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    Preparation, characterization and properties of activated carbon derived from rice husk
    (4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Perera, P. L. R. A.; Rajapakse, C. S. K.
    Rice, the staple food of the Sri Lankans is one of the important crops occupying 34% of the total cultivated area in the country. Thus, rice processing generates a large quantity of rice husk as waste material. The main objective of the present work was to investigate the potential of using this agricultural waste, rice husk as a precursor for the production of low-cost activated carbon (AC) as an adsorbent for the removal of heavy metals (Pb(II), Cd(II) etc.). Therefore, the present study was carried out to evaluate the effect of carbonization time and activating agent on AC production from rice husk and its Pb(II) removal capacity. Cleaned and dried rice husks samples (12.00 g) were separately carbonized at 400 °C under constant nitrogen flow for 60 minutes -150 minutes (60 min, 90 min, 120 min, 150 min) and chemically activated by HCl. The AC yield was calculated in each sample. In order to determine the lead removal percentages (Pb%) of AC derived from rice husk at different carbonized temperatures, first AC samples were added (1.00 g) separately to a Pb(II) standard solution (5.00 mg L-1), stirred for 1 hour at pH 7 at room temperature. The solutions were filtered and the residual Pb was determined by Atomic Absorption Spectrophotometry (AAS). All the experiments were performed in duplicate. Further, the AC with the highest Pb removal capacity was characterized by Scanning Electron Microscopy & Energy Dispersive Spectroscopy (SEM/EDAX), and Fourier Transform Infrared Spectroscopy (FT-IR). Proximate analysis, of the AC were also studied. The percent yield of AC prepared from rice husk with HCl activation, and its corresponding % Pb removal potential were fluctuated with increasing carbonization time. The highest AC yield (20.50%), the highest % Pb removal (93.31%) was observed for the AC prepared by carbonization of rice husk at 400 °C for 120 minutes with HCl activation. The results of the proximate analysis revealed that the ash content, moisture content volatile matter content and fixed carbon content of the AC were 32.47%, 34.94%, 24.20%, and 8.39% respectively. Based on the results, it can be concluded that AC derived from rice husk can be considered as an efficient and cost-effective adsorbent for the removal Pb(II) from wastewater
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    Influence and optimization of growth conditions on phenol degradation by Pseudomonas aeruginosa
    (4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Amirthalingam, S.; Dassanayaka, M. P.; Vivehananthan, K.
    With their relatively high toxicity, phenol and phenolics are water pollutants of major concern. The application of phenol biodegrading agents to treat phenol in wastewater has shown promising results. Pseudomonas aeruginosa is a well recorded phenol biodegrading bacteria. However, optimal growth parameters for efficient degradation of phenol may vary from one bacteria to another. Therefore, this study focused on testing the effect of growth conditions including strength and pH of the growth medium and inoculum size on phenol degradation by P. aeruginosa and to assess the phenol degradation efficiency by adding glucose as an additional carbon source. The bacterial strain of P. aeruginosa (MH031762) isolated from petroleum contaminated site in Sri Lanka was inoculated to Mineral Salt Media (MSM) with 1200 mgL-1 phenol under different growth conditions. Three-factor factorial design with three levels was used to determine the combination effect of strength (0.5x, 1x and 2x), pH (6.5, 7 and 7.5) of the medium and inoculum size (1%, 2% and 3%) on phenol degradation. Residual phenol in the medium inoculated with bacteria was measured using 4-aminoantipyrene spectrometric method under which the duration (in hours) it took for 50% phenol degradation was calculated. Under the growth conditions found to be as optimum, the biodegradation efficiency of phenol by P. aeruginosa was further tested by adding glucose as an additional carbon source at varying concentrations (0.1%, 0.25%, 0.50%, 0.75% and 1%). Pooled t-test was performed to test the phenol degradation efficiency in bio-stimulated media with glucose. According to the results, there was no combination effect by all the 3 factors together on phenol degradation by P. aeruginosa (P = 0.186). However, a significant impact was shown by the combination of the two factors, i.e. the strength and pH of the medium (P = 0.002). According to the Tukey’s test, quickest phenol degradation resulted in the double strength (2x) MSM with pH 7.5 (71.82 h). Among the 3 levels of inoculum sizes assessed, 3% showed the highest phenol degradation rate by showing the lowest time (64±4.5 h) to achieve degradation of the amount of phenol by 50%. Further, glucose in the level of 0.1% enhanced the phenol degradation rate, by degrading the same amount of phenol within 58.9±0.2 h. In conclusion, optimal growth conditions of P. aeruginosa for fast degradation of phenol were determined as 2x MSM, pH 7.5 with 3% inoculum size. Further, addition of 0.1% glucose in the medium enhanced the phenol degradation. The findings of this study provide valuable information for designing bioremediation protocols to treat phenol in industrial wastewater.
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    Equilibrium studies on the adsorption of heavy metals, dyes and phenol by phosphoric acid modified rice husk.
    (International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Parthiban, G.; Rifna, M. S. F.
    The removal of contaminants from wastewater is still far away from a satisfactory solution. In fact, the selection of a particular wastewater treatment technology should not be based uniquely on its efficiency, but should rather integrate environmental and economical aspects. Within this framework, the main objective of this study is the removal of various contaminants in wastewater including heavy metals (Cadmium and Copper), dyes (Methyl Red and Methylene Blue) and Phenolic compounds via an environmental friendly green technology method. In this study, grounded rice husk was examined as sorbent material which was chemically modified with Phosphoric acid (1.0 M) and was found to be effective in removing the contaminants. Batch studies were performed on synthetic wastewater at room temperature to evaluate the effects of various parameters such as contact time, pH, initial concentration of the solution and adsorbent dose on removal efficiency of the pollutants. The experiment was also applied to treat two samples of industrial wastewater containing Cadmium and Carmoisine E122. The removal efficiency was found to be pH dependant. The removal efficiency was higher for Phenol and Methyl Red at low pH values and it was shown that the removal efficiency was higher for heavy metals and Methylene Blue at higher pH values. The equilibrium was reached approximately in 2 hours for all the contaminants. Equilibrium sorption data were fitted into Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) isotherms. Of the four adsorption isotherms, the R2 value was higher for D-R isotherm for the adsorption of Cadmium (0.979), Freundlich and Temkin isotherms for the adsorption of Copper (0.945), Freundlich isotherm for the adsorption of Methyl Red (0.994), Temkin isotherm for the adsorption of Methylene Blue (0.953) and Langmuir isotherm for the adsorption of Phenol (0.987). Adsorption data were well described and adsorption isotherm constants were determined from the respective adsorption isotherm equations. The present study analyzed the adsorption of rice husk and concluded that treated rice husk gave comparatively better adsorption efficiency. The treated rice husk can be implemented on large scale industrial applications after field studies.