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Valorization of Macadamia Nut Shell Waste into Activated Carbons for Electrochemical Supercapacitor Electrodes
(2026-03-03)
Chaiammart, Nattapat
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Taechamahaphan, Ariya
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Chakartnarodom, Parinya
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Prakaypan, Wichit
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Ishizaki, Takahiro
Supercapacitors are promising energy storage devices owing to their high power density and excellent cycling stability. The conversion of biomass waste into activated carbon with hierarchical pore structures has emerged as a sustainable strategy for developing high-performance supercapacitor electrodes. Herein, activated carbons were synthesized from macadamia nut shell (MNS) waste via a two-step process comprising carbonization at 600 °C and subsequent chemical activation with potassium hydroxide (KOH) at 800 °C, using weight ratios of carbonized MNS to KOH of 1:1, 1:2, and 1:3. The resulting activated carbons exhibited an amorphous structure with a predominant microporosity. KOH activation substantially increased the specific surface area from 325 to 1362 m2 g–1 through gas evolution, etching, and potassium intercalation, thereby promoting the predominant micropore formation along with partial mesopore development. Increasing the KOH ratio induced greater structural disorder, widened micropores, increased the mesopore fraction, enriched C–O functionalities, and suppressed C═O and O–C═O groups. Electrochemical measurements in a 6 M KOH electrolyte using a three-electrode system revealed that the sample activated at a 1:3 ratio delivered a maximum specific capacitance of 170 F g–1 at 1 A g–1 and exhibited predominantly electric double-layer capacitor (EDLC) behavior with a minor pseudocapacitive contribution, as confirmed by power-law, Trasatti, and Dunn analyses. This performance is attributed to its large specific surface area, partially developed mesoporosity, and enhanced surface wettability. A symmetric coin-cell supercapacitor assembled using this material delivered an energy density of 5.4 W h kg–1 and a power density of 2500 W kg–1, while maintaining excellent cycling stability over 10,000 charge–discharge cycles at 3 A g–1. These results reveal the potential valorization of MNS-derived activated carbons as sustainable and efficient electrode materials for high-performance supercapacitors.
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Optimization of hydrothermal carbonization of Rhizoclonium riparium macroalgae using response surface methodology for high-performance solid biofuel production
(2026-01-01)
Chanpee, Sirayu
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Jadsadajerm, Supachai
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Manatura, Kanit
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Wongrerkdee, Sutthipoj
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Eiad-ua, Apiluck
Hydrothermal carbonization (HTC) was adopted as a promising approach for improving fuel quality for several high-moist biomass. In this study, the Rhizoclonium riparium macroalgae (RMA), an abundant marine alga in an aquaculture pond, was successfully converted into hydrochars as a sustainable solid biofuel. The Box Behnken design (BBD) was applied for the HTC experiment to investigate the individual and interactive effects of operating parameters, including HTC temperature, reaction time, and water ratio, on hydrochar physicochemical characteristics and fuel properties. The response surface optimization (RSM) revealed maximum mass yield (MY) of 79.1%, higher heating value (HHV) of 23.6 MJ/kg, and energy yield (EY) of 94.4%. The RSM-BBD of process parameters and their HTC effects showed that the decreasing MY and EY were significantly due to the HTC temperature and residence time. From ANOVA analysis, temperature, time, and water ratio were the most significant parameters responding to MY, HHV, and EY. The optimal conditions for hydrothermal carbonization (HTC) of RMA as a solid biofuel were determined to be a temperature of 200 °C, a duration of 2 h, and a water-to-biomass ratio of 1:1, producing the highest energy yield (EY) of 95.3%. Utilizing RSM-BBD to investigate HTC parameters for hydrochar production is a suitable effort for technical scalability.
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Green Synthesis of Activated Carbons from Coconut Coir Dust via Steam Activation for Supercapacitor Electrode Applications
(2025-12-01)
Kongtip, Jirayu
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Kanjulkeat, Natapol
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Ninneit, Thanapol
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Phanapadipong, Norapat
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Chaiammart, Nattapat
Activated carbons derived from coconut coir dust were synthesized via a two-step process combining carbonization and steam activation for application as electrode materials in supercapacitors. The influence of carbonization temperature (500–700 °C) on the morphological, structural, textural, and electrochemical properties of the resulting activated carbons was systematically investigated. Increasing the carbonization temperature led to a progressive collapse of the cellular structure and formation of a more compact and thermally stable carbon matrix, while the overall morphology remained largely unchanged after steam activation. The steam-activated carbon prepared from the carbonized sample at 700 °C (SA-CCD-7) exhibited the highest specific surface area (889 m2 g−1) and a well-developed hierarchical micro–mesoporous structure. Structural analyses confirmed the amorphous nature and an increase in structural disorder after activation, consistent with the enhanced pore development. Electrochemical measurements in 6 M KOH using a three-electrode system revealed that the SA-CCD-7 displayed a typical electric double-layer capacitor (EDLC) behavior, delivering the highest specific capacitance of 86 F g−1 at 1 A g−1 and retaining 81% of its initial capacitance at 20 A g−1, demonstrating excellent rate capability. The symmetric coin-cell supercapacitor device assembled with SA-CCD-7 as the electrodes achieved an energy density of 0.9–1.2 Wh kg−1 and a power density of 50–2500 W kg−1, along with remarkable cycling stability over 10,000 cycles with negligible capacitance loss. These findings highlight steam activation of coconut coir dust as a simple, scalable, and eco-friendly approach for producing biomass-derived carbon electrodes for sustainable energy storage applications.
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Oil palm leaf-derived nanoporous carbon via hydrothermal carbonization combined with NaOH microwave activation for tetracycline adsorption
(2025-11-01)
Chanpee, Sirayu
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Apinyakul, Naruemon
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Kaewtrakulchai, Napat
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Khemasiri, Narathon
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Eiad-ua, Apiluck
Generally, the increase in pharmaceutical industrial activities has led to a corresponding rise in water resource contamination. Efforts have been dedicated to addressing the urgent challenge of waste biomass disposal by developing recycling methods capable of producing bio-adsorbents. Adsorption is a promising approach for removing tetracycline contaminants, owing to its simplicity, stability, and cost-effectiveness. In this study, a low-cost activated biochar was successfully developed using oil palm leaf (OPL) via hydrothermal carbonization (HTC) combined microwave-assisted pyrolysis system (MAPS) using sodium hydroxide (NaOH). The HTC and MAPS processes enhanced high mass yield, porosity, energy efficiency, and reduced reaction time. NaOH treatment improved the porosity of the activated biochar derived from OPL, resulting primarily in a mesoporous structure. However, NaOH treatment via the MAPS process increased surface area and porosity. Among the samples tested, OPLC-NaOH-1:1 exhibited the largest surface area and highest porosity, making it the chosen candidate for further TC adsorption tests. The adsorption experiments revealed that the Langmuir isotherm model and the pseudo-second-order kinetic model accurately matched the experimental data, suggesting a mono-layered adsorption mechanism due to micropores and chemisorption interactions. Additionally, thermodynamic analysis indicated an endothermic and spontaneous reaction during the adsorption process. The adsorption of nanoporous carbon for TC was primarily regulated by pore filling, hydrogen bonding, electrostatic effects, and π-π interactions also playing a significant role. Overall, this study highlights the potential of utilizing OPL waste as a sustainable material for producing nanoporous carbon and underscores the effectiveness of nanoporous carbon for adsorbing antibiotics.
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NiO-YSZ anode composite material derived from mechano-chemical for solid oxide fuel cells application
(2025-06-01)
Srisuwan, Thanakorn
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Puengjinda, Pramote
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Kaewtrakulchai, Napat
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Chanpee, Sirayu
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Jadsadajerm, Supachai
This study investigates the effects of calcination time, milling duration, and sintering temperature on the properties of Nickel oxide and Yttria-stabilized zirconia (NiO-YSZ) anode composite materials for solid oxide fuel cell (SOFC) applications. NiO nanoparticles were synthesized from nickel (II) sulfate (Ni(II)SO<inf>4</inf>), with X-ray diffraction (XRD) confirming a face-centered cubic (FCC) structure. The crystallite size (21 nm) was achieved after 8 hours of calcination, while prolonged durations caused particle agglomeration. Ball-milling for 12 hours produced comparatively fine particles with an average of 706 nm, though extended milling led to grain growth and aggregation. Scanning electron microscopy (SEM) revealed nano aggregation. Sintering at 1200 °C improved the densification of the NiO-YSZ layer while increasing its porosity, which enhanced the reduction of NiO to metallic nickel (Ni). Electrochemical Impedance Spectroscopy (EIS) demonstrated lower impedance and improved electrochemical performance for cells cold-sintered at 1200 °C. These findings show the importance of optimizing processing conditions to enhance the performance of NiO-YSZ anode for SOFCs, offering valuable insights for advanced energy conversion technologies.
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Chemically activated carbons derived from cashew nut shells as potential electrode materials for electrochemical supercapacitors
(2025-06-01)
Chaiammart, Nattapat
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Vignesh, Veeramuthu
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Thu, Myo Myo
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Eiad-ua, Apiluck
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Maiyalagan, Thandavarayan
Supercapacitors are widely recognized as energy storage solutions due to their high power densities and long cycle lives. Furthermore, there is growing scientific and technological interest in converting biomass waste into carbon materials for manufacturing supercapacitor electrodes. In addition to their abundance and cost-effectiveness, the appeal of carbons derived from biomass lies in their tunable porosity, which enables the rational design of carbon materials to achieve the desired performance of supercapacitors. Here, we present the synthesis of activated carbons from cashew nut shells via potassium hydroxide (KOH) activation at different temperatures (650, 750, and 850 °C). The resulting materials exhibited amorphous and predominant microporous structures. Increasing the activation temperature led to a rise in specific surface area from 1534 to 2034 m2 g−1 and an increased proportion of mesopores. The electrochemical properties of these activated carbons for supercapacitor applications were investigated by cyclic voltammetry, galvanostatic charge–discharge, and impedance spectroscopic techniques in a 1 M sodium sulfate (Na<inf>2</inf>SO<inf>4</inf>) electrolyte. Using a three-electrode system, the activated carbons treated at 750 °C exhibited a maximum specific capacitance of 106 F g−1 at a current density of 0.5 A g−1 with a good rate capability; they retained 75 % at 10 A g−1 over a 1.0 V voltage window. Furthermore, a symmetric supercapacitor coin-cell, fabricated with activated carbons treated at 750 °C as the positive and negative electrodes, demonstrated an energy density of 2.43 Wh kg−1 at a power density of 1002 W kg−1. The cell exhibited 87 % capacitance retention at 1.0 A g−1 after 10,000 cycles. This work showcases the efficient and sustainable utilization of cashew nut shells as a carbon source for supercapacitor applications and highlights their value in a circular economy.
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Efficient and novel synthesis of Nb-doped SrTiO3 nanoparticles via microwave-assisted sol-gel auto-combustion
(2025-02-01)
Nunocha, Pornnipa
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Bongkarn, Theerachai
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Eiad-ua, Apiluck
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Channei, Duangdao
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Suriwong, Tawat
This study employed microwave-assisted sol-gel auto-combustion to synthesize niobium-doped strontium titanate (SrTi<inf>1-x</inf>Nb<inf>x</inf>O<inf>3</inf>, STNO) nanoparticles, targeting enhanced photocatalytic performance applications. The STNO with varying levels of Nb doping (x = 0 to 0.05), was successfully synthesized utilizing the rapid and novel microwave-assisted sol-gel auto-combustion technique. The synthesized nanoparticles consistently exhibited a pure cubic perovskite structure across all doping levels, as confirmed by Rietveld refinement, which also showed an increase in lattice parameters and unit cell volume with higher Nb content. Morphological analysis revealed uniformly cubic-shaped particles with sizes ranging from 60 to 180 nm. The bandgap energy (E<inf>g</inf>) remained unaffected by the varying Nb doping levels. Regarding photocatalytic activity for the degradation of methylene blue (MB) dye and tetracycline (TC) antibiotic under UV-A LED irradiation, the photocatalytic performance of STNO was significantly enhanced with increasing Nb content. The optimal photocatalytic decolorization was achieved at x = 0.05, aligning well with findings derived from photoluminescence (PL), E<inf>g</inf>, Nyquist plot analyses and band edge potentials. Therefore, microwave-assisted sol-gel auto combustion is one of the efficient and novel methods to synthesize metal oxide materials.
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Valorization of horse manure conversion to magnetic carbon nanofiber for dye adsorption by hydrothermal treatment coupled with carbonization
(2024-06-01)
Kaewtrakulchai, Napat
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Chanpee, Sirayu
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Pasee, Warit
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Putta, Ampol
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Chutipaijit, Sutee
Pollution of water resources has recently increased as a result of expanded industrial activity. Recycling waste biomass into bio-adsorbent material offers a cheap, easy, and eco-friendly solution. In this study, magnetic carbon nanofibers (MCNF) with a highly porous structure were developed from magnetite-preloaded horse manure by hydrothermal treatment followed by carbonization using different ratios of iron (III) nitrate and iron oxide as magnetic precursors. The produced MCNF had a very porous structure with specific surface area of 435.31 m2/g and high carbon content. The magnetic characteristics of MCNF promoted by the presence of iron oxide species. The saturated magnetization of MCNF obtained from a 5:5 ratio of the magnetic precursors (iron (III) nitrate: iron oxide) was 2.48 emu/g. Synthesized MCNF was applied as a bio-adsorbent for methylene blue (MB) removal from aqueous solution, with results showing excellent dye adsorption of 92–99 %. MB adsorption was facilitated by pore filling, electrostatic contact, hydrogen bonding, and ion complexation. Experimental results indicated that the Freundlich isotherm and pseudo-second-order kinetic models concurred with the observed MB adsorption data, suggesting that the adsorption mechanism involved multilayered micropore interactions between magnetite and MB chemisorption. The resulting magnetic adsorbent was successfully removed from the aqueous solution by physical separation. Findings indicated that horse manure-derived MCNF could be used as an efficient bio-adsorbent to remove organic contaminants in wastewater.
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Synthesis of nanoporous carbon from brewer waste by hydrothermal carbonization assisted chemical activation for carbamazepine adsorption
(2024-06-01)
Apinyakul, Naruemon
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Chanpee, Sirayu
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Kaewtrakulchai, Napat
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Khemasiri, Narathon
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Eiad-ua, Apiluck
Nanoporous carbon (NPC) has gained significant attention in wastewater treatment due to its effectiveness. The adsorption process, known for its simplicity, stability, and cost-effectiveness, is widely recognized as an efficient method for removing carbamazepine (CBZ) residues accumulate in the environment. However, the application of NPC is often hindered by challenges in the regeneration process after use, as well as issues related to large surface area, pore size, and functional groups. Fortunately, the samples in this study not only maintained their adsorption efficiency but also demonstrated the ability to be regenerated multiple times. Herein brewery waste was subjected to hydrothermal treatment at 200 °C for 1 h and followed by KOH and NaCl activation with different KOH:NaCl (w/w) ratios of 5:0, 4:1, 3:2, 1:1, 2:3, 1:4, and 0:5 to optimize the properties of malt husk derived nanoporous carbon (NPC). The optimal condition KOH:NaCl ratio of 1:1 had a maximum specific surface area of 906 m2/g with a total pore volume of 0.252 cm3/g. According to the adsorption test, the CBZ adsorption isotherm was well-fitted to the Langmuir model (R2 = 0.976) kinetic data were consistent with the pseudo-second-order model (R2 = 0.995). This suggests that the adsorption mechanism involves monolayer adsorption and chemisorption interaction. The Gibbs free energy and enthalpy of CBZ adsorption by NPC were found to be spontaneous and endothermic. The regeneration test revealed a 95.35% decrease in the adsorption capacity of NPC after 5 repeated cycles. Consequently, the study suggests a potential application of nanoporous carbon from MH as an alternative adsorbent for removing carbamazepine in wastewater.
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Biofuel upgrading via catalytic deoxygenation in trickle bed reactor: Crucial issue in selection of pressure regulator type
(2024-01-01)
Pongsiriyakul, Kanokthip
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Kiatkittipong, Worapon
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Lim, Jun Wei
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Najdanovic-Visak, Vesna
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Wongsakulphasatch, Suwimol
Trickle bed reactors (TBRs) are commonly used in various chemical and associated processes. The selection of a proper back pressure regulator (BPR) is crucial for maintaining the system's upstream pressure. In this study, we investigate the impact of BPR selection on deoxygenation reaction in a TBR with two typical types of BPR, including gas-phase type back pressure regulator (Gas-BPR) and multiphase type back pressure regulator (Multi-BPR). Notably, Gas-BPR introduces interruptions and pressure drops during the sampling step, impacting the hydrogen flow rate, while Multi-BPR ensures more consistent hydrogen flow. To examine the performance of BPR systems, hydrotreating experiments were conducted at 330 °C, 50 bar of hydrogen over Ni/γ-Al<inf>2</inf>O<inf>3</inf> catalyst using crude Pongamia pinnata oil as a feedstock and refined palm olein as a benchmark. Insignificant difference in the reaction performance between Multi-BPR and Gas-BPR systems was observed when using refined palm olein. Interestingly, there was a significant difference between the two systems when feeding with crude Pongamia pinnata oil. The multi-BPR system demonstrated superior performance, achieving 100% conversion of the feedstock over a prolonged period compared to the interrupted hydrogen flow in the Gas-BPR system. Further characterization of fresh and spent catalysts using N<inf>2</inf> sorption, XRD, SEM-EDS and TGA-DTG-DSC techniques revealed that a gum and coke formation was a reason for the rapid catalyst deactivation. Furthermore, the interrupted flow in the Gas-BPR system led to substantial gum production, ultimately causing a blockage in the reactor bed. Consequently, for feedstocks with high impurities, a robust continuous flow of hydrogen is essential. Thus, the study strongly recommends selecting Multi-BPR for continuous operation in TBRs to enhance efficiency and avoid catalyst deactivation.

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