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Article

Preparation of Chemically Activated Porous Carbon Derived from Rubber-Seed Shell for CO2 Adsorption

by
Syeda Saba Fatima
1,2,
Azry Borhan
3 and
Muhammad Faheem
4,*
1
Department of Chemical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar 32610, Perak, Malaysia
2
School of Engineering, RMIT University, Melbourne, VIC 3001, Australia
3
HICoE, Centre for Biofuel and Biochemical Research, Institute of Self-Sustainable Building, Department of Chemical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar 32610, Perak, Malaysia
4
Department of Chemical Engineering, University of Engineering & Technology, Lahore 54890, Pakistan
*
Author to whom correspondence should be addressed.
Processes 2025, 13(4), 1181; https://doi.org/10.3390/pr13041181
Submission received: 10 March 2025 / Revised: 8 April 2025 / Accepted: 11 April 2025 / Published: 14 April 2025
(This article belongs to the Section Materials Processes)
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Abstract

:
The utilization of agricultural biomass for the synthesis of carbonaceous adsorbents is an active research topic because of a wide range of precursors and good adsorption properties of the resulting adsorbent materials. Rubber-seed shell (RSS) is a suitable precursor for the synthesis of activated carbon (AC) due to its naturally high carbon content. In addition, it is available in large quantities due to the growing rubber plantations in Malaysia. In this work, activated carbon is produced via chemical activation of RSS for CO2 adsorption. A two-step and a modified three-step activation method using K2CO3 as an activating agent are used for the preparation of RSS-derived AC. AC samples prepared by both techniques are compared based on structural properties and CO2 adsorption capacity to identify the more effective synthesis method. Carbon content increased from 48.40 wt.% in the untreated RSS to >77 wt.% in prepared AC samples, indicating successful activation. BET surface area for AC2 and AC3 was 474.7 m2/g and 683.4 m2/g, respectively. The highest CO2 adsorption capacity of 60.06 mg/g at 25 °C was obtained for AC3. Overall, AC produced by the three-step activation has superior structural properties and CO2 adsorption performance.

1. Introduction

Global warming and climate change, associated with greenhouse gas (GHG) emissions, have directed attention toward the mitigation of CO2 emissions. Many separation techniques have been developed to control the rising amounts of CO2 released into the atmosphere on a daily basis. To date, liquid absorption, also known as the amine-scrubbing process, is widely used on an industrial scale to control CO2 emissions, especially in post-combustion carbon capture processes [1,2,3,4,5]. The absorption of CO2 is carried out using non-toxic solvents and is based on Henry’s law, where CO2 is selectively absorbed under high pressure and low temperature. The CO2 is then desorbed under reduced pressure and high temperature, thus regenerating the solvent and producing pure CO2 [6,7,8]. This process is used in several industrial processes with high CO2 content, including Selexol process, hydrogen production via methane pyrolysis, and natural gas and synthesis gas production [7]. Although this method is extensively applied on an industrial scale, it suffers several limitations, including high energy requirements for solvent regeneration, equipment corrosion, and serious concerns regarding poor solvent waste management [5,9]. In the early 2000s, adsorption emerged as a promising technique for CO2 separation because of its numerous advantages, including a wide range of solid adsorbents, high CO2 adsorption capacity, low capital investment, and easy operation [10]. Moreover, the original adsorption capacity of the adsorbent can be restored using temperature swing adsorption (TSA) and pressure swing adsorption (PSA) techniques [10,11]. TSA involves adsorbent regeneration by the application of heat, for example, by direct purging using steam or a nonadsorbing gas. The bed can also be heated to the desired regeneration temperature by an indirect application of heat to avoid the dilution of extracted CO2. The purge gas is then passed through the column for a brief period to capture the desorbed components and regenerate the adsorbent surface [12]. Conversely, PSA involves adsorbent regeneration by lowering the partial pressure. Thus, in PSA, the adsorption process occurs under high pressure, and desorption is achieved under near-ambient pressure with no external heat applied [13]. Generally, PSA is preferred to TSA due to shorter regeneration times, smaller equipment space, and lower cost of separated CO2 [14]. Typical adsorbent materials are highly porous and possess a large surface area for effective CO2 adsorption. Common adsorbents for CO2 capture include zeolites [15,16], metal–organic frameworks (MOFs) [17,18,19], activated carbon (AC) [20], and silica [21]. The adherence of CO2 molecules to the adsorbent surface can occur through physisorption or chemisorption. The key features, such as surface area, pore size, and the extent and type of functionalization of the adsorbent surface, affect their performance in gas adsorption [7]. High-performing adsorbents such as zeolite and silica are expensive to synthesize, limiting their commercial viability. Biomass-based adsorbents are a suitable alternative because of the abundance and availability of cheap raw materials. Moreover, the surface of these adsorbents can be modified to improve selectivity for CO2 adsorption in the presence of other gases (such as oxygen and nitrogen). Biomass-based activated carbon is widely studied for CO2 adsorption because it can be produced from a variety of feedstocks and cheaper materials that are otherwise discarded as waste. Although many adsorbent materials have been synthesized and tested for CO2 capture, there is still a long way before this technique can be employed on a commercial scale. Low CO2 partial pressure in flue gas remains a significant challenge because the resulting low driving force for separation leads to poor process economics [22]. Solid adsorbents can be used in fixed-bed or moving-bed assemblies. A major challenge with these designs is keeping the gas velocity low to prevent fluidization of the adsorbent bed. This results in exceedingly large equipment dimensions, especially at low CO2 concentrations [23]. Other design and operational difficulties include adsorbent handling and regeneration, unsteady state operation, and the interaction of adsorbent with the moisture, which is inherently present in flue gases.
In search of new adsorbents with high CO2 adsorption performance, AC obtained from biomass precursors has gained much attention due to the abundantly available precursors, inexpensive and easy synthesis, high thermal stability, and hydrophobicity [24,25]. Researchers have focused on the synthesis of solid adsorbents for CO2 capture using agricultural waste and industrial biomass. One of the promising precursors used in this context is the rubber-seed shell (RSS). Rubber is cultivated in large quantities in various Southeast Asian countries, with Indonesia, Thailand, and Malaysia being the top producers. About 95% production of natural rubber in Malaysia is dominated by small farmers. Rubber production, being an integral part of the country’s economy, contributes more than RM 20 billion per annum [26]. Despite easy availability, RSS is usually discarded as waste material. It has a naturally high carbon content, making it a suitable precursor for the adsorption processes [26].
AC can be synthesized by physical and chemical activation methods. The latter is preferred because of numerous advantages, including higher yield, lower synthesis time, and better control of the textural properties [27]. Chemical activation can be performed in one or two steps. In single-step activation, the raw material is directly mixed with the activating agent and pyrolyzed. In contrast, the two-step activation method comprises (i) pyrolysis, and (ii) chemical activation. In the pyrolysis step, the raw material is pyrolyzed at a high temperature, typically 400–1000 °C, under an inert atmosphere. In hydrolysis, the material is dispersed with an activating solution in an autoclave. The temperature is controlled for 2–24 h under fixed pressure to produce hydrochar. It has been reported that AC synthesized from the two-step chemical activation has a larger surface area and a higher adsorption capacity than single-step chemical activation [27]. A new three-step chemical activation has recently been introduced for the synthesis of AC. AC produced via three-step activation can provide higher surface area and pore volume, which ultimately results in better adsorption performance than the two-step activation [27]. For three-step activation, the first step is hydrothermal carbonization to produce hydrochar. In the second step, this hydrochar is pyrolyzed to produce biochar. The final step involves chemical activation using an activating agent of choice.
In chemical activation, the nature of the activating agent strongly affects the surface chemistry and adsorption performance of AC [28]. Several activating agents have been used, including KOH [24], ZnCl2 [29], H3PO4 [30], HNO3 [31], NH3 [32], and NaOH [33]. The selection of an activating agent depends on the targeted adsorption application. For typical CO2 adsorbents, chemicals such as KOH are used as activating agents to enhance the basicity of the carbon surface toward acidic CO2 molecules. Among the activating agents mentioned earlier, KOH is the most popular activating agent because it yields AC with high porosity [34]. In a comparison study on the efficiency of chemical agents, carbon activated by KOH and K2CO3 via an optimized carbonization process exhibited similar yields, surface area, and pore volume [35]. At low temperatures, the reaction of K-containing species in KOH leads to faster char gasification, which results in the formation of macropores [36]. Although KOH and K2CO3 work on a similar principle, the relatively mild nature of K2CO3 leads to a slower gasification reaction, which results in a higher percentage of micropores crucial for effective adsorption [37]. Moreover, K2CO3 is also used in food additives, making it suitable for practical applications [38]. As the use of environmentally friendly chemicals is desired in the industrial application of any process, K2CO3 is used as an activating agent in this work to synthesize RSS-derived AC.
The focus of this work is to make a comparison between the conventional two-step and the modified three-step chemical activation methods for the synthesis of RSS-derived AC using K2CO3 as an activating agent. AC produced by both methods is compared based on surface properties, chemical composition, and CO2 adsorption performance.

2. Materials and Methods

RSS were collected from Tersusun Tanah Hitam, Chemor, Perak 32100, Malaysia. The shells were knocked with a hammer to remove the white pulp. The shells were soaked in water overnight and washed thoroughly to remove dirt and impurities from the surface. The washed shells were dried in an oven at 110 °C for 24 h. The RSS was ground using a ball mill. Ground shells were sieved to obtain particles between 0.1–0.25 mm and stored in an airtight container.

2.1. Preparation of RSS-AC by Two-Step Activation Method

The two-step activation method involves (1) carbonization, followed by (2) chemical activation. A total of 30 g of ground RSS was soaked in 100 mL of 2 M K2CO3 solution for 24 h. The impregnated RSS powder was dried at 110 °C for 24 h. The dried RSS powder was carbonized in a tube furnace under a uniform N2 flow of 10 mL/min at 800 °C for 2 h. The sample was heated at a heating rate of 10 °C/min and cooled under uniform N2 flow. The activated RSS powder was washed with 0.1 M HCl solution to remove excess salt and ash. The mixture was filtered and washed with deionized water until neutral pH. The washed AC was dried at 110 °C for 24 h and stored in a desiccator. The RSS AC prepared by this method is referred to as AC2 in later sections.

2.2. Preparation of RSS-AC by Three-Step Activation Method

The three-step activation method involves (1) hydrothermal treatment, followed by (2) carbonization, and (3) chemical activation. A total of 30 g RSS powder was suspended in 10 mL distilled water and poured into a Teflon-lined autoclave for hydrothermal treatment to produce hydrochar. The hydrothermal treatment was performed at 190 °C for 24 h in a Teflon-lined autoclave under self-generating pressure conditions. This prolonged reaction time is necessary to overcome the potential mass transfer limitations in an unstirred autoclave. The resulting sample was carbonized in a tube furnace at 800 °C for 2 h and activated with K2CO3 in the same way as the two-step activation. The prepared AC sample was washed with 0.1 M HCl and deionized water and dried at 110 °C for 24 h. The dried AC was stored in an airtight container for further use. The RSS AC prepared by this method is referred to as AC3 in later sections.

2.3. Characterization of RSS-Derived AC

The structure and morphology of untreated RSS and AC samples were studied using Zeiss Supra 55 VP field emission scanning electron microscope (Carl Zeiss AG, Oberkochen, Germany) using different magnification scales. An EDX analysis was carried out to study elemental mapping for fresh and activated samples. Thermogravimetric analysis (TGA) was used to study the thermal stability of RSS using PerkinElmer TGA 4000 (PerkinElmer, Shelton, CT, USA). The TGA curve of the fresh RSSs was recorded under N2 at a heating rate of 10 °C/min from 28 to 800 °C. The composition of untreated RSS and prepared AC was determined using PerkinElmer 2400 Series II CHNS/O elemental analyzer (PerkinElmer, Shelton, CT, USA). The surface properties were studied using Brunauer–Emmett–Teller (BET) method. BET surface area, pore size distribution, total pore volume, and average pore diameter of all samples were measured through N2 adsorption isotherm at 77 K using Micromeritics TriStar II 3020 BET surface area analyzer (Micromeritics Instrument Corporation, Norcross, GA, USA). The adsorption capacity of prepared AC samples for CO2 (99.98% purity) was studied using HPVA II high-pressure volumetric analyzer (Micromeritics Instrument Corporation, Norcross, GA, USA).

3. Results

3.1. Structure and Morphology

The surface morphology of untreated RSS and prepared AC samples was examined to study changes in structural properties after carbonization and activation. Selected SEM images of untreated RSS are presented in Figure 1. It can be seen that untreated RSSs have an uneven and rough surface with no visible pores.
An array of fine pores is visible on the surface of AC after carbonization and activation, as shown in Figure 2. During the impregnation process, the surface of RSS is covered with K2CO3, which is decomposed into metallic K and CO during carbonization at high temperatures under an inert environment. The evolution of gaseous components during decomposition creates fine pores on the surface of AC. The decomposition reaction is completed in two steps as follows [39,40]:
K2CO3 + C → K2O + 2CO
K2O + C → 2K + CO
The high porosity of the prepared AC results from the chemical reaction between K2CO3 and carbon. The carbon matrix expands by metallic potassium intercalation, resulting in the formation of fine pores. Distribution of fine pores appears on the carbon structure, which acts as active sites for adsorption. A comparison of the structure of RSS before and after activation shows that K2CO3 works very well as an activating agent. The structure of the AC prepared by both activation methods shows good porosity. However, AC3 shown in Figure 2b has an array of very fine pores. Therefore, higher surface area and higher CO2 adsorption capacity are expected for AC prepared by the three-step activation method.
EDX analysis was performed to study the atomic composition and elemental mapping for the prepared AC samples. Carbon and oxygen are the main elements in both samples. Homogeneous distribution of both elements is visible in Figure 3. AC2 has a slightly higher carbon content (77.72 wt.%) than AC3 (77.14 wt.%). Potassium is scattered all over the surface and is because of residual K2CO3 used for activation. The amount of potassium is less than 2% in both samples.

3.2. Elemental Composition

Untreated RSS and prepared AC samples are compared based on the elemental composition presented in Table 1. The two main elements detected in the fresh and treated samples are carbon and oxygen. The acceptable range of carbon content for a good precursor should be more than 40% [41]. The selected RSS has a carbon content of 48.40%, which makes it a suitable precursor for the synthesis of AC. The carbon content has increased significantly after carbonization and activation. The increase in carbon content is due to the release of volatile matter during the carbonization step. AC prepared by the three-step chemical activation has a slightly higher nitrogen content. The difference in nitrogen content is likely due to the additional step of hydrothermal treatment in the three-step activation method. The addition of nitrogen improves the basicity of the carbon matrix and its affinity toward capturing acidic CO2 molecules. The weight content of hydrogen and oxygen has reduced significantly in the activated samples. This happens during carbonization when a major portion of the non-carbon components are released in the form of volatile matter, leaving the remaining structure richer in carbon.

3.3. Surface Area and Porosity

An analysis of surface properties is important for understanding the adsorption characteristics of the adsorbent material. The shape of the adsorption isotherm also provides significant information regarding the nature of the adsorption process. Figure 4 shows N2 adsorption isotherms of untreated RSS and prepared AC samples at 77 K. The isotherms are of type I according to the IUPAC classification, representative of microporous materials [42]. They show significantly higher adsorption in the low P/P0 region with a long plateau starting at P/P0 ≈ 0.5, which extends to P/P0 close to 1.0. This trend is typical of microporous solids found in the literature [43]. The N2 uptake of AC3 is higher than AC2 due to higher surface area and total pore volume.
The surface properties were obtained using BET surface area analysis and are presented in Table 2. The BET surface area of raw RSS is very low (1.14 m2/g). The surface area increases significantly for activated samples due to the formation of fine pores after carbonization and decomposition of K2CO3. Both the surface area and pore volume are higher for AC3 (683.4 m2/g and 0.37 cm3/g, respectively) than for AC2 (474.7 m2/g and 0.27 cm3/g, respectively). The higher value of BET surface area for AC3 is due to the additional step of hydrothermal treatment. Higher surface area indicates more active sites, which is expected to result in higher CO2 adsorption capacity. Both activation methods form microporous AC, as indicated by the percentage of micropores. The smaller value of average pore size for AC3 confirms the fine porosity of this sample, as indicated by SEM analysis.
The relevant surface properties, such as total pore volume and pore size, are estimated by applying the Horvath–Kawazoe equation to the N2 adsorption–desorption isotherm [44]. A distribution of pore sizes is shown in Figure 5. AC prepared by both activation methods has a large number of pores between sizes 0–50 nm. The IUPAC pore size classification has three categories: micropores (<2 nm), mesopores (2–50 nm), and macropores (>50 nm) [45,46]. AC samples prepared by both activation methods have both micropores and mesopores in their structure. However, due to a high percentage of micropores, they can be classified as microporous materials. Vaporization of potassium, which penetrates the carbon matrix during impregnation, opens the pores, thus generating microporosity. A high percentage of micropores is crucial for the adsorption of CO2 molecules [47].

3.4. Thermal Stability

The TGA profile is important to establish the carbonization temperature range. The TGA profile for untreated RSS (Figure 6) clearly shows several stages of weight loss as the temperature increases. The thermal events shown in Figure 6 agree with those reported earlier for other biomass precursors [33,35]. The initial weight loss of 7.9% can be attributed to the loss of moisture and the release of non-carbon elements in the form of volatile matter. The temperature range for initial weight loss is below 200 °C [48]. The second stage of decomposition occurs between 230 °C and 360 °C. This corresponds to a weight loss of 62.8% and results from the decomposition of hemicellulose and cellulose [48,49]. The weight loss in the second stage can be subdivided into two phases. The rapid weight loss at 230 °C happens when hemicellulose is decomposed, and the second weight loss at 320 °C results from the decomposition of cellulose. Lastly, the gradual weight loss from 450 °C to 600 °C is because of the consolidation of the carbon matrix. Thermal stability is observed above 600 °C. Biomass precursors with a high content of hemicellulose and cellulose produce highly microporous carbon adsorbents with high CO2 adsorption capacity. RSS, like other biomasses, is rich in cellulose and hemicellulose. This is reflected in the largest percentage of weight loss during the second stage.

3.5. CO2 Adsorption Study

The most promising samples prepared from both activation methods were selected for the CO2 adsorption study carried out by batch adsorption on HPVA II high-pressure volumetric analyzer at 25 °C. Complete details of the equipment design and the adsorption experiment are described elsewhere [50]. The experimentally measured values of CO2 adsorption capacity for the K2CO3-activated AC2 and AC3 samples are 55.74 and 60.06 mg CO2 per g of adsorbent, respectively. For AC prepared by activation using alkaline agents like NaOH, KOH, and K2CO3, CO2 adsorption is governed by physisorption [34,37]. When CO2 adsorption occurs predominantly by physisorption, low temperature is favorable because of the exothermic nature of the process. AC produced by the three-step activation shows a higher CO2 adsorption capacity because of its higher surface area and pore volume. Furthermore, additional π–π interactions formed due to hydrothermal treatment improve the adsorption capacity of AC. A comparison of the CO2 adsorption capacity for AC derived from other biomass precursors and those produced in this work is shown in Figure 7 and Table 3. Both AC2 and AC3 exhibit good adsorption capacity and have the potential to be used as green adsorbents for large-scale CO2 capture applications.
The CO2 adsorption capacity of the prepared AC is compared with the data reported for other solid adsorbents (Table 4). Some adsorbent materials such as KIT-6 and polymeric resin exhibit much higher values of the CO2 adsorption capacity. Unfortunately, these adsorbents suffer from other limitations such as high costs for synthesis and operational difficulties. The RSS AC prepared in this study using K2CO3 activation is an attractive choice because of its low cost and comparable CO2 adsorption performance.

4. Conclusions

RSS-derived AC prepared by K2CO3 activation shows good structural properties and CO2 adsorption performance. AC developed by both the two-step and three-step activation methods shows good porosity. The ultimate analysis indicates a significant increase in the carbon content of the treated samples. The prepared AC has a carbon content greater than 77 wt.%. BET surface area and pore volume of untreated RSS significantly increase after carbonization and activation. The percentage of micropores is 86.3% and 84.7% for AC2 and AC3, respectively. Surface area of AC3 is higher due to additional steps of hydrothermal treatment resulting in higher CO2 adsorption capacity. The highest adsorption capacity of 60.06 mg/g at 25 °C is obtained for AC3. These promising results indicate that the new chemical activation method using K2CO3 has successfully transformed biomass into a low-cost adsorbent with good adsorption capacity.

Author Contributions

Conceptualization, A.B.; methodology, S.S.F., A.B. and M.F.; validation, A.B. and M.F.; formal analysis, S.S.F., A.B. and M.F.; investigation, S.S.F.; resources, A.B.; data curation, S.S.F.; writing—original draft preparation, S.S.F.; writing—review and editing, A.B. and M.F.; supervision, A.B. and M.F.; funding acquisition, A.B. All authors have read and agreed to the published version of the manuscript.

Funding

This work is supported by Yayasan Universiti Teknologi PETRONAS (YUTP-FRG-2018 015LC0-068).

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 thankfully acknowledge Universiti Teknologi PETRONAS for providing research facilities and technical support. The authors also acknowledge the financial support from the Ministry of Higher Education, Malaysia (MOHE) to the Centre for Biofuel and Biochemical Research (CBBR) through the HICOE award.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. SEM images of the untreated ground rubber-seed shells.
Figure 1. SEM images of the untreated ground rubber-seed shells.
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Figure 2. SEM images of RSS-derived AC prepared by (a) two-step activation, and (b) three-step activation.
Figure 2. SEM images of RSS-derived AC prepared by (a) two-step activation, and (b) three-step activation.
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Figure 3. EDX analysis for elemental mapping on RSS-derived AC prepared by chemical activation methods: (a) AC prepared by two-step chemical activation, and (b) AC prepared by three-step chemical activation.
Figure 3. EDX analysis for elemental mapping on RSS-derived AC prepared by chemical activation methods: (a) AC prepared by two-step chemical activation, and (b) AC prepared by three-step chemical activation.
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Figure 4. Nitrogen adsorption isotherms for untreated RSS and AC at 77 K.
Figure 4. Nitrogen adsorption isotherms for untreated RSS and AC at 77 K.
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Figure 5. Pore size distribution for untreated RSS and AC prepared by chemical activation methods.
Figure 5. Pore size distribution for untreated RSS and AC prepared by chemical activation methods.
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Figure 6. TGA and DTG profiles of RSS under uniform N2 flow and a heating rate of 10 °C/min.
Figure 6. TGA and DTG profiles of RSS under uniform N2 flow and a heating rate of 10 °C/min.
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Figure 7. CO2 adsorption capacity at 1 bar versus specific surface area of various biomass-derived AC adsorbents.
Figure 7. CO2 adsorption capacity at 1 bar versus specific surface area of various biomass-derived AC adsorbents.
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Table 1. Elemental composition of untreated RSS and AC prepared by chemical activation methods.
Table 1. Elemental composition of untreated RSS and AC prepared by chemical activation methods.
ElementsUntreated RSSAC2AC3
Unitswt.%wt.%wt.%
Carbon48.4077.7277.14
Nitrogen0.740.380.65
Hydrogen6.862.942.74
Sulfur1.220.600.26
Oxygen *42.7818.3619.21
* Calculated by difference.
Table 2. Surface properties of untreated RSS and AC prepared by chemical activation methods.
Table 2. Surface properties of untreated RSS and AC prepared by chemical activation methods.
SampleBET Surface Areat-Plot Microporous Surface AreaExternal Surface AreaTotal Pore VolumeAverage Pore DiameterPercentage Micropores
SBETSmicSextVtD-
Unitsm2/gm2/gm2/gcm3/gNm%
RSS1.14-0.240.00318.30-
AC2474.7409.665.10.276.7886.3
AC3683.4579.2104.30.372.1684.7
Table 3. A comparison of the adsorption performance of various biomass-derived AC using the chemical activation method.
Table 3. A comparison of the adsorption performance of various biomass-derived AC using the chemical activation method.
AdsorbentActivating AgentCO2 Partial PressureTemperatureCO2 Adsorption CapacityReference
Units bar°Cmg/g
AC2K2CO312555.74This work
AC3K2CO312560.06This work
Palm kernel shellMgO12520.10[51]
Rubber seed shellKOH12554.16[52]
SargassumKOH12522.80[53]
Rice huskZnCl212558.52[29]
Coconut shellCO212573.04[54]
Table 4. A comparison of CO2 adsorption capacity for different carbonaceous and non-carbonaceous adsorbents.
Table 4. A comparison of CO2 adsorption capacity for different carbonaceous and non-carbonaceous adsorbents.
AdsorbentsCO2 Partial PressureTemperatureCO2 Adsorption CapacityReference
Unitsbar°Cmg/g
AC212555.74This work
AC312560.06This work
Palm kernel shell12533.40[55]
Ordered mesoporous silica12527.00[21]
PE-MCM-4112526.40[56]
Silica monoliths0.12549.70[57]
Nanoporous carbon17848.00[58]
Carbon nanotubes17311.30[59]
KIT-617374.00[60]
SBA-1512523.40[61]
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Fatima, S.S.; Borhan, A.; Faheem, M. Preparation of Chemically Activated Porous Carbon Derived from Rubber-Seed Shell for CO2 Adsorption. Processes 2025, 13, 1181. https://doi.org/10.3390/pr13041181

AMA Style

Fatima SS, Borhan A, Faheem M. Preparation of Chemically Activated Porous Carbon Derived from Rubber-Seed Shell for CO2 Adsorption. Processes. 2025; 13(4):1181. https://doi.org/10.3390/pr13041181

Chicago/Turabian Style

Fatima, Syeda Saba, Azry Borhan, and Muhammad Faheem. 2025. "Preparation of Chemically Activated Porous Carbon Derived from Rubber-Seed Shell for CO2 Adsorption" Processes 13, no. 4: 1181. https://doi.org/10.3390/pr13041181

APA Style

Fatima, S. S., Borhan, A., & Faheem, M. (2025). Preparation of Chemically Activated Porous Carbon Derived from Rubber-Seed Shell for CO2 Adsorption. Processes, 13(4), 1181. https://doi.org/10.3390/pr13041181

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