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Article

Rapid Preparation of g-C3N4/GO Composites via Electron Beam Irradiation for Enhanced Ofloxacin Removal

by
Zhiying Li
1,
Shaohua Guo
1,
Beibei Ni
1,
Zhuopeng Lin
1,
Tao Han
2,
Denghui Wang
1,
Jianqiu Lei
3 and
Ning Liu
1,4,*
1
School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093, China
2
Institute of Applied Radiation of Shanghai, School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China
3
Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
4
Shanghai Noncarbon Energy Conversion and Utilization Institute, Shanghai 200240, China
*
Author to whom correspondence should be addressed.
Catalysts 2025, 15(12), 1118; https://doi.org/10.3390/catal15121118
Submission received: 31 October 2025 / Revised: 16 November 2025 / Accepted: 18 November 2025 / Published: 1 December 2025
(This article belongs to the Special Issue Recent Advances in Catalytic Materials for Water and Air Treatment)
Browse Figures
Versions Notes

Abstract

In this study, a highly efficient graphitic carbon nitride/graphene oxide (X kGy-g-C3N4/GO, X: mean different irradiation dose of 200, 300, 400, and 500 kGy) adsorbent was successfully prepared by electron beam irradiation method (EBR) and used for the adsorption of ofloxacin (OFL). Structure and morphology characterization results confirmed the successful composite of g-C3N4 and GO through EBR. The effects of various conditions on the adsorption capacity, including irradiation dose, pH, adsorbent dosage, and initial OFL concentration were analyzed in detail through experiments. Results indicated that 400 kGy-g-C3N4/GO exhibited the maximum adsorption capacity for OFL (222.0 mg·g−1), and the adsorption performance was affected by pH through electrostatic interactions, reaching optimum at pH = 7.0. Coexisting ion experiments revealed that CO32− reduced OFL adsorption capacity. The adsorption isotherm and kinetics were best described by the Langmuir model (R2 = 0.984) and pseudo-second-order model (R2 = 0.995), respectively. Thermodynamic studies of adsorption indicated a spontaneous and exothermic in adsorption process (∆G0 = −25.21, ∆S0 = 0.050, and ∆H0 = −10.25). This research provides a fresh approach to the reasonable design of g-C3N4/GO composites as adsorbent with potential applications in OFL wastewater treatment.

Graphical Abstract

1. Introduction

With the acceleration of society’s development and the improvement of living standards, the production and use of antibiotics has increased [1,2,3]. However, antibiotics are relatively stable and difficult to metabolize, thus persisting in the environment and thereby posing threats to both environmental and human health [4,5]. Among them, fluoroquinolone antibiotics are widely used to treat bacterial infections in both humans and animals because of their low cost and good effects [6]. As a typical fluoroquinolone antibiotic, ofloxacin (OFL) has a triazine ring stable structure, thermal stability, and acid-base stability, making it difficult to remove from the environment for a long time [7]. Therefore, effectively addressing the pollution issues of OFL in the aquatic environment is of great significance.
There are various ways of removing OFL from water, such as photocatalysis [8], biotechnology [9], and adsorption methods [10]. Among these, adsorption technology has attracted much attention because its low cost, simple operation, and non-toxic and harmless [11]. In adsorption techniques, the effectiveness of various adsorbents including activated carbon (AC) [12], graphene oxide (GO) [13], and chitosan [14] in eliminating OFL from wastewater has been investigated. Recently, GO has earned great scientific interest in adsorption technology for its high specific surface area and tunable surface functionality [15,16]. Moreover, GO possesses abundant carboxyl, hydroxyl, and epoxy groups, which can interact with antibiotics via H-bonding [17]. However, GO has poor stability, and compounding GO with other materials to improve the stability of materials is a common strategy used to remove antibiotics from water bodies [18]. Graphitic carbon nitride (g-C3N4) composed of triazine and tris-triazine/heptazine units and rich in amine groups (-NH2, NH3-, and =N-), possesses significant adsorption capacity for a variety of pollutants. Furthermore, its readily adjustable surface properties could reduce preparation costs [19].
The preparation methods for traditional carbon-based adsorbents suffer from numerous issues, such as prolonged preparation times and the requirement for high temperatures and pressures [20]. By using a high-energy electron beam produced by an electron accelerator, the electron beam irradiation method (EBR) can interact with materials or organisms to alter their structure and properties [21,22]. Compared to traditional methods, the EBR technique offers faster preparation speeds, enabling rapid material synthesis within a short timeframe. Consequently, research on preparing adsorbents using EBR technology has been paid increasing attention [23].
Herein, EBR at different irradiation doses was used to prepare g-C3N4/GO composites for absorbing OFL from aqueous solutions. The successful synthesis of X kGy-g-C3N4/GO (X mean different irradiation dose of 200, 300, 400, and 500 kGy) via EBR was confirmed by microstructure and chemical characterization. The effects of various conditions (irradiation doses, temperature, pH, and coexisting ions) on adsorption performance were investigated. Additionally, the adsorption mechanism was further investigated using adsorption isotherms, kinetics, and thermodynamic simulations. This study demonstrates that X kGy-g-C3N4/GO has great potential for efficient adsorption of antibiotics.

2. Result and Discussion

2.1. Characterization of X kGy-g-C3N4/GO

The X-ray diffraction (XRD) patterns of GO, g-C3N4, and X kGy-g-C3N4/GO are displayed in Figure 1a. The XRD patterns of GO exhibited a peak at 11.0° corresponding to its (002) plane, while g-C3N4 displayed two peaks at 13.1° and 27.5° corresponding to their (100) and (002) crystal planes, respectively [24]. Notably, all the XRD patterns of X kGy-g-C3N4/GO showed both the characteristic peaks of g-C3N4 and GO, demonstrating that the composites were synthesized successfully with EBR and without altering the lattice structures and properties of the original GO and g-C3N4. The chemical bond structure was also investigated using Fourier transform infrared (FT-IR) (Figure 1b). It could be observed that X kGy-g-C3N4/GO exhibited multiple spectral bands in the wavenumber range of 1200–1700 cm−1, with absorption peaks at approximately 1240 cm−1, 1320 cm−1, 1403 cm−1, and 1631 cm−1 originating from CN heterocycle vibrations [24]. Furthermore, the peak at 808 cm−1 provided strong evidence for the presence of thiotriazinone units [25,26]. There was also a small characteristic peak at 1050 cm−1, which corresponded to the stretching vibrations of C-O of alkoxy groups [27]. All the X kGy-g-C3N4/GO had similar infrared absorption peaks that matched the characteristic adsorption peaks of GO and g-C3N4 [28,29], which further illustrated the successful synthesis of the X kGy-g-C3N4/GO.
N2 adsorption–desorption was measured to evaluate the specific surface area and porous structure of X kGy-g-C3N4/GO, the findings are shown in Table S1 and Figure 1c,d. The results demonstrated the presence of mesoporous structures in all X kGy-g-C3N4/GO materials by displaying the H3 hysteresis loop and characteristic Type IV isotherms, which was well in agreement with the pore size distribution of X kGy-g-C3N4/GO. It was obvious that both specific surface area and pore volume increased and then decreased with the increasing irradiation dose. The 400 kGy-g-C3N4/GO sample exhibited the largest specific surface (61.91 m2·g−1) (Table S1), indicating 400 kGy-g-C3N4/GO possessed the highest adsorption capacity and molecular transfer among these materials [30]. In fact, when the irradiation dose was higher than 400 kGy, the g-C3N4/GO composite had undergone excessive reduction, leading to significant removal of oxygen-containing functional groups on the GO. This weakened the interlayer support function, causing the collapse of the layered structure. Such collapse blocked some pores, resulting in a decrease in specific surface area and pore volume [31]. Concurrently, the high-energy irradiation generated numerous defects on the g-C3N4 and GO surfaces, inducing agglomeration or densification of the material to lower its surface energy and consequently further reducing the porosity [32]. Additionally, below 400 kGy, EBR enhanced the interfacial bonding between g-C3N4 and GO. However, at 500 kGy, excessive irradiation might lead to unstable bonding at the interface or the formation of unstable defect states, thereby weakening their synergistic effect and consequently affecting the pore structure and adsorption performance [33]. The combined influence of these multiple factors resulted in a significant decrease in specific surface area and pore volume at 500 kGy.
The morphology of the 400 kGy-g-C3N4/GO sample was researched with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) (Figure 2). As illustrated in Figure 2a, the 400 kGy-g-C3N4/GO retained the layered structure of GO [34], with flexible nano lumpy structures exhibiting edge curling observed on its surface, which corresponded to the morphological state of g-C3N4 [35]. The TEM image and high-resolution TEM (HRTEM) further confirmed the morphology of 400 kGy-g-C3N4/GO. In Figure 2b the TEM image revealed GO as thin, transparent layered structures with wrinkled edges, while g-C3N4 exhibited irregular, multi-sized, and rough-surfaced agglomerates uniformly dispersed within the GO matrix, which were highly in agreement with those from the literature [29,36]. The clear boundary between g-C3N4 and GO displayed in Figure 2c further implied the intimate integration of g-C3N4 and GO. Moreover, there was a crystal lattice distance of 0.32 nm which corresponded to the (002) crystal plane of g-C3N4. X-ray energy dispersive spectroscopy (EDS) analysis revealed uniform distribution of C, N, and O elements in the 400 kGy-g-C3N4/GO (Figure 2d–f). The results further implied that the 400 kGy-g-C3N4/GO were synthesized successfully by EBR.
The chemical state and surface element components of 400 kGy-g-C3N4/GO were investigated using X-ray photoelectron spectroscopy (XPS) (Figure 3). The XPS survey spectrum (Figure 3a) displayed that 400 kGy-g-C3N4/GO was composed of C, O, and N elements, which was in line with the result of EDS. The high-resolution XPS spectrum of C 1s (Figure 3b) could be fitted into three smaller peaks. The peaks at 284.8 eV, 286.9 eV, and 288.9 eV were attributed to the C-C, C-O, and N=C-N bond in the sample [24,37]. As for the N 1s XPS spectrum of the 400 kGy-g-C3N4/GO, the presence of graphitic sp2-hybridized carbon-nitrogen bonds was confirmed by the peak at 399.2 eV, which was generally ascribed to nitrogen atoms forming sp2-hybridized c-bonds with two carbon atoms (C-N-C). The two peaks at 400.5 and 401.7 eV corresponded to tertiary nitrogen (N-(C)3) and hydrogen-containing amino functional groups (C-N-H), respectively [24,38]. As for O 1s XPS spectrum of the 400 kGy-g-C3N4/GO, the peaks of 531.9 and 533.4 eV were attributed to C-O/C=O and O-H, respectively [39].

2.2. Adsorption Properties of X kGy-g-C3N4/GO

Under various conditions, such as irradiation dose, reaction time, X kGy-g-C3N4/GO dosage, initial OFL concentration, pH, and coexisting ions, the adsorption performance of X kGy-g-C3N4/GO for OFL in solution was studied.

2.2.1. Effect of Irradiation Dose and Reaction Time

The removal efficiency of X kGy-g-C3N4/GO for OFL at different irradiation doses as a function of adsorption time is presented in Figure 4a. In the initial 60 min, the adsorption capacity of X kGy-g-C3N4/GO for OFL increased significantly with the increasing reaction time and then achieved equilibrium at 6 h. This observation could be attributed to the abundance of available adsorption sites on the X kGy-g-C3N4/GO surface during the initial stage, enabling the OFL to reach the maximum adsorption quickly and increasing the adsorption capacity rapidly [40]. As the adsorption time increased, both the number of active sites in X kGy-g-C3N4/GO and the concentration of OFL decreased, leading to a slower adsorption process and eventually reached equilibrium [41]. Furthermore, it was found that the adsorption capacity of X kGy-g-C3N4/GO for OFL increases with higher irradiation doses, reaching a maximum at 400 kGy, which was connected to the results of specific surface areas. In summary, X kGy-g-C3N4/GO exhibited optimal adsorption performance at an irradiation dose of 400 kGy. Therefore, 400 kGy-g-C3N4/GO was selected for subsequent studies.

2.2.2. Effect of Adsorbent Dosage and Initial OFL Concentration

The effect of X kGy-g-C3N4/GO dosage on removal performance for OFL was monitored (Figure 4b). With increasing X kGy-g-C3N4/GO dosage from 120 to 240 mg·L−1, the number of available adsorption sites on the adsorbent surface increased, leading to enhanced removal capacity for OFL. Additionally, the effect of varying OFL concentrations on adsorption efficiency was investigated (Figure 4c). The results indicated that the adsorption capacity gradually increased as the initial OFL concentration increased from 20 to 45 mg·L−1. This trend could be attributed to the enhanced mass transfer driving force, which promoted the movement of the OFL molecules towards the adsorbent surface [41,42].

2.2.3. Effect of Coexisting Ions

The presence of anions in aqueous solutions may compete with OFL for active adsorption sites on the adsorbent surface, thereby hindering the adsorption of OFL [10]. Therefore, under optimized conditions, the impact of coexisting ions on the removal performance of 400 kGy-g-C3N4/GO was evaluated (Cl−, SO42−, CO32−, and NO3−) (Figure 4d). It could be observed that the presence of CO32− significantly reduced the adsorption of OFL in 400 kGy-g-C3N4/GO, while Cl− had almost no effect on the adsorption performance. Furthermore, as the ion concentration increased, the impact on 400 kGy-g-C3N4/GO became more pronounced.

2.2.4. Effect of pH

The pH of the solution could alter the ionization state of functional groups on the adsorbent surface, thereby enabling electrostatic interactions between the adsorbent and pollutants [43]. The zero-charge point (pHpzc = 3.3) of 400 kGy-g-C3N4/GO and the existence forms of OFL at different pH values are shown in Figure 5. In Figure 5a, OFL primarily existed as OFL+ at pH < 6.05, mainly existed as OFL0 at 6.05 < pH < 8.11, and predominantly existed as OFL− at pH > 8.11 [44]. As depicted in Figure 5b, the OFL adsorption capacity first increased and then decreased with rising pH (3.0–11.0), reaching a maximum at pH 7.0. This result was ascribed to the existence of electrostatic gravitational force between 400 kGy-g-C3N4/GO and OFL+ at pH < 7.0. As pH increased, the surface negative charge of 400 kGy-g-C3N4/GO further intensified, consequently the adsorption capacity was enhanced. When the pH was higher than 7.0, OFL predominantly adopted the OFL− form, there was electrostatic repulsion between the two and this lead to lower adsorption performance. At pH = 7.0, OFL predominantly existed as the neutral form OFL0, with electrostatic attraction nearly eliminated. However, the adsorption capacity still reached a peak of 222.0 mg g−1, indicating that electrostatic interactions were no longer the dominant mechanism. The abundant hydroxyl and amino groups on the composite surface formed hydrogen bonds with OFL. Additionally, the thiotriazinone and conjugated skeleton of the 400 kGy-g-C3N4/GO material acted as electron donors, generating π-π stacking interactions with OFL. Concurrently, hydrophobic effects further concentrated neutral molecules, resulting in electrostatic forces only having a minor auxiliary role near pH = 7.0.

2.2.5. Effect of Temperature

As shown in Figure 5c, the adsorption capacity of OFL on 400 kGy-g-C3N4/GO decreased monotonically with increasing temperature from 298 K to 318 K, indicating an exothermic process. The decline in adsorption capacity was attributed to the enhanced thermal motion of OFL molecules, which promoted their desorption, and a concomitant weakening of the interactions between OFL and the functional groups on the surface of 400 kGy-g-C3N4/GO [42].

2.3. Adsorption Kinetics

The kinetic study was performed by monitoring the adsorption capacity of OFL at various time intervals and fitting the experimental data to various kinetic models to gain information of the reaction rate between the adsorbent and adsorbate (Figure 6a,b) [45]. The findings of the kinetic fittings in relation to the various irradiation doses are shown in Table 1. The pseudo-second-order kinetics suited the relevance data better (R2 = 0.995). Additionally, the calculated values (230.6 mg·g−1) for the adsorption of the OFL on the 400 kGy-g-C3N4/GO showed high similarity to the experimental values (222.0 mg·g−1), indicating that the data fitted the model more effectively. This reaction process primarily occurred through chemisorption [46]. Furthermore, the pseudo-second-order adsorption capacity of the 400 kGy-g-C3N4/GO material prepared at the 400 kGy irradiation dose was 3.57 × 10−4 g·(mg·min−1), higher than that of other composites. This indicated that the composite material prepared at the 400 kGy adsorbed OFL significantly faster than those prepared at other irradiation doses.
The intra-particle diffusion model indicated that if qt exhibited a linear regression with t0.5 and the resulting regression line passed through the origin, then the reaction rate was influenced by intra-particle diffusion [47]. A certain level of boundary layer control was demonstrated by the linear regression curve in Figure 6b which was not crossing the origin. This implied that intra-particle diffusion might not be the only rate-limiting factor, and that additional mechanisms were also involved in controlling the adsorption [48].

2.4. Adsorption Isotherms and Thermodynamics

Figure 7 represents the Langmuir and Freundlich fitting results for the equilibrium data. The Langmuir model was detected to provide a good fit to the experimental data for different irradiation doses, as shown in Table 2 (400 kGy-g-C3N4/GO, 298 K, R2 = 0.984). Additionally, as the temperature increased from 298 K to 318 K, the adsorption capacity of 400 kGy-g-C3N4/GO for OFL gradually decreased, reaching its maximum value at 298 K. According to the adsorption isotherm model, the calculated value of the 400 kGy-g-C3N4/GO’s adsorption capacity for OFL was 239.6 mg·g−1, which was quite close to the experimental value (222.0 mg·g−1). Table 3 compares the maximum adsorption capacities of different adsorbents for OFL in different studies. Regarding the Freundlich model, the value of n provided an indication of the validity of the adsorption between the 400 kGy-g-C3N4/GO and OFL.
The temperature-dependent adsorption behavior of adsorbents had also been investigated at various temperatures (298, 308, and 318 K). The parameters of ∆G0, ∆H0, and ∆S0 derived from Gibbs-Helmholtz were further introduced to elucidate the thermodynamics. The obtained adsorption thermodynamic parameters are shown in Table 4. The spontaneous nature of the adsorption process was confirmed by the negative values of ∆G0. Furthermore, the ∆G0 values were more negative with increasing temperature, demonstrating that the adsorption process was more favorable with temperature decreases [55]. The negative value for ∆H0 indicated that the adsorption was an exothermic process. Finally, the positive ΔS0 value confirmed the randomness and the increased affinity of OFL during the adsorption [55].

2.5. Adsorption Mechanism

Figure 8a shows the FT-IR spectra of 400 kGy-g-C3N4/GO before and after loading with OFL. The peak at 3000–3500 cm−1 exhibited a redshift and broadening after loading with OFL, indicating hydrogen bonding between the -OH groups of 400 kGy-g-C3N4/GO and OFL. Additionally, following OFL adsorption, the peak at 808 cm−1 was enhanced, indicating the presence of π-π stacking between the aromatic rings of OFL and 400 kGy-g-C3N4/GO. Combined with the N2 adsorption–desorption analysis results discussed earlier, the adsorbent’s large specific surface area and mesoporous structure also provided numerous adsorption sites for OFL. These mesoporous structures and adsorption sites promoted the diffusion of OFL within the 400 kGy-g-C3N4/GO. pH results indicated that strong electrostatic attractions occurred between the -COOH and hydroxyl -OH in 400 kGy-g-C3N4/GO and OFL, which also promoted the adsorption. The possible adsorption mechanisms are shown in Figure 8b.

3. Materials and Methods

3.1. Chemicals and Reagents

The specific materials and reagents are detailed in the Supporting Information.

3.2. Adsorbents Preparation

3.2.1. Preparation for GO

GO was prepared via an optimized hummers method [56]. The main steps are as follows: (1) 3.0 g of graphite flakes and 1.5 g of NaNO3 were dissolved in H2SO4 (69 mL), cooled to 0 °C, followed by the slow addition of KMnO4 (9.0 g) below 20 °C, and subsequently stirred for 7 h at 35 °C; (2) another 9.0 g KMnO4 was added and stirred for 12 h and was subsequently cooled to room temperature, then, 400 mL ice water and 3 mL H2O2 (30%) was poured in the above solution; (3) the mixture was settled, and the supernatant was decanted, followed by washing with diluted HCl and dialysis (MD: 44 mm) for acid removal. When the solution pH approached 7.0, the product was freeze-dried to obtain GO.

3.2.2. Preparation of g-C3N4

Detailed preparation procedure for g-C3N4 is displayed in the Supporting Information.

3.2.3. Preparation of X kGy-g-C3N4/GO

A total of 180 mg of GO was dispersed in 60 mL of pure water, then thoroughly sonicated for half an hour. g-C3N4 (30 mg) was added into the GO solution, mixed thoroughly, then the mixture was transferred into a polyethylene plastic bag. Subsequently, the mixture was irradiated using a high-energy electron accelerator (GJ-2-II, Shanghai Xianfeng Power Plant, Shanghai, China) with a variable current of 0–10 mA, and an energy of 1.8 MeV at irradiation doses (200, 300, 400, and 500 kGy). The final composite was obtained, denoted as X kGy-g-C3N4/GO.

3.3. Characterization

Details of the characterization instruments were presented in Supporting Information.

3.4. Adsorption Experiments

For adsorption, 10 mg of X kGy-g-C3N4/GO was added to 50 mL of OFL solution (concentration ranged from 20 to 45 mg·L−1). Samples (1.5 mL) were collected at 2, 5, 10, 20, 40, 60, 120, 240, and 360 min, and the concentrations were detected using high-performance liquid chromatography (Waters 2695, Milford, MA, USA). The adsorption capacity of X kGy-g-C3N4/GO for OFL was investigated at different conditions, including irradiation dose (200–500 kGy), X kGy-g-C3N4/GO dosage (120–240 mg·L−1), coexisting ions at different concentrations (Cl−, SO42−, CO32−, and NO3−, 2 mM–5 mM), pH (3.0–11.0), and temperature (298–318 K). Each experiment was repeated at least three times, and the standard deviation was calculated. Equations (S1) and (S2) were used to calculate the adsorption capacity and removal rate, respectively, which were presented in Supporting Information [57].
Details of adsorption kinetics, isotherms, and thermodynamic calculation methods were shown in Supporting Information.

4. Conclusions

In this study, X kGy-g-C3N4/GO composites were successfully synthesized via EBR at different irradiation doses. Characterization results indicated that the EBR-synthesized composite material exhibited characteristic peaks and functional groups of both GO and g-C3N4, confirming the successful composite formation of the two materials. Adsorption experiments demonstrated that the 400 kGy-g-C3N4/GO material exhibited the optimal adsorption performance and maximum adsorption capacity (222.0 mg·g−1) for OFL. Within a certain range (20–45 mg·L−1), the adsorption performance of OFL over 400 kGy-g-C3N4/GO increased with initial OFL concentration increasing and exhibited the maximum ability at pH = 7.0. Concurrently, the presence of CO32− in the solution competed with OFL molecules for adsorption, reducing the adsorption performance. Kinetics and isotherm studies confirmed that the pseudo-second-order kinetics and Langmuir isotherm models accurately represented the adsorption process. According to the intra-particle diffusion model, both surface adsorption and intra-particle diffusion within particles had an impact on the adsorption process. Furthermore, the thermodynamic result of the process revealed the exothermic and spontaneous of the adsorption process. Consequently, the results of the present study suggest that the EBR synthesis is a viable method for preparing X kGy-g-C3N4/GO with enhanced OFL adsorption performance, and X kGy-g-C3N4/GO could be utilized as an adsorbent with high capability for OFL removal in practical applications.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/catal15121118/s1, Table S1: Physical parameters of materials at different irradiation doses; Section S2: Materials and Methods. References [58,59] are cited in the supplementary materials.

Author Contributions

Z.L. (Zhiying Li): Writing—original draft. S.G.: Validation, Visualization. B.N.: Data curation. Z.L. (Zhuopeng Lin): Investigation. T.H.: Methodology. D.W.: Data curation. J.L.: Supervision, Funding acquisition. N.L.: Writing—review and editing, Funding acquisition. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by National Natural Science Foundation of China (Nos. 12075152, 42177405, 12075147), Innovation Program of Shanghai Municipal Education Commission (2021-03-147), and Energy Science and Technology discipline under the Shanghai Class IV Peak Disciplinary Development Program for the financial support.

Data Availability Statement

The raw data supporting the conclusions of this article will be made available by the authors on request.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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Catalysts 15 01118 g001
Figure 1. (a) XRD patterns of GO, g-C3N4, and X kGy-g-C3N4/GO (the orange and purple regions from left to right correspond to peaks at 11.0°, 13.1°, and 27.5°), (b) FT-IR spectra (the colored region encompasses multiple spectral bands at 1200–1700 cm−1, corresponding to CN heterocycle vibrations, and the dashed line indicates a peak at 1050 cm−1, corresponding to the stretching vibration of the C-O bond in the alkoxy group), (c) N2 adsorption–desorption isotherms and (d) pore size distribution of X kGy-g-C3N4/GO.
Figure 1. (a) XRD patterns of GO, g-C3N4, and X kGy-g-C3N4/GO (the orange and purple regions from left to right correspond to peaks at 11.0°, 13.1°, and 27.5°), (b) FT-IR spectra (the colored region encompasses multiple spectral bands at 1200–1700 cm−1, corresponding to CN heterocycle vibrations, and the dashed line indicates a peak at 1050 cm−1, corresponding to the stretching vibration of the C-O bond in the alkoxy group), (c) N2 adsorption–desorption isotherms and (d) pore size distribution of X kGy-g-C3N4/GO.
Catalysts 15 01118 g001
Catalysts 15 01118 g002
Figure 2. (a) SEM image, (b) TEM image, (c) HRTEM image, and (d–f) EDS elemental mapping of 400 kGy-g-C3N4/GO.
Figure 2. (a) SEM image, (b) TEM image, (c) HRTEM image, and (d–f) EDS elemental mapping of 400 kGy-g-C3N4/GO.
Catalysts 15 01118 g002
Catalysts 15 01118 g003
Figure 3. XPS spectra of 400 kGy-g-C3N4/GO, (a) survey, (b) C 1s, (c) N 1s, (d) O 1s.
Figure 3. XPS spectra of 400 kGy-g-C3N4/GO, (a) survey, (b) C 1s, (c) N 1s, (d) O 1s.
Catalysts 15 01118 g003
Catalysts 15 01118 g004
Figure 4. Adsorption capacity for the removal of OFL using X kGy-g-C3N4/GO: (a) different irradiation doses, (b) 400 kGy-g-C3N4/GO dosage, (c) initial concentration of OFL, and (d) coexisting ions.
Figure 4. Adsorption capacity for the removal of OFL using X kGy-g-C3N4/GO: (a) different irradiation doses, (b) 400 kGy-g-C3N4/GO dosage, (c) initial concentration of OFL, and (d) coexisting ions.
Catalysts 15 01118 g004
Catalysts 15 01118 g005
Figure 5. (a) Zero-charge point of 400 kGy-g-C3N4/GO and the presence of OFL forms at different pH, (b) effect of pH, and (c) temperature on adsorption capacity of 400 kGy-g-C3N4/GO.
Figure 5. (a) Zero-charge point of 400 kGy-g-C3N4/GO and the presence of OFL forms at different pH, (b) effect of pH, and (c) temperature on adsorption capacity of 400 kGy-g-C3N4/GO.
Catalysts 15 01118 g005
Catalysts 15 01118 g006
Figure 6. Adsorption kinetics of OFL over X kGy-g-C3N4/GO (a) pseudo-first-model (dotted lines), and pseudo-second-model (solid lines), (b) intra-particle diffusion model.
Figure 6. Adsorption kinetics of OFL over X kGy-g-C3N4/GO (a) pseudo-first-model (dotted lines), and pseudo-second-model (solid lines), (b) intra-particle diffusion model.
Catalysts 15 01118 g006
Catalysts 15 01118 g007
Figure 7. Adsorption isotherms at different temperatures (a) Langmuir, and Freundlich (b) 298 K, (c) 308 K, (d) 318 K (solid line represents the Langmuir isotherm fitting, while the dotted line represents the Freundlich isotherm fitting).
Figure 7. Adsorption isotherms at different temperatures (a) Langmuir, and Freundlich (b) 298 K, (c) 308 K, (d) 318 K (solid line represents the Langmuir isotherm fitting, while the dotted line represents the Freundlich isotherm fitting).
Catalysts 15 01118 g007
Catalysts 15 01118 g008
Figure 8. (a) FT-IR spectra of 400 kGy-g-C3N4/GO before and after adsorption of OFL (blue region indicates the peak at 3000–3500 cm−1, while the red region corresponds to the peak at 808 cm−1), and (b) mechanism of OFL adsorption.
Figure 8. (a) FT-IR spectra of 400 kGy-g-C3N4/GO before and after adsorption of OFL (blue region indicates the peak at 3000–3500 cm−1, while the red region corresponds to the peak at 808 cm−1), and (b) mechanism of OFL adsorption.
Catalysts 15 01118 g008
Table 1. The adsorption kinetic parameters of OFL over X kGy-g-C3N4/GO.
Table 1. The adsorption kinetic parameters of OFL over X kGy-g-C3N4/GO.
ModelsAdsorbentsParameters
qt (mg·g−1)K1 (min−1)R2
Pseudo-first-order200 kGy-g-C3N4/GO
300 kGy-g-C3N4/GO
400 kGy-g-C3N4/GO
500 kGy-g-C3N4/GO		161.7
168.2
210.7
149.5		0.018
0.020
0.060
0.026		0.998
0.996
0.970
0.990
qt (mg·g−1)K1 (min−1)R2
Pseudo-second-order200 kGy-g-C3N4/GO
300 kGy-g-C3N4/GO
400 kGy-g-C3N4/GO
500 kGy-g-C3N4/GO		193.4
197.6
230.6
171.0		9.68 × 10−5
1.16 × 10−4
3.57 × 10−4
1.81 × 10−4		0.996
0.989
0.995
0.999
Intra-particle diffusion400 kGy-g-C3N4/GOKb mg·(g·min1/2)−1C (mg·g−1)R2
32.680.2970.991
16.8779.640.974
1.477196.80.977
Table 2. The adsorption isotherm parameters of OFL over X kGy-g-C3N4/GO.
Table 2. The adsorption isotherm parameters of OFL over X kGy-g-C3N4/GO.
LangmuirFreundlich
AdsorbentsT (K)KL (L·mg−1)qm (mg·g−1)R2nKF [(mg·g−1) (L mg−1)1/n]R2
200 kGy-g-C3N4/GO2980.97199.90.9794.12697.000.809
300 kGy-g-C3N4/GO2981.36206.00.9834.559109.70.797
400 kGy-g-C3N4/GO2982.16239.60.9845.182142.00.765
3081.75225.30.9915.016128.80.795
3181.72203.20.9924.970115.50.795
500 kGy-g-C3N4/GO2980.81182.90.9833.84683.100.855
Table 3. Comparison of the maximum capacity of various adsorbents for OFL.
Table 3. Comparison of the maximum capacity of various adsorbents for OFL.
AdsorbentAdsorption Capacity (mg·g−1)Optimum pHTemperature (K)Reference
Rice husk ash6.266.0-[49]
Fe3O4 Metal–organic framework218.0-298[50]
ZIF-8 MOF194.17.0298[51]
3D Graphene hydrogel134.0-363[52]
Raw cassava stem42.378.0328[53]
Amino functionalized molecularly imprinted silica261.17.0-[54]
400 kGy-g-C3N4/GO222.07.0298This Work
Table 4. The parameters of thermodynamic adsorption of OFL over 400 kGy-g-C3N4/GO.
Table 4. The parameters of thermodynamic adsorption of OFL over 400 kGy-g-C3N4/GO.
T (K)∆G0 (kJ·mol−1)∆H0 (kJ·mol−1)∆S0 (kJ·mol −1·K−1)
298−25.21−10.250.050
308−25.66
318−26.21
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Li, Z.; Guo, S.; Ni, B.; Lin, Z.; Han, T.; Wang, D.; Lei, J.; Liu, N. Rapid Preparation of g-C3N4/GO Composites via Electron Beam Irradiation for Enhanced Ofloxacin Removal. Catalysts 2025, 15, 1118. https://doi.org/10.3390/catal15121118

AMA Style

Li Z, Guo S, Ni B, Lin Z, Han T, Wang D, Lei J, Liu N. Rapid Preparation of g-C3N4/GO Composites via Electron Beam Irradiation for Enhanced Ofloxacin Removal. Catalysts. 2025; 15(12):1118. https://doi.org/10.3390/catal15121118

Chicago/Turabian Style

Li, Zhiying, Shaohua Guo, Beibei Ni, Zhuopeng Lin, Tao Han, Denghui Wang, Jianqiu Lei, and Ning Liu. 2025. "Rapid Preparation of g-C3N4/GO Composites via Electron Beam Irradiation for Enhanced Ofloxacin Removal" Catalysts 15, no. 12: 1118. https://doi.org/10.3390/catal15121118

APA Style

Li, Z., Guo, S., Ni, B., Lin, Z., Han, T., Wang, D., Lei, J., & Liu, N. (2025). Rapid Preparation of g-C3N4/GO Composites via Electron Beam Irradiation for Enhanced Ofloxacin Removal. Catalysts, 15(12), 1118. https://doi.org/10.3390/catal15121118

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