Fei Yee Yeoh

The Properties of Activated Carbon Fiber Derived from Direct Activation from Oil Palm Empty Fruit Bunch Fiber

Oil palm empty fruit bunch (EFB) is an abundant agricultural waste available in Malaysia. More than two million tonnes (dry weight) of extracted oil palm fiber are estimated to be generated annually. Usually the EFB is used as boiler fuel to produce steam in the palm oil mills. EFB fiber can be used to prepare activated carbon fiber (ACF) by carbonization and activation. Conversion of EFB fiber to ACF will reduce the amount of agricultural waste produced annually and it represents a potential source of adsorbents used for adsorption. The ACF has many advantages as compared to the conventional activated carbon found in powder or granular form. These advantages include large surface area, high adsorption capacity and high rates of adsorption from the gas or liquid phase. In this study, ACF produced from EFB fiber by single step direct activation process (ACF-D) was compared against ACF produced by conventional 2-step carbonization and activation (ACF-ND). The different properties between ACFs produced were investigated. The raw EFB and ACFs were characterized by a SEM and EDS, FTIR and XRD. The results show that EFB has carbon content of 63.33 weight percentage (wt %) with oxygen content of 36.67 wt %. ACF-D was found to have a high carbon content of 93.63 wt%, with low oxygen content (5.19 wt %). ACF-ND gave a higher carbon content up to 95.68 wt% and accompanied by a lower oxygen content (3.85 wt %).

Synthesis of Nanoporous Carbonated Hydroxyapatite Using Non-Ionic Pluronics Surfactant

Hydroxyapatite (HA) is a bioceramics that commonly used as bone substitute materials, coating materials and scaffolds in orthopedics. It is well known for its remarkable biocompatibility with natural human tissue. However, synthetic HA is different from biological apatite whereby apatites contain carbonate ion which is about 3-8wt% of the hard tissues of human body which described as carbonated hydroxyapatite (CHA). Hence, synthetic CHA may have a better bioactivity than HA and more widely used as biomaterials. This study described the synthesis and characterization of nanoporous carbonated hydroxyapatite (CHA) by co-precipitation method through self-organization mechanism with different type of non-ionic surfactants (P123 and F127). Diammonium hydrogen phosphate, (NH4)2HPO4 and calcium nitrate tetrahydrate, Ca (NO3)2.4H2O were used as starting materials for preparing the precursor for CHA powder. The ammonium carbonate, NH4HCO3 was used as the main source for carbonate ion. Synthesized powder was characterized using XRD, FESEM, EDS and FTIR. From the XRD result, pure HA phase was obtained for all samples. FTIR analysis results obviously showed the substitution of carbonate ion into the apatite and confirm the formation of CHA. The FTIR results also demonstrated that the surfactants had been removed completely through calcination process. SEM image revealed a sphere-like particle shape of CHA was produced after the calcinations. The mesoporous CHA with pore size 2-12 nm (F127) and 2-8 nm (P123) was synthesized.

Activated Carbon Fiber Derived from Pyrolysis of Palm Fiber

Palm empty fruit bunch (EFB) is an abundant by-product resulted from massive palm oil production in Malaysia as one of the worlds largest exporter and second largest producer of palm oil. This agricultural waste is usually disposed in nature, burnt in opened atmospheres, or used as a fuel for boilers. Such conventional handlings of EFB have created environmental concerns to Malaysia such as air pollution and release of green house gases (CH4 and CO2). This study made use of such biomass in the production of cost effective nanoporous material, namely activated carbon fiber (ACF) which able to diminish the problem of waste disposal, and at the same time to turn waste into wealth. This is especially beneficial when the ACF is used for environmental friendly application such as adsorbed natural gas (ANG) technology. ACF was formed from carbonaceous materials via process of carbonisation and activation. Both chemical and physical activations were carried out by using H2SO4 and CO2, respectively. In pyrolysis, carbonisation was conducted at temperatures i.e. 400, 600, 800 and 1000 °C in nitrogen (N2) atmosphere. Surface morphologies, microstructures, pore structures and surface chemistry of these samples were investigated for the characterisation of EFB fiber-derived ACF. Above 80% of the total pore volumes for the samples were contributed by the micropore as the major pore components in the ACF produced. The samples exhibited an high BET surface area , dominant micropore volume up and narrow pore size distribution in micro range (< 1.5 nm).

The Effect of Surfactant Extraction Method on Pore Characteristics of Mesoporous Carbonated Hydroxyapatite

Incorporated with pore sizes of 2-50 nm, CHA was found to be a promising drug delivery agent for disease treatment and could be a carrier for different types of proteins. A desired drug delivery system should consist of an ordered pore network, optimum pore size, and volume, as well as a high surface area, to allow a high drug adsorption rate, controllable drug loading, and release. However, until now, most results are still not up to expectation; since the BET surface area and pore volume obtained has been rather low, compared to the existing mesoporous silica. The objective of this work was to investigate the effect of surfactant washing on the pore characteristics and the importance of this step in the synthesis process of mesoporous carbonated hydroxyapatite (CHA). In this study, mesostructured CHA particles were prepared, via a self-assembly mechanism, between CHA and non-ionic surfactant (P123), using the co-precipitation synthesis method. The synthesized mesoporous CHA samples were washed five times using different types of solvents for surfactant removal. A sphere-like particle shape of CHA was observed under SEM for all samples; regardless of the type of solvent used. The formation of CHA was confirmed by FTIR analysis, where the carbonate ion peaks were observed in the spectrums. It was found that the mesoporous CHA with a high surface area was synthesized when high polarity solvents were used during surfactant washing. These results imply that high surface area mesoporous CHA can be obtained through surfactant washing, without applying calcination for surfactant removal, which may change the structure of the CHA during heat treatment.

Pore characteristics of mesoporous carbonated hydroxyapatite synthesised with different nonionic surfactant and carbonate concentration

Mesoporous carbonated hydroxypatite (CHA) is a promising drug delivery agent for disease treatment and could be a carrier for different types of drugs and antibiotics. It is still a challenge to introduce pores to carry drugs within the mesoporous CHA and obtain high surface area nanoparticles. This study investigates the effect of different types of nonionic surfactant and carbonate concentration on the pore characteristic of mesoporous CHA. Mesoporous CHA is synthesised through the coprecipitation technique using nonionic surfactants as pore templates i.e., P123 and F127 with different carbonate concentration. The axial view of transmission electron microscopy (TEM) images shows the pores formed within the particles are distributed randomly, while the parallel view demonstrates that nanopore channels are developed within the CHA particles. Nitrogen adsorption analysis provides the surface area and Pore Size Distribution (PSD) of the nanoparticles. The PSD shows that CHA synthesis with P123 and F127 has similar pore size, around 28.9 nm, but different surface area. The results confirm the different types of surfactant templates has a positive effect on the pore characteristic, while carbonate precursor concentration does not significantly change surface area and pore size.

Synthesis and Characterization of Mesoporous Hydroxyapatite

Among the porous media, hydroxyapatite (HA) possesses good biocompatibility and bioactivity properties with respect to bone cells and tissues, due to its similarity with the hard tissues of the body. In this study, mesoporous HA was synthesized using a soft-templating technique via a self-assembly between HA and cationic surfactant decyltrimethylammonium bromide (C10TAB), which is analogous to the synthesis of mesoporous silica MCM-41. This co-precipitation method involved formation of hexagonal-phase micelle template by the surfactant and the precipitation of HA surrounding the micelle. After ageing, calcination was carried out to remove the templates, revealing the pores as well as to produce more crystalline and more stable HA structure. This study showed that instead of hexadecyltrimethylammonium bromide (C16TAB) which was conventionally used, C10TAB could also be used to synthesize single-phase mesoporous HA with pore size ca. 3 nm. Ageing temperature of 120 °C, for 24 hours was found sufficient for the formation of mesoporous HA. The adsorption properties of mesoporous HA was able to be improved by increasing the water content of C10TAB-phosphate solution and by constant pH adjustment during the mixing of solutions.

Characterizations of Hydroxyapatite - Saccharomyces cerevisiae Complex for Bioethanol Production

Immobilized cell reactor (ICR) has been used widely for bioethanol production. It has been shown to improve the performance of fermentation efficiency. The immobilization of S.cerevisiae was simply performed by enriched cells cultured media harvested at exponential growth phase. Hydroxyapatite (HAp) was found to be a suitable candidate as a solid support of surface adsorption by S.cerevisiae. The strong affinity binding of phosphate backbone of S.cerevisiae and calcium ion in HAp had been proven the effectiveness of HAp as immobiliser, thus the yield from the fermentation process has been increased. However, specific characteristics for HAp-yeast complex such as size, porosity (pore size and pore volume), surface morphology and total surface area are the important factors that were needed to control in order to avoid the detachment of the microorganisms from solid support. The characterizations performed were Mastersizer for complex size determination, Scanning Electron Microscopy (SEM) for surface morphology and Brunauer, Emmett and Teller analysis (BET) for specific surface area determination.

Preparation and Characterization of Amine-Functionalised SBA-15

Ever since the first report of ordered mesoporous silica by the Mobil group, various preparation techniques for mesoporous were extensively studied. In addition to the desirable large surface area, surface of mesoporous silica could be modified for specific catalytic and sensor applications. In this present study, SBA-15 mesoporous silica was prepared and further surface modification was done using organoalkoxysilane (aminopropyl and ethylendiaminopropyl). The resulting bare mesoporous silica, anime-functionalised and diamine-functionalised mesoporous silica were characterized using FTIR, XRD, SEM and EDS for the analysis of incorporation of amine functional groups, phase analysis, powder morphology and elemental analysis.

Organic and Inorganic Acid Activation of Activated Carbon Fiber from Palm Oil Empty Fruit Bunch

Activated carbon fiber is known to posses better properties compared to granular and powdered variants, with significantly higher surface area and higher pore volume. Source of raw material and activation step are two crucial parameters for the pore development of activated carbon. Palm oil empty fruit bunch fiber contains naturally formed long open channels which offer better access of adsorbates into micropores. Chemical activation step typically involves inorganic acids such as phosphoric acid and sulfuric acid. However, such residues of inorganic acids might create unfavourable conditions for certain adsorption applications, if not removed properly from synthesized activated carbon fiber. Additionally, subsequent to the acid cleaning or removal step, most inorganic acids would eventually cause problems to the environment if acid disposal is not properly managed. This paper investigates on the effect of utilization of organic acids acetic acid and citric acid, as compared to commonly used inorganic acids, on the pore characteristics of palm oil empty fruit bunch fiber derived activated carbon fiber.