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- ItemDesalination ability of Murunkan clay - a laboratory simulated study(University of Peradeniya, 2015) Rathnayaka, R. M. C.Availability of portable water is becoming a problem. It is estimated that in the next 20 years the average per capita supply of clean water will decrease by one third. Desalination is one option for producing portable water from saline water, but most currently used water desalination technologies such as reverse osmosis, electro dialysis and distillation are energy and capital intensive. Natural clay found in Murunkan area in Sri Lanka has shown good cation removal capacity. The main objective of this study is to evaluate the ion removal capacity of Murunkan clay for desalination applications. Removal of Na²⁺ K⁺, Mg²⁺ and Ca²⁺ cations from saline water was investigated. Murunkan clay sample was ground, sieved through a 1 mm sieve and 109 of it was packed well in a 10 cm³ syringe within 2 glass wool barriers. 0.200 mol dm⁻³ NaCI solution was passed through it using a peristaltic pump and elluent was collected in 10 min time intervals and column saturation time was estimated by considering percentage removal of Na⁺ ions in each time period and analyzing it using Atomic Absorption Spectrophotometer. The same procedure was done using 0.100 mol dm⁻³ KCI solution and 0.100 mol dm⁻³ CaCl₂ solution. The estimated column saturation time was 60 min for K²⁺ ion and Na⁺ ions and that of 80 min for Ca²⁺ ions. Lagoon water sample collected from Jaffna lagoon was passed through 109 of Murunkan clay sample and amount of cations Na⁺, K⁺, Mg²⁺ and Ca²⁺ present in the elluent was estimated and percent removal of each cation by Murunkan clay was calculated. The elluent was passed through another Murunkan clay column and the same procedure was repeated. The same experiments were repeated using acid treated Murunkan clay sample. Better results were obtained with acid treated Murunkan clay. The initial concentrations of Na⁺, K⁺, Ca²⁺ and Mg²⁺ In lagoon water sample was found to be 20 400, 608, 500, 3 070 ppm respectively. After passing the lagoon water sample through two acid treated columns concentrations of Na⁺, K⁺, Ca²⁺ and Mg²⁺ in elluent were reduced to 2 940, 459, 46, 1 985 ppm respectively. The percentage removal of Na⁺, K⁺, Ca²⁺ and Mg²⁺ ions by repeated filtration through acid treated Murunkan clay was observed with removal of 85%, 24%, 91% and 35% respectively. It was observed that 667 g of acid treated Murunkan clay and 1000 g of raw Murunkan clay was required to desalinate 1 litre of lagoon water. The percentage removal of Na⁺, K⁺ and Ca²⁺ ions from 500, 600,700 , 800, 900 and 1000 mg dm⁻³ solutions of above cations by raw Murunkan clay was observed by passing each of the solutions through 109 Murunkan clay sample. Langmuir, Freundlich and Temkin isotherms were constructed to find the mechanism of ion removal capability in Murunkan clay . The Na⁺ ion removal data by Murunkan clay fit well with Langmuir, Freundlich and Temkin adsorption isotherms. Two steps in adsorption process were observed in the adsorption of K⁺ ions on Murunkan clay. The adsorption of Ca²⁺ ions on Murunkan clay obeys Langmuir, Freundlich and Temkin adsorption isotherms.
- ItemCharacterization of Deoxyribonucleases from pitcher juice of Nepenthes Distillatoria(University of Peradeniya, 2009) Ekanayaka, E. A. P.Nepenthes distillatoria is a carnivorous plant endemic to Sri Lanka, which grows in South West and Southern parts of the island. Preliminary studies indicated the presence of deoxyribonucleolytic (DNAase) activity in the crude pitcher juice of N. distillatoria. This study was carried out to partially purify the DNAases and characterize them in terms of their optimum temperature, optimum pH, and stability at room temperature and 37 °C and the effects of metal ions on their activity and molecular masses. First, the assay procedure was developed for analyzing DNAase activity in N.distillatoria using unpurified pitcher juice. This developed assay procedure was used throughout the study, to investigate the DNAase activity. In this study four major DNAases (DNAase I, DNAase II, DNAase ITI and DNAase [V) were partially purified from crude pitcher juice of N.distillatoria. Out of the four, two DNAases (DNAase IT and DNAase III) were further purified and molecular masses of these were determined to be 51 kDa and 37 kDa for DNAase II and DNAase III respectively using gel filtration method. SDS PAGE of DNAase II revealed the molecular mass to be about 51 kDa. DNAase II and DNAase III are stable at room temperature and 37 °C over a wide pH range (pH 3.0 — pH 8.0). However, more remaining activity is observed at acidic pHs. In all pHs DNAase II had over 50% activity remaining after 15 days of incubation at room temperature. At 37 °C after 15 days over 50% of activity of DNAase I remained at acidic pHs while it was less at pH 7.0 (46%) and 8.0 (26%). More than 59% of activity remained after 15 days at room temperature in all pHs for DNAase III. Interestingly the activity of DNAase III seem to diminish substantially at 37 °C. The effect of metal ions on both crude juice and the partially purified DNAase activity were analyzed using the same assay procedure. Results indicated that, for crude juice the optimum concentration of Zn²⁺ was 6 mM and resulted 42% enhancement of activity. Optimum concentration of Ca²⁺ was found to be 4 mM and resulted in 35% enhancement of activity. However, the activity seem to be unaffected by the presence of Mg²⁺ Activities of all four enzymes are positively enhanced by the presence of 1 mM of Zn²⁺ (DNAase I - 40%, DNAase II — 28%, DNAase III — 24%, DNAase IV — 29%). 1 mM concentration of Ca²⁺ also show positive enhancement of DNAase I (30%), DNAase II (14%) and DNAase III (13%). Furthermore it was observed that optimum concentration of Zn²⁺ for DNAase III was 7 mM and resulted 90% enhancement of activity. For DNAase II optimum concentration of Zn²⁺ was 4 mM at which activity enhanced by 61%. These results demonstrate the stability of the two major DNAases over a broad pH range both at room temperature and at 37 °C as well as their metal ion dependency. Their activity is enhanced by the presence of Zn²⁺ and Ca²⁺ ions. The difference of the separation on anion exchange column indicate that overall charge of these proteins differ. The differences of the molecular masses also indicates that these are different enzymes. Furthermore, these enzymes seem to be resistant to the proteinase activity in the crude pitcher juice. Therefore, DNAases present in the pitcher fluid of N. distillatoria may have remarkable properties to withstand high temperatures, a wide pH range as well as attack by proteinases. These features clearly indicate the wide applicability of the enzymes.
- ItemCyclodextrin-Mediated intercalation of Lycopene into cation-exchanged Montmorillonite(University of Peradeniya, 2015) Adikari, A. M. N. K.Lycopene present in tomato (Solanum lycopersicum L), has wide -ranging pharmacological characteristics including antioxidant, hypocholesterolemic and anticancer. However, lycopene has poor water solubility and is oxidised rapidly, resulting in poor systemic bioavailability. In the present study, new composites of layered H⁺- and AI³⁺ exchanged montmorillonite (MMT) clays ,β -cyclodextrin and lycopene were prepared, and releasing of lycopene from the composites at pH values of gastric and intestinal fluids was investigated. These clay composites are unique because they are expected to contain lycopene molecules in a toms-shaped channel (i.e. β-cyclodextrin) encased in a layered matrix of clay. H⁺- and AI³⁺ exchanged MMT clays were prepared by treating MMT with aqueous HCl and AICl₃ , respectively, employing standard procedures. Lycopene, isolated from tomato by solvent extraction (hexane:acetone:ethanol , 2: 1:1), was mixed with aqueou s solutions of β -cyclodextrin (β-CD) and cation-exchanged clay to obtain various clay composites, which were characterized by FT-IR spectroscopy. The amount of lycopene trapped in each clay composite was determined by UV-Vis spectroscopic analysis of lycopene remaining in the supernatant, at 471 nm. With Al³⁺ MMT and H⁺- MMT, the composites contained 97% and 92% of lycopene, respectively, when all three cornponents LYC, β-CD and the clay-were mixed together. The H⁺- MMT and A1³⁺MMT clays , when treated with β -CD initially, trapped 93% and 84% of lycopene, respectively. According to FT-IR spectra, appearance of new peaks which are characteristic of lycopene indicated the formation of a new composites containing lycopene. According to TGA, appearance of new decomposition step at 250-350 ⁰C indicated the formation of new composites. In the absence of β -CD , the characteristic FT-IR peaks were not observed for the clays. It was found that optimum stirring time for intercalation was 2 h. The amount of lycopene released when composites were stirred in buffer solutions was determined. Minute releasing of lycopene was observed in simulated gastric fluid (pH 1.2) and significant releasing of lycopene in simulated intestinal fluid (pH 7.4) after 6 h. It can be concluded that lycopene can be successfully trapped in cation-exchanged montmorillonite clays with the mediation of ~β -cyclodextrin and that the intercalated composites may pass through the acidic stomach and reach the intestine where lycopene is released
- ItemCoir dust as a low cost adsorbent to remove Cu²⁺, Zn²⁺ And Pb²⁺(University of Peradeniya, 2015) Weththasinghe, W. S. A.Water is an essential component for the life on earth. Out of the total water content, only 0.01% of is available as drinking water. As a result of industrialization accelerated during the last three decades, different kinds of pollutants, such as inorganic compounds, synthetic organic compounds, heavy metals, dyes, fertilizers and pesticides, were released to the natural water bodies resulting in extensive water pollution. Among these pollutants, heavy metals, which are extensively in many industries due to their unique properties, play a major role in pollution. Heavy metals , such as copper, cadmium and lead are widely used in industries leading to alarming health conditions and environmental risk. Among treatment processes available for the removal of heavy metals, adsorption is a state-of-the-art, 'efficient, cheap and widely used method. The major bottle neck of this method is lack of the availability of cheap adsorbents, and thus, natural adsorbents are becoming increasingly popular. Coir dust is fallen off from coconut husk when it is shredded during coir processing. Although it has been reported that coir dust can be used as a sorbent to remove heavy metal ions, detailed mechanistic and kinetics studies have not been reported. Hence, characterization and evaluation of the efficiency in heavy metal ion removal by coir dust was done during this study. Surface titration and methylene blue test were carried to determine the surface charge of coir dust and the surface area of coir dust, respectively. Stirring time, settling time and solution pH were optimized to evaluate the efficiency of heavy metal removal. Isotherm Studies and kinetics studies were done for further investigation of metal ion-coir dust interaction. FTIR spectroscopy reveals the presence of functional groups , such as carboxylic acid, alcohols and amine groups. According to the surface characterization, the PZC of coir dust occurs at pH 5 and the specific surface area is 285.3 m² g⁻¹. Neutral pH values are more favourable for the metal ion removal. Coir dust shows adsorption capacities of 34.60 mg g⁻¹., 27.02 mg g⁻¹. and 96.15 mg g⁻¹. for Cu, Zn and Pb, respectively. All the three metal ions obey the Langmuir adsorption isotherm. Kinetics study show that the interaction of Cu²⁺, Zn²⁺ and Pb²⁺ with coir dust obey pseudo second order and intra-particle diffusion, which reveals that intra- particle diffusion is the rate limiting step. By considering all the experimental data, it can be concluded that coir dust is an effective adsorbent to remove heavy metal ions effectively and economically.
- ItemA combined test for the median and the effects of five normality tests on the combined test(University of Peradeniya, 2010) Kumbalatara, K. A. C. D.Testing for the median (V) of a random variable X is a basic problem in statistics. When the distribution of X is symmetric and the moments are finite, the mean (z) and the median (v) are the same. For such situations a test regarding the median is equivalent a test regarding the mean. In particular when the distribution of X is normal a /-test can be used as the test for the median. Otherwise a nonparametric test like Binomial Sign test can be used as the test for the median. Therefore we considered the following “Combined Median test” for Ho:v= vovs Hₗ : v# Vo, where Vo is a given value. Step 1: Test for the normality of X. Step 2: If the normality is not rejected, do the t-test for the median. Step 3: otherwise, do the Binomial Sign test for the median. There are several tests available for the normality of X. In this study we investigated the effects of five well known normality tests, namely, the Kolmogorov-Smirnov test, Anderson Darling test, Shapiro-Wilk test, D'Agostino's K-Squared test and Cramer-von Mises test on the above Combined Median test. It was found that the significance level of the Combined Median test is closest to the nominal significance level when the Shapiro-Wilk test is used as the normality test in step 1. It was also found that the power of the Combined Median test does not depend on the normality test in step 1. The results were obtained using Monte Carlo studies with different distributions for X and different sample sizes. Based on these results, we recommend the Combined Median test with Shapiro-Wilk test for normality in step 1.