MDPI - Publisher of Open Access Journals

14 pages, 2974 KiB

Open AccessArticle

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

by Syeda Saba Fatima, Azry Borhan and Muhammad Faheem

Processes 2025, 13(4), 1181; https://doi.org/10.3390/pr13041181 - 14 Apr 2025

Viewed by 487

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. Full article

(This article belongs to the Section Materials Processes)

► Show Figures

Figure 1

17 pages, 3271 KiB

Open AccessArticle

Modeling of CO₂ Adsorption on Surface-Functionalized Rubber-Seed Shell Activated Carbon: Isotherm and Kinetic Analysis

by Syeda Saba Fatima, Azry Borhan, Muhammad Ayoub and Noraini Abd Ghani

Processes 2023, 11(10), 2833; https://doi.org/10.3390/pr11102833 - 26 Sep 2023

Cited by 10 | Viewed by 3294

Abstract

Currently, adsorption is considered a promising technology for CO₂ separation with a wide range of adsorbents. A detailed study of equilibrium and kinetics plays a crucial role in the design and operation of industrial adsorption units. In this study, isotherm and kinetics of CO₂ adsorption on two RSS-derived AC samples previously prepared in our laboratory were evaluated using equilibrium experiments for pure CO₂ at 25 °C and 40 °C and 1 bar. Blank and IL-functionalized AC showed CO₂ adsorption capacity of 2.16 mmol/g, 1.96 mmol/g, 1.12 mmol/g and 1.71 mmol/g at 25 °C and 40 °C, respectively. Langmuir, Freundlich, and Temkin equations were used to model adsorption isotherm in low-pressure regions. The obtained results revealed that the Freundlich model provides an accurate fitting to the experimental findings, which indicate that the adsorption process occurs in a heterogeneous phase. Additionally, kinetic analysis was performed by using four empirical models, namely pseudo-first order, pseudo-second order, Elovich, and Avrami’s fractional models. Among the considered kinetic models, the pseudo-second order model fits best for both blank and IL-functionalized AC. Intra-particle and Boyd’s film diffusion models were evaluated for the adsorption mechanism. Full article

► Show Figures

Graphical abstract

20 pages, 3261 KiB

Open AccessArticle

CO₂ Adsorption Performance on Surface-Functionalized Activated Carbon Impregnated with Pyrrolidinium-Based Ionic Liquid

by Syeda Saba Fatima, Azry Borhan, Muhammad Ayoub and Noraini Abd Ghani

Processes 2022, 10(11), 2372; https://doi.org/10.3390/pr10112372 - 12 Nov 2022

Cited by 28 | Viewed by 4790

Abstract

The serious environmental issues associated with CO₂ emissions have triggered the search for energy efficient processes and CO₂ capture technologies to control the amount of gas released into the atmosphere. One of the suitable techniques is CO₂ adsorption using functionalized sorbents. In this study, a functionalized activated carbon (AC) material was developed via the wet impregnation technique. The AC was synthesized from a rubber seed shell (RSS) precursor using chemical activation and was later impregnated with different ratios of [bmpy][Tf₂N] ionic liquid (IL). The AC was successfully functionalized with IL as confirmed by FTIR and Raman spectroscopy analyses. Incorporation of IL resulted in a reduction in the surface area and total pore volume of the parent adsorbent. Bare AC showed the largest S_BET value of 683 m²/g, while AC functionalized with the maximum amount of IL showed 14 m²/g. A comparative analysis of CO₂ adsorption data revealed that CO₂ adsorption performance of AC is majorly affected by surface area and a pore-clogging effect. Temperature has a positive impact on the CO₂ adsorption capacity of functionalized AC due to better dispersion of IL at higher temperatures. The CO₂ adsorption capacity of AC (30) increased from 1.124 mmol/g at 25 °C to 1.714 mmol/g at 40 °C. Full article

(This article belongs to the Special Issue Reinventing Processes for Sustainability via Process Intensification and Integration)

► Show Figures

Graphical abstract

19 pages, 5419 KiB

Open AccessFeature PaperArticle

Development of Rubber Seed Shell–Activated Carbon Using Impregnated Pyridinium-Based Ionic Liquid for Enhanced CO₂ Adsorption

by Nawwarah Mokti, Azry Borhan, Siti Nur Azella Zaine and Hayyiratul Fatimah Mohd Zaid

Processes 2021, 9(7), 1161; https://doi.org/10.3390/pr9071161 - 4 Jul 2021

Cited by 14 | Viewed by 4925

Abstract

In this study, rubber seed shell was used for the production of activated carbon by chemical activation using an ionic liquid, [C₄Py][Tf₂N] as an activating agent. Sample RSS-IL 800 shows the highest specific surface area of 393.99 m²/g, a total pore volume of 0.206 cm³/g, and a micropore volume of 0.172 cm³/g. The performance of AC samples as an adsorbent for CO₂ was also studied using a static volumetric technique evaluated at a temperature of 25 °C and 1 bar pressure. The CO₂ adsorption capacity for sample RSS-IL 800 was 2.436 mmol/g, comparable with reported data from the previous study. Results also show that the CO₂ adsorption capacity decreased at a higher temperature between 50 and 100 °C and increased at elevated pressure due to its exothermic behavior. The Langmuir model fits the adsorption data well, and the isosteric heat of adsorption proved that the physisorption process and exothermic behavior occur. Full article

(This article belongs to the Special Issue Novel Adsorbent for Environmental Remediation)

► Show Figures

Graphical abstract

20 pages, 5093 KiB

Open AccessArticle

Activation of Rubber-Seed Shell Waste by Malic Acid as Potential CO₂ Removal: Isotherm and Kinetics Studies

by Azry Borhan and Suzana Yusuf

Materials 2020, 13(21), 4970; https://doi.org/10.3390/ma13214970 - 4 Nov 2020

Cited by 21 | Viewed by 3082

Abstract

Carbon dioxide (CO₂) has been deemed a significant contributor to the climate crisis and has an impact on environmental systems. Adsorption is widely used among other technologies for carbon capture because of its many benefits. As a starting material for the production of activated carbon (AC) by chemical activation using malic acid due to its biodegradable and non-toxic properties, rubber seed shell (RSS) was used as agricultural waste from rubber farming. Sample A6, which was carbonized for 120 min at a temperature of 600 °C and impregnated at a ratio of 1:2, was identified to achieve the highest surface area of 938.61 m²/g with micropore diameter of 1.368 nm, respectively. Using the fixed volumetric approach measured at 25, 50, and 100 °C, the maximum CO₂ adsorption capability reported is 59.73 cm³/g of adsorbent. Using the pseudo-first order of Lagergren, the pseudo-second order and the Elovich model, experimental data is modeled. It appears that, based on the correlation coefficient, the pseudo-first order model is aligned with the experimental findings. Furthermore, the activation energy of under 40 kJ/mol indicated a physical adsorption occurs, indicating that the RSS chemically activated with malic acid is a fascinating source of CO₂ removal requirements. Full article

(This article belongs to the Special Issue Fundamentals of Adsorbents–Synthesis, Characterisation, Properties, and Application)

► Show Figures

Figure 1

14 pages, 3971 KiB

Open AccessFeature PaperArticle

Characterization and Modelling Studies of Activated Carbon Produced from Rubber-Seed Shell Using KOH for CO₂ Adsorption

by Azry Borhan, Suzana Yusup, Jun Wei Lim and Pau Loke Show

Processes 2019, 7(11), 855; https://doi.org/10.3390/pr7110855 - 14 Nov 2019

Cited by 78 | Viewed by 6652

Abstract

Global warming due to the emission of carbon dioxide (CO₂) has become a serious problem in recent times. Although diverse methods have been offered, adsorption using activated carbon (AC) from agriculture waste is regarded to be the most applicable one due to numerous advantages. In this paper, the preparation of AC from rubber-seed shell (RSS), an agriculture residue through chemical activation using potassium hydroxide (KOH), was investigated. The prepared AC was characterized by nitrogen adsorption–desorption isotherms measured in Micrometrices ASAP 2020 and FESEM. The optimal activation conditions were found at an impregnation ratio of 1:2 and carbonized at a temperature of 700 °C for 120 min. Sample A6 is found to yield the largest surface area of 1129.68 m²/g with a mesoporous pore diameter of 3.46 nm, respectively. Using the static volumetric technique evaluated at 25 °C and 1.25 bar, the maximum CO₂ adsorption capacity is 43.509 cm³/g. The experimental data were analyzed using several isotherm and kinetic models. Owing to the closeness of regression coefficient (R²) to unity, the Freundlich isotherm and pseudo-second kinetic model provide the best fit to the experimental data suggesting that the RSS AC prepared is an attractive source for CO₂ adsorption applications. Full article

(This article belongs to the Special Issue Green Technologies: Bridging Conventional Practices and Industry 4.0)

► Show Figures

Figure 1

Search Results (6)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI

Saved Queries

Search Filter Reset All

Years

Feature Papers

Subjects

Journals

Article Types

Countries / Regions

Search Results (6)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI