Browsing by Author "Perera, P.L.R.A."

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Graphite oxide coated sand composites for efficient removal of calcium ions from hard water: isotherm, kinetics, and adsorption mechanism
(Polish Ministry of Science, 2024) Perera, W.P.R.T.; Premasinghe, Niroshan; Fernando, W.S.K.; Perera, P.L.R.A.; Sandaruwan, Chanaka; Kumarasinghe, A.R.; Liyanage, Janitha A.
Even if granular media filtration effectively reduces the turbidity of water, its limited surface functionalities and physical properties may constrain its ability to effectively remove critical contaminants from water. In our research, we successfully synthesized a new type of porous material – multiple coated GO/sand (M-GO/S) by integrating ordinary river sand with graphite oxide (GO) for the adsorptive removal of calcium ions in terms of water softening. Prior investigations confirmed it could remove water turbidity and fluoride simultaneously. M-GO/S was characterized using microscopic and spectroscopic techniques. The results indicate the presence of an uneven coating of graphite oxide, and the nanocomposite contains oxygencontaining functional groups. Under given conditions, the M-GO/S nanocomposite demonstrated remarkable efficacy in removing 75% of calcium ions (a higher removal percentage than commercial coal powdered activated carbon) from simulated hard water: pH 8, 5.0 g dosage, 50 mg/L calcium ions, and 20 min contact time. The isotherm and kinetic data revealed that the adsorption mechanism primarily comprises multilayer adsorption by means of a chemical sorption process. The mechanism of the proposed M-GO/S nanocomposite for removing calcium ions from hard water is elucidated using (XPS) analysis. The presence of (-O-Ca-O-) chemical bonds on the surface of the nanocomposite after equilibration with calcium ions suggests the occurrence of chemical interactions between the calcium ions and oxygen-containing functional groups of the M-GO/S. Consequently, the synthesized M-GO/S nanocomposite can be identified as a promising candidate for hard water treatment.
Preparation, Characterization and Evaluation of Lead Adsorption Efficiency of Chitosan Coated Activated Carbon
(International Postgraduate Research Conference 2019, Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2019) Perera, P.L.R.A.; Rajapakse, C.S.K.
Heavy metal contamination in various water resources is of great concern because of the toxic effect on human beings and other animals and plants in the environment. Lead is a major element which is released to the environment including water bodies by many industries and it is well known that the presence of Pb(II) in water, even at very low concentrations, is extremely harmful to the human. Therefore, the aim of the present study was to investigate the Pb adsorption potential of chitosan coated activated carbon derived from rice husk (CCAC) in aqueous media. First, chitin was extracted from shrimp shell wastes by following a standard procedure and it was deacetylated to obtain chitosan (deacetylation percentage = 82%). In the preparation of activated carbon from rice husk, HCl acid (5 % v/v) was used as the activating agent. The adsorbent of the study, CCAC was then prepared by coating activated carbon derived from rice husk (20.00 g) with chitosan (3.00 g dissolved in 1% v/v acetic acid) to improve the stability and mechanical strength of chitosan. The surface morphology and the elemental composition of CCAC was examined by Scanning Electron Microscopy & Energy Dispersive Spectroscopy (SEM/EDAX). The novel adsorbent was further characterized by Fourier Transform Infrared Spectroscopy (FT-IR). In order to determine the Pb adsorption potential of CCAC, batch adsorption studies were conducted at room temperature at pH 7. The effects of various experimental parameters such as initial Pb (II) concentration, dose of adsorbent and shaking time on Pb adsorption to CCAC were evaluated. According to the results, the maximum lead removal percentage (89%) was observed at initial Pb (II) concentration of 2 ppm, adsorbent dosage of 1 g/L and 120 minutes of shaking time. Further, the equilibrium adsorption data were analyzed by the Langmuir isotherm model and the Freundlich isotherm model for Pb adsorption onto CCAC. Among the two models, Langmuir isotherm best fitted with the equilibrium data (R2= 0.9916) with a maximum adsorption capacity (q0) of 24.39 mg/g. Based on the results, it can be concluded that CCAC can be considered as an efficient and cost-effective adsorbent for the removal of heavy metals such as Pb from industrial wastewater.