Sustainable Removal of Phenol from Aqueous Media by Activated Carbon Valorized from Polyethyleneterephthalate (PET) Plastic Waste

Abstract

PET, one of the most commonly used plastics, presents significant environmental challenges due to its non-biodegradable nature. To address this, we developed a sustainable method to convert PET waste into high-performance activated carbon via chemical activation with phosphoric acid (H₃PO₄). The produced activated carbon was analyzed utilizing X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), nitrogen adsorption/desorption (BET), energy-dispersive X-ray (EDX), and Raman spectroscopy. The activated carbon produced had a macroporous architecture with a substantial surface area, pore diameter, and pore volume of 655.59 m²/g, 3.389 nm, and 0.120 cm³/g, respectively. The adsorption isotherm of activated carbon for phenol conformed to the Langmuir model, signifying single-layer adsorption with a maximal capacity of 114.94 mg/g, while the kinetic adsorption adhered to the second-order model at an optimal pH of 7. The study highlights the sustainable benefits of mitigating plastic waste pollution while producing a cost-effective and eco-friendly adsorbent for water treatment applications. This research underscores the potential for recycling PET waste into valuable materials for environmental remediation.

1. Introduction

Phenol is a naturally occurring chemical compound that is a white crystalline solid at ambient temperature. Phenol pollution in water is a significant environmental concern because of the toxicity of phenolic substances, which can harm aquatic ecosystems and human health. Phenols are organic compounds often introduced into water bodies through industrial activities such as petroleum refining [1], chemical manufacturing [2], pulp and paper production [3], and coal processing [4]. Phenols can also be found in pesticides [5], disinfectants [6], and pharmaceutical products [7]. Phenolic chemicals alter water’s color, taste, and odor, lowering its quality and rendering it unfit for human ingestion or other uses [8]. High or low phenol levels in aquatic environments can harm fish, algae, and other microbes [9]. Saha’s study reveals that phenol concentrations of 2.85 and 4.11 mg/L severely harm aquatic ecosystems, with phytoplankton affected even at 1.26 mg/L [10]. Weiyan Duan’s study shows phenol has toxic effects on four marine microalgae, with 96 h EC₅₀ values of 72.29, 92.97, 27.32, and 27.32 mg/L [11]. Human health risks include drinking or coming into contact with phenol-contaminated water, which can lead to various health problems. Short-term exposure may result in skin irritation, while long-term exposure can cause more severe effects, such as liver and kidney damage [12,13]. Some phenolic compounds are classified as possible carcinogens, raising concerns about long-term health risks [14,15]. According to the recommendations of WHO, the maximum amount of phenol that can be found in drinking water should not surpass 1 μg/L [16,17].

Treating phenol-contaminated water involves several methods to remove or degrade phenolic compounds to safe levels. The most common techniques include chemical oxidation [18], adsorption [19,20,21], biological treatment [18,22], advanced oxidation processes (AOPs) [23,24], membrane filtration [25,26], and electrochemical treatment [27,28]. The choice of each method depends on the phenol concentration, water quality, and treatment goals. Adsorption, with its high efficiency, adaptability, ease of design and operation, selective adsorbents, lack of harmful byproducts, regeneration of adsorbents, and cost-effectiveness, plays a crucial role in treating phenol in water. This method is widely used in water treatment applications, especially when environmental safety and high efficiency are priorities. The adsorption of 4-chlorophenol, phenol, and 4-cresol on carbon black, activated coke, and activated tire pyrolysis char was unaffected by ionic strength, with equilibrium reached in 2–3 h [21]. With a 2 g/L adsorbent dose, 150 mg/L starting concentration, and 90 min mixing time, Upendra’s research on phenol adsorption onto Saccharum officinarum biomass-activated carbon produced a maximum capacity of 64.59 mg/g [29]. Mojoudi’s investigation developed efficient activated carbon from oily sludge, achieving a maximal adsorption ability of 434 mg/g, which reached equilibrium in 30 min at an optimal pH of 6.0 [19]. Coal-derived powdered activated carbon, i.e., PAC800 and PAC1000, was used to treat phenolic wastewater, achieving the maximum adsorption capacities of 176.58 mg/g and 212.96 mg/g, respectively [30]. Studies have demonstrated that activated carbon serves as an extremely successful and commercially viable method for the phenol removal from wastewater, with ongoing advancements focused on enhancing efficiency, sustainability, and cost-effectiveness.

Activated carbon, or activated charcoal, is a highly porous carbon variant with an extensive surface area specifically designed to adsorb impurities from liquids or gasses. Its high adsorptive capacity and wide range of applications make it an essential material in various industries, particularly for purification and filtration processes. Activated carbon is produced from raw carbon-rich materials by enhancing their porosity and surface area. Typical raw materials include coal [30], wood [31], coconut shells [32], peat [33], sawdust [34], agricultural residues [35,36], and industrial waste [19,37]. The choice of material affects the properties of the final activated carbon, such as adsorption capacity, pore structure, and surface area. Activated carbon from plastic is an innovative approach to repurpose plastic waste into valuable materials with high adsorption capacities. This process converts plastic waste, a significant environmental concern, into activated carbon through carbonization and activation steps. The resulting activated carbon can be used for various applications, such as wastewater treatment, gas purification, and air filtration. The plastic waste could be recycled into many useful products [38,39]. Common types of plastic waste that can be used for the preparation of activated carbon include polyethylene (PE) [40,41], polypropylene (PP) [42,43], polystyrene (PS) [44], and other non-recyclable plastics [42,45]. Producing activated carbon from plastic usually involves two main stages: pyrolysis (carbonization) and activation. To our knowledge, there is scant literature on the synthesis of activated carbon from PET waste specifically for phenol removal from aqueous solutions. These studies include physical activation [46,47], chemical activation with KOH [48] and HNO₃ [49], and E Lorenc’s preparation of activated carbon using a mixture (1:1 w/w) of PET and coal-tar pitch under steam and CO₂ as activation agents at 800 °C [50].

This research concentrates on the synthesis of activated carbon with a large surface area derived from PET waste through chemical activation using H₃PO₄. The activated carbon adsorbent is utilized for the phenol removal from aqueous media, and a comprehensive characterization of its properties and adsorption behavior is conducted.

2. Experimental Section

2.1. Materials

Plastic bottles used to hold mineral water are a major source of PET plastic, which is used to make activated carbon. The plastic bottles were divided into tiny bits, roughly 0.5 to 1 mm, after being cleaned with water and dried in an oven. Chemical agents, such as 85% H₃PO₄, 99% KOH, 99% HCl, and 99% phenol, were acquired from Supelco (Darmstadt, Germany) and Xilong Chemical Company (Shantou, China). Every procedure utilized in the experiments used distilled water. Without any additional purification, all the substances were used just as they were received.

2.2. Preparation of Activated Carbon (AC)

A 30 g quantity of PET resin was added into a 250 mL glass cup containing 20 mL of H₃PO₄ solution, stirred magnetically, and heated at 60–70 °C for 5 h (which was optimized in our previous study). After that, the PET plastic was taken out and added into a drying oven at 120 °C for 8 h. After being impregnated with H₃PO₄, a ceramic bowl filled with PET resin was inserted inside a tube furnace. The calcination process was set up as follows: A 100 mL/min flow of N₂ gas was directed through the furnace tube to create an inert gas environment. Heating was performed in two steps at low and high temperatures corresponding to the charring and activation processes. The carbonization process was conducted at 400 °C for one hour at a 10 °C/min heating rate. After that, the temperature was raised to 800 °C for another hour. The furnace’s temperature was allowed to drop to room temperature after calcination. The charcoal sample was finely ground, filtered, and washed with water to create a neutral environment, and the sample was dried to obtain activated carbon. The preparation process of the activated carbon from PET plastic waste is shown in Figure 1.

2.3. The Point of Zero Charge (pHpzc)

The pH at the point of zero charge (pH_pzc) of the activated carbon was determined using the typical “drift method”, as described in Reference [51]. In summary, 0.05 g of the adsorbent was added into a series of flasks containing 25 mL NaCl solution (0.1 M) with different initial pH values (pH_i = 3, 5, 7, 9, 11). The flasks were shaken at 100 rpm at room temperature for 24 h. Then, the final pH value (pH_f) was measured. Finally, the pH_pzc value was estimated by plotting the ∆pH (pH_i-pH_f) against the pH_i. It should be emphasized that the pH_i of NaCl solution was changed using a 0.1 M solution of HCl or NaOH, and all pH_pzc experiments were carried out at room temperature.

2.4. Phenol Adsorption

In each adsorption investigation, batches of activated carbon were utilized as the adsorbent. A 0.5 g quantity of phenol was solubilized in 0.5 L of distilled water to prepare a stock solution. In a standard experiment, 250 mL flasks, each containing 50 mL of phenol solutions, were filled with a specified quantity of adsorbent (0.02 g of activated carbon), and the flasks were agitated at 100 rpm for 120 min at ambient temperature. All factors affecting phenol adsorption were analyzed. Independent tests involved batch studies varying solution pH (3–11), contact time (0–70 min at an initial phenol concentration of 30 mg/L), and phenol concentration (20–100 mg/L). The adsorption experiments were repeated three times. After adsorption, phenol solutions underwent centrifugation for 15 min at 5000 rpm. The absorbance wavelength of 270 nm was recorded utilizing an Agilent 8453 (Santa Clara, CA, USA) UV-Vis spectrometer.

The following formulation was used to determine the adsorption capacity (q_e, mg/g):

$$q_e={\displaystyle \frac{({\mathrm{C}}_0-C_e).V}{m}}$$

(1)

where C₀ (mg/L) is the initial content of phenol, C_e (mg/L) is the phenol’s concentration at equilibrium, V (L) is the volume of the phenol solution, and m (g) signifies the mass of activated carbon.

Phenol removal percentages (H, %) were determined using Equation (2).

$$H={\displaystyle \frac{({\mathrm{C}}_0-C_e).100}{C_o}}$$

(2)

2.5. Characterizations

Activated carbon’s crystal structure was examined by means of X-ray diffraction (XRD) using a Cu Kα radiation source (0.154 nm) and a D8-advance Bruker apparatus. The morphology of the adsorbent was assessed via scanning electron microscopy (SEM) utilizing Hitachi S-4600, equipped with an energy-dispersive detector for elemental analysis. The vibrational frequencies of the bonds in the activated carbon structure were determined using FT-IR spectroscopy on Bruker Tensor II, throughout a range of 400 cm⁻¹ to 4000 cm⁻¹. The surface area and porosity were assessed utilizing the N₂ adsorption/desorption method with the NOVA Touch 2LX/Quantachrome apparatus (Anton Paar QuantaTec Inc., Torrance, CA, USA). Raman spectra were obtained from the activated carbon utilizing a DXR3 Raman Microscope from Thermo Scientific (Waltham, MA, USA).

3. Results and Discussion

3.1. Characterizations of Activated Carbon

The structural characterization of the prepared AC was conducted using the XRD method, with the results presented in Figure 2a. The XRD pattern shows the peaks at 2θ = 26.42°, 42.36°, and 54.51° corresponding to the (002), (100), and (004) crystal planes that characterize the hexagonal structure graphite phase (PDF card 00-008-0415). The peaks are observed, indicating the amorphous characteristics of activated carbon [52]. In addition, as can be seen in the XRD pattern, two distinct sharp peaks appear at position 2θ = 14.84° and 22.76° that correspond to the (110) and (120) crystal planes, which characterize the carbon phase with a hexagonal structure (PDF card 00-050-0926). The presence of sharp peaks is attributed to residual ash in the activated carbon. The results validate the effective synthesis of activated carbon from plastic waste.

The results of the N₂ adsorption/desorption isotherm analysis and the pore size distribution of the activated carbon are illustrated in Figure 2b. According to Figure 2b, the N₂ adsorption/desorption isotherm curve shape of activated carbon is of type II according to UIPAC’s classification, which denotes a material with large capillaries (macroporous) and a hysteresis loop of type H3 and a flexible sheet-shaped material [53]. The BET surface area, diameter of pore, and pore volume of activated carbon are 655.59 m²/g, 3.389 nm, and 0.120 cm³/g, respectively.

The activated carbon’s morphology was analyzed using SEM imaging, as illustrated in Figure 2c,d. Activated carbon is evidently made up of sheet-shaped agglomerates that feature a smooth surface, with large macropores forming in between. The carbon surface, characterized by numerous pores, can enhance and facilitate the adsorption of detrimental organic pollutants.

The elemental analysis of activated carbon utilizing energy-dispersive X-ray spectroscopic technique is depicted in Figure 3a. The EDX spectra exhibit the distinct peaks corresponding to the elements C, P, and O. The appearance of C comes from the original PET plastic material (accounting for a percentage in terms of mass and most atoms). The appearance of P and O comes from the activator, H₃PO₄ acid (accounting for 1.87% and 9.06%). The EDX analysis results validated the existence of the elements in the initial material expected to be synthesized and showed the activation ability of H₃PO₄ acid.

The bonding structure of the prepared activated carbon was thoroughly examined through Raman spectra analysis, as illustrated in Figure 3b. The Raman spectra reveal two absorption bands characteristic of graphitic structure, positioned at 1336 cm⁻¹ (the D peak) and 1588 cm⁻¹ (the G peak). The G peak corresponds to the E_2g symmetry, arising from the in-plane vibrations of sp²-bonded carbon atoms. The D peak represents a breathing mode characterized by A_1g symmetry, which involves out-of-plane vibrations linked to the existence of structural defects [54,55]. Furthermore, as illustrated in Figure 3b, the strength of the D peak surpasses the value of the G peak, suggesting a disruption of sp² bonds and an increase in sp³ bonds, along with a transition from sp² to sp³ material. Consequently, these findings indicate that the activated carbon mainly comprised graphitic structures, with sp³ hybridization being the dominant form, aligning perfectly with the previously discussed XRD results.

The surface chemical characteristics of the synthesized AC were examined using the FT-IR spectral analysis, as illustrated in Figure 3c. The 3595 cm⁻¹ and 3452 cm⁻¹ peaks are ascribed to the O-H group bands, resulting from the band of water molecules [30,56]. The high-intensity stretching at 2360 cm⁻¹ is ascribed to C=C groups [19]. The band at 1018 cm⁻¹ is attributed to the C-O stretching vibration in heterocyclic rings [57,58]. The peak at 675 cm⁻¹ is attributed to the C-H out-of-plane band [19,56].

The adsorption characteristics of materials are influenced by their surface properties. The point zero charge (pH_pzc), commonly referred to as the isoelectric point (IEP), represents an essential characteristic quantity in this context. The pH value at which the material’s surface does not manifest a net electric charge is denoted here. pH_pzc influences the adsorption behavior of materials by facilitating interactions between the functional groups present on their surfaces and the adsorbates. The pH_pzc of the prepared activated carbon, as illustrated in Figure 3d, is determined to be 8.56. The activated carbon surface is charged positively when the solution pH is less than 8.56. In contrast, the surface will exhibit a negative charge when the pH solution exceeds 8.56 [59].

3.2. Phenol Adsorption

The adsorption behavior of pollutants on adsorbents in aqueous solutions is greatly affected by the pH solution. The findings of the study on how solution pH affects phenol adsorption by the produced activated carbon across various pH levels of 3 to 11 are shown in Figure 4.

Experimental data show that pH significantly affects the adsorption behavior of phenol by activated carbon. In the pH range of 5 to 9, phenol elimination efficacy is stable. The elimination effectiveness is much reduced at pH 3 and 11. The pH dependence of phenol adsorption regulated the surface charge of activated carbon and the form of phenol in the solution. Due to its known pK_a value of 9.99, phenol is regarded as a neutral molecule below this pH and as a phenolate anionic beyond this value [16]. Hence, the activated carbon’s negative surface and phenolate anions (C₆H₅O⁻) resist one other at pH 11 (solution pH > pH_pzc), and the adsorption yields decrease significantly. The positively charged adsorbent surface attracts phenolate anions at pH values below 9 (solution pH < pH_pzc), increasing the adsorption yield. A low pH of 3 introduces additional protons, which compete with phenol for activated carbon carbonyl sites. Thus, the phenol adsorption yield is only 75.43% at this pH. In their study, Soeyink et al. discovered that both low and high pH values were detrimental to phenol adsorption [60]. Subsequent studies have identified that the optimal pH for phenol removal using various forms of activated carbon is approximately 7 [19,30,58]. And phenol molecules adsorbed onto activated carbon at this pH level are neutral and not phenolate anions [16]. Therefore, in the next adsorption investigation, pH 7 was selected as the optimal value.

Adsorption kinetics, which examines the mechanisms of the adsorption process, is an essential aspect of adsorption studies. This study employed intra-particle diffusion and pseudo-first- and pseudo-second-order kinetic models to examine the processes and rate-controlling stages of the adsorption process. These models’ linear equations are provided as follows [61]:

$$\log (q_e-q_t)=\log q_e-{\displaystyle \frac{k_1}{2.303}}t$$

(3)

$${\displaystyle \frac{t}{q_t}}={\displaystyle \frac{1}{k_2{q}_e^2}}+{\displaystyle \frac{1}{q_e}}t$$

(4)

$$q_t=k_{id}{t}^{0.5}+C$$

(5)

The rate constants for pseudo-first-order adsorption (k₁ in L/min), pseudo-second-order adsorption (k₂ in mg/g.min), and intra-particle diffusion (k_id) are denoted by the variables q_t (mg/g) and q_e (mg/g), which are the quantities of phenol adsorbed on the substrate at time t and at equilibrium, respectively, while C (mg/g) signifies the velocity constant of intra-particle diffusion.

Figure 5 illustrates the linear adsorption kinetic graphs, while

Table 1. The kinetic parameters of prepared activated carbon for phenol adsorption.

Pseudo-First-Order			Pseudo-Second-Order				Intra-Particle Diffusion
qe (mg/g)	k1 (L/min)	R2	qexp. (mg/g)	qcal. (mg/g)	k2 (mg/g.min)	R2	Kid	C	R2
148.90	0.127	0.838	65.296	70.923	0.003	0.998	3.995	36.137	0.884

presents the associated fitting parameters for the experimental data.

Figure 5a depicts the effect of adsorption time and the adsorption kinetics on the adsorption performance of phenol by activated carbon. The results show that phenol concentration decreased significantly within the initial 50 min and nearly attained equilibrium after an extended contact duration. The explanation for this phenomenon is that the higher surface area of the prepared activated carbon with functional groups, numerous macrospores, and numerous unoccupied surface sites of activated carbon are favorable for the first stage of adsorption [30].

The correlation coefficients for the second-order model (R² = 0.998) surpass those for the first-order model (R² = 0.838) and the intra-particle diffusion model (R² = 0.884), according to the parameters associated with kinetics shown in Table 1. Additionally, there was a more noticeable discrepancy between the observed value of adsorption capacity (q_exp.) and the computed value (q_cal.) determined from the pseudo-first-order model, in contrast to the second-order kinetic model. This demonstrated that the pseudo-second-order model effectively characterized the adsorption, with chemisorption governing the phenol adsorption process [62]. Furthermore, the results in Figure 5d indicate that the linear relationship of q^t vs. t^0.5 does not pass through the origin. This indicates that the intra-particle diffusion had no discernible impact on the adsorption [61]. The adsorption of phenol onto activated carbon is characterized by its electronic structure, primarily involving sp² orbitals. Thus, it can be inferred that the adsorption mechanism in this system is attributed to the π-π interactions between the surface of carbon and the aromatic chains of phenol [16].

The adsorption isotherm evaluates the sorption mechanism and forecasts the maximum quantity of phenol that can be adsorbed onto the synthesized activated carbon. This study employed linearized isotherm models, specifically the Langmuir and Freundlich models, to suit the sorption process. Equations (6) and (7) show the models in their linearized forms [61]:

$${\displaystyle \frac{C_e}{q_e}}={\displaystyle \frac{1}{q_m}}{C}_e+{\displaystyle \frac{1}{q_m{K}_L}}$$

(6)

$${\mathrm{logq}}_e={\displaystyle \frac{1}{n}}{\mathrm{logC}}_e+\log K_F$$

(7)

The constants q_m, q_e, K_L, C_e, and K_F are the maximum capacity, equilibrium adsorption capacity, Langmuir constant, equilibrium phenol concentration, and Freundlich constant, respectively, determined in mg/g, L/mg, and mg/g. The heterogeneity factor is denoted by n, where 0 < n < 10.

A nondimensional constant called the equilibrium parameter or separation factor, the term “R_L”, is a crucial component of the Langmuir isotherm model. It is depicted by the equation below:

$$R_L={\displaystyle \frac{1}{1+K_L.C_0}}$$

(8)

Important information regarding the adsorbent–adsorbate compatibility is provided by the R_L parameter. For R_L to be advantageous, the adsorption process must fall within the range of 0 to 1. If R_L > 1, the adsorption is deemed unfavorable. An R_L value of 1 signifies a linear relationship in adsorption, while an R_L of 0 indicates that the adsorption is irreversible.

Table 2. Adsorption isotherm parameters of phenol adsorption on prepared AC.

	Langmuir Model				Freundlich Model
	qm (mg/g)	KL (L/mg)	RL	R2	KF ((mg/g) × (L/mg)1/n)	n	R2
Phenol	114.94	0.234	0.042–0.189	0.989	38.770	3.748	0.973

details the adsorption isotherm parameters, and Figure 6b,c show the representations of data from experiments generated from the Freundlich and Langmuir models.

Figure 6a shows how the generated activated material’s adsorption performance was affected by the starting phenol concentration. Figure 1 shows that sorption capacity increased from 42.13 mg/g to 109.77 mg/g, but removal percentage decreased from 91.90% to 44.83% when the starting phenol level increased from 18 mg/L to 100 mg/L. These effects occur because, for lower values of C₀, the ratio of the initial quantity of phenol molecules to the accessible surface area of the activated material is low, which leads to these consequences. In this instance, the adsorption is independent of the C₀ value; hence, an increased quantity of phenol molecules is adsorbed in the solution. A greater mass gradient between the adsorbent and the solution at elevated C₀ values facilitates the absorption of additional phenol molecules onto the adsorbent surface, resulting in enhanced adsorption capacity (q_e). There are fewer adsorption sites since the initial phenol molecules-to-accessible surface area ratio is large, which causes them to be saturated quickly. As a result, the adsorption rate drops, and there are more phenol molecules in the solution at the equilibrium concentration.

Table 2 displays the adsorption isotherm parameters; comparing the Freundlich and Langmuir models reveals that the former gives a better match to the data, with the former having a regression coefficient of R² = 0.989 and the latter of R² = 0.973. According to the Langmuir constant values (K_L), which fall within the range of 0.042 to 0.189 (0 < R_L < 1), the adsorption of phenol onto activated carbon is advantageous. According to the Langmuir model, a homogeneous adsorbent surface is indicated by the fact that phenol adsorption on activated carbon happens in a monolayer. When compared to values published in other investigations, the adsorption maximal (q_m) of 114.94 mg/g was found (

Table 3. The comparison of the maximum capacity for phenol adsorption with that of other adsorbents.

Adsorbents	Adsorption Capacity (mg/g)	Reference
Multiwalled carbon nanotubes	25.38	[16]
Activated carbon fibers	102.47	[63]
Activated carbon prepared from coconut shells	49.87	[64]
Activated carbon prepared from PET	117.63	[65]
Activated carbon prepared from Saccharum officinarum biomass	64.59	[29]
Coal-derived powdered activated carbon	176.58	[30]
Activated carbon from olive stone	120	[66]
Activated carbon from PET	114.94	This study

). Compared to previous studies, this study found a higher adsorption capability.

The properties of the activated carbon after phenol adsorption were analyzed using the SEM image and BET surface area. The results are shown in Figure 7. It can be obvious from Figure 7a that activated carbon retained a smooth surface, with large macropores formed on the pristine activated carbon. The surface area of activated carbon after phenol adsorption was determined to be about 603.19 m²/g, which was negligibly lower than that of the pristine activated carbon. These results indicate that the activated carbon prepared from plastic waste is durable for many cycles of phenol adsorption.

From the above results and literature, the adsorption mechanism of activated carbon from PET plastic waste is explained as follows: the adsorption of phenol onto activated carbon is likely driven by a combination of physical and chemical interactions. The high surface area and porous structure of activated carbon provide abundant sites for physical adsorption through Van der Waals forces. π-π interactions occur between the aromatic rings of phenol and the carbon’s graphitic surface [67]. Hydrogen bonding is facilitated by oxygen-containing functional groups on the carbon and the hydroxyl group of phenol [68]. Electrostatic interactions depend on pH and surface charge, while hydrophobic interactions enhance phenol affinity [19].

4. Conclusions

In short, this study successfully carbonized PET plastic trash at 400 °C and activated it at 800 °C using H₃PO₄ as an activator. The result was activated carbon. The activated carbon that was synthesized showed a large surface area of 655.59 m²/g, a sizable pore volume of 0.120 cm³/g, and a pore diameter of 3.389 nm. A solution pH of 7 proved optimal for the fast phenol adsorption by the synthetic activated carbon.

The Langmuir model was closely followed by the isotherm adsorption of phenol on activated carbon, signifying adsorption on a single layer with a maximum capacity of 114.94 mg/g. The pseudo-second-order model successfully predicted the kinetic data, showing that chemisorption governed phenol adsorption. The research results indicated that activated carbon made of PET might operate as a promising adsorbent for the removal of phenol in contaminated water.