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Preparation and characterization of coconut shell activated carbon black for electrophotography toner application
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2023-11-03) Samanmali, V.G.C.; Wijewardhana, G.D.M.H.; Mantilaka, M.M.M.G.P.G.; Madugalla, T.B.N.S.; Wijesinhe, W.P.S.L.
Coconut shells (CS) are one of the main domestic wastes that are abundantly used as a precursor to producing activated carbon black (ACB) for various purposes. This study investigated a low- temperature chemical activation method (LTCA) using NaOH to prepare ACB from CS to apply as the black colourant in toner production. Initially, the cleaned CSs were subjected to a pyrolysis process at 550 °C for 4 hrs, and the resulting coconut charcoal was activated using NaOH at 120 °C. The porosity of the resulting ACB was investigated at different charcoal and NaOH solution volume ratios. The chemical characteristics, surface morphology, surface area and crystallinity of the ACB, and mineralogy of initial coconut ash were examined using Fourier-transform infrared (FT-IR) spectroscope and scanning electron microscopy (SEM) and powder X-ray diffraction (PXRD) analyses. The current study found that the weight percentage of ash in a CS is 0.6% and consists of SiO₂, MgO, CaCO₃, MnO, TiO₂, CaO, Al₂O₃, Fe₂O₃, P₂O₅, and fixed carbon. The PXRD shows the increase of graphitic nature with increasing NaOH volume. The FT-IR proves that ACB consists of carbonyl groups, carboxylic groups, aromatic C=C bonds and aromatic C-H out-of-plane deform bonds as the main functional groups, indicating the formation of aromatic compounds. The SEM images indicate that increasing NaOH volume causes irregular-shaped micropores with large diameters compared to the low NaOH volume exhibiting spherical micropores. Therefore, it concludes that LTCA with less NaOH volume causes the slow removal of C as CO₃ ²⁻ from the ACB and increases the surface area. In the future, these ACBs will be used to produce toners to identify the eligibility as the colourant for electrophotography toners.
Investigating the sound absorption characteristics of coconut shell-based structures
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2023-11-03) Senarath, N.D.D.D.; Jayalath, J.A.C.P.; Mendis, D.R.A.
This study investigates the sound absorption characteristics of structures developed using two filler materials: coconut shell powder and charcoal powder, with natural liquid rubber as the binder. Selected filler material and the binder are readily available in Sri Lanka. The sound absorption coefficient, defined as the ratio of absorbed energy to incident energy indicating the amount of sound being absorbed by a material, was experimentally studied using the impedance tube method in the frequency range of 1000-3500 Hz. Samples were prepared by varying the volume ratio of the binder and the filler. The sound absorption property of the prepared samples was tested by using the impedance tube for different frequencies within the range. The structures were further improved by increasing their thickness and changing the surface roughness by introducing holes with different depths to improve sound absorption. The coconut shell powder structure of 50% volume ratio with 1.5 cm thickness and hole depth of 1.1 cm showed a sound absorption coefficient in the range of 0.80-0.83 for 2500 Hz and the range of 0.85-0.93 for 3000 Hz. This implies that the coconut shell powder structure absorbs over 80% of the incident sound energy with a 2500 Hz or 3000 Hz frequency. Further, the charcoal powder structure of 66% volume ratio with 1.5 cm thickness and hole depth of 1.1 cm exhibited sound absorption of over 60% beyond 2000 Hz within the tested frequency range. Both structures are versatile, cost-effective, and eco-friendly sound absorption structures for various acoustic applications for high frequencies due to their flexibility, ease of preparation, and thin profile.
Evaluation of the potential of canarium zeylanicum seed oil for biodiesel production
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2023-11-03) Keshiya, P.A.W.; Ganehenege, M.Y.U.
Canarium zeylanicum, Sri Lankan Kekuna is an endemic plant in Sri Lanka with a high amount (around 51.80%) of oil in its seed kernel. The gas chromatography (GC) results showed that C. zeylanicum had a promising free fatty acid profile, suggesting that producing biodiesel with C. zeylanicum as feedstock was feasible. The acid value and the saponification value of the oil were found to be 1.0 ± 0.1 (mg KOH ⁄ g) and 178 ± 1 (mg KOH ⁄ g), respectively. As the acid value was ~1.0, C. zeylanicum oil can be directly converted to biodiesel by transesterification without performing any pre-treatments. Therefore, transesterification of C. zeylanicum oil with methanol using potassium hydroxide as the catalyst was performed to produce methyl esters, which can be used as biodiesel. The optimum conditions for the transesterification were investigated by varying the parameters: methanol: oil molar ratio (3:1 – 9:1), catalyst concentration (0.50 – 1.5%), and temperature (303 – 343 K). Periodic acid titrations were carried out to evaluate the free glycerol content. The methyl ester concentration was assessed by mass balancing. The optimal triglyceride conversion (94%) was achieved at room temperature in the presence of 1% potassium hydroxide as the catalyst when the methanol: oil ratio was kept at 6:1. Biodiesel properties including flash point, fire point, calorific value, density, cloud point, pour point and kinematic viscosity at 40 o C of C. zeylanicum biodiesel were characterized according to the ASTM standards, and the results obtained were 60.0 ⁰C, 75.0 ⁰C, 40.56 MJ kg⁻¹, 0.8370 g cm- ³, 10.0 ⁰C, 6.3 ⁰C, and 7.2 mm s⁻¹, respectively. As both the flash point and the fire point are lower than the minimum standard value, and the viscosity is slightly higher than the standard range of 1.9-6.0 mm s-1, C. zeylanicum methyl esters exhibit unpromising biodiesel properties. However, blending with diesel could be employed to improve the properties of the final biodiesel blend.
Low-cost counter electrode prepared using activated carbon derived from rice husk for dye-sensitized solar cells
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2023-11-03) Weerasinghe, M.I.U.; Kumarage, P.M.L.; Amarathunga,I.G.K.D.; Bandara, T.W.M.J.; Kumara, G.R.A.
Dye-sensitized solar cells (DSSCs) have emerged as promising alternatives for efficient and cost-effective solar energy conversion devices. However, the high cost and limited availability of platinum (Pt), traditionally used as a counter electrode (CE) material, has motivated the search for sustainable and low-cost alternatives. This study explored the potential of using activated carbon synthesized from rice husk to prepare low-cost CE for DSSCs. Rice husk is an abundant agricultural waste product, and the present study reveals that the active carbon synthesized from rice husk can be used to prepare DSSC counter electrodes. At first, dried rice husk was carbonized and then activated by heating to 900 °C for 20 minutes and quenching several times. The spray pyrolysis method was used to prepare activated carbon CEs using polyvinylpyrrolidone binder and isopropanol solvent. A series of experiments showed that CEs prepared using activated carbon derived from rice husk are suitable for fabricating low-cost and highly efficient Pt-free DSSCs. With the usual N719 dye and liquid electrolyte (I⁻/I³⁻ ), the DSSC utilizing this biomass-derived active carbon CE achieved an energy conversion efficiency of 5.62%, while that for Pt-based CE is 7.73%. The average open circuit voltage (Voc) and short circuit current density (Jsc) of the active carbon-based cell are 0.68 V, 15.90 mA cm⁻² relative to the Pt-based cell.
Comparison of x-ray attenuation in the energy range of 50-80 keV in aluminium and zircon mineral encased in epoxy matrix
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2023-11-03) Sivakumar, V.; Weerasekara, A.D.K.M.; Jayalath, C.P.; Jayasinghe, A.; Bandara, T.M.W.J.; Wijayaratne,K.; Gnanarathne, D.M.T.; Nanayakkara, D.K.K.
X-rays are ionising radiation that can penetrate and be absorbed in varying degrees by different materials. They are used in a range of applications, including radiography. However, exposure to X-rays can have harmful effects. Hence, the appropriate use of radiation shielding is essential to prevent unnecessary exposure to radiation for radiation workers, patients, and the general public. Lead and lead-based compounds are commonly used as shielding materials. Given the hazards associated with lead-based compounds, there is a growing interest in developing leadfree shielding materials that can offer comparable shielding properties. The project aimed to synthesize a lead-free and cost-effective shielding material that could attenuate X-rays in the energy range of 50-80 keV using locally available minerals. Samples with various thicknesses were prepared using 80 wt% zircon sand with 150 µm particle size and by using epoxy as the matrix. These prepared samples were exposed to X-rays with energies ranging from 50 keV to 80 keV in 10 keV increments, with a standard aluminium step wedge as the reference. Images were obtained using a Fujifilm computed radiography system. Subsequently, grayscale values of the exposed regions of the images were processed by a software tool developed using Python programming language. The grayscale values of the prepared samples at various thicknesses were compared with those of aluminium at various thicknesses for each energy value. For the energy range mentioned above, the prepared composite samples with thicknesses varying from 1 mm to 4 mm exhibited an attenuation comparable to those of aluminium with 9 mm to 33 mm thicknesses. This study presents an opportunity to develop radiation shielding materials containing locally abundant natural minerals, such as zircon, for radiation protection in medical diagnostic procedures.