Malaysian Journal of Science

THE EFFECT OF CHEMICAL ACTIVATION AGENTS AND ACTIVATION TEMPERATURE ON THE PORE STRUCTURE OF RICE HUSK-DERIVED ACTIVATED CARBON

2024-02-04T12:56:11+08:00

This study investigates the optimization of production parameters for rice husk-derived activated carbon, aiming for its effective application in direct air capture (DAC) technology. Various chemical activation agents (potassium hydroxide [KOH], urea, and their combination) and activation temperatures (600°C, 700°C, and 800°C) were explored using pyrolysis. The resulting activated carbon's morphology was analyzed via scanning electron microscopy (SEM) and ImageJ. Results demonstrate that both activation agent choice and temperature significantly influence pore diameter size and quantity. Increased temperatures led to smaller pore diameters and higher pore quantities. The combination of KOH and urea at 800°C produced the most favorable particle size (0.811 μm), suitable for applications requiring a well-defined pore structure. This combination also exhibited the most even pore distribution and highest pore density. These findings provide valuable insights for optimizing the production of rice husk-derived activated carbon, aiding in the development of sustainable and effective sorbents for CO₂ capture in DAC technology. Additionally, they offer potential for broader applications of husk-activated carbon in various industrial and environmental fields.

IMMOBILISATION OF COPPER (I) OXIDE/ZINC OXIDE NANOPARTICLES ON THE GAS DIFFUSION LAYER FOR CO2 REDUCTION REACTION APPLICATION

2024-02-04T14:21:01+08:00

The electrochemical reduction of carbon dioxide (CO₂RR) represents a promising strategy for CO₂ mitigation, requiring highly efficient catalysts integrated into electrochemical devices to achieve high conversion rates and energy efficiencies for desired products. Establishing a gas diffusion electrode is crucial for practical applications of CO₂ electrochemical reduction reactions (CO₂RR). This study uses the air-spraying method to immobilise nano-catalysts onto a gas diffusion layer (GDL) with exceptional homogeneity. A composite of copper(I) oxide (Cu₂O) and zinc oxide (ZnO) nanoparticles in a 4:1 ratio was deposited onto the GDL. Surface morphology analysis revealed the successful immobilisation of cubic Cu₂O and hexagonal wurtzite ZnO with a uniform distribution, indicating potential improvements in CO₂RR performance. Contact angle measurements were conducted to assess surface hydrophobicity, comparing pristine GDL with Cu₂O/ZnO-based GDL. Although the contact angle on the surface of the Cu₂O/ZnO-based GDL slightly reduced from 143.69° to 134.82°, it maintained its hydrophobic nature. This reduction is attributed to Nafion, a binder in the catalyst ink mixture. The sustained high contact angle is crucial for the CO₂ reduction reaction process. X-ray diffraction (XRD) diffractograms of Cu₂O/ZnO-based GDL were compared with reference Cu₂O, ZnO, and bare GDL. The presence of all essential peaks confirms the successful immobilisation. The air-spraying technique effectively achieved a favourable distribution of active metals.

EXPERIMENTAL INVESTIGATION OF AMINE-BASED GRAPHENE NANOSUSPENSION FOR CO2 ABSORPTION

2024-02-04T14:45:10+08:00

Absorption is the most widely used carbon dioxide (CO₂) removal technology. The CO₂absorption performance of monoethanolamine (MEA), the most commonly used CO₂ absorbent, can be improved by suspending nanoparticles. This work examined the performance of graphene nanoplatelets (GNPs) as additives to enhance CO₂ absorption in MEA. The GNPs were characterized by HRTEM, FTIR, and XRD. The study examined the influence of GNP concentrations on CO₂ absorption at room temperature. The images from HRTEM confirmed that the implemented graphene consists of several layers of graphene sheets. Increasing the loading of particles increased the solubility of CO₂ until the optimum concentration was reached. From this work, it is evident that incorporating GNPs into MEA enhances the CO₂ absorption performance of MEA. Thus, the addition of nanoparticles to the absorbent can enhance its CO₂ absorptivity.

CHARACTERISATION OF EGG WHITE-IMPREGNATED ACTIVATED CARBON FOR CO2 ADSORPTION APPLICATION

2024-02-04T15:14:47+08:00

In this study egg white was used as a source of natural amino acids to modify the surface properties of palm shell activated carbon towards enhancing its CO₂ capture performance. A simple impregnation method was employed for this purpose. Characterisation analysis was performed on the egg white-impregnated activated carbon to examine any changes on its surface properties prior to CO₂ adsorption test. The modified adsorbent showed high thermal stability below 300°C and comprised of new amide functional group. Furthermore, the modified adsorbent exhibited 31% higher breakthrough time and maintained its CO₂ adsorption capacity at 0.3 mmol/g in comparison to raw activated carbon, regardless of the reduction of surface area and micropore volume by 17% and 18% respectively. These findings provide evidence on the prospect of egg white-impregnated activated carbon for CO₂ adsorption application which could pave the way for a new generation of affordable and eco-friendly adsorbents.

SYNTHESIS AND CHARACTERIZATION OF 2-(METHYLAMINO)ETHANOL-BASED DEEP EUTECTIC SOLVENTS FOR CO2 CAPTURE

2024-02-04T15:23:13+08:00

In recent years, deep eutectic solvents (DESs) have attracted the interest of many researchers for application in a wide range of industrial and scientific fields, including carbon dioxide (CO₂) capture. DESs exhibit favourable solvent properties for CO₂ removal applications; hence, they have become promising alternatives to common amine solutions and ionic liquids (ILs). In this context, a novel DES was synthesised by mixing 2 (methylamino)ethanol (2-MAE) as a hydrogen bond donor with choline hydroxide (ChOH) as a hydrogen bond acceptor with a molar ratio of ChOH:2-MAE of 1:1. The solubility of CO₂ in the prepared systems was determined and characterised before and after CO₂ absorption by measuring their physicochemical properties (density and viscosity) and analysing their FTIR spectra. The results showed that the DES and 2M DES aqueous solutions exhibited CO₂ absorption capacities comparable to those of other reported DESs. These physicochemical properties were comparable to those reported in the literature. Besides, the FTIR analysis of the studies systems after absorption indicates the formation of carbamate.

PRELIMINARY STUDY ON PERFORMANCE OF Zn-DOPED ZEOLITE IN LOW-TEMPERATURE CO2 ADSORPTION

2024-02-07T16:21:31+08:00

Zeolite has been identified as a potential low-temperature CO₂ adsorbent with the highest adsorption capacity among adsorbents in its category. However, its adsorption capacity remains relatively low, limiting its industrial application for CO₂ adsorption. Additionally, there is a need to increase the optimal adsorption temperature of this porous material to effectively adsorb CO₂ emitted from flue gas, which has an average temperature of 100 - 125°C. To address these challenges, a preliminary study on Zn-doped zeolite has been conducted. This study aims to investigate the ability of Zn-doped zeolite to enhance CO₂ adsorption capacity and its effect on the optimal temperature for CO₂ adsorption. Zinc-doped zeolite was synthesized by doping zinc oxide into natural zeolite using a zinc ion exchange method at different doping concentrations (0.2 M & 1.0 M). Undoped natural zeolite was studied as a benchmark. Their CO₂ adsorption performance was tested using TGA at 30°C, 50°C, and 100°C. The effects of temperature and doping concentration on adsorption capacity were investigated. The adsorbent samples were characterized using X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) analysis. It was found that increasing the temperature from 30°C to 50°C increased the CO₂ adsorption capacity, but the capacity decreased when the temperature was further increased to 100°C. Furthermore, increasing the doping concentration tended to enhance the CO₂ adsorption capacity. The highest adsorption capacity of 0.0281 g CO₂/g sorbent was observed in zinc-doped zeolite with a 1.0 M doping concentration at 50°C. The improvement was mainly attributed to the zinc oxide doped on the zeolite, which provided a functional group that formed chemical bonds with CO₂. This study also found that the adsorption rate of CO₂ was predominantly influenced by temperature, while the effect of doping concentration was less significant. All testing and characterization results suggested that the zinc-ion exchange method improved the CO₂ adsorption capacity of zeolite.

MORINGA OLEIFERA (MO) SEED SHELL BASED ADSORBENT FOR POTENTIAL CO2 CAPTURE: A CHARACTERIZATION STUDY

2024-02-07T16:57:15+08:00

This study characterizes activated carbon synthesized from Moringa oleifera (MO) seed husk with a greener activating agent, namely sodium carbonate, (Na₂CO₃) compared to traditional activating agent, potassium hydroxide (KOH). Synthesized in a conventional tube furnace with nitrogen supply, the resulting activated carbon after cooling and washing, were characterized for Brunauer-Emmett-Teller (BET), Fourier-Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) analyses and compared with that produced with KOH activation. Although fewer and larger mesoporous activated carbon with smaller BET surface area (18.4659 m²/g) were formed with Na₂CO₃ activation), compared to that of KOH activation (235.6034 m²/g), this study highlights the ability and potential of the greener activating agent (Na₂CO₃) to utilize biomass waste and successfully produce activated carbon with minimum environmental hazards. The synthesized adsorbent can be explored for CO₂ capture applications in future studies.

PERFORMANCE EVALUATION OF HYDROXYAPATITE PREPARED FROM EGGSHELLS IN CARBON DIOXIDE ADSORPTION

2024-02-07T17:14:06+08:00

Eggshell waste is typically produced from daily poultry consumption and industrial applications. They are a rich source of calcium in the form of carbonates and oxides, recognised as excellent hydroxyapatite sources (HAp). To date, limited studies have highlighted the modification of HAp with impregnation. In the present study, HAp was prepared via the precipitation method, and further modification of HAp using monoethanolamine (MEA) and deep eutectic solvent, particularly choline chloride:urea (ChCl:U), were explored for carbon dioxide (CO₂) capture. The morphological structures were studied using a scanning electron microscope, while properties were assessed using energy-dispersive X-ray spectroscopy techniques (SEM-EDX) and Brunauer-Emmett-Teller (BET). The CO₂ adsorption performance using raw and impregnated HAp was also evaluated. By introducing the chemisorption process, the impregnated ChCl:U-HAp with irregular crystallite agglomerates demonstrated a higher adsorption capacity and longer breakthrough time than raw HAp and MEA-HAp. This study confirms the feasibility of using eggshells to produce HAp as an effective adsorbent in CO₂ capture.

IONIC LIQUIDS AS POTENTIAL CO-CATALYST FOR CO2 ELECTROCHEMICAL REDUCTION

2024-02-04T14:37:47+08:00

Carbon dioxide electrochemical reduction (CO₂ER) presents numerous advantages in mitigating greenhouse gas emissions by converting CO₂ into value-added chemicals and can be integrated with renewable energy sources such as solar and wind. Nevertheless, establishing an electrochemically stable catalytic system that can effectively decrease the overpotential while maintaining high current density and faradaic efficiency is challenging. The precise mechanisms causing the reactions and the specific functions of the electrode with electrolytes are still not fully understood. Hence, a significant increase in attention has been paid to using ionic liquids (ILs) as electrolytes for CO₂ER. This phenomenon is attributed to the unique capabilities of ILs to reduce overpotential, increase current density, and improve electrochemical stability. Therefore, this study evaluated the effect of incorporating ILs into electrolytes to comprehend the cation and anion influences on CO₂ER reactions. Linear sweep voltammetry (LSV) and chronoamperometry (CA) were employed to examine the reduction peaks and current density values for different electrolytes, respectively. Consequently, a 0.1 M NBu₄PF₆ acetonitrile solution containing 1-ethyl-3-methylimidazolium tetrafluoroborate [EMIM][BF₄] demonstrated a significantly lower onset potential of the reduction by 320 mV. A reduced CO₂ER efficiency involving ILs with long alkyl chains was also observed. Meanwhile, a novel hypothesis concerning molecular orbitals for the CO₂ER reaction mechanism was discussed. Overall, various performance variables (reduction stability, applied potential, and current density) of CO₂ER were improved using cations with short alkyl chains, anions with high highest occupied molecular orbital (HOMO) levels, and appropriate solvation media. These findings can serve as selection criteria to aid in choosing appropriate ionic liquids for CO₂ electrochemical reduction (CO₂ER).

INVESTIGATION OF CARBON DIOXIDE ABSORPTION CAPACITY AND DISSOLUTION RATE WITH AMINO ACID SALT SOLUTIONS: SODIUM AND POTASSIUM GLYCINATE

2024-02-07T15:53:29+08:00

Global warming is a major world problem and causes climate change. The primary cause of global warming is carbon dioxide (CO₂) emissions. Ongoing studies are being conducted to mitigate the effects of this problem. Anthropogenic CO₂emissions occur by burning fossil fuels to generate power and heat. To combat this problem, CO₂ must be captured from point emission sources or directly from air. The conventional method to remove CO₂ at the point emission sources is post-combustion systems. In these systems, absorption process is generally used to diminish CO₂ emission and capturing at the source. Current researches aim to find an efficient and alternative solution to absorption. In this work, sodium glycinate (NaGly) and potassium glycinate (KGly), which are amino acid salt solutions, were investigated for CO2 absorption. Amino acid salt solutions have shown similar absorption kinetics and capacities to amine-based solutions due to same functional group. These solutions are usually more stable to oxidative degradation and have low volatilities, higher surface tensions and the viscosities are very close to waters. Experiments were performed using a stirred cell system at ambient temperature (20°C) and atmospheric pressure (91 kPa), in Ankara, Türkiye. In experiments, sodium glycinate and potassium glycinate concentration was ranged between 0.1 and 1.5 M. The experiments were also repeated with sodium hydroxide and potassium hydroxide in the same concentration range for comparison. In addition, the amino acid salt solutions examined in this study were compared with alkaline solutions and glycine in terms of total CO₂ absorption capacity and CO₂ dissolution rate. As a result of the experiments, the potassium glycinate solutions gave approximately 1.4 times better results than the sodium glycinate solutions at the highest concentration. Also, functional groups were determined by FTIR analysis of pure and CO₂-loaded potassium glycinate solution.