Introduction

Water pollution by organic compounds discharged from textile, printing, and pharmaceutical factories has caused many serious environmental problems. Due to their non-biodegradable nature and high toxicity, most of the organic pollutants may have negative effects on human and animal health, including mutations and cancer (Lim et al. 2020; Luu et al. 2020; Tran et al. 2020d). For example, the existence of methylene blue (MB), one of the most commonly used organic dyes, in wastewater can interfere with the photosynthesis and oxygen exchange of aquatic organisms (Dao et al. 2020; Tran et al. 2020c). Another hazardous organic refractory substance usually found in industrial and agriculture effluents due to its high solubility and long-term stability in water is 4-nitrophenol (4-NP) (Ismail et al. 2019). It has been reported to be toxic to aquatic life and cause several human health problems such as damaging the liver, kidneys, blood, and central nervous system (Liu et al. 2018). Because of these issues, finding effective methods for treating organic pollutants from wastewater has received much attention from many scientists over the past decade.

Recently, the reduction with sodium borohydride (NaBH4) is considered one of the most promising way for removing aromatic dyes and nitrocompounds because of its high efficiency and simplicity in implementation (Xu et al. 2020). However, the reduction is only favourable in the presence of catalysts, which are usually noble metal nanoparticles (NPs) (e.g., Ag. Au, Pt) owing to their unique photoelectric properties (Doan et al. 2020). Among these metal NPs, AgNPs are extensively used because they possess outstanding properties such as low-cost, easy synthesis, large surface to volume ration, different crystallographic facets, and excellent catalytic activity (Kavyani and Baharfar 2020; Nguyen et al. 2020). Nevertheless, ultrafine AgNPs with high surface energy tend to agglomerate in clusters, reducing their catalytic performance. Besides, the difficulty in recovering the nano-sized catalysts after use also limits their reusability and practical application. At present, the utilization of support materials such as polymer matrices, metal-organic frameworks, and carbon-based materials for immobilizing NPs has been reported as the most effective approach to overcome the above disadvantages (Le et al. 2020; Tran et al. 2021). The catalyst supports can hinder the aggregation, facilitate the recovery, and improve the stability and catalytic efficiency of NPs. As an emerging class of carbon-based materials, graphene oxide (GO) has shown excellent potential as a substrate for various catalysts and sensors due to its large surface area, tailorable surface chemistry, high mechanical strength and flexibility, and high chemical and thermal stability (Tran et al. 2020b). For instance, Kumari et al. successfully synthesized GO/AgNP composite using a sonochemical method and applied it for the degradation of MB dye. The study results revealed that the fabricated GO/AgNPs showed a superior catalytic activity compared with the pristine GO and AgNPs (Kumari et al. 2020). Investigating the reduction of 4-NP on polyacrylamide/polypyrrole/GO supported AgNPs, Mao et al. also demonstrated the crucial role of GO in enhancing the catalytic ability of the resultant nanocomposite (Mao et al. 2018). In recent years, GO is often integrated with Fe3O4 NPs to increase the recoverability and reusability of catalysts (Esmaeili et al. 2019; Kavyani and Baharfar 2020). With strong magnetic property, the presence of Fe3O4 NPs in catalysts makes them easily recovered by an external magnetic field.

In this context, the purpose of this study was to simultaneously combine the catalytic and magnetic functionalities of Ag and Fe3O4 NPs into the GO support for the catalytic reduction of MB and 4-NP solutions with NaBH4. This ternary nanocomposite was fabricated by the decoration of AgNPs onto the pre-synthesized Fe3O4@GO hybrid using beta-cyclodextrin (β-CD) as a capping agent. β-CD was chosen as a green substance for reducing Ag+ ions and stabilizing the formed AgNPs on the GO sheets due to its high biocompatibility and environmental friendliness, and its unique conformation. With the large structure and rich hydroxyl groups, β-CD can encapsulate AgNPs to restrict their agglomeration and well immobilize them to the GO surface by hydrogen bonding. The resulting hybrid nanocomposite was comprehensively characterized by various physicochemical technologies before evaluating its catalytic ability for MB and 4-NP. The stability, recoverability, and leaching of the developed catalyst were investigated for long-term use. The catalytic mechanism also discussed in detail.

Materials and methods

Materials

Natural graphite flakes (99% carbon basis, 50 mesh particle size), potassium permanganate (KMnO4, ≥ 99%), iron(III) chloride hexahydrate (FeCl3.6H2O, ≥ 99%), iron(II) sulfate heptahydrate (FeSO4.7H2O, ≥ 99%), sodium hydroxide (NaOH, ≥ 98%), hydrochloric acid (HCl, 37%), sodium nitrate (NaNO3, ≥ 99%), sulfuric acid (H2SO4, 98%), hydrogen peroxide (H2O2, 30%), ethanol (C2H5OH, 99%), β-cyclodextrin (C42H70O35, ≥ 97%), silver nitrate (AgNO3, ≥ 99%), methylene blue (C16H18ClN3S, ≥ 95%), sodium borohydride (NaBH4, ≥ 98%), and 4-nitrophenol (O2NC6H4OH, ≥ 99%) were purchased from Merck Company (Singapore).

Synthesis of Ag/Fe3O4@GO catalyst

Preparation of GO

The synthesis of GO was performed based on the Hummers’ method (Ma et al. 2019). Briefly, 0.5 g of graphite flakes were mixed with 0.5 g of NaNO3 in a heat-resistant glass flask cooled at 0 °C, followed by adding 23 mL of concentrated H2SO4 98%, and the resulting mixture was stirred vigorously for 4 h. Then, 3 g of KMnO4 was added to the mixture under constant stirring for another 2 h. After that, 46 mL of distilled water was dropped to the solution, the reaction temperature of 90–95 °C was adjusted by a water bath. Next, 10 mL of H2O2 (30%) was added to the flask, followed by stirring for 1 h. The product was then filtered and washed with distilled water until the pH of the solution reached 7. The obtained GO sample was dried at 60 °C for 24 h in a vacuum oven.

Preparation of Fe3O4@GO

The decoration of Fe3O4 NPs on the as-prepared GO sheets was performed through the co-precipitation reaction. In the first step, the GO solution (1 mg/mL) was prepared by dispersing 0.05 g GO into 50 mL of distilled water under ultrasound for 30 min. Next, 0.2332 g FeCl3.6H2O and 0.1119 g FeSO4.7H2O were added to the GO solution, and the mixture was stirred at 60 °C for 30 min before adding 2M NaOH solution to adjust the pH to 10. After vigorously stirred for another 30 min, the obtained Fe3O4@GO was separated by a magnet and washed with distilled water until the filtrate was neutral. Finally, the product was dried at 60 °C in a vacuum oven. For comparison, the pure Fe3O4 NPs were prepared by the same procedure without GO.

Embedded AgNPs on Fe3O4@GO

A calculated amount (0.05 mg) of the as-synthesized Fe3O4@GO was dispersed in distilled water (50 mL) under ultrasound for 30 min to obtain a clear solution (1 mg/mL). Then, 25 mL of 0.1M NaOH and 25 mL of 5 mM AgNO3 were added in 50 mL Fe3O4@GO solution at room temperature under stirring. Afterwards, 50 mL of β-CD solution (2 g/L) was added to the mixture, followed by ultrasonic irradiation for 30 min. The resulting composite was collected by a hand-magnet, washed with anhydrous ethanol, and dried at 60 °C for 24 h.

Characterization of catalyst

The structural characteristics, morphology, chemical composition, and magnetic properties of the as-synthesized materials were characterized by X-ray powder diffraction (XRD, Rigaku Ultima IV, Japan), Fourier-transform infrared spectroscopy (FTIR, Bruker Tensor 27, Germany), field emission scanning electron microscopy (FE-SEM, Hitachi S-4800, Japan), transmission electron microscopy (TEM, Hitachi H-7600, Japan), energy-dispersive X-ray spectroscopy (EDX, X-ray Micro Analyzer H-7593, Japan), and vibrating sample magnetometer (VSM, VSM-DMS 880, USA).

Catalytic study

The catalytic activity of the prepared materials was evaluated through the reduction of 4-NP and MB in the presence of NaBH4. For a typical experiment, 50 mL of the organic pollutant (0.05 mM of MB or 0.2 mM of 4-NP) was mixed with 5 mL of 0.1 M NaBH4 in a 100 mL beaker. Next, 10 mg of the catalyst was added to the mixture and vigorously shaken. After a selected time period, 2 mL of the mixture was extracted, the catalyst was separated by a hand-magnet, and the pollutant concentrations were determined by UV-Vis spectrophotometer (Agilent Cary 60, USA) at a maximum absorbance wavelength of 664 nm for MB or 405 nm for 4-NP. The removal efficiency of MB and 4-NP was calculated by Eq. 1.

$$ \mathrm{Removal}\ \mathrm{efficiency}\left(\%\right)=\frac{C_0-{C}_t}{C_0}.100\%=\frac{A_0-{A}_t}{A_0}.100\% $$
(1)

where C0 and Ct (mg/L) are the concentration of 4-NP/MB at time t = 0 and t = t, respectively, and A0 and At are the absorbance of 4-NP/MB at the beginning and at any time t, respectively.

Results and discussion

Formation of Ag/Fe3O4@GO

The formation of Ag/Fe3O4@GO composite can be divided into three steps, as illustrated in Scheme 1. In the first step, GO was obtained by oxidation of natural graphite using the Hummer’s method. The presence of oxygen-containing functional groups (-COOH, -OH, ketone, and epoxy) on the GO surface make it well dispersed in water by the hydrogen bonding (Liu et al. 2015). In the next step, Fe3+ and Fe2+ ions with a molar ratio of 2:1 were dispersed in the GO suspension. The introduced iron ions were then rapidly adsorbed onto the negatively charged surface of GO through electrostatic attraction. Fe3O4 particles were in situ formed on GO when NaOH was added to the mixture according to the reaction Eq. 2. (Yazdani and Seddigh 2016). Finally, the Ag/Fe3O4@GO composite was obtained by the decoration of AgNPs onto the Fe3O4@GO surface using β-CD as a reducing and capping agent. In this step, Ag+ cations were attracted to the Fe3O4@GO surface via electrostatic interaction, and then reduced to AgNPs by β-CD. Due to its special structure consisted of two hydroxyl rings forming a truncated cone, β-CD exhibited high level in controlling the morphology of AgNPs by limiting their shape and size within the boundaries of the hydroxyl rings (Nariya et al. 2020). Furthermore, the formation of networking between the formed AgNPs and β-CD through hydrogen bonding prevented the agglomeration of AgNPs, maintaining their high catalytic ability.

$$ {\mathrm{Fe}}^{2+}+{2\mathrm{Fe}}^{3+}\kern0.5em +{8\mathrm{OH}}^{-}\to {\mathrm{Fe}}_3{\mathrm{O}}_4+{\mathrm{H}}_2\mathrm{O} $$
(2)
Scheme 1
scheme 1

Schematic illustration of the fabrication of Ag/Fe3O4@GO catalyst

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Characterization of catalysts

The structure of the as-synthesized materials was characterized by XRD as shown in Fig. 1a. The XRD pattern of GO showed two characteristic peaks at 2θ of 10.5° and 42.6° (Le et al. 2019). The diffraction peaks at 2θ of 30.1°, 35.2°, 41.4°, 45.5°, 56.4°, and 62.5° ascribed to the (220), (311), (400), (422), (511), and (440) lattice planes of the cubic spinel crystal structure of Fe3O4 were detected in the XRD patterns of both Fe3O4/GO and Ag/Fe3O4@GO. According to the XRD spectrum of Ag/Fe3O4@GO, some new peaks also appeared at 2θ of 32.2°, 40.1°, 46.1°, and 78.4°, corresponding to the 111, 200, 220, and 311 crystallographic planes of the face-centered cubic silver crystals, respectively (Kadam et al. 2018; Tran et al. 2020a). It should be noted that the diffraction peaks for GO were not observed after the decoration of Fe3O4 and AgNPs, which was probably due to the overlapping of high-intensity peaks of Fe3O4 and AgNPs (Kavyani and Baharfar 2020). This phenomenon was also observed in the study of Liu et al. (Liu et al. 2015).

Fig. 1
figure 1

XRD pattern (a) and FTIR spectra (b) of GO, Fe3O4@GO, and Ag/Fe3O4@GO samples; c magnetic hysteresis loops of Fe3O4, Fe3O4@GO, and Ag/Fe3O4@GO samples. The inset image is a photograph of Ag/Fe3O4@GO after separation with an external magnetic field; d nitrogen adsorption-desorption isotherm of Ag/Fe3O4@GO

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Figure 1b shows the FTIR spectra of GO, Fe3O4@GO, and Ag/Fe3O4@GO. Obviously, the characteristic peaks of functional groups of GO were found in the FTIR spectra of all three samples. Concretely, the broad band appeared at 3473 cm−1 was related to the stretching vibration of the O–H group (Tran et al. 2018). The absorbance peaks at 1287, 1424, and 1668 cm−1 were indexed to C–O–C, C–O, and C=C stretching vibrations, respectively. The aromatic C–H bending was observed at 860 cm−1. The band at a wavelength of 582 cm−1 was assigned to the Fe–O vibrational band of Fe3O4 (Tran et al. 2020d). Regarding Ag/Fe3O4@GO, the characteristic band corresponding to the Fe–O bond was strong and red-shifted to a higher wavenumber of 612 cm−1 compared to that of 582 cm−1 of Fe3O4, suggesting that Fe3O4 was bound to the AgNPs (Li et al. 2013). These results proved the success of Ag/Fe3O4@GO synthesis.

Hysteresis loops of Fe3O4, Fe3O4@GO, and Ag/Fe3O4@GO composites are shown in Fig. 1c. All the samples incorporated with Fe3O4 NPs revealed a superparamagnetic behavior that was desirable for separation and reuse. Pure Fe3O4 exhibited a saturation magnetization at 57.6 emu/g. This value was slightly reduced to 50.1 emu/g when Fe3O4 NPs were wrapped with GO. In the case of Ag/Fe3O4@GO, the magnetization was further decreased to 45.7 emu/g. The decrease in the magnetization values was due to the increase of nonmagnetic materials (Ag, GO) (Li et al. 2013; Tran et al. 2020d). However, the magnetization level of Ag/Fe3O4@GO was still sufficient for the magnetic separation of nanocomposites from reaction mixtures, as displayed in the inset image of Fig. 1c. The Barrett-Joyner-Halenda (BJH) study of the isotherms of N2 adsorption/desorption and distribution of pore size can be seen in Fig. 1d. The adsorption capacity, reflective of porosity, increases sharply at the end of the isothermal adsorption part (Tran and Lee 2018). With a pore volume of 0.65 cm3/g, Ag/Fe3O4@GO has a Langmuir surface area of 301.86 m2/g.

The FE-SEM images of Fe3O4, GO, Fe3O4@GO, and Ag/Fe3O4@GO and the TEM image of Ag/Fe3O4@GO are presented in Fig. 2. The SEM image of the Fe3O4 NPs represented the spherical morphology of Fe3O4 nanoparticles (Fig. 2a). Mostly, the NPs are in sphere form and agglomerated, which is due to the solution form of the sample. The particles have a narrow size distribution of about 12 nm. Figure 2b shows the FE-SEM image of GO flakes, revealing them to have a wavy, folded shape. SEM images of the GO indicated that it consisted of several layers stacked on top of one another like silky sheets of paper. Meanwhile, Fig. 2c shows different morphologies and structures of Fe3O4 spheres and GO layer, indicating that the Fe3O4 NPs were successfully decorated on the GO flakes. From Fig. 2d, it can be observed that more NPs were distributed on the surface of GO. The surface of Ag/Fe3O4@GO became more rough compared with bare GO, manifesting that Ag/Fe3O4 was well anchored and dispersed on the GO surface. The TEM image (Fig. 2e) clearly illustrated the distribution of Ag and Fe3O4 NPs on the surface of GO. It can be seen that the cubic crystals of Fe3O4 and Ag NPs were uniformly decorated on the transparent GO sheet with a high density and narrow size distribution of 10–20 nm.

Fig. 2
figure 2

FE-SEM images of Fe3O4 (a), GO (b), Fe3O4@GO (c), and Ag/Fe3O4@GO (d), and TEM image of Ag/Fe3O4@GO (e) sample

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The chemical composition of the Ag/Fe3O4@GO composites was verified by Energy dispersed X-ray spectrometer (EDX) spectra, as shown in Fig. 3a. The peaks for Ag/Fe3O4@GO composite were ascribed to Ag, Fe, C, and O elements. The small peak at 0.3 keV and the highest peak at 0.4 keV were associated with C and O elements, respectively. Significantly, the peaks at 2.7, 2.8, and 3.0 keV were contributed by the Ag element (Tran et al. 2020a). Besides, the EDX peaks at 0.35 and 6.4 keV identified the existent of the Fe element (Anh Tran et al. 2021). As can be noted that the Ag/Fe3O4@GO composite had reasonable purity, and all of the peaks were ascribed to the elements of the resultant composite. Besides, the distribution of these elements in the matrix of the nanocatalyst was mapped by a wavelength-dispersive X-ray spectroscope that was coupled to the FE-SEM instrument. The obtained elemental maps are displayed in Fig. 3b–f, which clarified the presence of well-dispersed Ag and Fe elements in the prepared nanocomposite. This figure also signified the presence of C and O that contributed by GO and β-CD (Veisi et al. 2019).

Fig. 3
figure 3

a EDX spectrum of Ag/Fe3O4@GO; b–f correspond to the elemental mapping of composite Ag/Fe3O4@GO, C, O, Fe, and Ag, respectively.

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The catalytic activity of Ag/Fe3O4@GO

The catalytic activities of GO, Fe3O4@GO, and Ag/Fe3O4@GO were comparatively evaluated by measuring the reduction of MB and 4-NP with and without NaBH4. The removal rates of MB and 4-NP over the different synthesized catalysts are presented in Fig. 4a and b, respectively. Obviously, the removal performance of both pollutants without the catalysts was low, reached about 10% (for MB) and 20% (for 4-NP) within 60 min. In the presence of the catalysts, the pollutant removal was greatly improved. The removal of MB and 4-NP by the GO + NaBH4 and Fe3O4@GO + NaBH4 systems occurred rapidly at the first 20 min and reached equilibrium at the efficiency of 45–50% for MB and 40–45% for 4-NP after 30 min of reaction time. Without NaBH4, the Ag/Fe3O4@GO sample only removed 42% MB and 69% 4-NP after 60 min. Meanwhile, in the simultaneous existence of Ag/Fe3O4@GO and NaBH4, the reduction of both MB and 4-NP significantly enhanced. About 36% of MB remained in the aqueous solution after 4 min, and this value continued to plummet to 18% after 6 min (Fig. 4a). The MB removal quickly reached 98% for 10 min, and MB was almost completely decomposed after 14 min. In the case of 4-NP reduction, Ag/Fe3O4@GO exhibited the same catalytic behavior as for MB, and the complete reduction was achieved after 16 min.

Fig. 4
figure 4

Comparison of catalytic performances, time-dependent UV-Vis spectra, and linear fitting of ln(At/Ao) versus reaction time for MB (a, c, e and 4-NP b, d, f reduction

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The reduction of MB and 4-NP by Ag/Fe3O4@GO in the presence of NaBH4 was monitored using UV-Vis spectroscopy, as shown in Fig. 4 c and d. Thus, the catalytic activity of the prepared materials with the participation of NaBH4 was shown in order of Ag/Fe3O4@GO > GO > Fe3O4@GO. The highest catalytic activity of Ag/Fe3O4@GO was contributed mainly by AgNPs embedded on the Fe3O4@GO surface (Tran et al. 2020a). The pristine GO exhibited higher catalytic performance than Fe3O4@GO, possibly due to its higher adsorption capacity (Tran et al. 2020b).

Since the concentration of NaBH4 used in the catalytic process is much higher than that of MB and 4-NP, it is considered as a constant, and thus, the first-order kinetic equation (ln(At/Ao) = kt) can be applied to determine the rate constant (k, min−1) of the Ag/Fe3O4@GO composite (Doan et al. 2020). As shown in Fig. 4e and f, the plots of ln(At/Ao) versus reaction time had a linear relationship with high correlation coefficients (R2 = 0.989 for MB and R2 = 0.967 for 4-NP), indicating that the reduction of MB and 4-NP by Ag/Fe3O4@GO was well described the pseudo-first-order kinetics (Anh Tran et al. 2021). The apparent rate constants were found to be 0.448 and 0.304 min−1 for the MB and 4-NP, respectively. Compared with some other AgNPs-based catalyst (listed in Table 1), Ag/Fe3O4@GO exhibited relatively high catalytic activity, confirming its prospects for practical application.

Table 1 Comparison of the nanocatalysts for the reduction of MB and 4-NP in the presence of NaBH4
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Reusability study

To evaluate the stability of the catalyst, Ag/Fe3O4@GO was tested for the reduction of MB and 4-NP in the presence of NaBH4 over five successive cycles. As shown in Fig. 5a, the Ag/Fe3O4@GO manifested a negligible decrease of catalytic activity for both MB and 4-NP even after five recycles. The slight decline of catalytic efficiency by ∼2.64% is probably due to the loss of the catalyst during the recycling process. Notably, after five repeated use, the removal efficiency of Ag/Fe3O4@GO for MB and 4-NP still remained more than 97%, demonstrating high stability of the synthesized catalyst. XRD spectrum of Ag/Fe3O4@GO before and after reuse was investigated to evaluate its structural strength. As can be seen from Fig. 5b, there was no significant change in the positions and intensity of the diffraction peaks for the catalyst after using several times compared to the original. This result confirmed the high durability of Ag/Fe3O4@GO in the catalytic process. Moreover, the recoverability and leaching of the ternary Ag/Fe3O4@GO composite were also assessed. For these purposes, the recycled catalyst after the fifth run was recovered by magnetic separation, washed with distilled water several times and dried to constant weight. Next, the ratio of the catalyst mass after use to its initial mass was calculated for evaluating the recoverability, while the concentration of silver and iron dissolved in the solution was tested by inductive coupled plasma mass spectrometry (ICP-MS) (Agilent 7700 series, USA) for analyzing the leaching of the material. The obtained results revealed that the material was well recovered using the magnetic separation with a high recoverability of 98.3%. At the same time, the leaching of the Ag/Fe3O4@GO composite was negligible, as evidenced by the low total dissolved silver (0.06 mg/L) and iron (0.27 mg/L) concentrations in the solution after five reuses. It is worth noting that the leaching of Ag and Fe ions was acceptable for wastewater according to the European Union discharge standards (< 0.1 mg/L for Ag and 2 mg/L for Fe) (Le et al. 2020). Thus, with high stability and strength, as well as good magnetic separation behavior, Ag/Fe3O4@GO can be reused long-term for catalytic reduction of organic pollutants.

Fig. 5
figure 5

a Reusability of Ag/Fe3O4@GO for the catalytic reduction of MB and 4-NP with the presence of NaBH4; b XRD patterns of Ag/Fe3O4@GO before and after reuse

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Catalyst mechanism

The obtained results for MB and 4-NP reduction by different catalysts indicated that GO, Fe3O4@GO, Ag/Fe3O4@GO, or NaBH4 have low catalytic effectiveness when used individually. The fast reduction of both MB and 4-NP was guaranteed by the simultaneous presence of Ag/Fe3O4@GO and NaBH4. First, the MB and 4-NP molecules quickly adsorbed onto the surface of Ag/Fe3O4@GO via the following interaction forces: (i) the electrostatic attractions between negatively charged GO and positively charged adsorbates; (ii) π-π stacking interactions between the hexagonal skeleton of GO and the aromatic backbone of MB and 4-NP; and (iii) hydrogen-bonding interactions (Anh Tran et al. 2021b; Tran et al. 2020b). Next, the nucleophile (BH4−) in NaBH4 enhanced the catalytic activity of Ag by donating the electrons to the AgNPs and activating them for the reaction with the pollutants. In this system, AgNPs acted as a relay that received an electron from NaBH4 and transferred it to the pollutant molecules adsorbed in the Ag/Fe3O4@GO surface (Sharif et al. 2019). Furthermore, the large surface area and good electrical conductivity of GO ensured a fast mass and electron transport and facilitated the contact of pollutants with the catalyst surface. The main mechanistic pathways for the catalytic reduction of MB and 4-NP by Ag/Fe3O4@GO in the presence of NaBH4 is illustrated in Scheme 2.

Scheme 2
scheme 2

Proposed reaction-mechanism for the catalytic reduction of MB and 4-NP by Ag/Fe3O4@GO supported by NaBH4

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Conclusion

A highly efficient and stable ternary Ag/Fe3O4@GO catalyst for the reduction of organic pollutants in aqueous solution was successfully synthesized. β-CD appeared to be an excellent reducing and capping agent to decorate AgNPs on the GO sheet. The Ag/Fe3O4@GO nanocomposite/NaBH4 system exhibited extraordinary reduction ability with an efficiency of over 98% for both MB and 4-NP after 10 min of reaction. The reduction kinetics followed a pseudo-first-order model with a rate constant of 0.448 min−1 and 0.304 min−1 for MB and 4-NP, respectively. The unusual catalytic activity of the developed material was supported by the strong synergistic effect of its multipurpose components (GO, Fe3O4, and AgNPs). The Ag/Fe3O4@GO catalyst showed high recoverability of 98.3% due to the presence of superparamagnetic Fe3O4 NPs. Besides, the reusability study revealed that the designed composite possessed excellent stability (maintained over 97% after five repeated runs) and negligible leaching. Ultimately, the facile synthesis, high catalytic efficiency, and good reusability make the Ag/Fe3O4@GO nanocomposite a promising candidate for the application in catalytic reduction of organic pollutants from industrial wastewater.