Browsing by Author "Premachandra, J. K."

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Development and characterization of biodegradable films of cornstarch filled with methylcellulose and gelatin
(Faculty of Science, University of Kelaniya, Sri Lanka., 2021) Ranasinghe, W. R. A. D. S.; Jayasuriya, C. K.; Premachandra, J. K.
Synthetic plastics play a vital role in many applications such as packaging, electrical, electronics, medical, textiles, furniture, and structural applications due to desirable properties like light- weight, high strength, flexibility, and chemical inertness. However, when the products made from many synthetic plastics are discarded to the natural environment it takes a very long time for degradation. This results in environmental pollution. Therefore, the use of biodegradable plastics in place of non-degradable plastics has gained significant interest as one of the main plastic waste management methods. However, biodegradable plastics such as starch and Polylactic acid do not show desired mechanical properties. In this research, it was expected to synthesize biodegradable films with improved mechanical properties using cornstarch (CS) filled with methylcellulose (MC). Microcrystalline cellulose (MCC) was extracted from cotton fibers through alkali treatment and bleaching, followed by sulphuric acid hydrolysis. Then, MCC was converted to MC using dimethyl sulfate in the presence of acetone as the solvent. This conversion was analyzed by Fourier transform infrared spectroscopy (FTIR). Their FTIR spectra showed significant differences in the regions 2960-3650 cm-1, 2780-2950 cm-1, and 960-1160 cm-1, which indicates that the conversion has occurred. The degree of substitution of the methyl group for H in MCC was determined by an acid-base titration and the resulting value was 1.36 ± 0.02. Then, an aqueous solution of MC (0.5 g/100 mL) was prepared. In the presence of water, CS (4% w/v) was dissolved in different amounts of the prepared MC solution in order to have six solutions with the ratio of MC to CS as 0.00%, 0.625%, 1.25%, 3.125%, 6.125%, 12.125% (w/w). Acetic acid (1% v/v) was added to all these solutions. Afterwards, two series of solutions, series 1 and 2, were prepared by mixing 1% and 2% (v/v) of glycerol, respectively, into the resulting solutions. Similarly, the third series was prepared by mixing glycerol (1% v/v) and gelatin (1% w/v). Three series of films were prepared using these solutions following the casting method. The dried films were characterized on physical, chemical, mechanical, and thermal properties. The film with 0.625% (w/w) MC in series 3, showed the highest tensile strength of 14.06 MPa. Films with MC-1.25% (w/w) in each series showed the lowest water absorptivity, swelling, and solubility properties. All the films produced were transparent. The films tend to twist and swell when treated with chemicals such as NaOH, HCl, NaCl, and ethanol. Also, the transparency of some of the films was reduced after this chemical treatment. FTIR analysis, thermo-gravimetric analysis, and differential scanning calorimetry were performed on the films having optimum properties. These films showed thermal degradation between 323-335 °C, melting temperatures between 267-293 °C, and glass transition temperatures between 84-120 °C. The biodegradability of films was determined by performing a soil burial test. After three months, the films had disappeared. It can be concluded that the biodegradable films developed in this study have the potential to replace polyethylene in some short-term packaging applications.
The effectiveness of electrochemical oxidation in removal of sulforhodamine B textile dye from wastewater
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Aberathna, A. P. A. G.; Jayasuriya, C. K.; Premachandra, J. K.
The rapid expansion of industries has indirectly resulted in a substantial rise in environmental pollution due to the increased discharge of wastewater. Moreover, the lack of suitable and efficient methods for wastewater treatment has aggravated a crucial global issue concerning wastewater. In this context, the textile industry bears the primary responsibility for generating a significant volume of wastewater, primarily due to the processes of dyeing. Out of various wastewater treatment methods, the electrochemical oxidation method has emerged as an effective approach offering advantages of higher selectivity, minimal chemical utilization, energy efficiency, in-situ treatment capability, relatively faster treatment and reduced secondary waste generation. This method harnesses electrically charged electrodes to degrade and eliminate pollutants. In this study, the electrochemical oxidation of synthetic dye sulforhodamine B (Acid red 52), a xanthene dye, was employed to facilitate the removal of dye from wastewater. This dye is extensively used in the textile industry due to its enhanced colourfastness and superior stability across diverse processing conditions. However, its persistent nature poses significant environmental challenges. A series of experiments were conducted using graphite electrodes to optimize the electrochemical oxidation for the removal of dye from wastewater. The research investigated the effects of several parameters on the electrochemical oxidation process. These parameters encompass the applied potential (3 V, 5 V, 9 V), supporting electrolyte concentration (NaCl) (1 g L-1, 2 g L-1, 3 g L-1, 4 g L-1, 5 g L-1), treatment time (0.5 hours, 1 hour, 1.5 hours, 2 hours), and pH level (3, 4, 5, 7, 9) of the sample. The efficacy of sulforhodamine B degradation was assessed by UV-visible spectroscopy and chemical oxygen demand (COD) values. Furthermore, changes in conductivity and pH post-treatment were subjected to analysis. The analysis resulted in the determination of optimal parameters, including an applied voltage of 5 V, treatment time of 1 hour, pH of 7, and NaCl concentration of 3 g L-1. Under optimum conditions it was able to achieve 95.61% colour removal, 99.64% dye degradation, and 66.18% COD reduction. These results confirmed that electrochemical oxidation is an efficient method for removing sulforhodamine B from textile wastewater. To validate the effectiveness of the optimized conditions in practical situations, wastewater samples containing sulforhodamine B collected from a textile industry in Sri Lanka were also analysed under the optimal conditions found. The results obtained impart the use of the electrochemical oxidation method in degrading sulforhodamine B present in textile wastewater in a sustainable and cost-effective manner.
Pyrolysis of plastic waste into liquid fuel
(Faculty of Science, University of Kelaniya Sri Lanka, 2023) Uthpalani, P. G. I.; De Silva, D. S. M.; Weerasinghe, V. P. A.; Premachandra, J. K.
The accumulation of plastic waste in the environment has emerged as a significant global concern. The versatile properties of plastics, such as low weight, low cost and durability which led to their widespread use as substituents for traditional materials like wood, metals, ceramics, and glasses. However, the improper handling and disposal of plastic waste have imposed negative consequences for the environment. The non-biodegradable nature of plastics makes them persist in the environment for extended periods, causing pollution and posing threats to ecosystems. Pyrolysis of plastic waste has been studied extensively in recent years as an effective solution, by exposing the plastic waste to high temperatures in an oxygen-free environment to decompose it into fuel oil, char, and gases. In this study, the waste of four types of plastics samples, low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), and a mixture of these three types of plastics, were subjected to pyrolysis. Lab-scale, low-cost pyrolysis system was used to obtain liquid oils and herein, the non-condensed vapor was trapped into an organic solvent. Thermal pyrolysis or non-catalyzed pyrolysis resulted in a liquid yield of 65.64 ± 5.42 – 79.57 ± 1.66 wt.% at a temperature range of 340 – 360 ℃. Considering catalytic activity, high temperature stability, local availability, and abundance, four types of naturally available minerals were selected as potential catalysts for the pyrolysis of waste plastics. The mineral which resulted in the highest liquid yield was identified as the best-performing catalyst and used for further analysis. The catalyzed process resulted in an increased liquid yield of 71.79 ± 0.99 - 80.29 ± 1.76 wt.% at the temperature range of 290 – 320 ℃. The calorific value of the resulting oil in thermal and catalyzed pyrolysis processes were 10,850 -10,961 Kcal/kg and 10,556 - 11,473 Kcal/kg respectively. This reveals that the mineral selected is an ideal catalyst for pyrolysis of plastics and further indicates the quality enhancement of the fuel produced in catalyzed pyrolysis. Further, the fuel quality indicators; calorific values, density, kinematic viscosity, ash content, and water content of the resulting liquid oils under both catalyzed and uncatalyzed/thermal pyrolysis processes were significantly compatible with commercial grade diesel and kerosene fuel oils.
Pyrolysis of waste polypropylene to fuel oil
(Chemistry in Sri Lanka, 2022) Uthpalani, P. G. I.; Premachandra, J. K.; Weerasinghe, V. P. A.; De Silva, D. S. M.
Plastic waste accumulation in the environment has increased rapidly. This is mainly due to their versatile properties, which allow them to be used as substitutes for wood, metals, ceramics, and glass. They have diverse applications, as they are light-weight, durable, cost-effective, and stable products. However, the world is experiencing the adverse effects of plastic debris in the environment due to plastic waste mismanagement. Pyrolysis of plastic has been identified as an effective method of plastic waste management by converting the waste into fuel oil, char, and gases. The pyrolysis of waste polypropylene (PP) using a low-cost, simple lab-scale apparatus in the presence and absence of catalysts is discussed here. In the current research, the efficiency of the catalyst, Zeolite Socony Mobil-5 (ZSM- 5), in pyrolysis process was investigated. The generated volatile products were condensed into resultant liquid oil. Active carbon filters and organic solvents were used to trap the non-condensed gas fraction to prevent possible atmospheric pollution. The non-catalyzed pyrolysis of PP resulted a high liquid yield of 79.57 ± 1.66 wt. % with a low gaseous yield (14.64 ± 0.84 wt. %) at 330 °C while the ZSM-5 catalyzed process reduced the liquid yield to 56.88 ± 2.29 wt. % and increased the gaseous yield (38.13 ± 1.88 wt. %) at 280 °C. Then resultant liquids were fractionated based on the boiling points of several petroleum fractions (naphtha, kerosene, and diesel) and each fraction was analyzed by GC-MS to identify the constituent compounds. Accordingly, the non- catalyzed pyrolysis produced 3,3,5-trimethyl-heptane (C10H22), 4-methyl-2-undecene (C12H24), 1-dodecene (C12H24), and 2-methyl-1-hexadecanol (C17H36O) while the catalyzed pyrolysis with the ZSM-5 resulted 1-ethyl- 2-methyl-benzene (C9H12), 3,3,5-trimethyl-heptane (C10H22), (Cyclopentylmethyl)-cyclohexane (C12H22), and n-Nonylcyclohexane (C15H30) as the major constituents.
The use of electrooxidation for treating wastewater generated by automobile service stations
(Faculty of Science, University of Kelaniya Sri Lanka, 2022) Karunagaran, D. V.; Jayasuriya, C. K.; Premachandra, J. K.
Automobile service stations are water intensive and discharge oils, greases, detergents, degreasers and heavy-duty cleaning products during their operations. Hence, treating this effluent before releasing it to the environment is absolutely essential to prevent environmental pollution. Treating the wastewater to a level at which it can be reused for its operations would be economically beneficial to the industry. Also, most importantly, it helps to conserve one of the earth’s most precious resources, water. In this regard, several treatment methods have been proposed and some of those have been employed in Sri Lanka and around the world, including physical, chemical, biological and combined methods. Electrooxidation is an attractive method of treating wastewater, possessing several advantages over conventional treatment methods, such as offering relatively fast treatment, with no use of additional chemicals and no generation of sludge. For industrial applications, the use of graphite electrodes is very beneficial compared to other types of electrodes as they are relatively cheap and inert. The main objective of this study was to investigate the effectiveness of applying electrooxidation using graphite electrodes and sodium chloride as the supporting electrolyte to treat automobile service station wastewater. In addition, it was expected to optimise the applied voltage considering the number of electrodes and the treatment time. Further, it was evaluated whether gravity filtration using a filter of pore size 11 μm as a pre-treatment would improve the process efficiency. Wastewater samples obtained from a service station in Negombo, Sri Lanka, were analyzed for 3-day Biological Oxygen Demand (BOD3), Chemical Oxygen Demand (COD), oils and greases (OG), Total Dissolved Solids (TDS), Total Suspended Solids (TSS) and pH. The levels of COD and OG were detected as 356.70 mg/L and 2650 mg/L, respectively and their variation under different applied voltages (3 V, 5 V, 8 V), numbers of electrodes (2, 3, 4, 5, 6 electrodes) and treatment times (60 minutes, 120 minutes) were used as the basis to assess the efficiency of each treatment condition and select the optimum conditions. It was found that optimum conditions for the treatment process include applying 3 V, the use of 4 electrodes and 120 minute treatment time. The corresponding efficiency removal of the COD and OG were 73.0% and 97.1%, respectively, for the samples that were filtered. The percent removal efficiencies of the COD and OG were 62.2% and 70.4%, respectively by electrooxidation for unfiltered samples. The pH of the water was observed to be close to 7 after the electrooxidation of filtered samples. Further development of this method could be done by optimising other necessary parameters in order to fully improve the water quality up to the requirements for effluent discharge. An industrial scale study could be performed in order to study the applicability of this method to vehicle service stations of different scales, as well as the long-term costs associated with it.