Master of Science By Research

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Browsing Master of Science By Research by Author "Amarasinghe, BMWPK"

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    item: Thesis-Abstract
    Coir pith activated carbon for the removal of dyes, organics and heavy metals from aqueous solutions
    Dhanusekera, DW; Amarasinghe, BMWPK
    Adsorption of textile dyes, organics and heavy metals onto coir pith based adsorbents from aqueous solutions were studied. Raw coir pith and thermally activated coir pith at 700°C were used as adsorbents. Batch experiments showed that both adsorbents are capable of binding appreciable amounts of impurities from aqueous solutions. Thermally activated coir pith was superior to raw coir pith for dyes and phenol removal. Heavy metal adsorption capacities for both adsorbents were similar. Batch adsorption experiments were conducted in detail for dye removal to determine the factors affecting adsorption and kinetics of the process. Fixed bed column experiments were performed to study practical applicability and breakthrough curves were obtained. The maximum adsorption was observed at solution pH values between 5-9 for Methylene blue and Malachite green. Solution pH value of 2 showed maximum adsorption for Nylosan blue. The adsorbent to solution ratio and the dye concentration in the solution affect the degree of dye removal. The equilibrium data were satisfactorily fitted to Freundlich isotherm. The kinetic data fits to pseudo second order model and kinetic parameters were calculated. Column experiments showed 'S' shaped breakthrough curves and the results followed Bed Depth Service Time (BDST) model. Fixed bed adsorption capacities were lower compared to batch experiments.
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    item: Thesis-Abstract
    Extraction of rice bran oil using aqueous media
    Kumarasiri, MPM; Amarasinghe, BMWPK
    Rice bran oil is widely used in pharmaceutical, food and chemical industries due to its unique properties and high medicinal value. In this study extraction of rice bran oil from rice bran available in Sri Lanka, using aqueous media has been studied and key factors controlling the extraction and optimal operating conditions were identified. Several methods of bran stabilization were tested and the results were analyzed. The yield and quality of aqueous extracted oil was compared with hexane extracted oil. Aqueous extraction experiments were conducted in laboratory scale mixer-settler unit. Steaming, hot air drying, chemical stabilization and refrigeration control the lipase activity. Steaming is the most effective stabilization technique. The extraction capacity was highest at solution pH range 10 to 12. Higher oil yield was observed at higher operating temperatures (60°C - 80°C). Kinetic studies revealed that extraction was fast with 95 % or more of the extraction occurring within first 10 to 15 min of contact time. Highest oil yield of 161 mg! g and 131 mg! g were observed for aqueous extraction for par boiled bran and raw rice bran respectively. The quality of the aqueous extracted oil was compared with that of hexane extracted oil and it was found low in free fatty acid content. Iodine value and saponification value was similar to hexane-extracted oil, but the peroxide value was higher. Furthermore, the colour of aqueous-extracted oil was paler than solvent-extracted oil
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    item: Thesis-Abstract
    Optimal operating conditions & equilibrium characteristics of rice bran oil extraction
    Gangodavilage, NC; Amarasinghe, BMWPK
    Rice bran is the cuticle between the paddy husk and the rice grain and is obtained as a byproduct in rice processing. The bran contains 12-25 wt% oil and approximately 98% is extractable. Rice bran oil is a very important source of oil, both as an edible oil and non-edible oil. The oil has high medicinal value, due to presence of anti-oxidants, anti-cancer agents, cholesterol reducing agents, skin improving agents, antidandruff and anti-itching agents. The oil can also be used for production of soap, surfactants, cosmetic formulations, emulsifiers, textile auxiliaries, synthetic rubber products etc. In this work, extraction of rice bran oil from various brands of rice bran available in Sri Lanka has been studied. Experiments were conducted using pilot plant scale leaching unit and the soxhlet apparatus to extract rice bran oil using hexane as the solvent. The key factors controlling the extraction have been identified. Results show that the bran obtained from parboiled paddy has a higher yield of rice bran oil compared to the raw rice bran. Method of bran pretreatment, extraction temperature, extraction time, pellet size and free fatty acid content are the factors affecting oil extraction. Comparison of extraction results by various pretreatment methods shows an enhancement of oil extractability due to steaming. Analysis of the extracted oil shows that steaming is the most effective method of bran pre-treatment with respect to the FFA content. Pelletization of bran provides easy percolation and avoids channeling of the solvent and contamination of the oil from fine solids. Results show a decrease in extraction rate with time and this may be due to the fact that the solute has to diffuse from the interior of the pellet in the later stages of extraction. Extraction of rice bran oil using organic solvents was compared with aqueous extraction. The highest yield for aqueous extraction was obtained at 70°C and pH 12. Refined and raw rice bran oil and commonly used vegetable oils were analyzed and the results were compared. Tie line and mass transfer data necessary for batch and continuous leaching equipment design were determined.
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    item: Thesis-Abstract
    Reverse flow cyclones for collection of tea dust
    De Silva, IMBM; Amarasinghe, BMWPK
    Reverse flow cyclones are used most extensively in the chemical process industries for gas - solid separation. Cyclones are often employed to collect large particles (>5Ilm) that can be used not only as an air pollution control device, but also for recover particulate matter and size separation of particles. Common features found in locally designed cyclones are ineffective and crudely designed. Design of cyclone is more towards realizing a shape of the cyclone than the performance. Customized design approach gives a cyclone with greater collection efficiency, smaller in size or with lower pressure drop that would be found for a conventional standard design. Since the customized design procedure requires trial and error calculations, this research focused on the importance of the development of a computer package: "CycDesign" . Using this package, a pilot scale reverse flow cyclone is designed and fabricated. This unit was used to examine the suitability of abating the air pollution caused due to dust generated from the fluidized bed dryers in tea industries. Trials were also done for sawdust, cement, quarry dust, talc powder and silica sand. Inlet and outlet particle size distributions were measured. Above 90% Overall collection efficiencies were attained for all the types of dust tested. For tea dust 99.2% collected experimentally which was predicted as 100% by the computer package. Also the computer package can be used to predict performance and dimensionless parameters for a cyclone design. It predicts that a continual decrease of Stokes number based on cut diameter, with increasing Reynolds number Re, for cyclones having different height to diameter ratio HID. According to predictions, collection efficiency increases with HID ratio of the cyclone. The declining patterns of fractional efficiency can be visualized with decreasing pressure drop across the cyelone and particle density. A decrease in fractional efficiency can be observed with the increasing of gas flow rate, gas temperature, and gas density..
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    item: Thesis-Abstract
    Rice bran oil extraction : effect of bran type on oil yield and properties
    (2015-02-08) Kodituwakku, DS; Amarasinghe, BMWPK
    Rice is a unique crop of great antiquity and akin to progress in human cultivation. The rice seed mainly consists of the husk, rice bran, rice germ and white rice. Rice bran is the byproduct of the rice milling process. The rice bran contains 15-20 wt. % oil, out of which about 95% is extractable. Rice Bran Oil is a high-grade vegetable oil with some very unique characteristics that is excellent in both edible and non-edible ways. Rice bran oil is vastly superior to traditional cooking oils due to its flavor, stability properties, good fry-life at high temperatures and high level of natural antioxidants with nutraceutical value. It also has a significant hypocholesterolemic effect and an anti-cancer effect and takes care of the skin. Rice bran oil can be used in soap, detergent, paint, sunscreen products, hair conditioners, cosmetics, etc. as well. In this work effect of bran type on oil yield and properties has been studied for six varieties of rice available in Sri Lanka. IPA was used as the solvent in soxhlet apparatus to extract rice bran oil. Results show that the yield approximately varies from 18% to11% for the types of bran tested and this may be due to the difference in degree of milling, seeding times and genetic variations of paddy. The properties tested include FFA content, Iodine value, Saponification value, Unsaponifiable Matter and specific gravity. Differences for these values for different bran type arose due to the genetic variations of paddy. Highest FFA content recorded was 1.98% and the lowest was 1.25%. Fatty Acid composition has been determined and Mass Transfer Co-efficient has been calculated for the chosen types. Oleic, Linoleic and Palmitic are the Fatty Acids which have the highest values. Mass Transfer Coefficient was 4.264 x10 6ms-1 for AT307 variety and 4.258 x10 6ms-1 for BG352 variety. Oil extraction and analysis of raw and parboiled bran has also been experimented and results show that bran obtained from parboiled paddy has a higher yield of rice bran oil compared to raw rice bran. FFA content is lesser in oil obtained from parboiled bran than that of raw bran. Cross flow extraction was carried out for selected bran types and the triangle diagram was prepared. In cross flow extraction, % of oil extracted reduces from the first to the last stage in any variety. Suitability of rice bran oil extracted from varieties of bran available in Sri Lanka as a raw material for food items, pharmaceuticals and bio-fuel production was further studied. LD356 seems to be the best suited variety for biofuel production, from the varieties tested. BW364, which gives the highest unsaponifiable matter content, has the best potential for pharmaceutical production. For food applications, LD356 and AT307 are the best options in terms of fatty acid compositions. BG352 can be considered as the acceptable type for cosmetic and personal care industry.
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    item: Thesis-Abstract
    Rice husk based adsorbents for dye removal from wastewater
    Jayatunga, GK; Amarasinghe, BMWPK
    Adsorption of textile dyes onto rice husk based adsorbents from aqueous solutions was studied. Batch experiments were conducted to determine the effect of method or treatment of rice husk on adsorption. Raw rice husk, chemically or thermally activated rice husk were tested for adsorption of Malachite green and Nylosan blue. The maximum adsorption was observed at solution pH values above 6 for Malachite green and below 3 for NyIosan blue. The adsorbent to solution ratio, solution dye concentration, contact time and adsorbent particle size affect the degree or dye removal. Carbonizing at 700°C for 1 hr was observed as the optimum condition for thermal activation. Base washed rice husk and thermally activated rice husk showed high adsorption capacities compared to acid washed rice husk, phosphoric acid treated rice husk and raw rice husk. Malachite green dye showed high adsorption compared to Nylosan blue for all the varieties of rice husk based adsorbents tested. RH based adsorbents were compared with the commercially available granular activated carbon. Equilibrium data were satisfactorily fitted to Langmuir and Freundlich isotherms. Kinetic data were fitted to the Pseudo second order model and initial adsorption rates and rate constants were determined. Fixed bed column studies were conducted. for raw rice husk, base washed rice husk and thermally activated rice husk and breakthrough curves were obtained. Bed capacity, breakthrough time, length of the unused bed and time required for full bed exhaustion under ideal condition was calculated from breakthrough curves. Bed capacities for Malachite green and Nylosan blue for thermally treated rice husk were 45 and 30 mg/g respectively. Experimental data obtained from unsteady state fixed bed column studies were used for scale-up calculations and industrial scale fixed bed adsorber dimensions were estimated. Tests on real textile waste water consists of a mixture of dyes showed that Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) levels can be reduced to 210 mg/l and 30 mg/I respectively using thermally activated rice husk.
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    item: Thesis-Full-text
    The Optimum operating conditions for extraction of chlorophyll from Alternanthera sessilis(Linn.), cultivated in Sri Lanka
    Jinasena, MAM; Amarasinghe, ADUS; Amarasinghe, BMWPK; Prashantha, MAB
    Chlorophyll is widely extracted for industrial applications and is a key topic of scientific and commercial interest. Alternanthera sessilis, which is known as mukunuwenna in Sri Lanka, is one of best selections for the extraction of chlorophyll due to the good extraction efficiency, availability and low cost. In this work, the optimum operating conditions for the extraction of chlorophyll from A. sessilis using solvent extraction were studied using buffered 80% aqueous acetone. The results revealed that the best solvent volume to A. sessilis weight ratio, which gives the highest yield of chlorophyll, was 5 ml/g. The effect of temperature and the extraction time on the extraction was also studied. The optimum temperature of extraction is 50°C and the optimum time of extraction is 45 minutes. The mass transfer of chlorophyll from A. sessilis at 20°C and 30°C was modeled mathematically, using general mass transfer equations. The experimental results showed that the degradation of chlorophyll beyond the temperature of 30°C is significant. The saturation solubility of chlorophyll a was 54.06 and 107.6μg/ml and that for chlorophyll b was 23.13 and 29.68 μg/ml at the temperatures of 20 and 30°C respectively. Furthermore, the optimum pre-processing method and the storage conditions were studied as post harvest operations for A. sessilis. The optimum method of pre processing was identified as mechanical grinding. For one day storage, ambient air conditions (indoor) were the optimum conditions; and for a longer storage time it was the refrigerator conditions (15oC). Using the extract, commercial chlorophyll, Sodium copper chlorophyllin has produced with a 33.3% conversion of chlorophyll and its derivatives, using a modified process. The kinetics of degradation of chlorophyll of the produced sodium copper chlorophyllin follows a first order relationship between the concentration and the time. The relationship between the rate constant and the temperature follows the Arrhenius behavior. The activation energy for chlorophyll a and b are 3.014 and 2.78 kcal/mol respectively. The rate constants for chlorophyll a and b at different temperatures are also obtained.