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Abstract

Owing to the COVID-19 pandemic, huge amounts of disposable face masks have been manufactured and used, and these discarded face masks have to be treated. In this study, we propose a simple approach for reusing the nonwoven polyester fabric (NWPF) from disposable face masks. In this approach, NWPF is utilized as a supporter for coating of a layer of graphene oxide/Fe₃O₄/chitosan (GFC) to form a GFC/NWPF adsorbent at room temperature via a simple spray coating method that does not require any solvent. The specific properties of GFC, NWPF, and the GFC/NWPF adsorbent were analysed via X-ray diffraction, transmission electron microscopy, ultraviolet–visible spectroscopy, vibrating sample magnetometry, and field-emission scanning electron microscopy. Results showed that the presence of NWPF enhanced the adsorption capacity of GFC towards organic dyes. At high concentrations of the organic dyes, the adsorption efficiency of the GFC/NWPF adsorbent to the dyes reached 100% within 24 h. The adsorption capacity ( $q_{\max}$ ) of the GFC/NWPF adsorbent to methylene blue, methyl orange, Congo red, and moderacid red was 54.795, 87.489, 88.573, and 29.010 mg g⁻¹, respectively, which were considerably higher than that of bulk GFC (39.308, 82.304, 52.910, and 21.249 mg g⁻¹, respectively).

1. Introduction

Organic dyes are widely used in many industries, such as textile, paper, rubber, plastic, leather, cosmetic, pharmaceutical, and food industries. However, the wastewater produced by these industries contains dyes and their products that contribute to water pollution, causing negative effects on humans and the environment, such as preventing the absorption of oxygen and sunlight and disrupting the respiration and growth of aquatic organisms. Furthermore, it causes adverse effects on the ability of microorganisms to decompose organic substances in wastewater [1–3]. Therefore, researchers have developed various wastewater treatment methods and have successfully applied them in removing colorants. These methods can be divided into three main categories, namely, biological, chemical, and physical methods [1]. Although physical and chemical methods, such as adsorption, photocatalysis, photocatalytic decomposition, membrane separation, ultrasonication, and wet air oxidation, are effective, they can only be applied when the concentration of the dissolved substances is sufficiently high. Moreover, some methods are expensive and still produce toxic by-products. By comparison, biological treatment methods include removing dyes via anaerobic and aerobic systems and fermenting activated sludge from filamentous fungi, yeasts, bacteria, and bacterial and fungal biomes. However, these methods also have disadvantages, such as long processing time and poor performance in removing dyes with a durable and a high-molecular polymeric structure. Moreover, the composition of these organic dyes in wastewater often harms the microorganism biomes/populations used in the sludge [4]. Among the aforementioned wastewater treatment methods, adsorption is considered one of the preeminent methods owing to its advantages, such as easy implementation, generation of nontoxic substances during the treatment process, high efficiency, and low cost [5]. Furthermore, various adsorbent materials from traditional materials can used in adsorption, such as activated carbon, clay, agricultural by-products, banana peels, straw [5], rice husk [6], and red mud [7].

Graphene oxide (GO) and its composite-based adsorbents are excellent in adsorbing organic compounds, including organic dyes, as well as heavy metal ions [8–14]. GO is notable for its simpler fabrication and easier dispersion in water than other materials [15, 16]. Accordingly, GO is easy to use with a high adsorption efficiency. Functional molecules are utilized to generate functional groups to improve the adsorption capacity of GO to heavy metal ions or organic dyes. Chitosan (CS) molecule has several functional groups, such as primary −OH, secondary –OH, and −NH₂ groups. In these groups, the O and N atoms still have undivided electron pairs, making them the chemically active centres of CS. These groups are considered nucleophilic reagents and can participate in several specialized chemical responses [17] or complexed with almost all heavy metals and transition metals to help separate heavy metals from aqueous media easily [18]. Recently, Fe₃O₄ nanoparticles have been utilized to generate the magnetic property for adsorbents, thereby allowing them to be recovered and reused. In additions, the presence of Fe₃O₄ nanoparticles can improve the porosity of adsorbents [1, 2, 19, 20]. Therefore, GO/Fe₃O₄/CS (GFC) materials have excellent adsorption and recovery and regeneration abilities [21–23]. Hence, they are applied in the removal of organic dyes [2] and heavy metal ions [20].

Nonwoven fabric (NWPFs) is widely used in the production of medical disposable face masks and clothes [24–27]. NWPF can be combined with nanomaterials to enhance their properties, such as antibacterial, waterproof, and fireproof properties [28, 29]. The COVID-19 pandemic has necessitated the manufacturing and use of huge amounts of disposable face masks, and these discarded masks have to be treated [26]. Several recent reports have proposed using the NWPF extracted from discarded face masks and clothes as an adsorbent for the clean-up of waters polluted with petroleum and oil products [30], as a support of photocatalysts [31–33] or as a reinforcement of cement composites [27].

In this study, we propose a new approach for reusing NWPF. In this approach, NWPF is extracted from discarded disposable face masks as a support of a GFC nanocomposite adsorbent. The GFC/NWPF absorbent is fabricated by coating GFC onto NWPF via a simple and solvent-free spray coating method at room temperature (RT). Results showed that the presence of NWPF enhanced the adsorption capacity of the GFC absorbent to various organic dyes. Therefore, the GFC/NWPF absorbent will not only improve the adsorption capacity of GFC but also contribute to the efficient reuse of NWPF.

2. Experimental

2.1. Chemicals and Reagents

Graphite (99 wt.%, $d = 60$ −120 μm) was purchased from Vietnam Graphite Group (Vietnam). Sulfuric acid (H₂SO₄, 98 wt.%, AR), sodium nitrate (NaNO₃, AR), potassium permanganate (KMnO₄, AR), iron (III) chloride hexahydrate (FeCl₃.6H₂O, AR), iron (II) sulfide heptahydrate (FeSO₄.7H₂O, AR), sodium hydroxide (NaOH, 99 wt.%, AR), glacial acetic acid (CH₃COOH, 99 wt.%, AR), and hydrogen peroxide (H₂O₂, 33 wt.%, AR) were bought from Xilong Chemical Company (China). Methylene blue (MB), methyl orange (MO), Congo red (CR), and moderacid red (RS) were procured from Van Minh Chemical Company (Vietnam).

GO was prepared from graphite flakes following Hummer’s method as described in previous reports [2, 20, 34, 35]. The GO product obtained was characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) (Fig. SI.1). CS was prepared from shrimp shells in our laboratory in accordance with a previously published procedure [36]. The deacetylation degree (DD%) of CS was 85.0%; its average molecular weight ( $M_{w}$ ) was 32.8 kDa. A 10 mg mL⁻¹ CS solution was prepared by dissolving 5 g of CS in 500 mL of 1% ( $v / v$ ) acetic acid solution and stirring overnight at RT to obtain a homogeneous and colorless solution. Fe₃O₄ nanoparticles were prepared by coprecipitating a mixture of iron (III) chloride hexahydrate and iron (II) sulfide heptahydrate at the molar ratio of 2 : 1 [2, 20, 34]. NWPF was extracted from discarded disposable face masks, washed with soap, sonicated with 95% ( $v / v$ ) ethanol for 5 min, and dried at 80°C.

2.2. Preparation of the GFC/NWPF Absorbent

The GFC/NWPF absorbent was manufactured by coating a layer of GFC ink onto NWPF via a simple spray coating method. The GFC ink was prepared by mixing 0.22 g GO, 0.85 g Fe₃O₄, and 0.36 g CS. Afterwards, the mixture was dissolved in 100 mL 1 wt.% acetic solution and 0.5 mL glycerol by using a homogenizer under ultrasonic conditions for 30 min to obtain a black homogeneous ink of the GFC nanocomposite. The GFC ink was spray-coated onto the NWPF at RT. Finally, the NWPF was dried at 60°C for 2 h. This process was repeated five more times to increase the thickness of the coating. Finally, the NWPF was soaked in 1 M NaOH solution overnight, washed until it reached neutral pH, and dried at 80°C for 24 h to obtain the GFC/NWPF absorbent. Subsequently, the GFC/NWPF absorbent was cut into $1 cm \times 1 cm$ samples for later use. The process of preparing the GFC/NWPF absorbent is illustrated in Scheme 1.

Scheme 1

The process of fabricating a new adsorbent by coating graphene oxide/Fe₃O₄/chitosan (GFC) coated onto nonwoven polyester fabric (NWPF) extracted from discarded disposable face masks.

2.3. Adsorption Procedures

A piece of $1 cm \times 1 cm$ GFC/NWPF sample (each sample contained 1.49 mg of the GFC powder) was immersed in 10 mL of an organic dye solution (MB, MO, CR, or RS). The mixture was incubated at various contact times at different temperatures. The pH of each solution was adjusted from 2 to 10 by adding 0.1 M HCl and 0.1 M NaOH solutions. The concentration of dye residues in the solution after the adsorption process was measured via UV-Vis spectrometry and by using suitable calibration curves (Figs. SI.3–SI.6). The adsorption capacity of the GFC/NWPF absorbent to the organic dyes was compared with that of bulk GFC by using 0.0194 g of the GFC powder instead of the GFC/NWPF sample. The dye removal efficiency of each composition in the composite was determined by testing various NWPF samples (Table 1). Dye removal efficiency ( $R$ , %) was calculated using the following equation (1): $\begin{matrix} (1) & R (%) = (\frac{C_{o} - C_{e}}{C_{o}}) \times 100 . \end{matrix}$

Table 1

Removal efficiency ( $R$ %) of MB and MO by various coated NWPF samples at different pH levels.

Sample codes		M2	M3	M4	M5	M6	M7	M8	M9
Compositions	NWPFs	+^(a)	+	+	+	+	+	+	+
	GO	—^(b)	+	—	—	+	+	—	+
	CS	—	—	+	—	—	+	+	+
	Fe₃O₄	—	—	—	+	+	—	+	+

Acidic medium	$R$ %^(c) for MB	31.71	103.70	31.08	26.71	34.68	31.65	25.64	27.04
Acidic medium	$R$ % for MO	4.55	34.65	31.48	14.95	26.07	27.97	57.01	53.51

Neutral medium	$R$ % for MB	29.20	101.32	25.78	35.69	91.54	35.08	31.66	40.33
Neutral medium	$R$ % for MO	4.58	20.73	17.78	6.73	14.67	6.68	9.64	8.19

Basic medium	$R$ % for MB	35.08	105.37	39.78	39.78	99.25	99.82	46.63	86.66
Basic medium	$R$ % for MO	6.59	17.95	8.49	7.15	13.67	10.99	6.89	7.59

^(a)Presence; ^(b)absence; ^(c)removal efficiency ( $R$ %).

The amount of dye uptake by the GFC absorbent ( $q_{e}$ , mg.g⁻¹) was calculated as follows (equation (2)): $\begin{matrix} (2) & q_{e} = \frac{C_{0} - C_{e}}{m_{a}} . \end{matrix}$

The Langmuir equation (3) and the Freundlich equation (4) isotherms were linearized into the following forms: $\begin{matrix} (3) & \frac{C_{e}}{q_{e}} = \frac{1}{K_{L} \times q_{\max}} + \frac{1}{q_{\max}} \times C_{e}, \\ (4) & \log q_{e} = \log K_{F} + \frac{1}{n} \times \log C_{e}, \end{matrix}$ where $C_{0}$ and $C_{e}$ (mg L⁻¹) are the initial and equilibrium concentrations of organic dyes in solution, respectively; $m_{a}$ is the mass of GFC (g L⁻¹); $q_{e}$ and $q_{\max}$ are the equilibrium organic dye concentration on the adsorbent and the maximum adsorption capacity of the adsorbent (mg g⁻¹), respectively; $K_{L}$ is the Langmuir constant (L mg⁻¹), which is related to the free energy of adsorption; $K_{F}$ is the Freundlich constant (L g⁻¹); and $n$ (dimensionless) is the heterogeneity factor.

2.4. Characterization and Methods

The XRD patterns of each GFC sample were obtained at RT by using a D8 Advance diffractometer (Bruker ASX) with CuKα radiation ( $λ = 1.5406$ Å) within the range of $2 θ = 10 - 60$ ° at a scanning rate of 0.02 s⁻¹. The morphology of the GFC nanocomposite and the GFC/NWPF samples was analysed via TEM (JEOL) at $100 kV \times 200,000$ magnification and FE-SEM (Hitachi S-4500), respectively. The magnetic behaviours of the samples were measured via vibrating sample magnetometry (VSM 880, DMS/ADE Technologies, USA) at fields ranging from −10 kOe to 10 kOe at 25°C with an accuracy of 10⁻⁵ emu. The concentration of organic dye residues in solution after the adsorption process was determined via UV-Vis spectrometry by establishing their calibration curves at the concentrations of 0.625, 1.25, 2.5, 5, 10, and 20 mg L⁻¹. Moreover, the calibration curves were established at pH 4, 5, 7, and 9. Afterwards, the spectra of these solutions were measured via UV-Vis spectrometry by using an Agilent 8453 UV-Vis spectrophotometer system within the wavelength range of 200–1200 nm. Subsequently, their optical density (OD) at the maximum adsorption was used to establish the calibration curves (OD vs. $C_{mg / L}$ ). The UV-Vis spectra and calibration curves are shown in the supporting information (SI) from Figs. SI.3 to SI.6.

3. Results and Discussion

3.1. Characterization of GFCs

The Fe₃O₄ nanoparticles agglomerated quite strongly because of their large specific surface energy; thus, the nanoparticles tended to agglomerate to reduce the surface energy (Figure 1(a)). The thickness of GO sheets was thin, only over 5 μm in size (Figure 1(b)). Spherical ferromagnetic particles of a fairly uniform size with an average diameter of about 30 nm scattered on the surfaces of GO and CS attached onto the thin GO sheets (Figures 1(c) and 1(d)). These spherical particles helped the Fe₃O₄ particles to attach onto the GO layer tightly. TEM results indicated that the GFC materials were successfully synthesized. No obvious peak could be observed from the XRD spectrum of CS (Figure 1(e), curve (i)). By contrast, a strong intensity peak (001) at $2 θ = 11.90$ ° could be observed from the XRD spectrum of GO (Figure 1(e), curve (ii)). The peak (002) of graphite at $2 θ = 27$ ° disappeared (Fig. SI.1b), indicating that GO was successfully synthesized. These results were similar to those of a previous study [37]. Both the XRD spectra of Fe₃O₄ (Figure 1(e), curve (iii)) and GO/Fe₃O₄/CS (Figure 1(e), curve (iv)) indicated that the synthesized Fe₃O₄ material was a single phase and had a low diffraction baseline, suggesting a complete crystalline phase. In the XRD spectrum of bare Fe₃O₄ nanoparticles (Figure 1(e), curve (iii)), six diffraction peaks appeared at 30.10°, 35.40°, 43.10°, 53.40°, 57.00°, and 62.50°, which corresponded to the (220), (311), (400), (422), (511), and (440) peaks of Fe₃O₄ (JCPDS File, PDF No. 65−3107) [11, 13, 22, 23], thereby confirming the formation of the magnetic spinel nanocrystal phase of Fe₃O₄. Comparing with that of pure Fe₃O₄, the diffraction spectrum of the GO/Fe₃O₄/CS sample retained the peaks of Fe₃O₄. Thus, CS and GO coatings did not affect the phase change in Fe₃O₄. The extension line in the figure was evaluated using the Debye–Scherrer equation, which describes the relationship between the width in XRD spectrum and particle size, as follows: $d = (k λ / β c o s θ)$ , where $d$ is the thickness of the crystal, $k = 0.89$ (the Debye–Scherrer constant), $λ = 0.15406$ nm (X-ray wavelength), $β$ is the width at half-height of the peak, and $θ$ is the Bragg angle. The average crystal size of Fe₃O₄ in the bare Fe₃O₄ sample was 30 nm, whereas that of the calculated sample was 35 nm. This result was consistent with the TEM images (Figure 1). The magnetic property of GFC was tested with magnets. GFC exhibited strong interactions with the magnets (Figure 1(c), inserted figure). Theoretically, CS and GO are nonmagnetic. Thus, the magnetic property of the GO/Fe₃O₄/CS material was due to the presence of Fe₃O₄. The magnetization curves of the Fe₃O₄ and GO/Fe₃O₄/CS samples (Figure 1(f)) demonstrated that they have superparamagnetic properties. The magnetic saturation ( $M_{s}$ ) of the Fe₃O₄ sample was ~80 emu g^-1 (Figure 1(f), curve (i)), whereas that of the GFC sample was ~40 emu g^-1 (Figure 1(f), curve (ii)). Therefore, the coverage of CS and GO on the Fe₃O₄ particles substantially reduced the magnetization. As results show, the Ms of the GFC sample was still high (40 emu g^-1); thus, it was able to coat NWPF and endowed GFC/NWPF with magnetic properties to separate the GFC/NWPF after absorption process using an external magnet for the regeneration and circulation. According to the FTIR spectra of CS and GFC (Fig. SI.2), the main specific groups in CS included an adsorption at 3578 cm⁻¹, which was attributed to the stretching vibration of the O–H group; a band at approximately 2881 cm⁻¹, which was ascribed to the stretching vibration of C–H; and characteristic adsorption bands at 1674 and 1589 cm⁻¹, which corresponded to C=O stretching and N–H blending in the amide groups, respectively [38–41]. However, in the FTIR spectrum of GFC, these specific bands of amide groups shifted to 1597, 1516, and 1394 cm⁻¹, respectively. The presence of amine and amide groups on the GFC surface plays an important role in organic dye removal [38–43].

Figure 1

(a–d) TEM images of (a) Fe₃O₄ nanoparticles, (b) GO, and (c, d) GO/Fe₃O₄/CS (GFC) nanocomposite (inset: magnetic property of GFC nanocomposite); (d) XRD patterns of (i) CS, (ii) GO, (iii) Fe₃O₄, and (iv) GO/Fe₃O₄/CS; (f) VSM of (i) Fe₃O₄ and (ii) GO/Fe₃O₄/CS.

(b)

(c)

(d)

(e)

(f)

3.2. Characterization of NWPF and the GFC/NWPF Absorbent

The GO/Fe₃O₄/CS materials were coated onto NWPF via a simple spray coating method. Five coats were applied to create a sufficiently thick and even coating. The mass density ( $d$ , g cm⁻²) of the GFC coated onto the 1 cm² NWPF samples was calculated as follows: $\begin{matrix} (5) & d = \frac{m_{GFC (g)}}{S_{NWPF} ({cm}^{2})}, \end{matrix}$ where $m_{GFC}$ is the amount of GFC used for coating (g) and $S_{NWPF}$ is the total area of NWPF covered (cm²). In this experiment, $m_{GFC} = 0.22$ g of $GO + 0.85 g of F e_{3} O_{4} + 0.36 g of CS$ (=1.43 g) and $S_{NWPFs} = 959$ cm²; hence, $d = 1.49$ mg GFC cm⁻².

SEM images of NWPF and the GFC/NWPF absorbent are shown in Figure 2. The polyester fibres in NWPF were slippery and even, their surface was smooth, and it consisted of overlapping nonwoven fibres that were pressed by heat (Figures 2(a), 2(c), 2(e), and 2(g)). By comparison, after GFC was coated onto NWPF, the surface of the polyester fibres in the GFC/NWPF absorbent became rough and rugged (Figures 2(b), 2(d), 2(f), and 2(h)), and the coating cracked at some points (Figures 2(d), 2(f), and 2(h)). Moreover, the size of the fibres considerably increased. By contrast, the GO sheets (Figures 2(d) and 2(h)) and the Fe₃O₄ nanoparticles (Figure 2(h), inserted figure) became rumpled. These results indicated that GFC was successfully coated onto the surface of NWPF via the simple spray coating method adopted herein. Thus, this method can be employed in fabricating GFC/NWPF absorbents on a large scale.

Figure 2

SEM and FESEM images of (a, c, e, g) NWPF and (b, d, f, h) GFCs/NWPF.

3.3. Adsorption of Organic Dyes on GFC and GFC/NWPF Absorbents

3.3.1. Optimization of Adsorption Conditions

The adsorption conditions were optimized including the pH and compositions of the GFC/NWPF adsorbent to enhance its adsorption of organic dyes. Eight coated NWPF samples with different compositions were prepared (Table 1). Their ability to absorb MB (a cationic dye) and MO (an anionic dye) was evaluated at different pH 5, 7, and 9. Organic dyes can be classified into three types: cationic organic dyes with a positive charge, anionic organic dyes with a negative charge, and nonionic organic dyes with no charge. Therefore, the adsorption of the dyes onto the adsorbents can be achieved via electrostatic interactions between dye ions and groups of opposite charge as the functional groups on an adsorbent’s surface. However, this classification is only relative because an organic dye can be an anionic or a cationic dye depending on the environment (pH) (Table 2). The surface of the GFC/NWPF absorbent had abundant amine groups (−NH₂) from CS and –COOH. The −OH groups of GO are suitable for nonionic dyes when they are in a neutral environment. In an acidic environment, these groups will become –NH₃ ^⊕, −COOH₂ ^⊕, and −OH₂ ^⊕; thus, they are suitable for absorbing MO, RS, and CR. Moreover, in an alkaline environment, these functional groups will become –NH₂, −COO^⊖, and –O^⊖, respectively, which are suitable for absorbing MB [1, 2, 35, 44–47].

Table 2

Comparison of the adsorption capacity of the adsorbents assessed herein.

Dyes	Conditions	Adsorbents	Adsorption model		Comparison of $q_{\max}$ (mg g⁻¹) with that of other adsorbents
Dyes	Conditions	Adsorbents	Langmuir	Freundlich
Methylene blue (MB)	$pH = 9$ , RT, $T = 2$ h	GFC/NWPFs	$C_{e} / q_{e} = 0.018 * C_{e} + 0.096$ $R^{2} = 0.980$ and $q_{\max} = 54.795$ mg g⁻¹	$\log q_{e} = 0.108 * \log C_{e} + 1.245$ $R^{2} = 0.927$	GO−β-cyclodextrin−chitosan@Fe₃O₄: $q_{\max} = 84.32$ mg g⁻¹[52]; CS/Fe₃O₄/GO: $q_{\max} = 30.01$ mg g⁻¹ [2]; Fe₃O₄/C core−shell structure: $q_{\max} = 44.38$ mg g⁻¹ [53]
Methylene blue (MB)	$pH = 9$ , RT, $T = 2$ h	GFC	$C_{e} / q_{e} = 0.025 * C_{e} + 0.125$ $R^{2} = 0.970$ and $q_{\max} = 39.308$ mg g⁻¹	$\log q_{e} = 0.193 * \log C_{e} + 1.245$ $R^{2} = 0.742$
Methyl Orange (MO)	$pH = 4$ , RT, $T = 2$ h	GFC/NWPF	$C_{e} / q_{e} = 0.011 * C_{e} + 0.401$ $R^{2} = 0.9108$ and $q_{\max} = 87.489$ mg g⁻¹	$\log q_{e} = 0.736 * \log C_{e} + 0.550$ $R^{2} = 0.990$	γ−Fe₂O₃/chitosan composite film: $q_{\max} = 29.41$ mg g⁻¹ [54]; amine/Fe₃O₄−resin composite: $q_{\max} = 101$ mg g⁻¹ [55]
Methyl Orange (MO)	$pH = 4$ , RT, $T = 2$ h	GFC	$C_{e} / q_{e} = 0.012 * C_{e} + 0.569$ $R^{2} = 0.878$ and $q_{\max} = 82.304$ mg g⁻¹	$\log q_{e} = 0.753 * \log C_{e} + 0.411$ $R^{2} = 0.978$
Congo red (CR)	$pH = 4$ , RT, $T = 2$ h	GFC/NWPF	$C_{e} / q_{e} = 0.011 * C_{e} + 0.905$ $R^{2} = 0.947$ and $q_{\max} = 88.573$ mg g⁻¹	$\log q_{e} = 0.725 * \log C_{e} + 0.310$ $R^{2} = 0.994$	XG−g−PAM/SiO₂ nanocomposite: $q_{\max} = 209.2$ mg g⁻¹ [56]; spherical microparticles MgO−GO: $q_{\max} = 227$ mg g⁻¹ [57]
Congo red (CR)	$pH = 4$ , RT, $T = 2$ h	GFC	$C_{e} / q_{e} = 0.019 * C_{e} + 0.212$ $R^{2} = 0.945$ and $q_{\max} = 52.910$ mg g⁻¹	$\log q_{e} = 0.388 * \log C_{e} + 1.020$ $R^{2} = 0.9342$
Moderacid red (RS)	$pH = 4$ , RT, $T = 2$ h	GFC/NWPF	$C_{e} / q_{e} = 0.034 * C_{e} + 0.433$ $R^{2} = 0.939$ and $q_{\max} = 29.010$ mg g⁻¹	$\log q_{e} = 0.548 * \log C_{e} + 0.545$ $R^{2} = 0.963$	Fe₃O₄ nanoparticles and amine/Fe₃O₄−resin composite: $q_{\max} = 40.2$ and 99.4 mg g⁻¹, respectively [55]; Fe₃O₄@GPTMS@P−Lys: $q_{\max} = 134.7$ mg g⁻¹ [58]
Moderacid red (RS)	$pH = 4$ , RT, $T = 2$ h	GFC	$C_{e} / q_{e} = 0.047 * C_{e} + 0.902$ $R^{2} = 0.899$ and $q_{\max} = 21.249$ mg g⁻¹	$\log q_{e} = 0.560 * \log C_{e} + 0.297$ $R^{2} = 0.871$

Figure 3(a) shows that GO/NWPF sample (coded M3) adsorbed MB very well for all medium with removal efficiency ( $R$ %) which was 100%. Besides, all adsorbents containing GO, i.e., GO/Fe₃O₄/NWPFs (coded M6), GO/CS/NWPFs (coded M7), and GFC/NWPFs (coded M9) samples, performed good adsorption MB in basic medium (pH 9) with the highest $R$ % values that were obtained, which were 99%, 99%, and 86%, respectively. On the contrary, without GO, the $R$ % values were low for MB adsorption on NWPFs (coded M2) or CS/NWPFs (coded M4), or Fe₃O₄/NWPFs (coded M5) or CS/Fe₃O₄/NWPFs (coded M8) samples. Figure 3 also shows that the $R$ % values were higher than that for neutral medium (pH 7) (Figure 3(b)) or acidic medium (pH 5) (Figure 3(c)). Obtained results imply that, for efficiency removal of MB in solution, the adsorption process should be carried out in alkaline medium, and GO presented in GO/CS/NWPFs played an important role towards MB removal.

Figure 3

Effects of pH on MB adsorption onto the GFC/NWPF absorbent: (a) pH 5, (b) pH 7, and (c) pH 9 (inserted images: corresponding color of MB solutions before and after the adsorption process).

In removing the anionic dye MO (Figure 4), the $R$ % values for all samples were very low (<20%) at pH 9 (Figure 4(a)) and 7 (Figure 4(b)). However, in an acidic medium (pH 5), their $R$ % values were higher (Figure 4(c)). The $R$ % value for MO adsorption onto the M6 (GO/Fe₃O₄/NWPF) and M7 (GO/CS/NWPF) samples was 26%–27%. Furthermore, the $R$ % value was 31%–35% for the M3 (GO/NWPF) and M4 (CS/NWPFs) samples and 53%–58% for the M8 (CS/Fe₃O₄/NWPF) and M9 (GFC/NWPFs) samples. The $R$ % values were very small for MO adsorption onto the M2 (NWPF) (4%) and M5 (Fe₃O₄/NWPF) (14%) samples. These data indicated that MO removal was more difficult to achieve than MB removal in the systems proposed herein. This difference can be attributed to the structure of MO: it has two oppositely charged centres, namely, a positively charged centre from –N^⊕(CH₃) and a negatively charged centre from –SO₃ ^⊖. Hence, both CS (which contains –NH₃ ^⊕) and GO (which contains –COO^⊖ and –OH₂ ^⊕) play an important role in MO adsorption via electrostatic interactions. Therefore, the M9 sample (GFC/NWPF, which contained both CS and GO components) was able to satisfactorily remove anionic dyes (including MO, RS, and CR) in the acidic medium (pH 5). The attractive forces required to adsorb dye molecules (MB, MO, CR, and RS) onto the surface of the GFC/NWPF adsorbent were not only attributed to electrostatic interactions; it also included due to π−π stacking interactions, i.e., the strong interaction between the π-conjugated electron systems of MB, MO, CR, and RS molecules (Table SI.1) with the π-conjugated electrons of GO via π−π stacking interactions [1, 2, 31, 32, 42, 43, 48–51]. Accordingly, increasing the content of GO improved the adsorption capacity ( $q_{\max}$ ). However, increasing the content of GO should be limited owing to economic (the price of the adsorbent will increase) and technical (the release of GO from the adsorbent into the solution should be avoided) considerations.

Figure 4

Effects of pH on MO adsorption onto the GFC/NWPF absorbent: (a) pH 5, (b) pH 7, and (c) pH 9 (inserted images: corresponding color of MO solutions before and after the adsorption process).

The effects of the absorbents’ components on dye adsorption capacity were evaluated. Five coated NWPF samples (S1, S2, S3, S4, and S5) were fabricated and tested for MB adsorption (Figure 5). Figure 5(a) shows the UV-Vis spectrum of the MB solution after adsorption by GFC powder for 2 h at RT and pH 9. The S1, S2, S3, S4, and S5 samples had compositions of GO, Fe₃O₄, and CS by mass ( $m_{GO}$ : $m_{Fe 3 O 4}$ : $m_{CS}$ ) of 50 : 40 : 10, 50 : 10 : 40, 0 : 50:50, 10 : 60 : 30, and 10 : 40 : 50, respectively. The adsorption efficiency of each sample was very different: the samples with high GO content (S1 and S2) had very large adsorption capacity ( $R$ % was 98.03% and 98.0%, respectively). When doped with Fe₃O₄ and CS, the efficiency of the samples with low GO content substantially increased. The S4 sample had only 10% GO, but its adsorption efficiency was large ( $R$ % was 95.55%). However, when excessive amounts of CS were added, the $R$ % value dramatically decreased to 77.08% in the S5 sample (containing 50 wt.% CS) and even down to 0% in the S3 sample (containing 0 wt.% GO and 50 wt.% CS). Adding excessive amounts of CS considerably reduced the porosity of the materials. Therefore, GO should be added as much as possible while limiting the content of CS to 10 wt.%−40 wt.%. However, the production costs of GO are high. Thus, instead of adding 40 wt.%−50 wt.% of GO to remove MB at $R % > 90 %$ in 2 h, $R % > 90 %$ can still be achieved when 10 wt.% of GO is added by simply extending the adsorption time to 24 h (Figure 5(b)). When the content of GO was increased from 20 wt.% to 50 wt.%, the value of $R$ % did not increase (Figure 5(b)). Therefore, the addition of 10 wt.% of GO is the best level that achieves the optimum technical−economic efficiency.

Figure 5

(a) UV-Vis spectra of samples after adsorption of MB solutions (inserted images are the colors of the MB solutions before and after adsorption onto GO/Fe₃O₄/CS [percent by weight, wt.%]: S1 [50 : 40 : 10], S2 [50 : 10 : 40], S3 [0 : 50 : 50], S4 [10 : 60 : 30], and S5 [10 : 40 : 50]). (b) Influence of GO content on MB removal at various times and (i) $C_{0} = 5$ mg L⁻¹ and (ii) $C_{0} = 20$ mg L⁻¹.

(b)

3.3.2. Comparison of the Adsorption of MB, MO, CR, and RS onto the GFC/NWPF Absorbent and Bulk GFC

The adsorption efficiency of bulk GFC was compared with that of the GFC/NWPF absorbent under the same conditions with the same amount of GFC converted. Both the powder and coated samples achieved very good adsorption efficiency for MB, MO, CR, and RS, and the color of the solutions was almost completely eliminated (Figure 6). In all cases, the GFC/NWPF samples seemed to remove the colorants better than the GFC: $R$ % was 97.98% and 96.11% for MB (Figure 6(a)), 96.25% and 94.86% for MO (Figure 6(b)), 97.15% and 84.47% for CR (Figure 6(c)), and 83.68% and 78.22% for RS (Figure 6(d)), respectively. Differences in color could also be observed with the naked eye (pictures inserted in the figures). This result confirmed that coating GFC is necessary to improve its adsorption performance.

Figure 6

UV-Vis spectra of colorant solutions after adsorption of (a) MB, (b) MO, (c) CR, and (d) RS onto (i) GFC (red dot–dash) and (ii) GFC/NWPF (black solid) (inserted image: color of colorant solutions before and after adsorption).

(b)

(c)

(d)

3.3.3. Adsorption Isotherms of MB, MO, CR, and RS onto the GFCs/NWPF Absorbent

The adsorption isotherms of MB, MO, RS, and CR on both bulk GFC and the GFC/NWPF absorbent were built according to the Langmuir and Freundlich models by using equations (3) and (4) (Table 2 and Figs. SI.7–SI.10). On the basis of the correlation coefficient ( $R^{2}$ ), the process by which the organic dyes absorb on both bulk GFC and the GFC/NWPF absorbent was more consistent with the Langmuir model than with the Freundlich model. The maximum adsorption capacity ( $q_{\max}$ ) of the GFC/NWPF absorbent for all organic dyes was higher than that of bulk GFC (Table 2). Results indicated that the presence of NWPF enhanced $q_{\max}$ . Compared the absorption efficiency for MB, MO, RS, and CR of the various reported materials, the $q_{\max}$ values for MB or MO of the developed hybrid materials herein including bulk GFC and the GFC/NWPF adsorbents are competitive and lower for RS and CR adsorption (Table 2). However, an advantage of the developed bulk GFC and GFC/NWPF adsorbents is they can be made via a simple synthesis process.

4. Conclusions

NWPF was extracted from discarded disposable face masks and used as a support to prepare a GFC nanocomposite-based adsorbent. GFC was successfully onto NWPF. The presence of NWPF enhanced the adsorption efficiency of GFC for the organic dyes MB, MO, CR, and RS. In all cases, the coating improved the adsorption performance of the GFC materials. The adsorption efficiency of the GFC/NWPF adsorbent for these organic dyes was higher than that of bulk GFC with the same mass. Obtained results demonstrated that the adsorption efficiency of the GFC/NWPF adsorbent was different for MB, MO, CR, and RS dyes and can be competitive to previously reported materials implying that the GFC/NWPF absorbent has a high application potential.

Footnotes

Data Availability

The data used to support the findings of this study are included within the article.

Conflicts of Interest

The authors declare that they have no conflict of interest.

Acknowledgments

This work was supported by the Vietnam Ministry of Education and Training (under project number B2020-BKA-15).

Supplementary Materials

References

Tran

H. V.

Hoang

L. T.

Huynh

C. D.

An investigation on kinetic and thermodynamic parameters of methylene blue adsorption onto graphene-based nanocomposite

Chemical Physics 2020 535, article 110793

8055615

10.1016/j.chemphys.2020.110793

Tran

H. V.

Bui

L. T.

Dinh

T. T.

D. H.

Huynh

C. D.

Trinh

A. X.

Graphene oxide/Fe3O4/chitosan nanocomposite: a recoverable and recyclable adsorbent for organic dyes removal. Application to methylene blue

Materials Research Express 2017 4

8055615

3 Article number 035701

10.1088/2053-1591/aa6096

2-s2.0-85016828700

Vallinayagam

Rajendran

Lakkaboyana

S. K.

Soontarapa

Remya

R. R.

Sharma

V. K.

Kumar

Venkateswarlu

Koduru

J. R.

Recent developments in magnetic nanoparticles and nano-composites for wastewater treatment. Journal of Environmental

Chemical Engineering 2021 9

8055615

6, article 106553

10.1016/j.jece.2021.106553

Fernández

Larrechi

M. S.

Callao

M. P.

An analytical overview of processes for removing organic dyes from wastewater effluents

TrAC Trends in Analytical Chemistry 2010 29

8055615

10 1202 1211

10.1016/j.trac.2010.07.011

2-s2.0-77957752944

Zhang

Kan

Dong

Yan

Jiang

Yang

Cheng

Adsorption of anionic dyes from aqueous solutions using chemically modified straw

Bioresource Technology 2012 117

8055615

40 47

10.1016/j.biortech.2012.04.064

2-s2.0-84861160551

Ajmal

Rao

R. A. K.

Anwar

Ahmad

Adsorption studies on rice husk: removal and recovery of Cd(II) from wastewater

Bioresource Technology 2003 86

8055615

2 147 149

10.1016/S0960-8524(02)00159-1

2-s2.0-0037209536

Genç

Tjell

J. C.

McConchie

Schuiling

Adsorption of arsenate from water using neutralized red mud

Journal of Colloid and Interface Science 2003 264

8055615

2 327 334

10.1016/S0021-9797(03)00447-8

2-s2.0-0043064247

Debnath

Maity

Pillay

Impact of process parameters on removal of Congo red by graphene oxide from aqueous solution

Journal of Environmental Chemical Engineering 2014 2

8055615

1 260 272

10.1016/j.jece.2013.12.018

2-s2.0-84892664600

Peng

Liu

Song

A review on heavy metal ions adsorption from water by graphene oxide and its composites

Journal of Molecular Liquids 2017 230

8055615

496 504

10.1016/j.molliq.2017.01.064

2-s2.0-85010766622

10.

Robati

Mirza

Rajabi

Moradi

Tyagi

Agarwal

Gupta

V. K.

Removal of hazardous dyes-BR 12 and methyl orange using graphene oxide as an adsorbent from aqueous phase

Chemical Engineering Journal 2016 284

8055615

687 697

10.1016/j.cej.2015.08.131

2-s2.0-84942546613

11.

Choi

J.-S.

Lingamdinne

L. P.

Yang

J.-K.

Chang

Y.-Y.

Koduru

J. R.

Fabrication of chitosan/graphene oxide-gadolinium nanorods as a novel nanocomposite for arsenic removal from aqueous solutions

Journal of Molecular Liquids 2020 320, article 114410

8055615

10.1016/j.molliq.2020.114410

12.

Joshi

D. J.

Koduru

J. R.

Malek

N. I.

Hussain

C. M.

Kailasa

S. K.

Surface modifications and analytical applications of graphene oxide: a review

TrAC Trends in Analytical Chemistry 2021 144, article 116448

8055615

10.1016/j.trac.2021.116448

13.

Lingamdinne

L. P.

Koduru

J. R.

Karri

R. R.

A comprehensive review of applications of magnetic graphene oxide based nanocomposites for sustainable water purification

Journal of Environmental Management 2019 231

8055615

622 634

10.1016/j.jenvman.2018.10.063

2-s2.0-85056793173

14.

Lingamdinne

L. P.

Koduru

J. R.

Chang

Y. Y.

Naushad

Yang

J. K.

Polyvinyl alcohol polymer functionalized graphene oxide decorated with gadolinium oxide for sequestration of radionuclides from aqueous medium: Characterization, Mechanism, and Environmental Feasibility Studies

Polymers 2021 13

8055615

21, article 3835

10.3390/polym13213835

15.

Dreyer

D. R.

Park

Bielawski

C. W.

Ruoff

R. S.

The chemistry of graphene oxide

Chemical Society Reviews 2010 39

8055615

1 228 240

10.1039/b917103g

2-s2.0-77949880674

16.

J.-G.

L.-Y.

Yang

Liu

Chen

X.-H.

Jiang

X.-Y.

Chen

X.-Q.

Jiao

F.-P.

Graphene nanosheets as novel adsorbents in adsorption, preconcentration and removal of gases, organic compounds and metal ions

Science of the Total Environment 2015 502

8055615

70 79

10.1016/j.scitotenv.2014.08.077

2-s2.0-84907494758

17.

Elwakeel

K. Z.

Environmental application of chitosan resins for the treatment of water and wastewater: a review

Journal of Dispersion Science and Technology 2010 31

8055615

3 273 288

10.1080/01932690903167178

2-s2.0-77951138355

18.

Szymczyk

Filipkowska

Jóźwiak

Kuczajowska-Zadrożna

The use of chitin and chitosan for the removal of reactive black 5 dye 2015

Progress on Chemistry and Application of Chitin and Its Derivatives XX

10.15259/PCACD.20.26

2-s2.0-84945190717

19.

Tran

H. V.

Hoang

L. T.

Huyen

H. T. T.

Electrochemical Synthesis of Graphene from Waste Discharged Battery Electrodes and Its Applications to Preparation of Graphene/Fe3O4/Chitosan-Nanosorbent for Organic Dyes Removal 2021

Zeitschrift für anorganische und allgemeine Chemie

10.1002/zaac.202100313

20.

Tran

H. V.

Tran

T. L.

T. D.

Nguyen

H. M. T.

Dang

L. T.

Graphene oxide enhanced adsorption capacity of chitosan/magnetite nanocomposite for Cr (VI) removal from aqueous solution

Materials Research Express 2019 6

8055615

2, article 025018

10.1088/2053-1591/aae55c

2-s2.0-85057756661

21.

Sheng

Yang

Ren

Yang

Wang

Efficient removal of arsenate by versatile magnetic graphene oxide composites

RSC Advances 2012 2

8055615

32 12400 12407

10.1039/C2RA21623J

2-s2.0-84871043775

22.

Nguyen

T. N.

Pham

H. T. B.

Tran

H. V.

H. D.

Nguyen

K. V.

Tran

L. D.

Magnetic chitosan nanoparticles for removal of Cr (VI) from aqueous solution

Materials Science and Engineering: C 2013 33

8055615

3 1214 1218

10.1016/j.msec.2012.12.013

2-s2.0-84873412881

23.

Tran

H. V.

Tran

L. D.

Nguyen

T. N.

Preparation of chitosan/magnetite composite beads and their application for removal of Pb (II) and Ni (II) from aqueous solution

Materials Science and Engineering: C 2010 30

8055615

2 304 310

10.1016/j.msec.2009.11.008

2-s2.0-72749118485

24.

Elisabeth

Covid-19: are cloth masks still effective? And other questions answered

British Medical Journal 2021 372, article n432

8055615

10.1136/bmj.n432

25.

Karim

Afroj

Lloyd

Oaten

L. C.

Andreeva

D. V.

Carr

Novoselov

K. S.

Sustainable personal protective clothing for healthcare applications: a review

ACS Nano 2020 14

8055615

10 12313 12340

10.1021/acsnano.0c05537

26.

Torres

F. G.

De-la-Torre

G. E.

Face mask waste generation and management during the COVID-19 pandemic: an overview and the Peruvian case

Science of The Total Environment 2021 786, article 147628

8055615

10.1016/j.scitotenv.2021.147628

27.

Sadrolodabaee

Claramunt

Ardanuy

de la Fuente

A textile waste fiber-reinforced cement composite: comparison between short random fiber and textile reinforcement

Materials 2021 14, article 3742

8055615

10.3390/ma14133742

28.

Asif

A. K. M. A. H.

Hasan

M. Z.

Application of nanotechnology in modern textiles: a review

International Journal of Current Engineering and Technology 2014 8

8055615

2 227 231

10.14741/ijcet/v.8.2.5

29.

Madou

M. J.

Manufacturing Techniques for Microfabrication and Nanotechnology 2011

CRC press

30.

Neznakomova

Boteva

Tzankov

Elhag

Non-woven textile materials from waste fibers for cleanup of waters polluted with petroleum and oil products

Earth Systems and Environment 2018 2

8055615

413 420

10.1007/s41748-018-0048-8

2-s2.0-85067851809

31.

Dao

M. U.

Nguyen

T. T. T.

V. T.

Hoang

H. Y.

T. T. N.

Pham

T. N.

Nguyen

T. T.

Akhmadullin

R. M.

H. S.

Tran

H. V.

Tran

D. L.

Non-woven polyester fabric-supported cuprous oxide/reduced graphene oxide nanocomposite for photocatalytic degradation of methylene blue

Journal of Materials Science 2021 56

8055615

10353 10366

10.1007/s10853-021-05965-4

32.

Huo

Wang

Zhuang

Zhao

Gao

Dou

Wang

Facile fabrication of recyclable and macroscopic D-g-C3N4/sodium alginates/non-woven fabric immobilized photocatalysts with enhanced photocatalytic activity and antibacterial performance

Journal of Materials Science 2021 56

8055615

31 17584 17600

10.1007/s10853-021-06454-4

33.

Luo

Wang

Hao

Preparation and characterization of platinum nanoparticles supported by non-woven fabric for formaldehyde decomposition

Fibers and Polymers 2019 20

8055615

2099 2105

10.1007/s12221-019-7109-y

34.

T. D.

Tran

L. T.

Dang

H. T. M.

Tran

H. T. T.

Tran

H. V.

Graphene oxide/polyvinyl alcohol/Fe3O4 nanocomposite: an efficient adsorbent for Co (II) ion removal

Journal of Analytical Methods in Chemistry 2021 2021

8055615

6670913

10.1155/2021/6670913

35.

Tran

L. T.

Tran

H. V.

T. D.

Bach

G. L.

Tran

L. D.

Studying Ni (II) adsorption of magnetite/graphene oxide/chitosan nanocomposite

Advances in Polymer Technology 2019 2019

8055615

8124351

10.1155/2019/8124351

2-s2.0-85071163159

36.

Tran

H. V.

Trinh

A. X.

Huynh

C. D.

H. Q.

Facile hydrothermal synthesis of silver/chitosan nanocomposite and application in the electrochemical detection of hydrogen peroxide

Sensor Letters 2016 14

8055615

32 38

10.1166/sl.2016.3531

2-s2.0-84957887584

37.

H.-M.

Choi

S.-H.

Huh

S. H.

X-ray diffraction patterns of thermally-reduced graphenes

Journal of the Korean Physical Society 2010 57

8055615

6 1649

10.3938/jkps.57.1649

2-s2.0-78650357754

38.

Pei

Guo

Wang

Preparation, characterization and application of magnetic Fe3O4-CS for the adsorption of orange I from aqueous solutions

PLoS One 2014 9

8055615

10, article e108647

10.1371/journal.pone.0108647

2-s2.0-84907546079

39.

Liu

Wen

Chen

Wang

Synthesis of porous Fe3O4 hollow microspheres/graphene oxide composite for Cr(VI) removal

Dalton Transactions 2013 42

8055615

41 14710 14717

10.1039/C3DT50955A

2-s2.0-84880594382

40.

ul Haque

Nasar

Inamuddin

M. M. R.

Applications of chitosan (CHI)-reduced graphene oxide (rGO)-polyaniline (PAni) conducting composite electrode for energy generation in glucose biofuel cell

Scientific Reports 2020 10, article 10428

8055615

10.1038/s41598-020-67253-6

41.

Yadav

Rhee

Y. Y.

Park

S. J.

Hui

Mechanical properties of Fe3O4/GO/chitosan composites

Composites Part B: Engineering 2014 66

8055615

89 96

10.1016/j.compositesb.2014.04.034

2-s2.0-84901931033

42.

Rong

Qiu

Zhang

Wang

Yang

Adsorption–photodegradation synergetic removal of methylene blue from aqueous solution by NiO/graphene oxide nanocomposite

Powder Technology 2015 275

8055615

322 328

10.1016/j.powtec.2015.01.079

2-s2.0-84924964531

43.

Yang

Xie

Pang

Song

Wen

Zhao

Preparation of reduced graphene oxide/poly(acrylamide) nanocomposite and its adsorption of Pb(II) and methylene blue

Langmuir 2013 29

8055615

10727 10736

10.1021/la401940z

2-s2.0-84883228944

44.

H. C.

Dwivedi

A. D.

T. T.

Seo

S.-H.

Kim

E.-J.

Chang

Y.-S.

Magnetite graphene oxide encapsulated in alginate beads for enhanced adsorption of Cr(VI) and As(V) from aqueous solutions: role of crosslinking metal cations in pH control

Chemical Engineering Journal 2017 307

8055615

220 229

10.1016/j.cej.2016.08.058

2-s2.0-84983528573

45.

Nguyen

N. T.

Nguyen

N. T.

Nguyen

V. A.

In situ synthesis and characterization of ZnO/chitosan nanocomposite as an adsorbent for removal of Congo red from aqueous solution

Advances in Polymer Technology 2020 2020

8055615

3892694

10.1155/2020/3892694

46.

Shi

Yang

Zhu

Yang

Yuan

Yang

Liu

Removal of Pb²⁺, Hg²⁺, and Cu²⁺ by chain-like Fe₃O₄@SiO₂@chitosan magnetic nanoparticles

Journal of Nanoscience and Nanotechnology 2016 16

8055615

1871 1882

10.1166/jnn.2016.10712

2-s2.0-84959419487

47.

Tran

H. V.

Nguyen

H. V.

D. V.

T. D.

Nguyen

B. T.

D. H.

Carbon coated MFe₂O₄ (M=Fe, Co, Ni) magnetite nanoparticles: a smart adsorbent for direct yellow and moderacid red dyes

Korean Journal of Chemical Engineering 2021

10.1007/s11814-021-0905-2

48.

Thangavel

Raghavan

Krishnamoorthy

Venugopal

Visible-light driven photocatalytic degradation of methylene-violet by rGO/Fe₃O₄/ZnO ternary nanohybrid structures

Journal of Alloys and Compounds 2016 665

8055615

107 112

10.1016/j.jallcom.2015.12.192

2-s2.0-84954514304

49.

Al-Kahtani

A. A.

Taleb

M. F. A.

Photocatalytic degradation of Maxilon C.I. basic dye using CS/CoFe₂O₄/GONCs as a heterogeneous photo-Fenton catalyst prepared by gamma irradiation

Journal of Hazardous Materials 2016 309

8055615

10 19

10.1016/j.jhazmat.2016.01.071

2-s2.0-84957578939

50.

Song

X. L.

Zhong

Lin

Chen

J.-R.

Biocompatible G-Fe₃O₄/CA nanocomposites for the removal of methylene blue

Journal of Molecular Liquids 2015 212

8055615

63 69

10.1016/j.molliq.2015.08.059

2-s2.0-84941268969

51.

Zhu

Jiang

Liu

You

Yao

Preparation of chitosan—graphene oxide composite aerogel by hydrothermal method and its adsorption property of methyl orange

Polymers 2020 12

8055615

9 2169

10.3390/polym12092169

52.

Fan

Luo

Sun

Qiu

Synthesis of magnetic β-cyclodextrin–chitosan/graphene oxide as nanoadsorbent and its application in dye adsorption and removal

Colloids and Surfaces B: Biointerfaces 2013 103

8055615

601 607

10.1016/j.colsurfb.2012.11.023

2-s2.0-84871369190

53.

Zhang

Kong

Novel magnetic Fe₃O₄@ C nanoparticles as adsorbents for removal of organic dyes from aqueous solution

Journal of Hazardous Materials 2011 193

8055615

325 329

10.1016/j.jhazmat.2011.07.033

2-s2.0-80053275929

54.

Jiang

Y.-Q.

Zhu

H.-Y.

Yao

Xiao

Removal of methyl orange from aqueous solutions by magnetic maghemite/chitosan nanocomposite films: adsorption kinetics and equilibrium

Journal of Applied Polymer Science 2012 125

8055615

S2 E540 E549

10.1002/app.37003

2-s2.0-84862003659

55.

Song

Gao

Xing

Han

Duan

Song

Jia

Adsorption–desorption behavior of magnetic amine/Fe₃O₄ functionalized biopolymer resin towards anionic dyes from wastewater

Bioresource Technology 2016 210

8055615

123 130

10.1016/j.biortech.2016.01.078

2-s2.0-84956682604

56.

Ghorai

Sarkar

A. K.

Panda

A. B.

Pal

Effective removal of Congo red dye from aqueous solution using modified xanthan gum/silica hybrid nanocomposite as adsorbent

Bioresource Technology 2013 144

8055615

485 491

10.1016/j.biortech.2013.06.108

2-s2.0-84881551478

57.

Zhu

Cheng

Jiang

Adsorptive removal of an anionic dye Congo red by flower-like hierarchical magnesium oxide (MgO)-graphene oxide composite microspheres

Applied Surface Science 2018 435

8055615

1136 1142

10.1016/j.apsusc.2017.11.232

2-s2.0-85035758135

58.

Zhang

Y.-R.

Huang

Wang

Q.-R.

Zhao

B.-X.

A magnetic nanomaterial modified with poly-lysine for efficient removal of anionic dyes from water

Chemical Engineering Journal 2015 262

8055615

313 318

10.1016/j.cej.2014.09.094

2-s2.0-84949117074

Graphene Oxide/Fe 3 O 4 /Chitosan−Coated Nonwoven Polyester Fabric Extracted from Disposable Face Mask for Enhanced Efficiency of Organic Dye Adsorption

Abstract

1. Introduction

2. Experimental

2.1. Chemicals and Reagents

2.2. Preparation of the GFC/NWPF Absorbent

2.3. Adsorption Procedures

2.4. Characterization and Methods

3. Results and Discussion

3.1. Characterization of GFCs

3.2. Characterization of NWPF and the GFC/NWPF Absorbent

3.3. Adsorption of Organic Dyes on GFC and GFC/NWPF Absorbents

3.3.1. Optimization of Adsorption Conditions

3.3.2. Comparison of the Adsorption of MB, MO, CR, and RS onto the GFC/NWPF Absorbent and Bulk GFC

3.3.3. Adsorption Isotherms of MB, MO, CR, and RS onto the GFCs/NWPF Absorbent

4. Conclusions

Footnotes

Data Availability

Conflicts of Interest

Acknowledgments

Supplementary Materials

References