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Article

Performance of Powdered Activated Coke Produced by One-Step Rapid Process from Lignite: Phenol Adsorption from Synthetic Wastewater and Hydrothermal Regeneration

by
Guifang Chen
1,*,†,
Hao Xu
2,†,
Shouyan Chen
1 and
Dachuan Zhao
3
1
National Engineering Laboratory for Reducing Emissions from Coal Combustion, Engineering Research Center of Environmental Thermal Technology, Ministry of Education, Shandong Key Laboratory of Energy Carbon Reduction and Resource Utilization, School of Energy and Power Engineering, Shandong University, Jinan 250061, China
2
National Energy Weizhen (Shandong) Test and Analysis Co., Ltd., Jinan 250061, China
3
School of Environmental Science and Engineering, Shandong University, Qingdao 266237, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Water 2025, 17(8), 1161; https://doi.org/10.3390/w17081161
Submission received: 19 February 2025 / Revised: 10 April 2025 / Accepted: 11 April 2025 / Published: 13 April 2025
(This article belongs to the Special Issue Adsorption Technologies in Wastewater Treatment Processes)
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Abstract

:
Low-cost powdered activated coke (PAC) produced by a one-step rapid method with lignite was used as an adsorbent for the advanced treatment of phenol-containing wastewater to evaluate the feasibility of replacing high-cost commercial powdered activated carbon. Characterization using infrared spectral analysis, SEM, and BET showed that the PAC mesopores were well developed. PAC exhibited a high adsorption performance for phenol in static experiments. The adsorption was almost in equilibrium within 20 min, and the removal efficiency reached 85.4% with 1.5 g L−1 PAC and 99.9% with 4 g L−1 PAC. As common components in wastewater, NaCl and Na2SO4 did not exhibit significant competitive adsorption with phenol in PAC. The adsorption process occurred in accordance with the Langmuir model and the pseudo-second order kinetic model. Furthermore, the effects of hydrothermal regeneration on PAC adsorbing phenol were studied, and the adsorption capacity of PAC after five regeneration cycles was 86.1% of that of the new PAC, which still had good adsorption performance. PAC offers significant advantages in terms of adsorption capacity, economic feasibility, regeneration, and recycling, providing a practical solution to the problem of phenol-containing wastewater pollution.

1. Introduction

With the implementation of increasingly strict discharge standards, advanced treatment is necessary to further reduce the concentration of pollutants in wastewater. Several advanced wastewater treatment methods have been developed, including Fenton oxidation [1], electrochemical oxidation [2,3], biochemical methods [4], adsorption [5,6], and membrane separation [7]. Among these, adsorption is considered one of the most appropriate methods for treating wastewater because it effectively removes multiple pollutants simultaneously and is simple to operate. However, the selection of an adsorbent is the core issue in this process [5,6,8]. Powdered activated carbon, with its well-developed pore structure and large specific surface area, is suitable for the adsorption of pollutants from wastewater [9,10]. However, the high cost of commercial powdered activated carbon limits its large-scale application. In addition to high raw material prices, the main reason for the high price of current commercial powdered activated carbon is its complicated production process, which requires a long production chain, including carbonization, cooling, and activation. High temperatures are required for both carbonization and activation, which are completed using different equipment, and a significant amount of energy is wasted during the transfer process.
The research team of the author developed a one-step rapid method to produce low-cost powdered activated coke (PAC) with lignite [11,12,13]. Carbonization and activation were performed in the same device during the one-step method to avoid heat loss. PAC prepared by our team, which has similar adsorption properties to powdered activated carbon, such as economic durability, rich surface functional groups, large specific surface area, and more developed pore structure [14,15], demonstrated good adsorption capacity for NOx and SO2 in exhaust gas pollutants [16,17]. Compared to powdered activated carbon, PAC has a well-developed pore structure with more meso- and macropores, which is more suitable for adsorbing macromolecular organic compounds in wastewater [18]. The objective of this study was to explore the effectiveness of PAC as a low-cost adsorbent for the removal of organic compounds from wastewater. The powdered activated coke (PAC) used in this study was prepared from low-rank lignite coal using a one-step process of carbonization and activation, which greatly simplified the production process and reduced the cost to one-third that of commercial powdered activated carbon. However, the treatment of wasted activated carbon and PAC is difficult and expensive, which restricts the wide application of commercial powdered activated carbon and PAC. Effective regeneration is important. The PAC adsorbing pollutants from wastewater contained high water content, leading to high energy consumption using traditional thermal regeneration [19]. Hydrothermal regeneration involves placing adsorption-saturated waste activated coke in a water environment, and under a certain temperature, pressure, and atmosphere, the desorption of adsorbent on the activated coke is realized by using the special properties of subcritical/supercritical water. This method has a high regeneration efficiency and can realize the decomposition and oxidative degradation of adsorbed macromolecules of organic matter, which is applicable to the regeneration of powdered activated coke in the field of wastewater treatment [20,21]. Hydrothermal regeneration occurs in water at lower temperatures, which can avoid energy and carbon loss [22,23]. However, the effect of hydrothermal regeneration on wasted PAC is not clear.
Due to its high toxicity, difficult treatment, and wide distribution in wastewater, phenol was selected as the typical organic pollutant in this paper. The influences of adsorption time, particle size, pH, temperature, initial phenol concentration, dose, and inorganic salt competitive adsorption for phenol removal with PAC were investigated, and the effect of hydrothermal regeneration of wasted PAC was studied. The optimal adsorption and regeneration conditions, adsorption kinetics, and adsorption thermodynamic models were demonstrated, providing basic data for seeking low-cost adsorbents for phenol.

2. Experimental Procedure

2.1. Materials

Analytically pure phenol, sodium hydroxide, sodium chloride, sodium sulfate, and concentrated hydrochloric acid were supplied by Sinopharm Chemical Reagent Co. Commercially activated carbon produced from coconut shells was purchased from Shandong Nanke Activated Carbon Co. The apparatus and equipment employed in the experiment are listed in Table 1.

2.2. Experimental Method

2.2.1. Preparation of PAC

Figure 1 shows the complete flow schematic of the experiment. The PAC used in this experiment was prepared from lignite coal. During the one-step method of charring activation, O2/CO2/H2O was used as the reaction atmosphere. The specific preparation method for PAC has been described in the literature [11,12,13].
The prepared PAC was then washed repeatedly with ultrapure water (resistivity ≥ 18 MΩ-cm) to remove surface dust until the ultrapure water was visibly clear. Further, PAC was dried in a constant temperature oven at 104 °C for 24 h, then cooled and removed for further analysis.
The dried PAC was crushed and passed through a standard sieve with different pore sizes to obtain PACs with particle sizes of 1180~1400 μm, 590~710 μm, 297~350 μm, 124~150 μm, 74~89 μm, and <61 μm.
The specific information on granular bioactivated carbon, powdered living activated carbon, and PAC used in the experiment is shown in Table 2.

2.2.2. Characterization

Several instruments were used to analyze PAC with a particle size of less than 61 μm after sieving. The particle size of the activated coke was measured using a laser particle size meter (Beckman, LS13320). The specific surface area and pore structure were determined through Brunauer-Emmett-Teller (BET) analysis using an N2 adsorption meter (Quantachrome, Autosorb IQ) via nitrogen adsorption at 77 K FTIR spectra were obtained using a Fourier-transform infrared spectrometer (Thermo Fisher, Nicolet 6700) to determine the functional groups of the adsorbents. A thermal field emission scanning electron microscope (SUPRATM55) was used to scan the powdered activated coke to characterize its surface morphology.

2.2.3. Adsorption Experiments

A series of 250 mL Erlenmeyer flasks was prepared, each containing 100 mL of phenol solution at a predetermined concentration. For each flask, PAC was added at 0.05, 0.1, 0.15, 0.20, 0.25, 0.30, 0.40, and 0.60 g (corresponding to 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, and 6.0 g L−1, respectively) into 100 mL of solution to investigate the adsorption behavior. The flasks were then placed in a thermostatic water bath unit with the addition of a stirrer running at 150 rpm, and adsorption tests were conducted at set temperatures and times, with temperatures and reaction times recorded. Subsequently, the solution of PAC and phenol was separated by filtration through a vacuum filtration unit with a 0.45 micron aqueous membrane. Then, the filtrate was analyzed for phenol solution concentration using a UV spectrophotometer at 260 nm. The effects of each parameter (PAC particle size, adsorbent dose, initial concentration, adsorption time, co-existing salt ions, and pH) on adsorption were then measured.
All adsorption experiments were performed in triplicate, and the average values were determined as the output data. The change in the concentration of the phenol solution before and after the experiment was analyzed to calculate the adsorption of phenol by the adsorbent. The adsorption removal efficiency (q%) and amount (qe, mg g−1) of phenol adsorbed in water at any moment were calculated according to Equations (1) and (2), respectively.
The adsorption removal efficiency was calculated as follows:
q = c o − c e × 100 % / c 0
where q is the adsorption and removal efficiency of phenol (%), co is the initial concentration of phenol solution (mg L−1), and ce is the concentration of phenol solution after adsorption equilibrium is reached (mg L−1).
The adsorption capacity was then calculated using:
q e = c o − c e × V / m
where qe represents the amount of adsorbed phenol at equilibrium (mg g−1), m is the mass of the adsorbent (g), and V is the volume of the sample solution (L).

2.2.4. Adsorption Isotherms and Thermodynamics

Adsorption isotherm modeling is an important tool for studying adsorption phenomena and understanding the adsorption process. Currently, adsorption isotherms are represented by a number of theoretical and empirical models; however, no single model satisfies all adsorption mechanisms. Among them, the Langmuir and Freundlich models have been frequently applied for the simulation of adsorption isotherms in the adsorption treatment of exhaust gases and wastewater.
The Langmuir equation assumes that there are a finite number of adsorption sites on the surface of the adsorbent, that only one molecule can be adsorbed at each site, that there are no interactions between the adsorbed molecules, and that the adsorption is considered to be a monomolecular layer case to reach equilibrium. The basic form of the Langmuir isotherm is usually described by Equation (3) [24,25,26].
q e = q m K a C e / 1 + K a c e
where ce is the concentration of the solution at adsorption equilibrium (mg L−1), qm is the saturated adsorption amount of a single molecular layer (mg g−1), and Ka is the constant of the Langmuir model (L mg-1).
Unlike the Langmuir model, the Freundlich model assumes that the adsorbent surface is non-uniform with multiple adsorption sites and is commonly used to characterize multilayer adsorption systems or non-uniform adsorption surfaces. The basic form of the Freundlich isotherm is shown in Equation (4) [27,28].
q e = k f c e 1 n
where Kf is the adsorption constant reflecting the adsorption amount (mg g−1) ( L mg−1)1/n, and n is the adsorption constant reflecting the intensity of the adsorption temperature.

2.2.5. Adsorption Kinetics

Adsorption kinetics describe the reaction pathways and equilibrium time. The commonly used adsorption kinetic models are described as follows.
Lagergren posits that the adsorption rate is primarily governed by physical adsorption, with the assumption that the adsorption process is driven by diffused molecules within the adsorbate. The pseudo-first-order model is typically characterized by Equation (5) [28].
q t 1 = q e 1 − q e 1 e − K 1 t
where qe represents the amount of adsorbed phenol at time t (mg g−1), t denotes the adsorption time (min), qe1 denotes the unit adsorption amount at equilibrium (mg g−1), and K1 represents the pseudo-first adsorption rate constant (1 min−1).
Assuming that the adsorption rate depends mainly on chemisorption, the pseudo-second-order model is given by Equation (6) [29,30,31].
t / q t = 1 / K 2 q 2 e 1 + t / q e 1
where t denotes the adsorption time (min), qe1 denotes the unit adsorption amount at equilibrium (mg g−1), and K2 denotes the pseudo-second adsorption rate constant, (g(mg min)−1).

2.2.6. Regeneration Experiments

The hydrothermal regeneration system consists of a hydrothermal reactor, a condenser, a temperature controller, and a gas source. The hydrothermal kettle model was GSH-0.1 L, purchased from Weihai Chemical Machinery Co., Ltd., and equipped with a liquid and gas inlet and product outlet, which can achieve temperature and pressure control. Specific design parameters were as follows: design pressure, 30 MPa; working pressure, ≤ 25 MPa; design temperature, 575 °C; and working temperature, ≤ 550 °C.
Regeneration process: Five grams of waste-activated coke was weighed into the hydrothermal reactor, and 50 mL of ultrapure water was added to the hydrothermal reactor, which was then sealed. The reaction temperature was set at 280 °C using a temperature controller, and the hydrothermal kettle was heated [32,33]. After reaching the set temperature, the sample was regenerated for 30 min, and the heating was stopped. When the reactor was completely cooled, the regenerated PAC was filtered using a 0.45 µm filter membrane and dried at 104 °C for 2 h.
In order to investigate the regeneration rate after hydrothermal regeneration, the experimental conditions for the adsorption of phenol by the activated coke after regeneration were kept the same: phenol concentration of 40 mg/L, PAC particle size < 61 μm, dosage of 1.5 g/L, reaction time of 20 min, pH 7, and reaction temperature of 20 °C. The experiments were performed under the above-mentioned conditions.
The regeneration rate was calculated as follows:
R e = q t q t n × 100
where Re represents the regeneration efficiency (%); qt is the amount of phenol adsorbed by the initial activated coke (mg g−1); qtn represents the amount of phenol adsorbed by the n-th regenerated active coke (mg g−1), and n is taken as 1, 2, 3, 4, and 5.
The experiments were repeated to explore the adsorption capacity of PAC after multiple regenerations.

3. Results and Discussion

3.1. Characterization of PAC

FTIR spectra were used to determine the presence of functional groups on the surface of PAC (<61 μm).
As shown in Figure 2, a number of adsorption peaks were detected, which could be attributed to various functional groups, such as oxygen-containing and nitrogen-containing functional groups, which usually occupy the main active sites on the surface of the original activated coke. PAC exhibited strong absorption peaks at 1580 cm−1 and 1396 cm−1, attributed to the COO- stretching vibration; the bands at 1110 cm−1 and 3420 cm−1 were attributed to C-O-C and -OH stretching of adsorbed water molecules, while the weak bands at 2936 cm−1 and 780 cm−1 were attributed to the presence of methyl, methylene, and other side chains [34,35]. After adsorption, PAC had a weaker absorption peak at 1580 cm−1 than that of the original PAC, indicating a significant decrease in the COO- stretching vibration. This change suggests that phenol chemically reacted with COO- on the surface of the activated coke during the adsorption process [36].
Figure 3 shows the morphological structure of the PAC (<61 μm) surface observed via SEM. The left side magnification of 20 KX shows that the pore structure of the activated coke is well developed, and the surface shows an uneven and rough pit-like structure, which is favorable for the adsorption process. After the adsorption experiments, the SEM on the right side confirms that the pore size is clogged by the adsorbed phenol.
Figure 4 shows the pore size distribution of PAC (<61 μm) used in the experiments. The average and median particle sizes of the PAC were 38 μm and 25 μm, respectively, and most of the PAC was distributed in the range of 20–60 μm.
The pore properties of PAC (<61 μm), GBAC, and PBAC were investigated using BET analysis, and the results are presented in Table 3. PBAC exhibited a higher microporous volume and narrower average pore width compared to GBAC. This can be attributed to the inherent lignocellulosic structure of the coconut shells (Table 2), which promotes microporosity during activation [9]. In contrast, PAC exhibited a larger medium-to-large pore volume, consistent with its wider pore size distribution. Micropores were not well developed, while mesopores were dominant for PAC, which is beneficial for the adsorption of macromolecular pollutants in water [37,38,39].

3.2. Effects of Influencing Factors

Adsorption tests were conducted to study the effects of different factors on the adsorption of phenol, and the results are shown in Figure 5. Adsorption experiments were performed by changing one of the influencing factors to investigate the influencing patterns.
Figure 5a shows the effect of PAC particle size on the adsorption of phenol. Clearly, the amount of adsorbed phenol increased significantly with a decrease in the particle size of PAC. The amount of phenol adsorbed using PAC (<61 μm) was approximately five times greater than that adsorbed by PAC with particle sizes between 1180 and 1400 μm. This is due to the increased specific surface area and pore volume of smaller PAC particles, which also effectively shortens the internal diffusion distance, reduces the internal diffusion resistance, and accelerates the mass transfer process, thus causing an increase in adsorption capacity [39,40].
The effect of PAC dose (0~6 g L−1) on the adsorption of phenol is shown in Figure 5b. The phenol removal efficiency increased from 42.8% to 98.2% as the PAC dose increased from 1 to 3 g L−1. The increased dose increases the number of active sites available for adsorption, thereby improving phenol removal. However, the adsorption efficiency changed slightly when the dose of PAC was greater than 3 g L−1.
Figure 5c shows the effect of solution pH (2~12)on the rate of phenol adsorption. It can be seen that when the solution pH was in the range of 2~8, the removal efficiency of phenol by PAC showed no significant change with pH variation. When pH > 10, the removal efficiency of phenol decreased sharply with an increase in pH, and the turning point was consistent with the dissociation constant pKa of phenol (pKa = 9.95) [41]. When pH > 10, phenol exists mainly in its conjugated base form, and electrostatic repulsion with the negatively charged activated coke surface leads to a decrease in the removal of phenol [42]. Therefore, the removal of phenol from wastewater using PAC should be performed in solutions with pH < 10, to achieve the desired adsorption effect.
The time (0–120 min) dependence of phenol adsorption by PAC was assessed during the experiments, as shown in Figure 5d. The rate of phenol adsorption by PAC varied rapidly, and 77.7% of the total phenol was removed within 5 min; once the reaction time exceeded 20 min, the phenol removal reaction tended to equilibrium. This is due to the larger specific surface area of PAC, which contains more free and unsaturated groups that facilitate the adsorption process [43].
Figure 5e shows the effect of the initial phenol concentration (40–120 mg L−1) on phenol removal. Under experimental conditions, the phenol adsorption rate decreased as the initial concentration of the phenol solution increased; however, the amount of phenol adsorbed by PAC increased markedly. This is due to the fact that the number of active sites available for the adsorption of phenol molecules is fixed with the constant amount of activated coke dosing. With an increase in the initial concentration of phenol, the concentration gradient of the solute between the solution liquid phase and solid phase increases, which increases the driving force of phenol from the liquid phase to the surface of the activated coke molecules, so that the adsorption capacity increases with the concentration of phenol solution [10,44], and the trend of the increase in the adsorption amount is not weakened, which indicates that the activated coke still has a better effect on the removal of the phenol wastewater of higher concentrations.
Figure 5f shows the influence of co-existing salt ions on the adsorption of phenol. The removal of phenol decreased with higher NaCl concentrations and increased with higher Na2SO4 concentrations. Hassan A. Arafat et al. [45] studied the influence of NaCl on the adsorption of phenol on activated carbon, and believed that adding inorganic salt electrolyte to the solution would result in the salting out effect of weak electrolyte in the solution, which would reduce or increase the solubility of phenol. However, the solubility change caused by the salting-out effect was small and was generally not considered. The experimental results also showed that the inorganic salts NaCl and Na2SO4 did not significantly compete with phenol adsorption in PAC.
A comparison of the phenol adsorption effects between PAC and commercial biological activated carbon produced by coconut shell is shown in Figure 6. The maximum adsorption capacities of GBAC (granular biological activated carbon, 2000 μm~4000 μm), PAC (<61 μm), and PBAC (powdered biological activated carbon, <61 μm) in the experiments were 7.72, 24.0, and 34.6 mg g−1, respectively [46,47]. Even when the dose was increased to 5 g L−1 for GBAC, the removal efficiency was only 73%. The removal efficiency for 1.5 g L−1 PAC was almost the same as that for 1 g L−1 PBAC. The price of PAC is one-third that of PBAC. The low cost of PAC is due to the low price of lignite as a raw material and the simplification of the production process to avoid energy waste. Therefore, it is suitable to replace commercially available activated carbon with PAC.

3.3. Thermodynamic and Kinetic Analysis of Adsorption

3.3.1. Adsorption Isotherm

To determine the adsorption capacities of PAC, phenol solutions of 40, 60, 80, 100, and 120 mg L−1 were prepared, and the reaction temperatures were controlled at 20, 30, and 40 °C. The remaining experimental conditions were maintained as follows: PAC particle size < 61 μm, reaction time of 20 min, pH 7, and the volume of phenol solution was 100 mL. The experiment was performed under the above conditions.
The experimental results were fitted using Equations (3) and (4) to obtain linear fit plots of the Langmuir and Freundlich isotherms, as shown in Figure 7 and Figure 8, while Table 4 lists the relevant parameter values
The fitted correlation coefficients in Table 4 indicate that the Langmuir model is more suitable than the Freundlich model for describing the isothermal adsorption process of phenol by PAC. The Langmuir equation was fitted with a higher R2 than the Freundlich equation, indicating that the surface adsorption sites of the activated coke were uniformly distributed and that the adsorption process occurred in a monolayer [37,45,46].

3.3.2. Adsorption Kinetics

The kinetic properties of the adsorption process were examined to determine the rate-limiting step of the process. Pseudo-first kinetic and pseudo-second kinetic models are shown in Figure 9, and the parameters of the adsorption kinetics model are shown in Table 5.
If the adsorption process is mainly influenced by liquid film diffusion, it should be consistent with the pseudo-first-order model and can be used to calculate the adsorption rate. The pseudo-second-order model is considered a chemical reaction.
As shown in Figure 9, the linear correlation coefficient R2 of the fitted pseudo-first kinetic model was 0.9514, which differed significantly from the experimental data. Therefore, phenol adsorption by PAC does not conform to the pseudo-first-order kinetic model, and it can be assumed that the liquid film diffusion process is not a rate-limiting step in the phenol adsorption process. The linear correlation coefficient R2 was 0.9892, obtained by fitting the pseudo-second-order model, indicating that the pseudo-second-order model provided a good fit to the adsorption data. Furthermore, the equilibrium adsorption amount qe (22.71 mg g−1) in Table 5, calculated using the pseudo-second-order model, is very close to the experimental value (23.23 mg g−1), indicating that the process of phenol adsorption by PAC is consistent with pseudo-second-order kinetics [10,36,44]. Therefore, the adsorption of phenol is controlled by chemisorption. The changes in the functional groups, as shown in the FTIR spectra (Figure 2), also confirm that the adsorption process involves a chemical reaction.

3.4. The PAC Regeneration

The wasted PAC generated from the adsorption of phenol-containing wastewater was regenerated using the hydrothermal method.
Figure 10 shows the regeneration efficiency of PAC for phenol after several cycles of adsorption–desorption. However, the regeneration efficiency exceeded 100% for cycle 1, indicating that the adsorption capacity of PAC after hydrothermal regeneration was even higher than that of the new PAC. Under a subcritical working pressure of 22 MPa, the liquid exhibits many unique properties, such as low viscosity and high diffusion coefficient, which are conducive to penetration into the interior of the activated coke particles, not only to release the adsorbed phenol but also to have a certain activation effect, promoting pore generation conducive to the formation of a uniform pore structure [32,48]. After five regeneration cycles, the adsorption capacity of PAC was 86.1% of that of the new PAC, which still had good adsorption performance. Therefore, PAC is a recyclable adsorbent with hydrothermal regeneration, which can further reduce the cost of wastewater treatment.

4. Conclusions

In this study, PAC prepared from lignite using a one-step method of charring and activation was used to adsorb phenol in wastewater. The results showed that PAC exhibited good adsorption performance for phenol in water. Phenol adsorption onto PAC was dependent on pH, with an ideal pH of less than 10. The phenol removal efficiency increased with increasing PAC dose. The removal efficiency for 1.5 g L−1 PAC was almost the same as that of 1 g L−1 commercial powdered activated carbon, while the price of PAC was only one-third of that of commercial powdered activated carbon. The adsorption equilibrium was reached in approximately 20 min. NaCl and Na2SO4 did not exhibit significant competitive adsorption with phenol in PAC. The Langmuir isotherm fitted well with the experimental data obtained from the adsorption tests, indicating that the adsorption process occurs as a monolayer process. The adsorption kinetics were in accordance with the pseudo-second kinetic model, indicating that chemical adsorption was the rate-limiting step, which was also confirmed by the FTIR spectrum. The hydrothermal method was effective for the regeneration of PAC adsorbing phenol in wastewater, and PAC still exhibited good adsorption performance for phenol after five regeneration cycles. This study provides a potential low-cost substitute for commercial powdered activated carbon.
Preliminary progress has been made in the study of the phenol and adsorption properties of PAC, but there is still a lot of work that needs to be further studied:
(1) To better simulate practical applications, the dynamic adsorption performance of PAC should be studied, and a powdered activated coke depth treatment process should be designed for small particle size characteristics. (2) Fractal dynamics models, such as the Vermeulen equation, were not used in this study because the available data could not support high-dimensional parameter optimization. Future studies will incorporate in situ characterization techniques to analyze the diffusion paths in depth. (3) Although this study conducted experiments on the effect of coexisting ions on the adsorption of phenol by PAC, the actual composition of wastewater is often much more complex; therefore, it is necessary to conduct adsorption studies on multicomponent ion systems and actual industrial wastewater.

Author Contributions

Conceptualization, G.C.; Methodology, G.C.; Software, S.C.; Validation, S.C. and D.Z.; Formal analysis, H.X.; Investigation, H.X.; Resources, G.C. and S.C.; Data curation, H.X.; Writing – original draft, H.X.; Writing – review & editing, G.C. and S.C.; Visualization, D.Z.; Supervision, D.Z.; Project administration, D.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by the Natural Science Foundation of Shandong Province (grant numbers ZR2023 ME170).

Data Availability Statement

The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.

Acknowledgments

The authors sincerely thank the help from his lab colleagues on the research and life.

Conflicts of Interest

Hao Xu was employed by the company National Energy Weizhen (Shandong) Test and Analysis Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Abbreviations

The following abbreviations are used in this manuscript:
PACpowdered activated coke.
GBACgranular biological activated carbon.
PBACpowdered biological activated carbon.

References

  1. Dobrosz-Gómez, I.; Quintero-Arias, J.D.; Gómez-García, M.Á. Fenton advanced oxidation process for the treatment of industrial textile wastewater highly polluted with acid-black 194 dye. Case Stud. Chem. Environ. Eng. 2024, 9, 100672. [Google Scholar] [CrossRef]
  2. Fan, X.; Li, S.; Sun, M.; Song, C.; Xiao, J.; Du, J.; Tao, P.; Sun, T.; Shao, M.; Wang, T. Degradation of phenol by coal-based carbon membrane integrating sulfate radicals-based advanced oxidation processes. Ecotoxicol. Environ. Saf. 2019, 185, 109662. [Google Scholar] [CrossRef]
  3. Smith, S.J.; Lauria, M.; Ahrens, L. Electrochemical Oxidation for Treatment of PFAS in Contaminated Water and Fractionated Foam-A Pilot-Scale Study. ACS EST Water 2023, 3, 1201–1211. [Google Scholar] [CrossRef]
  4. Wang, Y.; Chen, H.; Wang, Y.; Lv, Y. Study on the biological treatment of phenolic-containing wastewater. Mod. Chem. Ind. 2017, 37, 58–62. [Google Scholar]
  5. Othman, A.M.; Mohammed, R.R.; Ismail, M. Adsorption of phenol from aqueous solution using granular activated carbon from walnut shell. AIP Conf. Proc. 2023, 2834, 23. [Google Scholar]
  6. Al-Ananzeh, N.; Bani-Melhem, K.; Khasawneh, H.E.; Tawalbeh, M.; Al-Qodah, Z.; Al-Bodour, A. Investigating the potential of using solid waste generated from stone cutting factories for phenol removal from wastewater: A study of adsorption kinetics and isotherms. Results Eng. 2023, 20, 10404. [Google Scholar] [CrossRef]
  7. Piekutin, J.; Kotowska, U.; Puchlik, M. Application of an integrated process for the removal of organic compounds of the phenols group from water. Desalination Water Treat. 2023, 301, 63–70. [Google Scholar] [CrossRef]
  8. Wen, W.; Wen, C.; Wang, D.; Zhu, G.; Yu, J.; Ling, P.; Xu, M.; Liu, T. A review on activated coke for removing flue gas pollutants (SO2, NOx, Hg0, and VOCs): Preparation, activation, modification, and engineering applications. J. Environ. Chem. Eng. 2024, 12, 11964. [Google Scholar] [CrossRef]
  9. Mi, Y.; Wang, W.; Zhang, S.; Guo, Y.; Zhao, Y.; Sun, G.; Cao, Z. Ultra-high specific surface area activated carbon from Taihu cyanobacteria via KOH activation for enhanced methylene blue adsorption. Chin. J. Chem. Eng. 2024, 67, 106–116. [Google Scholar] [CrossRef]
  10. Shahrashoub, M.; Bakhtiari, S. The efficiency of activated carbon/magnetite nanoparticles composites in copper removal: Industrial waste recovery, green synthesis, characterization, and adsorption-desorption studies. Microporous Mesoporous Mater. 2021, 311, 110692. [Google Scholar] [CrossRef]
  11. Zhou, B.X.; Wang, T.; Xu, T.M.; Li, C.; Li, J.; Fu, J.; Zhang, Z.; Song, Z.; Ma, C. Comparative study on the preparation of powdered activated coke for SO2 adsorption: One-step and two-step rapid activation methods. Fuel 2021, 288, 119570. [Google Scholar] [CrossRef]
  12. Wang, T.; Zhou, B.X.; Li, C.; Xu, T.; Fu, J.; Ma, C.Y.; Song, Z. Preparation of powdered activated coke for SO2 removal using different coals through a one-step method under high-temperature flue gas atmosphere. J. Anal. Appl. Pyrolysis 2021, 153, 104989. [Google Scholar] [CrossRef]
  13. Yan, M.; Ren, J.; Zhu, Z.; Zhou, B.; Chen, B.; Gao, Y.; Wang, T.; Ma, C. Effect of coal type on the physical properties and CO2 adsorption performance of activated coke prepared by a single-step method. Energy Sources Part A Recovery Util. Environ. Eff. 2023, 45, 5281–5296. [Google Scholar]
  14. Wang, T.; Liu, K.; Zhang, Z.; Zhou, B.X.; Ma, C.Y. Primary study on the pilot-scale experiment of preparation for powdered activated coke from lignite. Huadian Technol. 2020, 42, 81–87. [Google Scholar]
  15. Gao, X.; Zhang, Y.Q.; Wang, Z.Q.; Zhao, J.T.; Huang, J.J. Study on perparation and adsorption performance of active coke from lignite. Coal Convers. 2015, 38, 79–83. [Google Scholar]
  16. Feng, T.; Zhang, S.Z.; Li, J.; Xia, X.; Li, L.; Zhao, X.; Ma, C.Y. Experimental and thermodynamic study on SO2 reduction to elemental sulfur by activated coke and pyrolysis gas: Influence of the reaction atmosphere. Int. J. Hydrogen Energy 2020, 45, 20120–20131. [Google Scholar] [CrossRef]
  17. Li, J.; Zhang, L.Q.; Zhao, X.Q. Insights into the effect of generation temperature on physico chemical properties and SO2 removal over powdered activated coke. Fuel 2021, 288, 119715. [Google Scholar] [CrossRef]
  18. Shen, L.; Wang, W.; Li, T.; Cui, Y.; Wang, B.; Yu, G.; Wang, X.; Wei, D.; Xiao, J.; Deng, S. Powdered activated coke for COD removal in the advanced treatment of mixed chemical wastewaters and regeneration by Fenton oxidation. Chem. Eng. J. 2019, 371, 631–638. [Google Scholar] [CrossRef]
  19. Wang, Y.; Wu, G.; Zhang, Y.; Su, Y.; Zhang, H. The deactivation mechanisms, regeneration methods and devices of activated carbon in applications. J. Clean. Prod. 2024, 476, 26. [Google Scholar] [CrossRef]
  20. Sahu, U.K.; Tripathy, S.; Gouda, N.; Mohanty, H.S.; Sahu, M.K.; Panda, S.P.; Krishna, Y.M.; Samantaray, S.; Kumar, V.S.R.; Banu, N.; et al. Activated Carbon-Modified Iron Oxide Nanoparticles for Cr(VI) Removal: Optimization, Kinetics, Isotherms, Thermodynamics, Regeneration, and Mechanism Study. Water Air Soil Pollut. 2023, 234, 561.1–561.20. [Google Scholar] [CrossRef]
  21. Baruah, M.; Kumar, S.; Ezung, S.L.; Jamir, L.; Sinha, U.B.; Sinha, D. Preparation of Co-doped TiO2 activated carbon nanocomposite and its photocatalytic degradation of phenol wastewater. Inorg. Chem. Commun. 2024, 166, 13. [Google Scholar] [CrossRef]
  22. Ledesma, B.; Román, S.; Sabio, E.; álvarez-Murillo, A. Improvement of spent activated carbon regeneration by wet oxidation processes. J. Supercrit. Fluids 2015, 104, 94–103. [Google Scholar] [CrossRef]
  23. Salvador, F.; Martin-Sanchez, N.; Sanchez-Montero, M.J.; Montero, J.; Izquierdo, C. Regeneration of activated carbons contaminated by phenol using supercritical water. J. Supercrit. Fluids 2013, 74, 1–7. [Google Scholar] [CrossRef]
  24. Kinniburgh, D.G. General purpose adsorption isotherms. Environ. Sci. Technol. 1986, 20, 895–904. [Google Scholar] [CrossRef] [PubMed]
  25. Chen, P.Y.; Li, Z.Q.; Long, X. Adsorption of Diethylenetriamine from Water by Activated Carbon: Kinetics, Isotherms and Thermodynamics. Sep. Sci. Technol. 2023, 58, 21. [Google Scholar] [CrossRef]
  26. Langmuir, I. The constitution and fundamental properties of solids and liquids Part I Solids. J. Am. Chem. Soc. 1916, 11, 2221–2295. [Google Scholar] [CrossRef]
  27. Freundlich, H.Z. Concerning adsorption in solutions. Z. Fur Phys. Chem. 1906, 57, 444–485. [Google Scholar]
  28. Ho, Y.S.; McKay, G. Sorption of dye from aqueous solution by peat. Chem. Eng. J. 1998, 70, 115–124. [Google Scholar] [CrossRef]
  29. Li, X.; Cui, Y.; Du, W.; Cui, W.; Huo, L.; Liu, H. Adsorption Kinetics and Mechanism of Pb(II) and Cd(II) Adsorption in Water through Oxidized Multiwalled Carbon Nanotubes. Appl. Sci. 2024, 14, 1745. [Google Scholar] [CrossRef]
  30. Ho, Y.S.; McKay, G. Pseudo-second order model for sorption processes. Process Biochem. 1999, 34, 451–465. [Google Scholar] [CrossRef]
  31. Nekouei, F.; Nekouei, S.; Tyagi, I.; Gupta, V.K. Kinetic, thermodynamic and isotherm studies for acid blue 129 removal from liquids using copper oxide nanoparticle-modified activated carbon as a novel adsorbent. J. Mol. Liq. 2015, 201, 124–133. [Google Scholar] [CrossRef]
  32. Li, Z.; Chen, G.; Ma, H.; Huang, F.; Xu, H.; Zhang, L.; Yuan, X.; Zhang, X.; Chen, S.; Zhou, P. Research on the hydrothermal regeneration of powdered activated coke in wastewater treatment. J. Environ. Chem. Eng. 2023, 11, 1. [Google Scholar] [CrossRef]
  33. Sufnarski, M.D. Regeneration of Granular Activated Carbon Using Hydrothermal Technology; Texas University Department of Engineering: Austin, TX, USA, 1999. [Google Scholar]
  34. Hulicova-Jurcakova, D.; Seredych, M.; Lu, G.Q.; Bandosz, T.J. Combined Effect of Nitrogen- and Oxygen-Containing Functional Groups of Microporous Activated Carbon on its Electrochemical Performance in Supercapacitors. Adv. Funct. Mater. 2009, 19, 438–447. [Google Scholar] [CrossRef]
  35. Hao, P.-y.; Meng, Y.-j.; Zeng, F.-g.; Yan, T.-t.; Xu, G.-b. Quantitative study of chemical structures of different rank coals based on infrared spectroscopy. Spectrosc. Spectr. Anal. 2020, 40, 787–792. [Google Scholar]
  36. Zheng, M.; Han, Y.; Xu, C.; Zhang, Z.; Han, H. Selective adsorption and bioavailability relevance of the cyclic organics in anaerobic pretreated coal pyrolysis wastewater by lignite activated coke. Sci. Total Environ. 2019, 653, 64–73. [Google Scholar] [CrossRef] [PubMed]
  37. Wang, L.; Gao, Q.; Li, Z.; Wang, Y. Improved Removal of Quinoline from Wastewater Using Coke Powder with Inorganic Ions. Processes 2020, 8, 156. [Google Scholar] [CrossRef]
  38. Tamai, H.; Yoshida, T.; Sasaki, M.; Yasuda, H. Dye adsorption on mesoporous activated carbon fiber obtained from pitch containing yttrium complex. Carbon 1999, 37, 983–989. [Google Scholar] [CrossRef]
  39. Li, L.; Quinlivan, P.A.; Knappe, D.R.U. Effects of activated carbon surface chemistry and pore structure on the adsorption of organic contaminants from aqueous solution. Carbon 2002, 40, 2085–2100. [Google Scholar] [CrossRef]
  40. Lin, J.Q.; Yang, S.E.; Duan, J.M.; Wu, J.J.; Jin, L.Y.; Deng, Q.L. The Adsorption Mechanism of Modified Activated Carbon on Phenol. MATEC Web Conf. 2016, 67, 03040. [Google Scholar] [CrossRef]
  41. Feng, Y.; Tian, B.; Xia, B.; Cui, J.; Yang, M. Characterization of phenol ionization state in aqueous solution and transfer feature in electrodialysis. Chin. J. Environ. Eng. 2018, 12, 2466–2474. [Google Scholar]
  42. Tong, K.; Lin, A.; Ji, G.; Wang, D.; Wang, X. The effects of adsorbing organic pollutants from super heavy oil wastewater by lignite activated coke. J. Hazard. Mater. 2016, 308, 113–119. [Google Scholar] [CrossRef] [PubMed]
  43. Wu, Y.; Zhang, N.; de Lannoy, C.-F. Upcycling wildfire-impacted boreal peats into porous carbons that efficiently remove phenolic micropollutants. J. Environ. Chem. Eng. 2021, 9, 105305. [Google Scholar] [CrossRef]
  44. Poddar, A.; Shetty, S.; Nagose, N. Removal of Methylene Blue from Waste Water Using Activated Carbon Prepared by Impregnating it with KOH and Cacl2. Int. J. Adv. Res. Sci. Commun. Technol. 2022, 5, 18. [Google Scholar]
  45. Arafat Hassan, A.; Franz Marcus Pinto Neville, G. Effect of Salt on the Mechanism of Adsorption of Aromatics on Activated Carbon. Langmuir 1999, 15, 5997–6003. [Google Scholar] [CrossRef]
  46. Shen, X.; Hussain, T.; Mitchek, M.; Wong, J.; Reible, D. Evaluating the Sorption Kinetics of Polychlorinated Biphenyls in Powdered and Granular Activated Carbon. Water Res. 2023, 236, 10. [Google Scholar] [CrossRef] [PubMed]
  47. Kamarudin, N.S.; Dahalan, F.A.; Zubir, A.A.A.; Hasan, M.; Ibrahim, N.; Lutpi, N.A.; Nazri, R.N.H.R.; Parmin, N.A. Comparative Study of Powdered Activated Carbon and Granular Activated Carbon in Metaldehyde Adsorption: Unraveling Isotherm and Kinetic Insights. Environ. Qual. Manag. 2024, 34, 1. [Google Scholar] [CrossRef]
  48. Oesterle, P.; Gallampois, C.; Jansson, S. Fate of trimethoprim, sulfamethoxazole and caffeine after hydrothermal regeneration of activated carbon. J. Clean. Prod. 2023, 429, 139477. [Google Scholar] [CrossRef]
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Figure 1. Schematic diagram of PAC phenol removal and regeneration.
Figure 1. Schematic diagram of PAC phenol removal and regeneration.
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Figure 2. FTIR spectra of PAC before and after adsorption.
Figure 2. FTIR spectra of PAC before and after adsorption.
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Figure 3. SEM of PAC at 20 KX; left side before adsorption and right side after adsorption.
Figure 3. SEM of PAC at 20 KX; left side before adsorption and right side after adsorption.
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Figure 4. Particle size distribution of PAC.
Figure 4. Particle size distribution of PAC.
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Figure 5. (a) Effect of particle size on phenol adsorption (PAC, 150 mg; c0, 40 mg L−1, 100 mL; pH, 7; time, 20 min; temperature, 20 °C; co-existing salt ions, 0 mg L−1). (b) Effect of dose on phenol adsorption (PAC, < 61 μm; c0, 40 mg L−1, 100 mL; pH, 7; time, 20 min; temperature, 20 °C; co-existing salt ions, 0 mg L−1). (c) Effect of pH on phenol adsorption (PAC, <61 μm, 150 mg; c0, 40 mg L−1, 100 mL; time, 20 min; temperature, 20 °C; co-existing salt ions, 0 mg L−1). (d) Effect of adsorption time on phenol adsorption (PAC, <61 μm, 150 mg; c0, 40 mg L−1, 100 mL; pH, 7; temperature, 20 °C; co-existing salt ions, 0 mg L−1). (e) Effect of initial concentration on phenol adsorption (PAC, <61 μm, 150 mg; solution, 100 mL; pH, 7; time, 20 min; temperature, 20 °C; co-existing salt ions, 0 mg L−1). (f) Effect of coexisting ions on phenol adsorption (PAC, <61 μm, 150 mg; c0, 40 mg L−1, 100 mL; pH, 7; temperature, 20 °C; time, 20 min).
Figure 5. (a) Effect of particle size on phenol adsorption (PAC, 150 mg; c0, 40 mg L−1, 100 mL; pH, 7; time, 20 min; temperature, 20 °C; co-existing salt ions, 0 mg L−1). (b) Effect of dose on phenol adsorption (PAC, < 61 μm; c0, 40 mg L−1, 100 mL; pH, 7; time, 20 min; temperature, 20 °C; co-existing salt ions, 0 mg L−1). (c) Effect of pH on phenol adsorption (PAC, <61 μm, 150 mg; c0, 40 mg L−1, 100 mL; time, 20 min; temperature, 20 °C; co-existing salt ions, 0 mg L−1). (d) Effect of adsorption time on phenol adsorption (PAC, <61 μm, 150 mg; c0, 40 mg L−1, 100 mL; pH, 7; temperature, 20 °C; co-existing salt ions, 0 mg L−1). (e) Effect of initial concentration on phenol adsorption (PAC, <61 μm, 150 mg; solution, 100 mL; pH, 7; time, 20 min; temperature, 20 °C; co-existing salt ions, 0 mg L−1). (f) Effect of coexisting ions on phenol adsorption (PAC, <61 μm, 150 mg; c0, 40 mg L−1, 100 mL; pH, 7; temperature, 20 °C; time, 20 min).
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Figure 6. Comparison of the phenol adsorption effects between GBAC, PAC, and PBAC (c0, 40 mg L−1, 100 mL; pH,7; time, 20 min; temperature, 20 °C; co-existing salt ions, 0 mg L−1).
Figure 6. Comparison of the phenol adsorption effects between GBAC, PAC, and PBAC (c0, 40 mg L−1, 100 mL; pH,7; time, 20 min; temperature, 20 °C; co-existing salt ions, 0 mg L−1).
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Figure 7. Langmuir isotherms of phenol adsorption onto PAC.
Figure 7. Langmuir isotherms of phenol adsorption onto PAC.
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Figure 8. Freundlich isotherms of phenol adsorption onto PAC.
Figure 8. Freundlich isotherms of phenol adsorption onto PAC.
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Figure 9. Pseudo-first-order and pseudo-second-order models for phenol adsorption onto PAC.
Figure 9. Pseudo-first-order and pseudo-second-order models for phenol adsorption onto PAC.
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Figure 10. Influence of regeneration cycling times on PAC regeneration efficiency (regeneration temperature, 280 °C; time, 30 min; pressure, 22 MPa).
Figure 10. Influence of regeneration cycling times on PAC regeneration efficiency (regeneration temperature, 280 °C; time, 30 min; pressure, 22 MPa).
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Table 1. Apparatus and equipment used in the experiments.
Table 1. Apparatus and equipment used in the experiments.
Machine NameModelManufacturer
Double beam UV/VIS spectrophotometerTU1901Beijing General Instruments Co., Ltd. (Beijing, China)
Electronic balanceSQPSartorius Mechatronics T&H GmbH (Beijing, China)
Constant temperature magnetic stirring water bathHH-2Changzhou Langyue Instrument Manufacturing Co., Ltd. (Changzhou, China)
Scanning electron microscopeSUPRATM55Carl Zeiss AG (Oberkochen, Germany)
pH meter PHS-3 EShanghai INESA Analytical Instrument Co., Ltd. (Shanghai, China)
Laser diffraction analyzer LS 13 320 XRBeckman Instruments Inc. (Brea, CA, USA)
Fourier Transform Infrared SpectrometerNicolet 6700Thermo Fisher Scientific(Waltham, MA, USA)
Automatic Surface Area and Pore Size AnalyzerAutosorb-iQQuantachrome Instruments(Boynton Beach, FL, USA)
Table 2. Adsorbent material information and price list.
Table 2. Adsorbent material information and price list.
AbsorbentRawParticle Size (µm)ManufacturerPrices
(USD/t)
PAC (powdered activated coke) lignite coal<61 μmLaboratory of one-step preparation of activated coke at Shandong University (Jinan, China)487
GBAC (granular biological activated carbon)coconut shell2000~4000Shanghai Activated Carbon Factory Co.278
PBAC (powdered biological activated carbon)coconut shell<61 μmShanghai Activated Carbon Factory Co. (Shanghai, China)1391
Table 3. Pore properties of absorbent.
Table 3. Pore properties of absorbent.
AbsorbentBET Surface Area (m2/g)Micropore Specific Area (m2/g)Total Pore Volume (cm3/g)Micropore Volume (cm3/g)Average Pore (nm)
PAC514.41341.2920.6000.0154.822
GBAC786.363705.5640.5140.3683.046
PBAC987.264910.2810.7020.4662.332
Table 4. Isotherm model parameters of phenol adsorption onto the surface of PAC.
Table 4. Isotherm model parameters of phenol adsorption onto the surface of PAC.
TemperatureLangmuirFreundlich
qm (mg g−1)Ka (L mg−1)R2Kf
((mg g−1) (L mg−1)1/n)		nR2
293 K52.210.12540.977914.560.29630.9297
303 K52.660.1060 0.980313.360.31210.9148
313 K50.130.11390.986413.870.29080.8997
Table 5. Kinetics model parameters data for the adsorption of phenol.
Table 5. Kinetics model parameters data for the adsorption of phenol.
TemperaturePseudo First OrderPseudo Second Order
qe (mg g−1)K1 (1 min−1)R2qe (mg g−1)K2 (g.(mg min)−1)R2
293 K21.911.8210.951422.710.14090.9892
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Chen, G.; Xu, H.; Chen, S.; Zhao, D. Performance of Powdered Activated Coke Produced by One-Step Rapid Process from Lignite: Phenol Adsorption from Synthetic Wastewater and Hydrothermal Regeneration. Water 2025, 17, 1161. https://doi.org/10.3390/w17081161

AMA Style

Chen G, Xu H, Chen S, Zhao D. Performance of Powdered Activated Coke Produced by One-Step Rapid Process from Lignite: Phenol Adsorption from Synthetic Wastewater and Hydrothermal Regeneration. Water. 2025; 17(8):1161. https://doi.org/10.3390/w17081161

Chicago/Turabian Style

Chen, Guifang, Hao Xu, Shouyan Chen, and Dachuan Zhao. 2025. "Performance of Powdered Activated Coke Produced by One-Step Rapid Process from Lignite: Phenol Adsorption from Synthetic Wastewater and Hydrothermal Regeneration" Water 17, no. 8: 1161. https://doi.org/10.3390/w17081161

APA Style

Chen, G., Xu, H., Chen, S., & Zhao, D. (2025). Performance of Powdered Activated Coke Produced by One-Step Rapid Process from Lignite: Phenol Adsorption from Synthetic Wastewater and Hydrothermal Regeneration. Water, 17(8), 1161. https://doi.org/10.3390/w17081161

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