Browsing by Author "Karunathilaka, R. M. M. K."

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Adsorption of Methylene blue on leaves of Guinea Grass (Panicum maximum)
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Weerathunga, M. A. O. Y.; Dinusha, M. D. N.; Karunathilaka, R. M. M. K.; Priyantha, N.
Massive amounts of industrial pollutants released to the environment because of industrial expansion, which is needed to fulfil the demands of the ever-increasing population, have become a global threat. Consequently, the use of effective treatment methodologies is a necessity, and such methodologies should not only be economical, but also be environmentally friendly. In this respect, biosorption has become a sound alternative for removing toxic industrial dyes. Although many biosorbents have been researched, attempts on their practicability have not been much attended to. This study focuses on the use of Guinea grass (Panicum maximum) leaves, a biosorbent that has not been extensively investigated, for the removal of methylene blue (MB), a common dye used in textiles and other industries. The fibrous nature of this biosorbent would make it suitable for surface modification as needed. Biosorbent for this investigation was prepared by mature leaves of guinea grass, collected randomly from Kandy district, cut into 1.0 – 2.0 cm lengths followed by thorough washing with tap water and deionised water, and then crushing followed by thorough washing again with deionised water until the supernatant became colourless. Samples were then dried at 120 °C for 2.0 h. Parameter optimisation was conducted using 50.0 mL of 10 ppm MB solutions, with one parameter varied at a time while keeping the others unchanged. This process led to optimal values of 0.25 g of adsorbent dosage, 20 minutes of shaking time, 20 minutes of settling time, and a pH of 5.66, based on absorption measurements recorded at 664 nm, achieving an excellent removal rate of 97.5% is obtained. Moreover, this biosorption system reaches equilibrium in a very short time owing to the fibrous nature which is advantageous for extension of bench work toward large-scale removal of MB from contaminated industrial effluents. It is further determined that the transfer of MB from solution to the biosorbent surface follows the pseudo secondorder kinetics model with a high correlation coefficient (R2) of 0.9889.
Comparison of adsorption characteristics of Ni(II) on fibres of Agave americana and areca nut husk
(Faculty of Science, University of Kelaniya Sri Lanka, 2024) Wickramasinghe, W. R. M. N. R.; Vithana, P. V. A. S.; Karunathilaka, R. M. M. K.; Priyantha, N.
Heavy metal contamination is of major concern at present due to its adverse impacts on humans and the environment. Among many heavy metal remediation methods, biosorption has become attractive in the recent past due to its low-cost and environmentally sustainable nature. Nevertheless, fibrous biosorbents have not been much explored, especially for the removal of Ni(II) species. Though Ni is a micronutrient that contributes to certain cellular functions in the human body and plants, higher concentrations of it could impose adverse health effects as well as ecological damage. Hence, Ni remediation should be carried out before releasing industrial effluent to the environment. This work is thus based on a comparative study to investigate the adsorption potential of Agave americana fibre and Areca nut husk fibre for the removal of Ni(II) ions from aqueous solutions. This study aims to optimize experimental parameters varying one parameter at a time throughout a broad range keeping others constant for the two biosorbents separately. Both Agave americana fibre and Areca nut husk fibre exhibit significant adsorption capacities toward the adsorption of Ni(II) ions with average removal of 90.39% and 93.27%, respectively, in batch experiments, conducted using 10 mg L-1 Ni(II) solution under optimized conditions of 60 min shaking time, 20 min settling time, ambient pH, ambient temperature and 150 rpm agitation speed for an optimum dosage of 20.00 g L-1 of the biosorbents. Adsorption isotherm studies, conducted using Ni(II) solutions of initial concentrations in the range from 10 mg L-1 to 350 mg L-1, show that the Langmuir model is a better fit for the two types of fibre with higher regression coefficients of 0.9836 and 0.9937 than those of the Freundlich model for Agave americana and Areca nut husk fibre, with the maximum adsorption capacities of 1.03 mg g-1 and 1.68 mg g-1 respectively. These studies could be extended for the design of treatment plants for large-scale removal of Ni(II) ions from contaminated water.