Browsing by Author "Jayasuriya, C.K."
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Item Arsenic Removal from Water by Using Rice Husk Ash(Uva Wellassa University of Sri Lanka, 2016) Edirisinghe, N.P.; Premachandrd, B.A.J.K.; Jayasuriya, C.K.Arsenic is a toxic heavy metal present in water in organic and inorganic forms. It is highly toxic in its inorganic form. Long-term exposure to inorganic arsenic, mainly through drinking water, can lead to various health issues. The current research focuses on removing arsenic from water by the adsorption method using Rice Husk Ash (RHA). Particularly, RHA was used to check its suitability for arsenic removal since it will enable a value addition to the agricultural by-product. Rice husks were washed, dried and ground and then separated into different particle sizes using sieve analysis. Ashes from the rice husks were produced using a muffle furnace at 5 different temperatures as 300 °C, 400 °C, 500 °C, 600 °C and 700 °C. The resulting ashes were used as the absorbent in the columns through which 75 ppb arsenate solutions were passed. The experiments were carried out to determine the effects of particle size, charred temperature, pH and the use of RHA treated with phosphoric acid. Amounts of arsenic adsorbed were determined by using Atomic Absorption Spectrophotometry. Maximum adsorption was observed for RHA with particle sizes in the range (150 -500) 1.1.111 and the lowest for RHA with particle sizes in the range (125 -150) p.m. This result is deviated from the expected results. Theoretically, adsorption should be higher for small particles due to larger surface area. The maximum adsorption occurs at a charred temperature of 600 °C. Decreasing adsorption efficiencies after pH 7.0 for untreated RHA and after pH 7.5 for treated RHA were observed and it could possibly be due to the adsorption of more hydrogen ions due to high ion migration rate and high ion concentration. However, further investigation is required to study the effect of pH on the adsorption of arsenate by untreated and treated RHA. Keywords: Water, Purification, Arsenic, AdsorptionItem Degradation of vulcanized natural sesame oils(Uva Wellassa University of Sri Lanka, 2015) Rathnayake, R.M.M.D.; Jayasuriya, C.K.Vulcanized rubber products used in various applications cause serious environmental issues due to their very slow degradation (Treloar, 2005, Blackley, 1997). The present research focuses on enhancing degradation of vulcanized rubber products which are discarded after their usage. Due to the unsaturated nature, rubber molecules are susceptible to degradation in the presence of peroxide radicals (Adhikari, et al 2000). Therefore, it is expected that the peroxide radicals produced in the oxidation of natural oils can enhance degradation. The oxidation of a natural oil increases with it’s degree of unsaturation which increases the rate of degradation. Therefore, highly unsaturated locally available soybean and sesame oil were used in the study. Materials and Methods Vulcanized rubber samples were prepared according to the tire tread formulation. Technically specified rubber (TSR) (100.00 g) was added into the internal mixer and allowed to crush well. Then stearic acid (2.00 g) and zinc oxide (5.00 g) were added and mixed well. After about 3 minutes carbon black (N 375 black) (73.00 g) and process oil (naphthenic oil) (5.00 g) were collected into the internal mixer. Finally, antidegradent N- isopropyl- N- phenyl-p- phenylenediamine (IPPD) (2.70 g) and wax (1.00g) were added and allowed to mix well. The prepared mixture was taken out from the internal mixer and set aside to cool. After cooling, the mixture was processed in the two roll mill for about 7- 8 minutes at the same time adding the accelerator N- tert- butyl- 2- benzothiazolesulferamide (TBBS) (1.00 g) and sulphur (2.50 g). Finally a thick rubber sheet was obtained. Then the sample was cooled for 16 h and vulcanization of the samples was carried out in the hydraulic hot press at 150 ºC for 28 minutes to produce sheets of thickness approximately 3 mm (White, 1995). The resulting rubber sheets were cut into square pieces (7.5 × 11.0 cm ) and immersed in soybean and sesame oil for different period of times at room temperature. In addition, the effect of these oils on degradation in the presence of sun light and copper catalyst, only for 5-week time period was also studied. At the end of the each time period, samples were taken out from the oil and wiped well before testing and characterization. Tensile properties (ISO 37-1977) and tear strength (ISO 34-1979) were determined with reference to the vulcanized rubber sample which was not immersed in oil (blank). The thermal properties were obtained by exposing the samples to a temperature range of (23-500) °C at an increasing rate of 5 °C min Results and Discussion Stress- Strain curves for natural rubber samples immersed in soybean oil and in sesame oil are given in Figures 1 and 2, respectively. According to the results all the samples immersed in sesame oil and soybean oil, have reduced their tensile strengths compared to the blank. The tensile strength values of the samples immersed in soybean oil for equal time period are lower than those immersed in sesame oil. According to the results, when the exposure time is increased the tensile strength values in both type of oils have decreased significantly. The greater losses of tensile strengths were shown by the samples in the presence of sun light and copper catalyst. Similar pattern of results were obtained for tear strength (Figure 3). TGA results show that the degradation temperatures of all the samples immersed in sesame oil and soybean oil have been reduced compared to the blank sample. The degradation temperatures of the samples, immersed in soybean oil are lower than those immersed in sesame oil for the same time period.Item Development of a mosquito-repelling paint(Uva Wellassa University of Sri Lanka, 2015) Kanagasundram, T.; Jayasuriya, C.K.Mosquito-borne diseases affect millions of people worldwide each year. They are the carriers of many harmful diseases such as West Nile Virus disease; Malaria, Dengue Fever, Chikungunya, Lyme disease, etc. (Aremu et al., 2009). A mosquito repellent is a substance applied to skin, clothing, or other surfaces which discourages mosquitoes from landing or climbing on that surface. However, existing products used for mosquito control have varying degrees of effectiveness (Patel et al., 2012). In this research, attempts were made to develop a mosquito repelling paint. In general, paints are stable mechanical dispersions of pigment, binder and solvent. Upon evaporation of the solvent, the pigment and binder form a continuous film that can be protective or decorative or both. Also some additives are normally added to paint formulation in order to tailor the paint to a specific purpose. In this research, Neem oil was used as an additive on emulsion paint for the purpose of developing a mosquito-repelling paint. Methodology Neem oil was extracted from Neem seeds by mechanical pressing method. A known quantity of Neem oil was added to the desired amount of the pure paint. The mixture was stirred vigorously for 20 minutes by using a magnetic stirrer. The above procedure was repeated for four different pure paint/ Neem oil ratios of 90:10, 88:12, 85:15 and 80:20. Two paints, one light and other dark were used in the study. The samples prepared using the light colour paint with varying amounts of Neem oil were named as L10, L12, L15 and L20, respectively. The samples prepared using the dark colour paint with varying amounts of Neem oil were named as D10, D12, D15 and D20, respectively. A box with desired dimension was prepared using cardboard in which the upper part was removed and replaced with a glass. The modified paint was applied to two vertical surfaces and pure paint which was used as the control was applied to the rest of the two vertical surfaces of the box. Then it was allowed to dry. The mosquitoes were caught by using a net and then placed them in the box already coated with paint. The above procedure was repeated for the samples prepared with both light and dark colour paints. The mosquito-repellency of the paints were calculated by counting the number of mosquitoes landed on each vertical surface over a testing period of 4 hours between 17.00 h and 21.00 h. Readings were taken at each 30 min interval, at 25- 30 °C and a relative humidity of 60 – 80% under both the presence and absence of light. Finally, the effect of Neem oil on desired paint properties such as glossiness, contrast ratio, abrasion resistance and water resistance were determined. Results and Discussion The mosquito-repellency was calculated according to the number of mosquitoes that were prevented from landing compared to the number of mosquitoes that landed on the control by using the following equation (Kazembe et al., 2012).Item Investigation on Suitability of Banana Fiber as a Filler Material in Natural Rubber Latex-Based Household Gloves(Uva Wellassa University of Sri Lanka, 2016) Kirushanthi, T.; Edirisinghe, D.G.; Jayasuriya, C.K.With increasing demand for polymer based household items, waste disposal has become an environmental issue. Thus, researchers are concerned on producing cost effective products, which are also biodegradable. The objective of this study is to investigate the possible use of banana fiber as a filler material in making natural rubber based household gloves with improved biodegradability and cost effectiveness while retaining the desired properties. In this study, long banana fibers were extracted mechanically and ground using a blender. Then, they were sieved and size less than 400 p.m particles were selected. These were chemically treated using 4% sodium hydroxide and 2% of sodium sulfite. Natural rubber latex compounds were prepared changing banana fiber content. The films were made using casting method. The physico-mechanical properties of films, including tensile, tear and accelerated aging properties were analyzed and compared with the control sample in which no banana fiber was added. Tensile and tear strength have decreased with increasing fiber percentage compared to the control sample. This may be due to the poor interaction between rubber matrix and banana fiber. Banana fiber added natural rubber latex films exhibited, in comparison, a higher Young's modulus at 100% elongation than the control sample. Results also showed that the elongation at break has decreased steadily with the increasing of the fiber loading. Increase in the modulus and the decrease in percentage elongation may be attributed to the restriction of molecular chain movements resulting from the presence of fiber in the rubber matrix. Significant increase in retention value can be seen when higher amounts of fiber was incorporated suggesting enhanced durability in the condition of heat, oxygen and ozone. Use of nano-sized fiber particles, better coupling agent and an alternative fiber dispersing method may improve the mechanical properties. Keywords: Biodegradable, Natural rubber, Latex glovesItem Preparation and Characterization of a Mosquito Repellent Paint(Uva Wellassa University of Sri Lanka, 2016) Arunraj, A.; Jayaweera, N.; Jayasuriya, C.K.Paints are used to decorate, protect and extend the life of natural and synthetic materials. The current research focuses on a different aspect on which paint can be utilized. The objective of this study was to develop a mosquito-repelling paint while maintaining the desired paint properties. In this regard, neem oil, one of the known mosquito repellents was used as an additive in emulsion paint formulation. A series ofpaint samples were made according to the interior paint formulation by varying the amount of neem oil. The reference sample was prepared without adding neem oil. In addition, properties were also compared with a commercial paint sample. For each 500 g of emulsion paint, neem oil was added in amounts to prepare samples with neem oil percentages 4 wt%, 8 wt% and 12 wt%. Various paint properties of thus prepared paint samples were investigated. The mosquito repellency of the paint samples were monitored by counting the mosquitoes flying on to the surfaces coated with the paint at 30-minute intervals for 4 hours. Neem oil added paint samples show improved mosquito repellency, however, it could be retained only for few days. This drawback could possibly be remedied by using a proper bonding agent to prevent volatility of the active ingredient. According to the results, opacity and glossiness of the paints with neem oil are lower compared to those of the industrial paint sample. Some improvements in these properties could possibly be achieved by maintaining pH in the neem oil added samples close to that of the industrial sample. According to the results, water resistance is significantly reduced upon adding neem oil compared to the industrial paint sample. Further research must be carried out with a proper bonding agent to retain the desired paint properties as well as the mosquito repellency. Keywords: Mosquito-repelling paint, neem oilItem Reducing Photocatalytic Degradation of Exterior Paint Prepared with TiO2(Uva Wellassa University of Sri Lanka, 2016) Dissanayake, S.D.M.A.S.S.; Jayaweera, N.; Jayasuriya, C.K.Titanium dioxide (Ti02) is the most widely used white pigment in the paint industry. TiO, is a photocatalyst under ultraviolet (UV) light. When it absorbs UV radiation, a UV photon which overcomes the energy gap between the valence and conduction bands of TiO, creates an electron-hole pair. The hole then reacts with water to produce hydroxyl radicals followed by a series of other reactions that produce more and more hydroxyl radicals which react with the organic matter to form water and carbon dioxide leading to the destruction of the polymeric binder of the paint film. This effect could be reduced by mixing the pigment with an inert oxide such as silica. The current research focuses on reducing photocatalytic effect of TiO2 and thereby increasing the durability of the paint. A series of emulsion paint samples were prepared according to an exterior paint formulation by varying the ratio Ti02:Si02. Formation of photocatalytic oxides were determined by measuring the absorbance using Orange II solution. Samples were exposed to UV radiation by applying them on small watch glasses as thin layers. The solution absorbance values on the samples were measured before and after exposure to UV radiation and recording absorbance at 60 min, 120 min and 240 min. The best sample with the lowest photocatalytic effect was used to determine paint properties. The lowest photocatalytic effect was observed for the sample containing 20% SiO2 and 80% of TiO2 and the paint properties were determined for that sample. Most of the properties are comparable with those of the industrial paint. However, viscosity and opacity are significantly reduced. It could be due to the undesired particle size of silica incorporated. Further investigations must be carried out to determine the optimum particle sizes which give the lowest photocatalytic effect with enhanced paint properties. Keywords: Photocatalytic Effect, Paint, Titania, PigmentItem Reinforcement of natural rubber using silica and zeolite mixed fillers(Uva Wellassa University of Sri Lanka, 2015) Dilhan, L. W. S.; Rathnayake, R. M. M. D.; Jayasuriya, C.K.Among the main ingredients added in the compounding process of Natural Rubber (NR), fillers play a major role. The purpose of adding fillers into the rubber matrix is 2-fold: to reduce the production cost or to give reinforcement. (Blackley, 1997). A reinforcing filler would increase the mechanical properties such as tensile strength, elongation at break, and tear resistance of the rubber vulcanizate. Increasing the area of contact between rubber matrix and filler particles, and increasing the degree of bonding between the two phases seem to be the most important factors in providing the strong reinforcement effect (Treloar, 2005). The current research is focused on a combination of two fillers, namely silica and zeolite, to provide a reinforcing effect on NR. Silica is in general widely used for reinforcement of NR. On the other hand, zeolites were considered due to their unique porous structure which would enhance the area of contact between the phases. Methodology Materials Double Centrifuged Natural Rubber Latex (DCL) with 60% dry rubber content (stabilized with ammonia) provided by Dipped Product Industries in Sri Lanka was used in the preparation of the samples. Mineral samples, Silica and Zeolite were purchased from Glorchem, Colombo. The agent, Zincmercaptobenzothiozole (ZMBT), Zincdiethyldithiocarbamate (ZDDC), Diphenylguanidine (DPG), etc) were of commercial grades. Procedure The samples were prepared using NR latex compound formulation used for glove manufacture. The mineral samples were ground using “TEMA mill” and were sieved to get the particle sizes in the range of (45 – 60) µm. A stabilized natural rubber was obtained by adding potassium laurate (20%) and KOH (10%, 2.50 g) to natural rubber latex (60%, 167 mL). ZnO (1.00 g), Zincdiethyldithiocarbamate (0.20 g), Zincmercaptobenzothiozole (1.00 g), Diphenylguanidine (1.20 g), antioxidant (1.50 g), dispersing agent (0.20 g) and Sulphur (1.40 g) were ground together using a mortar and a pestle. The ground mixture was dissolved in distilled water (8.30 mL) using a magnetic stirrer to obtain the dispersion. The stabilized NR solution and the dispersion were mixed together and distilled water was added to dilute the total dry rubber content of the solution up to 40%. This sample was labelled as “NR” and was used as the control sample. The amount of mineral needed to make up 1%, 2%, 3%, 4% and 5% of the final weight of the sample was calculated and added to the dispersion. In this research, two series of samples were prepared: first series was prepared by adding silica as the mineral and was labeled “Sil” and the second series was prepared by adding a 1:1 mixture of Silica and Zeolite as the mineral and was labeled “Mix”. Calculated amounts of sieved minerals were added to both series. The solutions (NR, Sil and Mix) were then filtered and poured into small glass tanks, covered and left overnight to dry. The samples were then cured for 3.5 min at 120 °C using the hot box oven (Gallencamp). The entire procedure was triplicated. The mechanical property analysis was based on tensile and tear strength. The samples with optimum mineral percentages showing the best tensile and tear properties were subjected to the structure determination by Fourier Transformed Infrared (FTIR) analysis and thermal properties by thermogravimetric analysis (TGA).Item Synthesis and characterization of in-situ precipitated silica filled rubber composite(Uva Wellassa University of Sri Lanka, 2015) Amarathunga, H.P.; Jayasuriya, C.K.In-situ precipitated silica can be used to replace carbon black partly in tires as well as in other rubber materials to increase strength, to reduce rolling resistance and heat build-up and hence to bring down the fuel consumption in tires. There have been numerous efforts to improve silica dispersion in conventional rubber/silica composites such as varying the chemistry and content of the coupling agents (Bokobza, 2006), improving the mixer rotor design (Miloskovska et al., 2012), ultrasound pre-treatment of the silica particles (Prasertsri et al., 2011), but dispersion still remains a serious issue for conventional rubber/silica composites. The current research was carried out to enhance the properties of rubber such as tensile strength, swelling properties, hardness, water absorption properties and density using in situ precipitated silica. A relatively high cost method for reinforcing natural rubber (NR) using in-situ precipitated silica by swelling method has been reported previously (Murakami et al., 2000). The present work aims to prepare in-situ precipitated silica filled rubber composites with a better in-situ silica dispersion within rubber matrix than conventional silica composites using a low cost method (using solvent combination) of sol-gel technique. Methodology Sample was compounded according to the tire tread formulation (Murakami et al., 2000). The resulting sample was half cured and was cut in to five pieces (15 cm × 5 cm). Using a swelling test, the best solvent combination of Toluene:T-butylalcohol was found to be 70:30 volume ratio. Four half-cured samples were soaked for different times in a solution containing the best solvent and Tetraethylorthosilicate (TEOS). Next they were soaked in 10% aqueous .n-butylamine for two days and the samples were dried. Finally, the remaining half of the curing process was carried out and in- situ silica percentage in each sample was calculated. Using the same procedure, four more samples were prepared by gradually increasing the in situ silica percentage by weight. A sample without in- situ precipitated silica was used as the reference. Mechanical properties of the samples such as tensile strength, modulus, tensile strain at break and hardness were determined. Finally, samples were characterized for its density, swelling in toluene and water absorption. Results and Discussion Results of swelling analysis are graphically represented in Figure 01. In principle, the presence of inorganic filler should lead to a reduction of the swelling ratio with respect to the unfilled vulcanized rubber, since the filler does not absorb the solvents during the experiment. In the present case an opposite trend is observed. Results show that the swelling ratio is increased with increasing silica percentage thus decreasing the cross linking density of the rubber matrix (Kapgate et al., 2012). This clearly indicates an interfering effect of the sol–gel reaction of TEOS to silica on the vulcanization * process of the rubber (Morselli et al., 2013) and the extent of the cross linking of the natural rubber phase was limited.