School of Chemical and Bio Engineering
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Browsing School of Chemical and Bio Engineering by Author "Abubeker, Yimam (Asst. Prof.)"
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Item Evaluation, Characterization and management of Naturally Occurring Radioactive Materials and disused radioactive waste in Water and Soil Samples(AAU, 2017-12) Belete, Derib; Abubeker, Yimam (Asst. Prof.)In this study radiological hazards to members of the public and workers from exposure to natural radioactivity as a result of mining activities from Kenticha Tantalum Mines in Ethiopia, have been studied through several exposure pathways using direct gamma spectrometry to determine 238 U, 232 Th, 40 K, 226 Ra and 222 Rn in tantalum ore, soil, waste, waste tailing and water samples. Additionally, cancer risk assessment associated with NORM was estimated. The average activity concentrations of 238 U, 232 Th, 40 K, 226 Ra and 222 Rn in tantalum ore were 78.653±1.431Bq/kg, 24.945±0.492 Bq/kg, 603.170±55.013 Bq/kg, 69.478±31.0 Bq/kg and 112.554±50.249 kBq/m 3 , respectively. In soil the activity concentrations were 69.354±1.081 Bq/kg, 15.479±0.231 Bq/kg, 718.880±65.531Bq/kg, 68.923±1.7Bq/kg and 111.655±2.681 kBq/m 3 , respectively and in solid waste samples 110.496±1.907 Bq/kg, 15.009±0.274 Bq/kg, 607.269±55.375 Bq/kg, 98.300±38.6 Bq/kg and 159.246±62.607 kBq/m 3 respectively. The values were generally above the worldwide average activity concentrations in all samples, except thorium-232.This might be due to the high contents of 238 U decay families and 40 K in the granite – pegmatite rocks of Kenticha area. The corresponding average external dose rate at 1m above the ground in air for tantalum ore, soil and solid waste samples were 76.407 nGy/h, 71.337 nGy/h, 85.408 nGy/h, respectively which were above worldwide average value of 60 nGy/h. The annual equivalent doses were also estimated as 0.021±0.003 mSv, 0.020±0.001 mSv and 0.023±0.004 mSv for ore, soil and solid waste samples, respectively and were found to be lower than the worldwide average of 2.42 mSv/y. Likewise, the radon emanation coefficient which is the fraction of radon generated within the grains of materials and escaped to the pore space, varied from 82±2% to 85±2% for ores, from 82±2% to 84±2% for soil, and from 53±15% to 83±15% for solid waste samples. Also, the radon exhalation rate varied in the range of 41.7±25.7 to 87.3±25.7 mBq/m 2 .s for ores, from 56.2±1.4 to 58.1±1.4 mBq/m 2 s for soil and from 53.3±32.1 to 120.2±32.1 mBq/m 2 s for solid waste, respectively. The radium equivalent activity, external hazard index, internal hazard index and representative gamma index, for all samples were estimated and generally found to be within recommended international values. Annual effective dose was evaluated from only external gamma dose rate. However, the relatively high values in all the other parameters measured implies that the Kenticha tantalum mine and its environments shown the significance of naturally occurring radioactive material. Therefore, the results from this study will ignite in decisionmaking for future set-up of further research for the management of NORM wastes in Kenticha tantalum mine and for the emerging mining industry in Ethiopia. Radioactive material containing Cs-137, Ra-226, Co-60, Sr-90 and Am-241 were treated using the developed method. In the method different type of materials (cement, sands, concrete, etc.) were tested for absorption of radiation emitted from the source as well as suitability of the material for storage for long time. It was found that the best materials to be used in radioactive waste treatment is Concrete, where the surface dose reduced from 150 to 3 µsave/h. In addition, design of storage container was proposed (with specification). Finally, based on indications of the present research findings and scientific background, recommendations were forwarded to help on amending nuclear waste management problems or indicate for other possible alternatives such as radiation map of Ethiopia.Item Particle Board Production from Maize Cob(AAU, 2018-11) Dagne, Abetie; Abubeker, Yimam (Asst. Prof.)Particleboard is a wood-based panel product manufactured under pressure and temperature from the particles of wood or other any lignocellulosic fibrous materials and a binder. This study presented an experimental work which investigates the potentiality maize cob in the production of particle board using modified starch adhesives and wood glue (top bond) as an alternative source of adhesive and also studied effects of control variables in the product. A general factorial design was used for to prepare 27 experiments by varying control parameters. The maize cob particle, modified starch, wood glue (top bond) and the mixed ratio adopted were 69.2% : 15.4, 17.9%, 20.3% and 15.4% respectively, thoroughly mixed manually by using the mixer. The mixture was then poured into a mould with a dimension 100mm × 100mm × 15mm. The particleboard was compacted using a hydraulic press in two compacts. The panels of densities were varied between 6840kg/m 3 and 9083.33kg/m . Percentage of water absorption was increased with increasing time of immersion. An average moisture content of all boards was found to be 11.43%. The average internal bonding was 0.132 N/mm 2 relatively low internal bonding compared with urea and phenol formaldehyde resin made PB. The results showed that the maize cob, starch and wood glue (top bond) combination have high potential to be used indoor application for ceiling roof or by laminating Formica or veneers, it can be used for building and furniture applications.Item Production and Characterization of Biodiesel from Avocado Peel Oil (APO)(AAU, 2018-07) Tafere, Aga; Abubeker, Yimam (Asst. Prof.)Biodiesel is as alternative energy source and a promising potential that grows rapidly, due to its great contribution to the environment, renewable, non-toxicity, biodegradability, essentially sulfur free and its role as a strategically source of renewable energy in substitution to diesel oil and contributes a minimal amount of net greenhouse gases. In this study, biodiesel production from waste avocado peel oil was investigated in laboratory approach. Experimental results evaluate the major optimum process parameters for basecatalyzed transesterification on biodiesel yield as well as its properties. The most important variables affecting methyl ester yield during the transesterification reaction are the molar ratio of alcohol to oil and the reaction temperature. From this thesis, the optimum operating conditions for the extraction of oil from avocado peel oil. For this, particle size of 2.6 mm, solvent type N-hexane and extraction time of 3-5 hr were considered. A general factorial design was applied to investigate the effect of process variables on oil yield and biodiesel. Maximum oil yield of 40.6% was obtained for particle size of 2.6 mm at extraction time of 5 hr. A 95.2% FAME conversion was also obtained using a methanol/oil ratio of 6:1, 1.21g NaOH, reaction time 67.5min and 60 0 C reaction temperature. The important properties (characterization) of the experimental biodiesel sample of the biodiesel (pH, specific gravity, API specific gravity, density, kinematic viscosity, cloud point, cetane number, iodine value, and high heating value) well-matched the relevant international standards for biodiesel quality, were compared to those of ASTM and EN standards for biodiesel. The comparison shows that the avocado peel oil used as a raw material for biodiesel production as an alternative fuel.Item Production and Characterization of Oil from Brassica Nigra Seeds Using the Solvent Extraction Method(AAU, 2018-11) Getachew, Chane; Abubeker, Yimam (Asst. Prof.)The objective of this study was the production and characterization of oil from Brassica Nigra seeds using the soxhlet extraction method were undertaken. In the soxhlet extraction a n-hexane was chosen to determine the effect of extraction time (2,4 and 6 hours), extraction temperature (65,70 and 75℃) and solid to solvent ratio (0.08,0.1 and 0.12) on yield of extraction oil. Firstly, the oil extract was characterized by density, moisture content, specific gravity, viscosity and refractive index, saponification value, iodine value, acid value, peroxide value and the results were compared with literature. The results showed that there is no difference from the seed oil extract from the Brassica nigra seeds which was producing in other parts of the world. therefore, the extraction and physicochemical properties of seed oil from Brassica nigra seed using a soxhlet extraction method has been carried out. A Box-Behnken Design (BBD) was applied to extraction process using Design Expert software and linear regression model was obtained growing the individual effect of extraction time, solid to solvent ratio and extraction temperature as parameter and their interaction in the entire extraction process. For the soxhlet extraction, the maximum oil yield has been determined as 46.205% after the extraction time of 2 hours with solid to solvent ratio (0.12g/mL) at extraction temperature of 70℃ and the minimum oil yield 34.97% was found at the extraction time of 4 hours with extraction temperature of 65℃ at solid to solvent ratio (0.08 g/mL). Therefore, increasing solid to solvent ratio, extraction temperature and decreasing extraction time will increase the amount of oil extracted.the selected seed oil properties (specific gravity,viscosity, density, Saponification Value, Acid Value, Iodine Value, Peroxide Value and refractive index) of the extracted oil were determined and the result of characterization of the oil indicated that the viscosity at 21ºC ( 9.16*10^-6 m2/s) and specific gravity at 20℃ ( 0.89346), density(0.8891g/cm3), Saponification Value(172.788 mgKOH/gm), Acid Value(2.992 ), Iodine Value(95.26), Peroxide Value(2.14) and refractive index(1.45504) .Item Utilization of waste animal bone as a heterogeneous solid base catalyst for transesterification of Jatropha oil(AAU, 2018-06) Kaleab, Bizuneh; Abubeker, Yimam (Asst. Prof.)Heterogeneous catalyst plays a vital role in transesterification process, especially in view of cost and reusability. In this study, heterogeneous solid base catalyst was prepared by impregnating the waste animal bone with different weight percent (wt%) KOH solution followed by drying and calcination at 900 °C for 3 hr. Having screened the catalytic performance and basicity of animal bone loaded with different K-compounds, 12 wt% KOH loaded on animal bone was chosen. The physico-chemical properties of animal bone, support and the KOH-impregnated calcined animal bone catalyst were characterized by means of titration (for basicity of catalyst), Fourier Transform Infra-Red (FT-IR) spectroscopy and X-Ray Diffraction (XRD) spectroscopy measurements. Thermogravimetric Analysis (TGA) was also performed for the selected catalyst. Catalytic performance of the catalyst was evaluated by transesterificating Jatropha oil with methanol in batch reactions. The Box-Behnken Design (BBD) of the Response Surface Methodology (RSM) was employed to investigate the effects of reaction temperature, catalyst loading and methanol to oil molar ratio on Fatty Acid Methyl Ester (FAME) yield. Maximum yield of 96.74% was obtained at 11.56:1 methanol to oil molar ratio, 5.08 wt% catalyst loading, 64.05 ii | P a g e o C reaction temperature and 500 rpm stirring speed in 3 hr reaction time. Reusability studies indicated that the prepared catalyst could be applied to at least three consecutive batches of the transesterification reaction without any significant loss of activity. The effects of temperature (313, 321.3, 329.6, and 338 K) and time (1, 2, 3, and 4 hr) at optimum conditions on the conversion of the oil into FAME were also investigated. The results obtained indicated a pseudo-first order kinetics for the transesterification reaction using the prepared catalyst. The activation energy obtained was 38.55 KJ.mol -1 . The physical, chemical and fuel properties of the produced FAME met the standard specifications.