Surface Modification of Wood Activated Carbon by CVD of NH₃ to Improve Its Micropore Volume and Adsorption to Carbamazepine

Introduction

Carbamazepine (CBZ), a classic antiepileptic drug approved in 1974, is widely acknowledged for its therapeutic efficacy. It exhibits a bioavailability of 58% to 85% and a high protein binding rate of approximately 80% to 85%.^1,2 Despite its effectiveness, CBZ poses challenges due to its complex metabolism, narrow therapeutic window, and significant individual differences in drug metabolism. Adverse drug reactions are not uncommon, as evidenced by Ding Yiduo et al’s retrospective study, which highlighted CBZ’s involvement in a substantial number of cases.³ Blood perfusion is a blood purification method based on the principle of small molecule toxicants being adsorbed by adsorbents, typically activated charcoal. It is the most effective treatment method for Carbamazepine poisoning after it has been absorbed into the blood.^4–6 At present, there are many studies on the removal of carbamazepine by adsorption methods, and most of these studies are used for sewage treatment.^7,8 In contrast, this study is more inclined to discover a specific hemoperfusion adsorbent with stable physical and chemical properties.

In the wider context, pharmaceuticals and personal care products (PPCPs) have emerged as pollutants of concern, encompassing various antibiotics, painkillers, and antihypertensive drugs.⁹ Among these, CBZ is often used as an indicator of PPCPs pollution due to its persistence in water bodies and high detectability.¹⁰ This situation calls for an urgent need to develop efficient and practical methods for mitigating CBZ pollution in aquatic environments.^11,12

Activated carbon, with its developed pore structure and excellent adsorption properties, is extensively utilized in environmental protection, medical treatment, scientific research, and other fields.¹³ Notably, its application in medical blood purification further highlights its versatility.^14,15 Within this framework, Chemical Vapor Deposition (CVD) emerges as a promising technique. CVD involves gaseous substances reacting on solids to produce solid sediments, encompassing steps like the formation of volatile substances, transportation of the reaction gas, and chemical reactions on solids to produce solid substances.¹⁶ Our study explores the potential of CVD, specifically ammonia chemical vapor deposition (NH₃-CVD), in modifying activated carbon to enhance its efficacy in adsorbing CBZ from water bodies, addressing a critical environmental and public health issue.

Materials and Methods

Reagents and Instruments

Reagents

Carbamazepine (CBZ): > 99%, Shanghai Huzhen Biotechnology.

Ammonia Solution: (25–28%), Chongqing Chuandong Chemical Group.

Wood (Chinese fir) Activated Carbon: (80–100 mesh), Chengde Ji bei Yan Shan Activated Carbon.

Instruments

Thermal Stirrer: DF-101S, Gongyi Yuhua Instrument.

Sintering Furnace: OTF Series, Hefei Kejing Material Technology.

UV-Visible Spectrophotometer: MODEL U-3010, Hitachi.

Nitrogen Adsorption Instrument: JW-BK122W, Beijing Jing wei Gao bo.

XPS: XSAM800, Kratos.

FTIR: Nicolet iS20, Thermo Scientific.

Modification of Activated Carbon

In our experimental procedure, we modified wood activated carbon using ammonia chemical vapor deposition (NH₃-CVD). The process involved the following steps:

Preparation of Ammonia Gas

Measured 200.0 mL of ammonia water into a 500 mL round-bottom flask.

Conducted oil bath heating in three stages to release ammonia gas: first at 60°C for 30 minutes, then 80°C for 30 minutes, and finally at 100°C for 30 minutes.

Modification Process

Placed 10 g of wood activated carbon in a tubular furnace.

Initially, pumped N₂ (50 mL/min) to remove air from the furnace during the heating phase.

Once the temperature reached 700°C, introduced NH₃ (150 mL/min) into the furnace, maintaining this flow for 90 minutes.

Post-Reaction Treatment

After the reaction, allowed the activated carbon to cool to room temperature.

Washed the carbon with water until the pH stabilized, and then dried it for later use.

The modified activated carbon obtained at 700°C was labeled W-7.

Similarly, we modified additional samples of activated carbon at 600°C and 500°C, labeled as W-6 and W-5, respectively. For comparison, wood activated carbon without NH₃ modification was washed to a constant pH and labeled as W-0.

Characterization of Activated Carbon

Pore Size Determination

Instrument

JW−BK122W Static Nitrogen Adsorption.

Methodology

Multi-point method.

Procedure

Degassed activated carbon at 120°C for 1 hour. Specific surface point range selected was between 0.05 and 0.3.

Adsorption Gas

Nitrogen.

Adsorption Temperature

Liquid nitrogen bath −196°C.

Surface Element Analysis (XPS)

Instrument

XSAM800 Multifunctional Surface Analysis Electron Spectrometer.

Settings

Al target X-ray gun operated at 12 kV × 15 mA. Background vacuum in analysis chamber maintained at 2 × 10^-7 Pa.

Calibration

Spectrometer corrected with CU2P3/2, Ag3d5, and AU4F7/2 standard samples using FAT method; Data normalized to C1s peak at 284.8 eV.

Scanning Parameters

Full spectrum scan step size: 150ms/0.65ev. Fine structure spectrum: 150 ms/0.05 ev.

Data Analysis

N1s nuclear grade spectral peaks fitted using XPSpeak software.

Infrared Detection (FTIR)

Instrument

Thermo Scientific Nicolet iS20 Infrared Spectrometer.

Settings

Detector: DTGS KBr; Beam splitter: KBr.; Sample scanning: 32 times.; Background scanning: 32 times.; Resolution: 4.000; Moving mirror speed: 0.4747.; Aperture: 80.00.

Kinetic Adsorption and Isothermal Adsorption

UV Spectrophotometry Analysis

Figure 1A: Shows CBZ scanning results in the λ (225–400) nm range. CBZ exhibited stable maximum absorption at λ = 284 nm.

Figure 1 (A) UV scan of CBZ; (B) Working curve of adsorption experiments.

Figure 1B: Working curve for CBZ adsorption experiment with a correlation coefficient R²= 0.9993, indicating strong correlation between absorbance and concentration. The linear equation y = 0.0477x + 0.0775 was used for quantitative analysis.

Kinetic Adsorption Experiments

CBZ Solution

Used 50 mg/L concentration for kinetic studies.

Contact Time Range

Experiments conducted over a period of 0 to 600 minutes.

Procedure

Weighed 0.030 g of activated carbon.

Mixed it with 0.090 L of CBZ solution in a 150 mL conical flask.

Placed the flask in a water bath shaker set at 37°C and 110 rpm.

Measured absorbance of the supernatant at λ = 284 nm.

Calculation

Adsorption capacity (Q) determined using Lambert-Beer’s law.

Lambert-Beer’s Law Application

C₁/C₂=A₁/A₂ (1)

q_t=(C₀-C₁)V/m (2)

Equation

C₁ and C₂ are different concentrations of CBZ (mg/L) within the linear range; A₁ and A₂ are corresponding absorbance values. The adsorption capacity (q_t) at a specific time, C_e (the concentration at qt time), C₀ (initial concentration), V (volume of solution), and m (mass of activated carbon) were used in calculations.

Within a specific concentration range, there is a stable linear relationship between the concentration of carbamazepine solution and the absorbance. In the adsorption experiment, according to the linear equation, the concentration of the solution can be calculated by measuring the absorbance of the solution, and the adsorption capacity of the activated carbon for the drug can be calculated according to Formula (2).

Kinetic Models: Tested the fit of the data using intraparticle diffusion, Lagergren’s quasi-first-order and quasi-second-order kinetic models to analyze adsorption kinetics.

Isothermal Adsorption Experiments

CBZ Solutions

Initial concentrations of 20, 30, 40, 50, 60, and 70 mg/L.

Contact Time Range

Experiments conducted over a period of 0 to 600 minutes.

Same Procedure

As kinetic experiments.

Isothermal Models

Performed fitting tests using Langmuir and Freundlich isothermal models to evaluate the adsorption process.

Results

Texture Results of Activated Carbon

In line with the International Union of Pure and Applied Chemistry (IUPAC) standards, pore sizes in powder materials are categorized as micropores (less than 2 nm), mesopores (2–50 nm), and macropores (greater than 50 nm). Our study’s BET analysis revealed significant changes in the specific surface area and micropore volume of wood activated carbon following NH₃-CVD modification. Table 1 summarizes the main textural parameters of the activated carbon before and after modification.

Table 1 Texture of Modified Wood-Based Activated Carbon

The most notable observation was in sample W-6, which exhibited the largest increase in both specific surface area and micropore volume among the modified samples. The specific surface area and micropore volume of W-6 were measured at 846.531 m²/g and 0.398 cm³/g, respectively. This enhancement is crucial as micropore adsorption is reported to be the predominant mechanism for activated carbon to adsorb small molecular compounds.⁹ Additionally, the micropore structure is a significant contributor to the overall specific surface area of activated carbon. Consequently, the observed increase in specific surface area and micropore volume is expected to significantly improve the adsorption performance of the activated carbon.

Figure 2 presents diagrams of micropores (A) and mesopores (B) in wood activated carbon before and after modification. The micropore size distribution is primarily within the range of 0.2 to 1.0 nm, while the mesopore size predominantly falls between 2.5 and 17 nm. Analyzing these diagrams in conjunction with the data in Table 1, we observe that the hierarchy in terms of micropore volume capacity is W-6 > W-7 > W-5 > W-0.

Figure 2 Pore volume and pore size distribution of wood activated carbon: (A) micropore, (B) mesopore.

Under our experimental conditions, an interesting phenomenon was noted: when the reaction temperature reaches 600°C, further temperature increase tends to disrupt the micro-pore structure of the activated carbon. The micropore volume of activated carbon first increases and then decreases with the increase of the modification reaction temperature. This effect was somewhat mitigated due to the original carbon’s abundant micropore distribution, leading to a less pronounced increase in micropore volume post-modification, as evidenced in Figure 2A.

Furthermore, Figure 2B reveals a slight decrease in mesoporous volume following modification, aligning with the trends observed in Table 1. This suggests that the NH₃-CVD modification process, while enhancing micropore volume, may simultaneously lead to a reduction in mesoporous volume, impacting the overall porosity of the activated carbon.

X-Ray Photoelectron Spectroscopy (XPS) Analysis Results

Figure 3 depicts the XPS full spectrum analysis results, comparing wood activated carbon samples before and after the NH₃-CVD modification process. The analysis primarily identifies the presence of three elements: Carbon (C), Nitrogen (N), and Oxygen (O). Notably, the most significant change observed is in the nitrogen content on the surface of the activated carbon.

Figure 3 XPS Full spectrum of wood-based activated carbon before and after modification.

Prior to modification, the nitrogen content on the activated carbon’s surface was markedly low. However, post-modification with NH₃-CVD, there is a substantial increase in the surface nitrogen content. This indicates that the modification process effectively incorporates nitrogen into the carbon structure, potentially altering its adsorption characteristics and chemical properties. The presence of almost no other elements except C, N, and O suggests the purity of the sample and the specificity of the modification effect.

Table 2 provides a detailed analysis of the main elements present on the surface of wood activated carbon, comparing the samples before and after NH₃-CVD modification. The data clearly demonstrates that the modification process substantially increases the nitrogen content on the surface of the activated carbon. Concurrently, there is a noticeable decrease in the percentage of oxygen elements following modification.

Table 2 Analysis of XPS Element Content in Wood Activated Carbon

These alterations in elemental composition align with the results depicted in Figure 3. The increase in nitrogen content post-modification underscores the effectiveness of the NH₃-CVD process in altering the chemical properties of the activated carbon surface, potentially enhancing its adsorption capabilities. Simultaneously, the reduction in oxygen content further confirms the specificity of the modification effect, as the process primarily influences nitrogen integration while reducing oxygen presence. However, for adsorption, the action of oxygen is “supersaturated”.

As shown in the Figure 4, Research indicates that nitrogen-doped activated carbon typically exhibits three primary forms of nitrogen:^17,18

Figure 4 3D diagram of Three main forms of N in activated carbon.

Pyridinic-N: In this form, nitrogen atoms replace carbon atoms in the six-membered rings of the activated carbon structure. This substitution alters the electronic and chemical properties of the carbon lattice.

Pyrrolic-N: This configuration involves the substitution of a carbon atom with a nitrogen atom in a five-membered ring. Pyrrolic nitrogen shares some characteristics with pyridinic nitrogen, influencing the carbon structure similarly.

Graphitic-N: Here, a nitrogen atom replaces a carbon atom in the activated carbon’s lattice without creating a vacancy. It remains bonded to three carbon atoms, maintaining the integrity of the six-membered ring. This type of doping can impact the electronic properties of the carbon material.

These different nitrogen configurations contribute to the varied chemical and adsorption properties of nitrogen-doped activated carbon, influencing its effectiveness in specific applications.

Figure 5 illustrates the binding energy peaks identified in the XPS analysis of the modified wood activated carbon. These peaks correspond to the different nitrogen configurations within the carbon structure:

Figure 5 N1s XPS spectra for W-0, W-5, W-6 and W-7.

Figure 6 Dynamic adsorption curve of wood-based activated carbon.

Pyridinic-N: A peak at 398.5 ± 0.3 eV indicates the presence of pyridinic-N, where nitrogen atoms are incorporated into six-membered rings, replacing carbon atoms.

Pyrrolic-N: The peak at 400.20±0.3 eV is attributed to pyrrolic-N, representing nitrogen atoms substituting for carbon atoms in five-membered rings.

Graphitic-N: A peak at 401.3±0.3 eV signifies graphitic-N, where nitrogen atoms replace carbon atoms in the lattice, retaining the structure of the six-membered rings.

These findings, consistent with literature,^19–21 confirm the successful doping of nitrogen in various structural forms within the activated carbon, potentially enhancing its adsorptive properties and chemical interactions.

Utilizing the Lorentz-Gaussian function, we fitted the fine structure spectrum of nitrogen in four activated carbon samples using XPSpeak software. The calculated contents of each nitrogen component are detailed in Table 3. When correlated with the findings from Figure 5, it becomes evident that NH₃-CVD modification not only increases the total nitrogen content on the surface of activated carbon but also alters the proportion of the three nitrogen chemical states.

Table 3 XPS N1s Data Analysis of Wood-Based Activated Carbon

Post-modification, the content of graphitic-type nitrogen decreased in the W-5, W-6, and W-7 samples. Interestingly, as the modification temperature varied between 500°C and 700°C, the predominant form of nitrogen in the samples changed: at 600°C, pyrrolic nitrogen was the primary form, while at 700°C, pyridinic nitrogen dominated. This shift suggests that at higher temperatures, the carbon-NH₃ reaction intensifies, facilitating a rearrangement of C-N bonds towards a more stable chemical state, namely pyridinic nitrogen.^22,23

The study also delves into the role of hydrogen bonding as a major contributor to intermolecular forces. Hydrogen bonding occurs due to electron cloud skewing when hydrogen atoms covalently bond with highly electronegative atoms like fluorine, oxygen, or nitrogen. This leaves the hydrogen atom electron-deficient and the electronegative atom electron-rich, leading to an attraction between hydrogen atoms in one molecule and electronegative atoms in another.

In the context of activated carbon, graphitic nitrogen, bonded with three carbon atoms, exhibits a balanced electron cloud distribution with similar electron absorption abilities as carbon, thus unable to form hydrogen bonds with CBZ molecules. Conversely, pyridinic and pyrrolic nitrogen, bonded with two carbon atoms and one hydrogen atom, can easily form hydrogen bonds with CBZ molecules. This capability significantly enhances the adsorption performance of CBZ on activated carbon, as these forms of nitrogen provide active sites for hydrogen bonding.

Kinetic Adsorption Experiment

Figure 6 illustrates the time-dependent adsorption capacity of wood activated carbon for CBZ, both before and after NH₃-CVD modification. The graph clearly shows a significant change in the adsorption capacity of the samples post-modification. Compared to the unmodified carbon, the three activated carbons treated with NH₃-CVD exhibited superior adsorption and removal abilities for CBZ.

A key observation from the figure is that the majority of CBZ adsorption occurs within the first 4 hours. Initially, the concentration of CBZ in the solution decreases rapidly as it is adsorbed onto the activated carbon. However, after 4 hours, the rate of adsorption slows down. This change is attributed to the transition from adsorption driven by concentration differences to a state nearing adsorption saturation, where the concentration of CBZ in the activated carbon increases, and the driving force for further adsorption diminishes.

Consequently, beyond the 4-hour mark, there is no significant increase in the adsorption amount with the extension of time, indicating that the activated carbon approaches its adsorption capacity limit. This finding is critical in understanding the adsorption dynamics of CBZ on activated carbon and optimizing the use of NH₃-CVD modified carbon for efficient CBZ removal.

To comprehensively examine the adsorption characteristics of CBZ on activated carbon samples, we applied Intraparticle diffusion, Lagergren’s quasi-first-order and quasi-second-order kinetic equations for kinetic fitting of the adsorption process.^24–26 These models are instrumental in deciphering the adsorption kinetics and are defined by their respective dynamic equations:

Intraparticle diffusion model: q_t=Kt^1/2+C (3)

Pseudo−first−order model: In(q_e-q_t)=Inq_e-K₁t (4)

Pseudo−second−order model: t/q_t=1/K₂q_e²+t/q_e (5)

These models are defined by key parameters that describe the adsorption process:

t: Adsorption time (minutes); K: Intraparticle diffusion rate constant (mg/g•min^1/2); C: Adsorption constant (mg/g), reflecting the boundary layer effect, calculated based on the intercept of the fitted straight line. q_t: Represents the adsorption capacity (mg/g) of CBZ at any given time (mg/g). q_e: Denotes the maximum adsorption capacity (mg/g) when the adsorption process reaches equilibrium. (R_{O, T, 1, 2})²: is the correlation coefficient of the fitting. K₁ and K₂: These are the rate constants for the quasi-first-order and quasi-second-order kinetics, respectively.

The intraparticle diffusion fitting parameters are listed in Table 4. The C value is not equal to zero, indicating that both physical adsorption and chemical adsorption exist in the adsorption process. According to the characteristics of the two adsorption types, it can be known that stage one is physical adsorption and stage two is chemical adsorption. By comparing the K_O and K_T values, it can be known that physical adsorption is the main adsorption method for carbamazepine by the four activated carbon samples.

Table 4 Fitting Parameters of Intraparticle Diffusion Mode

Table 5 Fitting Parameters of the Dynamic Mode

By fitting our experimental data to these models, we quantitatively analyzed the rate and extent of CBZ adsorption on both unmodified and NH₃-CVD modified activated carbon. Figure 7 in our study illustrates this fitting, showcasing diagrams of the kinetic adsorption of CBZ. These diagrams provide a comparative visual representation of the adsorption behavior before and after the modification, highlighting the differences in adsorption kinetics and capacities brought about by the NH₃-CVD process.

Figure 7 (A) Dynamics fitting of quasi-first-order; (B) Dynamics fitting of quasi-second-order.

Table 5 outlines the parameters derived from the kinetic analysis of CBZ adsorption on activated carbon. These parameters were calculated from the slope and intercept obtained from the linear equations fitted using the quasi-first-order and quasi-second-order dynamic models. Notably, the saturated adsorption capacity values, as determined by the quasi-first-order kinetics, closely align with the actual measured values. This is further supported by the high correlation coefficients (R₁)², all exceeding 0.987. Such strong linear correlation indicates that the quasi-first-order kinetic model fitting is robust and reliable.

Furthermore, the consistency of these results with the theoretical expectations of the model suggests that the adsorption behavior in our system is predominantly characterized by single-layer adsorption.²⁷ This finding is crucial for understanding the mechanism of CBZ adsorption on activated carbon, particularly in highlighting the efficiency and nature of the adsorption process post-NH₃-CVD modification.

Isothermal Adsorption Experiment

In our investigation, we explored how the adsorption capacity of activated carbon samples varied in CBZ solutions with different initial concentrations, keeping the volume of the CBZ solution and the mass of the activated carbon sample constant.

As demonstrated in Figure 8, a notable trend was observed. When the initial CBZ concentration was below 50 mg/L, the adsorption capacity (qe value) of the activated carbon increased significantly with the rising concentration of CBZ. However, beyond this concentration threshold (above 50 mg/L), the increase in adsorption capacity plateaued, showing no substantial rise with further increases in CBZ concentration.

Figure 8 Isothermal adsorption curve of wood-based activated carbon.

This phenomenon can be explained by the limited number of available adsorption sites on the activated carbon. At lower drug concentrations, the number of CBZ molecules per unit volume of the solution is the primary factor influencing the adsorption capacity. Yet, as the concentration reaches and exceeds 50 mg/L, each adsorption site becomes surrounded by sufficient CBZ molecules for adsorption. Consequently, beyond this concentration, the number of adsorption sites becomes the limiting factor, not the concentration of the drug in the solution.²⁸ Hence, even with continued increases in CBZ concentration, the adsorption capacity of the activated carbon does not show significant enhancement.

To further clarify the adsorption mechanism of CBZ on wood activated carbon, Langmuir and Freundlich mathematical models were used to fit the adsorption behavior. Langmuir model: assume that the adsorption process occurs on a uniform surface.^27–29 and its linear form is as follows:

Langmuir model: 1/q_e=1/q_m+1/(q_mC_eK_L) (6)

The adsorption fitting figure is shown in Figure 9A, where K_L is the fitting constant of Langmuir model, C_e is the equilibrium concentration (mg/L), q_e is the adsorption amount at equilibrium (mg/g), and q_m is the theoretical maximum adsorption amount (mg/g). (R_L)² is the correlation coefficient of the fitting.

Figure 9 Fitting diagram of Langmuir (A) and Freundlich (B) models.

Figure 10 Infrared detection results (W-7x: Sample W-7 saturated adsorption of CBZ).

Freundlich model: Assuming that the adsorption behavior occurs on the non-uniform surface, the adsorption situation depends on the distribution of active sites and exponential energy on the carbon surface, and its linear form is as follows:²⁴

Freundlich model: Inq_e=InK_F+(InC_e)1/n (7)

Where k_F is Freundlich constant (heterogeneous factor),n value is related to adsorption affinity. (R_F)² is the correlation coefficient of the fitting. When 1 < n < 10 indicates that the adsorption effect is good, indicating that the adsorption equilibrium tends to the occurrence of adsorption behavior.³⁰ In Figure 9B, the parameters k_F and n can be calculated by the intercept and slope of the fitting curve.

In Table 6, the Langmuir model fitting correlation coefficient (R_L)² ranges from 0.947 to 0.995, while the Freundlich model yields correlation coefficients (R_F)² between 0.917 and 0.952. Therefore, the Langmuir model exhibits a superior goodness of fit. However, it is noteworthy that there exists a substantial deviation between the maximum adsorption capacity q_m obtained from Langmuir fitting and the actual value q_e. Considering relevant reports,³¹ we conclude that the Freundlich model aligns better with the isothermal curve study.

Table 6 Fitting Parameters of Langmuir and Freundlich Models

In the Freundlich fitting results, n values greater than 1 and less than 10 indicate that the adsorption of CBZ by wood activated carbon is a favorable removal process occurring on heterogeneous surfaces.

Experimental Results of Infrared Detection

Figure 10 displays the infrared spectrum scanning results of W-0, W-7, and W-7X samples, with sample W-7X obtained through saturated adsorption of CBZ on sample W-7. Analyzing the results in conjunction with the XPS analysis, the wide peak signal in the wavenumber range of 3700 to 3000 is attributed to N-H and O-H stretching vibration. Notably, in the figure, the signal at 3430 for W-7X is significantly stronger than that of the other two samples and is even comparable to the signal at wavenumber 1000 for W-7X.

As mentioned before, the doping of nitrogen elements on the surface of activated carbon is beneficial for the formation of intermolecular hydrogen bonds with carbamazepine molecules. Based on relevant reports, the peak range of infrared spectra for intermolecular hydrogen bonding falls within the interval (3550–3400), the presence of hydrogen bonds significantly enhances the infrared absorption in this region.^32,33 This observation implies that there are numerous intermolecular hydrogen bonds in the W-7X samples. These results provide further evidence that the formation of intermolecular hydrogen bonds is a crucial factor contributing to the effective adsorption of CBZ on wood activated carbon.

Conclusion and Discussion

This study demonstrates that NH₃-CVD modification significantly enhances the adsorption performance of wood activated carbon for carbamazepine (CBZ). The modification increases the micropore volume, crucial for small molecule drug adsorption. Furthermore, the increased nitrogen content on the activated carbon surface, particularly in the form of pyridine and pyrrole nitrogen, facilitates hydrogen bonding with CBZ, enhancing adsorption. This explains why W-7, despite having a smaller surface area and micropore volume than W-6, shows greater CBZ adsorption capacity. Kinetic adsorption experiments align well with the quasi-first-order kinetic model; among the isothermal adsorption models, the Freundlich model accurately reflects CBZ adsorption on wood activated carbon, suggesting that CBZ adsorption on wood activated carbon is a single-layer process on heterogeneous surfaces.

The introduction of nitrogen into activated carbon has been a focus in recent research, It does not damage the structural stability of activated carbon but enhancing adsorption properties. The present study has demonstrated that NH₃-CVD modified wood activated carbon can significantly enhance the adsorption capacity of activated carbon for CBZ; and the potential applications of this new type of adsorbent material in the fields of environmental protection and medical have been effectively explored before the improvement of blood compatibility studies.