate, 480 nm min−1). Brunauer−Emmett− Teller (BET) surface areas of the samples were obtained by N2physisorption measurements (Quantachrome; degassing at 120 °C prior to measurement). Thermogravimetric analyses were performed with a DTA-TG Shimadzu (10 K min−1; air 30 mL min−1; up to 1000 °C). The morphologies of the samples before and after ball milling were investigated by scanning electron microscopy (SEM, Phenom) equipped with energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM Fei Technai G2). TEM of the samples was dispersed by ultrasonicating in ethanol and loading one drop of the prepared suspensions onto a carbon coated copper grid. Xray photoelectron spectroscopy (XPS) was analyzed using an SPECS EA200 analyzer with Mg Kα radiation (deconvolution was realized based on a Gaussian−Lorentzian model). The oxygen/carbon ratio (O/C) was calculated based on the elemental composition measured with an elemental analyzer (Elementar Vario Micro). Raman spectra were obtained using a Renishaw InVia spectrometer (UK) with the 514 nm line of an Ar+ ion laser in the range of 1200−3000 nm. Application of GO for MB Removal. The carbon material (12.5 mg) was added to the MB solution (50 mL; 30 mg L−1) in a 250 mL flask. The pH of the aqueous solutions was adjusted with 0.1 and 0.01 mol L−1 NaOH and HCl. Adsorption experiments were carried out in dynamic mode using a horizontal shaker (agitation speed: 200 rpm) at room temperature for 1−60 min. All experiments were conducted in duplicate, and the averages were obtained. After each adsorption experiment, the suspensions were centrifuged (6,000 rpm; 10 min). The final concentration of MB dye in the solution was analyzed by a UV−vis spectrophotometer (PerkinElmer Lambda 35; 664 nm, cuvette path length, 10 mm) using deionized water as a blank. The Lambert−Beer law was used to calculate the remaining MB concentration after adsorption. The removal efficiency of MB was calculated according to the following equation:30−32 cMB,initial − cMB,t Removal% = · 100 cMB,initial (1)

EXPERIMENTAL SECTION

Chemicals and Reagents. Graphite flakes were purchased from Sigma-Aldrich Chemical Co., USA. Graphene oxide nanocolloids (2 mg mL−1) and silicon dioxide were obtained from Sigma-Aldrich Chemical Co., Germany. Methylene blue (MB) was obtained from Merck, Germany. Deionized water was used throughout the experiments. Preparation of GO by Ball Milling. The feed sample graphite is denoted as G. The ball milling experiments were carried out in a planetary ball mill Pulverisette 7 (Fritsch GmbH, Germany) under ambient conditions. The milling parameters were set as described in Table 1. The ball size was 5 mm for both grinding materials. The rotation frequency was maintained at 600 rpm. After 8 h, the milling was interrupted for 10 min before restarting. The product samples were denoted as A-6h, B-16h, and C-24h (stainless steel) and D-6h, E-16h, and F-24h (zirconia). The mass yield of the milled product was determined by weighing the samples after ball milling. The

where cMB,initial and cMB,t are the initial MB and the MB concentration after a certain time t [mg L−1], respectively.

■

RESULTS AND DISCUSSION Synthesis. The mass yield becomes a vital parameter that must be considered and optimized for the large-scale production of graphite/graphene oxide. Thus, the weight of the starting material (graphite) before and after ball milling were measured (Table 2). Although carbon yields of >85% were obtained for the recovered material in all experiments, 6359


Research Article

ACS Sustainable Chemistry & Engineering

Table 2. Yields Obtained from the Ball-Milling Synthesis of GOs and BET Data of the Samples and Pristine Graphitea samples graphite (G) A-6hb B-16hb C-24hb D-6hc E-16hc F-24hc

total yield [g (%)] 1.49 1.46 1.45 1.40 1.36 1.35

± ± ± ± ± ±

0.00 0.01 0.01 0.00 0.01 0.01

(100 ± 0.0) (98.3 ± 0.5) (97.6 ± 0.5) (100 ± 0.0) (96.8 ± 0.5) (96.2 ± 0.3)

carbon yield [g (%)] 1.40 1.25 1.21 1.31 1.21 1.15

± ± ± ± ± ±

0.00 0.01 0.01 0.03 0.00 0.01

(97.1 (88.3 (86.1 (96.9 (92.3 (87.9

± ± ± ± ± ±

0.1) 0.3) 0.4) 0.2) 0.4) 0.1)

ABET [m2 g−1]

Amicropores [m2 g−1]

Aexternal surface [m2 g−1]

1 250 621 666 128 469 730

1 93 231 265 34 166 293

0 195 386 396 94 302 437

a

Reaction conditions: see Table 1. bMilling tools, stainless steel; jar volume, 80 mL; initial mass of graphite = 1.49 g. cMilling tools, zirconia; jar volume, 80 mL; initial mass of graphite = 1.40 g. Note: the total yield of one milling cycle is 2.89 g (steel) and 2.80 g (zirconia).

increasing the milling time provided little advantage with respect to the yield, as some powder stuck on the balls and the milling jar walls. A similar effect was observed for the mass yield, showing a less pronounced effect of the milling time. Values of 96% to complete recovery were achieved. The total filling degree of the milling beaker Φtotal, the volumetric filling degree of the milling balls ΦMB,material, and the volumetric filling degree of the grinding stock ΦGS,packing were found to be 0.049, 0.017, and 0.032, respectively, for the ball milling with stainless-steel balls (see Table 1; for calculations, see SI S1−S4). The filling degree is an essential parameter that influences the trajectories of the milling balls and the contact between the balls and powder. Additionally, optimizing the filling degree is crucial for large-scale synthesis with ball mills, without requiring an increase in the jar volume and/or a replacement ball mill. Stolle et al.33 reported that Φtotal ranges from 0 to 1, which corresponds to the empty and completely filled milling beaker, respectively. Furthermore, the residual free volume for the milling ball movement (1-Φtotal) in the present experiments was 0.951. The calculated volumetric filling degree of the milling balls in regard to the packing volume ΦMB,packing (eq S4) was 0.2, which is 45 min, which is presumably due to oxygen uptake by the powders. Using the ideal gas law, the amount of oxygen uptake by graphite during milling was calculated from the pressure drop (starting value, 21 mg; for milling atmosphere volumes, see Table 1). On the basis of the pressure drop, the oxygen contents were 12 and 13 mg after milling for 16 h with milling tools made from stainless steel and zirconia, respectively, and thus, the amounts of oxygen uptake by the carbon material were 9 and 8 mg, respectively. We assume that only oxygen is converted in this process, as no significant increase in the nitrogen content in the solid products was detected from elemental analysis (cf. the following section). Product Morphology. The medium particle sizes (d50, Figure S2) of pristine graphite, A-6h, and D-6h were 612, 14, and 29 μm, respectively. An increase in the milling time resulted in a decreased d50: 11 (B-16h), 13 (E-16h) 8 (C-24h), and 10 μm (F-24h). The morphologies of graphite and the ball milled samples are shown in Figure 2. The starting material (Figure 2a, SEM and TEM) consisted of flakes. Micrographs revealed a change in the sample morphology after ball milling.36−38 Figure 2c−f of SEM shows a significant reduction of the particle size after ball milling. Figure 2c−g of TEM depicts the irregular and stacked layered of the milled samples which are characteristic of graphite oxide as stated in Ma et al.39 and Mhamane et al.40 The graphite structure changed as a result of the graphite layers sliding due to the impact forces from ball collisions.38 For instance, SEM of graphite milled under 0.3 MPa nitrogen for 24 h at 150 min−1 (ball-to-powderratio: 132:1, stainless steel) confirmed the absence of flake-like structures and, instead, showed irregular sphere-like particles with a broad particle size distribution.36 Furthermore, Energy dispersive X-ray spectroscope (EDX) measurements were conducted for all the studied materials (Figure 3). EDX showed the relative element concentration on the surface of our products to check the possible contamination during ball milling. It is proven that there was no iron contamination from the milling materials, and the inset table shows the presence of

Figure 1. Temperature and pressure measured online during the ball milling of graphite with stainless-steel and zirconia milling tools. The beaker volume was 80 mL for both materials. 6360


Research Article


Figure 2. SEM micrographs (left) and TEM images (right) of (a) pristine graphite, (b) A-6h, (c) B-16h, (d) C-24h, (e) D-6h, (f) E-16h, and (g) F24h. For sample notation, see Table 1.

milled with stainless steel for 6, 16, and 24 h were 4.4, 4.6, and 4.3 nm, respectively. For ball milling with the zirconia balls, the average pore sizes were 4.7, 4.5, and 4.2 nm. Similar average pore sizes of GO (4.8 nm; Hummers method) have been reported in the literature.47 Product Composition. For milling with stainless-steel balls, elongation of the milling time resulted in an oxygen increase from 2.54 to 13.24% for pristine graphite and C-24h, respectively (Figure 5). For the use of zirconia balls, the oxygen concentration increased to 13.10% after 24 h of ball milling. To understand the reason for this oxygen content increase, further experiments were conducted under argon (Ar) and oxygen (O2) gas conditions, and the O/C ratios are provided in the SI (Figure S1). The oxygen content increased under air, Ar, and O2 conditions, but this increase was slower during milling under Ar. This increase may be due to the introduction of oxygen into the milling jar from vessel leakage during the milling process.48 Therefore, the experiments were conducted under air conditions to facilitate the scale-up process. These results indicated that the milled samples possessed a large amount of oxygen functional groups on their surface.41 Moreover, the ball-milled samples possessed different oxidation degrees after different milling times.41 Using stainless-steel balls, the O/C ratios of the produced GOs were 0.06 (A-6h), 0.15 (B-16h), and 0.16 (C-24h). Figure 5 illustrates that changing the milling material to zirconia results in a similar O/ C ratio after 24 h (0.15). Posudievsky et al.49 reported an increase in the O/C ratio from 0.017 to 0.125 after 3 h of ball milling of graphite in the presence of Na2SO4. Comparison of the GO produced with different chemical oxidation methods resulted in materials with O/C ratios ranging from 0.062 to 0.5.50 Thermal analyses of graphite and the milled samples revealed a general decreasing thermal stability as the milling time

oxygen in the samples in addition to the carbon as indicated in elemental analysis (EA; Table S3). The surface areas of the samples were determined using the BET method (Figure 4). The products generated by ball milling with stainless steel and zirconia possessed average surface areas of 666 and 730 m2 g−1, respectively. Notably, the present method acquired higher surface areas for the prepared GO samples than those previously reported in the literature. Using a combination of 5 and 7 mm milling balls, Dash et al. obtained GO with a 188 m2 g−1 surface area after 24 h of milling.41 Antisari et al.42 reported that 20 h of ball milling of graphite in the presence of water increased its surface area from 6 to 43 m2 g−1. Using DMF as a solvent resulted in a surface area increase from 23 to 35 m2 g−1 after 15 h of milling, also indicating a higher degree of graphite exfoliation.43 During graphite milling, as the surface area increased, the particle size reduced, and a new surface was generated,44 indicating that no large clusters formed. Štefanić et al.45 reported that the level of contamination gradually dropped with a prolonged milling time, which can be attributed to a reduction in the grain size as in indicated in our case (Figure 2 and 3). Adsorption−desorption experiments confirmed the existence of micropores in the ball milled samples (Table 2). Noticeably, the difference between the surface areas of samples B-16h and C-24h was rather small. On the other hand, for the milling experiment with zirconia, larger differences in the surface areas after 16 (E-16h) and 24 h of milling (F-24h) were observed due to the higher energy input, as the stainless-steel milling balls provided a higher kinetic energy. Therefore, the surface area increased faster. According to IUPAC classification, all the samples showed type IV isotherms, characterized by the existence of micropores and mesopores (1.5−100 nm)46 and high adsorption energies. The average pore size of graphite was 8.9 nm. However, the average pore sizes of the graphite samples 6361


Research Article


Figure 3. Graphical representation of EDX for (a) graphite, (b) A-6h, (c) B-16h, (d) C-24h, (e) D-6h, (f) E-16h, and (g) F-24h. For sample notation, see Table 1.

milling is in accordance with the elemental analysis results (Figure 5) and Raman spectroscopy (cf. the following text). The C 1s spectra of the feed and ball milled samples are illustrated in Figure 7. For pristine graphite (Figure 7a), a peak at 284.1 eV indicates the presence of sp2 carbon. The prepared GO samples (Figure 7b−g) displayed the characteristic peaks of the C−C skeleton and hydroxyl (C−OH), ether and epoxy (C−O−C), and carbonyl/carboxyl (CO/COOH) groups at 284.0−284.5, 286.0−286.2, 286.5−286.6, and 288.4−288.6 eV, respectively. The decreased peak area % corresponding to the C−C skeleton (284 eV) combined with the increasing peak area corresponding to oxidized carbon indicates the oxygenation of graphite to yield GO (Table 3). In addition, prolonged milling seemed to enhance the formation of ether, epoxy, carbonyl, and carboxyl groups. Deconvoluted data for the O 1s peaks are shown in the SI (Figure S3 and Table S5). Furthermore, XRD is shown in Figure S5. Raman spectroscopy is a powerful analytical technique to characterize carbon-based nanomaterials.10 The main features in the Raman analysis of graphene and its derivatives are the positions of the G and D bands and their overtones (2D). The G band is attributed to sp2 hybridized carbon bonds (in-plane vibrations of the aromatic carbon structure), while the D band is an indication of structural defects (loss of hexagonal symmetry of disordered graphite).55,56 The Raman spectra of

increased (Figure 6). Mass loss was attributed to three events: (i) the release of sorbed water and the desorption of gases (T < 200 °C), (ii) the removal of oxygen-containing groups and amorphous carbon (200 ≤ T < 400 °C),51 and (iii) the pyrolysis/combustion of more-stable oxygen-containing groups and the remaining carbon skeleton (T ≥ 400 °C).52 Under high-temperature pyrolysis and combustion (700 ≤ T ≤ 1,000 °C), the weight losses of graphite (G), A-6h, B-16h, and C-24h were 10, 50, 88, and 95%, respectively. A similar trend was observed for the samples prepared with zirconia milling tools, revealing 18, 55, and 80% weight losses (for details, see SI; Table S4). The polydispersities of the graphene materials were estimated from TGA using the temperature ranges (ΔT) and the average combustion temperatures (T1/2).53 Figure 6c shows that the produced GOs are located in the temperature region of 580−710 °C, whereas the characteristic temperature range for graphitic materials is 800−950 °C. The determined T1/2 values are in accordance with previously reported results.41,54 Furthermore, the ΔT value is related to the polydispersity of the product. The produced GOs (B-16h, C-24h, E-16h, and F24h) have lower polydispersities than those of graphite, A-6h, and D-6h. Spectroscopic Characterization. The overview XPS spectra (Figure 7) showed C 1s and O 1s peaks in all the samples. An increase in the O 1s intensity upon prolonged ball 6362


Research Article


evidence for the presence of defects, such as bond-angle disorder and vacancies,57 in the graphite material. After ball milling, the samples revealed more intense D bands and broadened G bands. The observed line broadening is a result of the presence of more defects.58 Furthermore, the shoulder of the G band (D′) is characteristic of the presence of few-layered graphene.19,20 Figure 8c shows the relationship between the IG/ ID′ ratio and the oxygen content after ball milling. When the IG/ ID′ ratios are compared between the steel and zirconia ball milled samples, the intensity ratio decreased from 6.6 (A-6h) and 7.1 (D-6h) to 1.9 (C-24h and F-24h) for the steel and zirconia milled samples, respectively (Figure S4). Consequently, the degree of oxidation was estimated from the IG/ ID′ ratio.59 The position of the 2D band not only shifted to lower values but also became more symmetrical with an increasing milling time. This position reached 2696 (C-24h) and 2695 cm−1 (F-24h). In the literature, ball milling of graphite in the presence of KMnO4 or (NH4)2S2O8 resulted in a carbonaceous material with a 2D band at 2690 cm−1, characteristic of monolayer GO sheets.60 The intensity ratios of the D and G bands (ID/IG), representing the structural defects, are summarized in Table 4 for graphite, commercial GO, and the ball milled samples. The ID/IG ratio of graphite is rather low (0.1) due to its large grain size (cf. Figure 2 and Figure S2). After 24 h of ball milling, the ID/IG ratio gradually increased to 0.84 (C-24h) and 0.95 (F24h) with an increasing milling time (ID/IG for GO: 0.97). This indicates increased structural distortion (structural imperfections created by the hydroxyl, carboxyl, and epoxide groups on the carbon basal plane) and size reduction of the in-plane sp2 domain caused by the induced mechanical stress.41 According to McDonald et al.,61 the ID/IG ratio of GO is always ∼0.95, indicating a large amount of defects within the crystal lattice. Moreover, the ID/IG ratio is useful to calculate the in-plane sp2 crystallite size (La):19,41

Figure 4. N2-adsorption−desorption isotherms of pristine graphite and the ball-milled samples (for sample notation, see Table 1).

La = 2.4·10−10 ·

4 λlaser ID/IG

(2)

where λ is the wavelength of the laser source (nm). In graphite, La is 168 nm, and Table 4 reveals that the La values of the samples decrease with increasing milling time. A La of 20 nm was found for sample C-24h, whereas the sample prepared with zirconia (F-24h) possessed a value of 22 nm. The decreased La with an increasing milling time is likely due to the breaking of crystallites due to the increasing degree of oxidation.41 Similar values have been reported for samples prepared with stainlesssteel balls of different sizes for 24 h (18.5 nm). 41 Krishnamoorthy et al.57 calculated the in-plane sp2 crystallite size (La) of GO synthesized using a modified Hummers method (KMnO4 and conc. H2SO4, followed by ultrasonication). Increasing the amount of oxidant from 1 to 6 g resulted in decreased La values of 18.2 and 13.8 nm. Notably, the ID/IG ratio is inversely proportional to the in-plane sp2 crystallite size (La), as shown in Table 4. Herdman et al.62 confirmed the same inverse relationship between the ID/IG ratio and La with La values greater than 2 nm with relatively low disorder. GO solutions. The ball milled carbon materials were dispersed in deionized water. Suspensions prepared from samples milled for 6 h showed no significant absorbance (A6h and D-6h). Aqueous dispersions of samples prepared by

Figure 5. Elemental compositions of pristine graphite and the ballmilled samples (for sample notation, see Table 1).

graphite and the ball milled samples are shown in Figure 8a,b, and the Raman shifts for the D, G, D′, and 2D bands are summarized in Table 4. The Raman spectrum of graphite revealed D, G, and 2D bands at 1350, 1576, and 2711 cm−1, respectively. The intense G band in graphite is due to firstorder scattering of the E2g mode, and the small D band is 6363


Research Article


Figure 6. Thermogravimetric curves for (a,b) pristine graphite and the ball-milled samples (for sample notation, see Table 1) as well as (c) a thermophase diagram.

Figure 7. XPS overview spectra for the graphite samples milled with stainless-steel (top left) and zirconia (top middle) milling tools. Deconvolution of the C 1s peak for (a) pristine graphite and (b) samples A-6h, (c) B-16h, (d) C-24h, (e) D-6h, (f) E-16h, and (g) F-24h.

However, the absorbance peaks of GO produced with zirconia (E-16h and F-24h) occurred at 267 and 264 nm. In comparison, the absorbance peak of commercial graphene

milling with stainless-steel balls revealed absorbances at 265 and 263 nm for B-16h and C-24h, respectively (Figure 9). 6364


Research Article

ACS Sustainable Chemistry & Engineering Table 3. Carbon Functionalities of Pristine Graphite and the Ball Milled Samples from the XPS Spectra (Figure 7)a area percentage [%] graphite (G) A-6hb B-16hb C-24hb D-6hc E-16hc F-24hc

C−C

C−O

82.6 67.3 60.4 55.1 62.0 62.1 53.6

17.4 20.7 17.3 29.5 38.1 15.8 14.2

C−O−C

Table 4. Positions of the D, G, D′, and 2D Bands in the Raman Spectra and the ID/IG, IG/ID′, and La Values of Pristine Graphite (G), Commercial Graphene Oxide (GO), and the Ball-Milled Samples (Figure 8)a

O/C ratio [-] O−CO

12.0 14.0 5.3

8.3 10.1

12.8 15.4

9.3 16.8

XPS

EA

0.05 0.07 0.17 0.21 0.06 0.11 0.20

0.03 0.06 0.15 0.16 0.05 0.11 0.15

G GO A-6hb B-16hb C-24hb D-6hc E-16hc F-24hc

a

O/C ratio based on the ratio of the integrated O 1s and C 1s peaks in the overview spectra and elemental analysis (EA). Reaction conditions: see Table 1. bMilling tools, stainless steel; jar volume, 80 mL; initial mass of graphite = 1.49 g. cMilling tools, zirconia; jar volume, 80 mL; initial mass of graphite = 1.40 g. Note: the total yield of one milling cycle is 2.89 g (steel) and 2.80 g (zirconia).

D [cm−1]

G [cm−1]

1350 1349 1354 1350 1350 1352 1346 1350

1576 1599 1574 1576 1574 1573 1570 1577

D′ [cm−1]

2D [cm−1]

ID/IG

1614 1613 1608 1612 1605 1605

2711 2710 2708 2700 2696 2679 2694 2695

0.10 0.97 0.26 0.70 0.84 0.25 0.31 0.77

IG/ID′

La [nm]

6.6 2.4 1.9 7.1 4.6 1.9

168 17 64 24 20 67 54 22

a Reaction conditions: see Table 1. bMilling tools, stainless steel; jar volume, 80 mL; initial mass of graphite = 1.49 g. cMilling tools: zirconia; jar volume, 80 mL; initial mass of graphite = 1.40 g.

oxide nanocolloids (0.4 mg mL−1) was observed at 240 nm with a shoulder 335 nm. The small shifts in the red spectral region is related to the lower oxidation degree of the ball milled GO. Although Posudievsky et al.60 applied (NH4)2S2O8 as an additional oxidant during ball milling, these authors reported similar absorption spectra (255 nm). As the particle size is reduced compared to pristine graphite (Figure S2), the surface morphology changes, which enhances the dispersive ability and hydrophilicity due to oxygen functionalization.36 Moreover, solutions of the prepared GOs showed a linear relationship between the absorbance and the GO solution concentration, thus obeying the Beers-Lambert law (cf. Figure S6 in the SI). Application for MB Adsorption. The ball milled graphite samples (cf. Table 1) were tested for their suitability to remove MB from aqueous solution. The removal efficiencies (eq 1) of MB (30 mg L−1) for B-16h and C-24h increased to 99.3 and

99.6%, respectively, after 15 min. The pH of the solution, which can change the surface charges of the adsorbent and adsorbate, is an important factor.63 According to the literature,64,65 the pH values of the solutions were adjusted to 8−9 to obtain high MB removal efficiencies. Here, the removal efficiencies at pH 8.5 reached 99.3% and 99.5% for B-16h and C-24h, respectively (Figure 10). The removal rate reached equilibrium values at an adsorption time of 30 min. Notably, the remaining solution was almost colorless. The small difference between B-16h and C24h in MB adsorption is likely due to their similar surface areas (cf. Table 2). The fast adsorption rate is a merit of the prepared GO. In comparison, graphite (G) removed only 48.1% of MB after 15 min at pH 4.5, while at pH 8.5, a removal efficiency of only 54.2% was found. The increasing removal efficiency is in agreement with the increased oxygen% in the ball milled samples (see Figure 5 and Table 3), indicating that oxygen-

Figure 8. (a,b) Raman spectra of pristine graphite and the ball-milled samples. (c) Relationship between IG/ID′ and the oxygen content % after ball milling (for experimental conditions, see Table 1). 6365


Research Article


́ et al.66 stated that small process. Furthermore, Pérez-Ramirez adsorbent sizes endow advantages, such as rapid equilibrium rates, high adsorption capacity, and effectiveness over a broad pH range. Yang et al.67 found that the adsorption of MB onto activated carbon or carbon nanotubes requires more than 1 h to reach equilibrium. In recent years, different routes have been established to synthesize GO materials and test these materials for their MB removal efficiencies. Table 5 summarizes these results, indicating that samples produced by ball milling are comparable or even better regarding their removal efficiencies.

■

Figure 9. UV−vis absorption of graphene oxide and the ball-milled samples dispersed in water (for sample notation, see Table 1).

CONCLUSIONS

Mechanochemical ball milling is an environmentally friendly synthetic technology for the production of GO. A one-step, dry production route was developed to synthesize GO without the need for additional oxidants other than air. The absorbance peaks of the produced GO reached 263 and 264 nm with a small peak at 338 nm. Small shifts in the red spectral region were related to lower oxidation degrees compared to those of GO produced from chemical methods. However, other characterization techniques showed that the produced ball milled GO was comparable to GO synthesized via chemical pathways. For instance, TGA showed that the weight loss was caused by the pyrolysis of oxygen-containing functional groups. The oxidation degree of the produced GO increased with an increasing milling time, as indicated by XPS, elemental analysis, and EDX. EDX analysis proved no iron contamination arised from the milling process. This oxidation degree was independent of the material used for the milling balls and jars (stainless steel or zirconia). However, the rate of oxygen increase in the material as the milling time increased was more pronounced for stainless-steel ball milling materials (due to their higher density) than that for zirconia materials. The intensity ratios of the D and G bands (ID/IG) for GO produced with stainless-steel (0.84) and zirconia balls were lower than that for GO produced by chemical methods, indicating a smaller amount of defects within the crystal lattice of the ball milled samples. Moreover, the BET surface area of GO synthesized via ball milling was >650 m2 g−1 containing microand mesopores, enabling its application as an interesting material for energy and environmental applications. The produced GO proved efficient for MB removal (greater than 99% removal after 1 min).

Figure 10. Effects of the absorption time and pH on the MB removal efficiency from aqueous solutions of (a) pristine graphite, (b) B-16h, andC-24h.

containing functional groups, especially hydroxyl, epoxy, carbonyl, and carboxyl groups, play key roles in the adsorption

Table 5. Comparison of the Experimental Conditions for MB Removal with Different Adsorbents adsorbent a

graphite oxide graphite oxidea porous graphite oxideb graphite oxidec graphite oxided PVA/graphene oxide compositea agar/graphene oxide compositee GOf GOf

cMB,initial [mg L−1]

madsorbent [mg]

Vsolution [mL]

pH

t [min]

MB removal [%]

Ladsorbent [mg g−1]

ref

125 12 NA 45 45 80 200 30 30

0.6 25 NA 1 1 25 20 12.5 12.5

1.2 50 NA 20 20 50 50 50 50

6 9 6.8 9 9 9.2 6 5 8.5

5 300 NA 360 360 NA 1,560 15 1

99 98.8 99 24 35 90 95.4 99.3 99.3

250 243 200 216 306 122 476 278 278

67 68 29 69 69 59 70 this study this study

a

Modified Hummers method. bHydrothermal method. cCommercial. dMagnetic graphene oxide by coprecipitation method. eModified Hummers method and vacuum freeze-drying. fDry ball milling (sample B-16h). 6366


Research Article


■

nanocomposites for sensitive detection of nitrite. J. Mater. Chem. A 2015, 3 (30), 15529−15539. (11) Ali, M. E.; Ullah, M.; Maamor, A.; Hamid, S. B. A. Adv. Mater. Res. 2014, 356−361. (12) Baláz,̌ P. In Mechanochemistry in Nanoscience and Minerals Engineering; Springer: Berlin, Germany, 2008; DOI: 10.1007/978-3540-74855-7_2. (13) Zhu, H.; Cao, Y.; Zhang, J.; Zhang, W.; Xu, Y.; Guo, J.; Yang, W.; Liu, J. One-step preparation of graphene nanosheets via ball milling of graphite and the application in lithium-ion batteries. J. Mater. Sci. 2016, 51 (8), 3675−3683. (14) Siebeck, S.; Nestler, D.; Podlesak, H.; Wielage, B. In Integration of Practice-Oriented Knowledge Technology: Trends and Prospectives; Springer, 2013. (15) León, V.; Rodriguez, A. M.; Prieto, P.; Prato, M.; Vázquez, E. Exfoliation of Graphite with Triazine Derivatives under Ball-Milling Conditions: Preparation of Few-Layer Graphene via Selective Noncovalent Interactions. ACS Nano 2014, 8 (1), 563−571. (16) Zhao, W.; Fang, M.; Wu, F.; Wu, H.; Wang, L.; Chen, G. Preparation of graphene by exfoliation of graphite using wet ball milling. J. Mater. Chem. 2010, 20 (28), 5817−5819. (17) Coleman, J. N. Liquid exfoliation of defect-free graphene. Acc. Chem. Res. 2013, 46 (1), 14−22. (18) Zhang, M.; Liu, L.; He, T.; Wu, G.; Chen, P. Melamine assisted solid exfoliation approach for the synthesis of few-layered fluorinated graphene nanosheets. Mater. Lett. 2016, 171, 191−194. (19) Leon, V.; Quintana, M.; Herrero, M. A.; Fierro, J. L. G.; Hoz, A. d. l.; Prato, M.; Vazquez, E. Few-layer graphenes from ball-milling of graphite with melamine. Chem. Commun. 2011, 47 (39), 10936− 10938. (20) Liu, L.; Xiong, Z.; Hu, D.; Wu, G.; Chen, P. Production of high quality single- or few-layered graphene by solid exfoliation of graphite in the presence of ammonia borane. Chem. Commun. 2013, 49 (72), 7890−7892. (21) Sun, P.; Kuga, S.; Wu, M.; Huang, Y. Exfoliation of graphite by dry ball milling with cellulose. Cellulose 2014, 21 (4), 2469−2478. (22) Wang, X.; Guo, Y.; Yang, L.; Han, M.; Zhao, J.; Cheng, X. Nanomaterials as sorbents to remove heavy metal ions in wastewater treatment. J. Environ. Anal. Toxicol. 2012, 2, 154. (23) Chowdhury, S.; Balasubramanian, R. Recent advances in the use of graphene-family nanoadsorbents for removal of toxic pollutants from wastewater. Adv. Colloid Interface Sci. 2014, 204, 35−56. (24) Gollavelli, G.; Chang, C.-C.; Ling, Y.-C. Facile synthesis of smart magnetic graphene for safe drinking water: heavy metal removal and disinfection control. ACS Sustainable Chem. Eng. 2013, 1 (5), 462− 472. (25) Dong, S.; Sun, Y.; Wu, J.; Wu, B.; Creamer, A. E.; Gao, B. Graphene oxide as filter media to remove levofloxacin and lead from aqueous solution. Chemosphere 2016, 150, 759−764. (26) Ge, H.; Wang, C.; Liu, S.; Huang, Z. Synthesis of citric acid functionalized magnetic graphene oxide coated corn straw for methylene blue adsorption. Bioresour. Technol. 2016, 221, 419−429. (27) Van Hoa, N.; Khong, T. T.; Quyen, T. T. H.; Trung, T. S. Onestep facile synthesis of mesoporous graphene/Fe 3 O 4/chitosan nanocomposite and its adsorption capacity for a textile dye. Journal of Water Process Engineering 2016, 9, 170−178. (28) Sivashankar, R.; Sathya, A.; Vasantharaj, K.; Sivasubramanian, V. Magnetic composite an environmental super adsorbent for dye sequestration−A review. Environmental Nanotechnology, Monitoring & Management 2014, 1, 36−49. (29) Kong, D.; Zheng, X.; Tao, Y.; Lv, W.; Gao, Y.; Zhi, L.; Yang, Q.H. Porous graphene oxide-based carbon artefact with high capacity for methylene blue adsorption. Adsorption 2016, 22 (8), 1043−1050. (30) El Din Mahmoud, A.; Fawzy, M. In Phytoremediation: Management of Environmental Contaminants; Ansari, A. A., Gill, S. S., Gill, R., Lanza, G. R., Newman, L., Eds.; Springer International Publishing: Cham, Switzerland, 2016; Vol. 3; DOI: 10.1007/978-3319-40148-5_7.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acssuschemeng.8b00147. Details of the calculations of the ball-milling parameters and characterization methods (EA, TGA, XPS, particle size distribution, Raman spectroscopy, XRD, and UV−vis absorption spectroscopy) (PDF)

■

AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]; alaa-mahmoud@alexu. edu.eg. ORCID

Alaa El Din Mahmoud: 0000-0001-6530-9816 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS Alaa El Din Mahmoud thanks the ‘‘Deutscher Akademischer Austausch Dienst’’ (DAAD) and the Egyptian Ministry of Higher Education for his Ph.D. scholarship. We express our thanks to Professor Lothar Wondraczek (Otto-Schott-Institute for Material Research, Jena) for Raman measurements and Dr. Bernd Schroeter (Institute for Solid State Physics, Jena) for XPS measurements.

■

REFERENCES

(1) Agharkar, M.; Kochrekar, S.; Hidouri, S.; Azeez, M. A. Trends in green reduction of graphene oxides, issues and challenges: a review. Mater. Res. Bull. 2014, 59, 323−328. (2) Khan, M.; Tahir, M. N.; Adil, S. F.; Khan, H. U.; Siddiqui, M. R. H.; Al-warthan, A. A.; Tremel, W. Graphene based metal and metal oxide nanocomposites: synthesis, properties and their applications. J. Mater. Chem. A 2015, 3 (37), 18753−18808. (3) Blake, P.; Brimicombe, P. D.; Nair, R. R.; Booth, T. J.; Jiang, D.; Schedin, F.; Ponomarenko, L. A.; Morozov, S. V.; Gleeson, H. F.; Hill, E. W.; et al. Graphene-Based Liquid Crystal Device. Nano Lett. 2008, 8 (6), 1704−1708. (4) Marcano, D. C.; Kosynkin, D. V.; Berlin, J. M.; Sinitskii, A.; Sun, Z.; Slesarev, A.; Alemany, L. B.; Lu, W.; Tour, J. M. Improved synthesis of graphene oxide. ACS Nano 2010, 4 (8), 4806−4814. (5) Gao, W. In Graphene Oxide: Reduction Recipes, Spectroscopy, and Applications; Gao, W., Ed.; Springer International Publishing: Cham, Switzerland, 2015; DOI: 10.1007/978-3-319-15500-5_1. (6) McDonald, M. P.; Morozov, Y.; Hodak, J. H.; Kuno, M. In Graphene Oxide: Reduction Recipes, Spectroscopy, and Applications; Gao, W., Ed.; Springer International Publishing: Cham, Switzerland, 2015; DOI: 10.1007/978-3-319-15500-5_2. (7) Mohanpuria, P.; Rana, N. K.; Yadav, S. K. Biosynthesis of nanoparticles: technological concepts and future applications. J. Nanopart. Res. 2008, 10 (3), 507−517. (8) Sharma, R. K.; Gulati, S.; Mehta, S. Preparation of Gold Nanoparticles Using Tea: A Green Chemistry Experiment. J. Chem. Educ. 2012, 89 (10), 1316−1318. (9) Ambrosio-Martin, J.; Fabra, M. J.; López-Rubio, A.; Gorrasi, G.; Sorrentino, A.; Lagaron, J. M. Assessment of Ball Milling as a Compounding Technique to Develop Nanocomposites of Poly (3Hydroxybutyrate-co-3-Hydroxyvalerate) and Bacterial Cellulose Nanowhiskers. J. Polym. Environ. 2016, 24, 241−254. (10) Bharath, G.; Madhu, R.; Chen, S.-M.; Veeramani, V.; Mangalaraj, D.; Ponpandian, N. Solvent-free mechanochemical synthesis of graphene oxide and Fe3O4-reduced graphene oxide 6367


Research Article

ACS Sustainable Chemistry & Engineering (31) Mahmoud, A. E. D.; Fawzy, m.; Radwan, A. Optimization of Cadmium (CD2+) removal from aqueous solutions by novel biosorbent. Int. J. Phytorem. 2016, 18 (6), 619−625. (32) Mahmoud, A. E. D.; Fawzy, M. Statistical Methodology for Cadmium (Cd2+) Removal from Wastewater by Different Plant Biomasses. J. Biorem. Biodegrad. 2015, 6 (304), 2. (33) Stolle, A.; Schmidt, R.; Jacob, K. Scale-up of organic reactions in ball mills: process intensification with regard to energy efficiency and economy of scale. Faraday Discuss. 2014, 170, 267−286. (34) Stolle, A. Technical Implications of Organic Syntheses in Ball Mills. Ball Milling Towards Green Synthesis: Applications, Projects, Challenges 2014, 7 (31), 241. (35) Wieczorek-Ciurowa, K. Mechanochemical Synthesis of MetallicCeramic Composite Powders. In High-Energy Ball Milling: Mechanochemical Processing of Nanopowders; Woodhead Publishing Ltd., 2010; p 193. (36) Xing, T.; Sunarso, J.; Yang, W.; Yin, Y.; Glushenkov, A. M.; Li, L. H.; Howlett, P. C.; Chen, Y. Ball milling: a green mechanochemical approach for synthesis of nitrogen doped carbon nanoparticles. Nanoscale 2013, 5 (17), 7970−7976. (37) Chang, D. W.; Choi, H.-J.; Jeon, I.-Y.; Seo, J.-M.; Dai, L.; Baek, J.-B. Solvent-free mechanochemical reduction of graphene oxide. Carbon 2014, 77, 501−507. (38) Estrada-Guel, I.; Robles-Hernandez, F. C.; Martínez-Sánchez, R. In Mater. Charact.; Pérez Campos, R., Contreras Cuevas, A., Esparza Muñoz, R., Eds.; Springer International Publishing: Cham, Switzerland, 2015; DOI:10.1007/978-3-319-15204-2_18. (39) Ma, J.; Yang, M.; Yu, F.; Zheng, J. Water-enhanced removal of ciprofloxacin from water by porous graphene hydrogel. Sci. Rep. 2015, 5, 13578. (40) Mhamane, D.; Ramadan, W.; Fawzy, M.; Rana, A.; Dubey, M.; Rode, C.; Lefez, B.; Hannoyer, B.; Ogale, S. From graphite oxide to highly water dispersible functionalized graphene by single step plant extract-induced deoxygenation. Green Chem. 2011, 13 (8), 1990− 1996. (41) Dash, P.; Dash, T.; Rout, T. K.; Sahu, A. K.; Biswal, S. K.; Mishra, B. K. Preparation of graphene oxide by dry planetary ball milling process from natural graphite. RSC Adv. 2016, 6 (15), 12657− 12668. (42) Antisari, M. V.; Montone, A.; Jovic, N.; Piscopiello, E.; Alvani, C.; Pilloni, L. Low energy pure shear milling: a method for the preparation of graphite nano-sheets. Scr. Mater. 2006, 55 (11), 1047− 1050. (43) Deng, S.; Zhu, Y.; Qi, X.; Yu, W.; Chen, F.; Fu, Q. Preparation of polyvinylidene fluoride/expanded graphite composites with enhanced thermal conductivity via ball milling treatment. RSC Adv. 2016, 6 (51), 45578−45584. (44) Xing, T.; Li, L. H.; Hou, L.; Hu, X.; Zhou, S.; Peter, R.; Petravic, M.; Chen, Y. Disorder in ball-milled graphite revealed by Raman spectroscopy. Carbon 2013, 57, 515−519. (45) Štefanić, G.; Krehula, S.; Štefanić, I. Phase development during high-energy ball-milling of zinc oxide and iron−the impact of grain size on the source and the degree of contamination. Dalton Transactions 2015, 44 (43), 18870−18881. (46) Condon, J. B. Surface Area and Porosity Determinations by Physisorption: Measurements and Theory; Elsevier, 2006. (47) Azizi, A.; Torabian, A.; Moniri, E.; Hassani, A. H.; Ahmad Panahi, H. Adsorption performance of modified graphene oxide nanoparticles for the removal of toluene, ethylbenzene, and xylenes from aqueous solution. Desalin. Water Treat. 2016, 57 (59), 28806− 28821. (48) Lucks, I.; Lamparter, P.; Mittemeijer, E. Uptake of iron, oxygen and nitrogen in molybdenum during ball milling. Acta Mater. 2001, 49 (13), 2419−2428. (49) Posudievsky, O. Y.; Khazieieva, O.; Kozarenko, O.; Dyadyun, V.; Koshechko, V.; Pokhodenko, V. Effect of the Nature of Exfoliating Agents on the Structure of Graphenes with Various Degrees of Oxidation Obtained by Mechanochemical Treatment. Theor. Exp. Chem. 2016, 52 (1), 3−9.

(50) Shamaila, S.; Sajjad, A. K. L.; Iqbal, A. Modifications in development of graphene oxide synthetic routes. Chem. Eng. J. 2016, 294, 458−477. (51) Sur, U. K.; Saha, A.; Datta, A.; Ankamwar, B.; Surti, F.; Roy, S. D.; Roy, D. Synthesis and characterization of stable aqueous dispersions of graphene. Bull. Mater. Sci. 2016, 39 (1), 159−165. (52) Narayana, M. V.; Jammalamadaka, S. N. Tuning Optical Properties of Graphene Oxide under Compressive Strain Using Wet Ball Milling Method. Graphene 2016, 5 (02), 73. (53) Green, A. A.; Hersam, M. C. Emerging Methods for Producing Monodisperse Graphene Dispersions. J. Phys. Chem. Lett. 2010, 1 (2), 544−549. (54) Kothiyal, N.; Sharma, S.; Mahajan, S.; Sethi, S. Characterization of reactive graphene oxide synthesized from ball−milled graphite: its enhanced reinforcing effects on cement nanocomposites. J. Adhes. Sci. Technol. 2016, 30 (9), 915−933. (55) Lin, J.; Chen, D.; Dong, J.; Chen, G. Preparation of polyvinylpyrrolidone-decorated hydrophilic graphene via in situ ball milling. J. Mater. Sci. 2015, 50 (24), 8057−8063. (56) Fu, J.; Wei, C.; Wang, W.; Wei, J. L.; Lv, J. Studies of structure and properties of graphene oxide prepared by ball milling. Mater. Res. Innovations 2015, 19 (sup1), S1−277−280. (57) Krishnamoorthy, K.; Veerapandian, M.; Yun, K.; Kim, S.-J. The chemical and structural analysis of graphene oxide with different degrees of oxidation. Carbon 2013, 53, 38−49. (58) Li, J.; Zeng, X.; Ren, T.; van der Heide, E. The preparation of graphene oxide and its derivatives and their application in biotribological systems. Lubricants 2014, 2 (3), 137−161. (59) Yang, X.; Li, Y.; Du, Q.; Wang, X.; Hu, S.; Chen, L.; Wang, Z.; Xia, Y.; Xia, L. Adsorption of Methylene Blue from Aqueous Solutions by Polyvinyl Alcohol/Graphene Oxide Composites. J. Nanosci. Nanotechnol. 2016, 16 (2), 1775−1782. (60) Posudievsky, O. Y.; Khazieieva, O. A.; Koshechko, V. G.; Pokhodenko, V. D. Preparation of graphene oxide by solvent-free mechanochemical oxidation of graphite. J. Mater. Chem. 2012, 22 (25), 12465−12467. (61) McDonald, M. P.; Morozov, Y.; Hodak, J. H.; Kuno, M. In Graphene Oxide; Springer, 2015. (62) Herdman, J. D.; Connelly, B. C.; Smooke, M. D.; Long, M. B.; Miller, J. H. A comparison of Raman signatures and laser-induced incandescence with direct numerical simulation of soot growth in nonpremixed ethylene/air flames. Carbon 2011, 49 (15), 5298−5311. (63) Zhang, W.; Zhou, C.; Zhou, W.; Lei, A.; Zhang, Q.; Wan, Q.; Zou, B. Fast and Considerable Adsorption of Methylene Blue Dye onto Graphene Oxide. Bull. Environ. Contam. Toxicol. 2011, 87 (1), 86−90. (64) Guo, Y.; Deng, J.; Zhu, J.; Zhou, X.; Bai, R. Removal of mercury(ii) and methylene blue from a wastewater environment with magnetic graphene oxide: adsorption kinetics, isotherms and mechanism. RSC Adv. 2016, 6 (86), 82523−82536. (65) Liu, T.; Li, Y.; Du, Q.; Sun, J.; Jiao, Y.; Yang, G.; Wang, Z.; Xia, Y.; Zhang, W.; Wang, K.; et al. Adsorption of methylene blue from aqueous solution by graphene. Colloids Surf., B 2012, 90, 197−203. (66) Pérez-Ramírez, E. E.; de la Luz-Asunción, M.; MartínezHernández, A. L.; Velasco-Santos, C. In Semiconductor PhotocatalysisMaterials, Mechanisms and Applications; InTech, 2016. (67) Yang, S.-T.; Chen, S.; Chang, Y.; Cao, A.; Liu, Y.; Wang, H. Removal of methylene blue from aqueous solution by graphene oxide. J. Colloid Interface Sci. 2011, 359 (1), 24−29. (68) Li, Y.; Du, Q.; Liu, T.; Peng, X.; Wang, J.; Sun, J.; Wang, Y.; Wu, S.; Wang, Z.; Xia, Y.; et al. Comparative study of methylene blue dye adsorption onto activated carbon, graphene oxide, and carbon nanotubes. Chem. Eng. Res. Des. 2013, 91 (2), 361−368. (69) Guo, Y.; Deng, J.; Zhu, J.; Zhou, X.; Bai, R. Removal of mercury (II) and methylene blue from a wastewater environment with magnetic graphene oxide: adsorption kinetics, isotherms and mechanism. RSC Adv. 2016, 6 (86), 82523−82536. 6368


Research Article

ACS Sustainable Chemistry & Engineering (70) Chen, L.; Li, Y.; Du, Q.; Wang, Z.; Xia, Y.; Yedinak, E.; Lou, J.; Ci, L. High performance agar/graphene oxide composite aerogel for methylene blue removal. Carbohydr. Polym. 2017, 155, 345−353.

■

NOTE ADDED AFTER ASAP PUBLICATION This paper was published ASAP on April 4, 2018 with an incorrect version of the Supporting Information. The corrected version was published ASAP on April 10, 2018.

6369


Sustainable Synthesis of High-Surface-Area Graphite Oxide via Dry

Recommend Documents