Browsing by Author "Weerasooriya, R."

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Adsorptive transport of chromate by suspended solids in Kelani river
(Sri Lanka Association for the Advancement of Science, 2006) Duminda, S.L.A.; Liyanage, J.A.; Weerasooriya, R.
Fabrication of reduced graphene oxide – nano iron (rGO-nZVI) anode for electrocoagulation treatment to regulate excess fluoride in water
(Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Halpegama, J.U.; Nanayakkara, K.G.N.; Herath, A.C.; Rajapakse, R.M.G.; Weerasooriya, R.
Due to excess fluoride in drinking water, over millions of people are being affected globally with dental and bone problems. The World Health Organization (WHO) guidelines specify 1.5 mg /L fluoride in drinking water as the maximum permissible contaminant limit (MCL). However, in dry climatic zones and tropical countries, the water consumption is high, therefore in a lower fluoride value than WHO MCL may suitable for the dry zone of Sri Lanka. The situation aggravates further in dry zone (Sri Lanka) as the fluoride in groundwater sometimes exceeds 5 mg/L. Presently water treatment methods based on adsorption, co-precipitation, membrane technology and ion exchange are used to mitigate enriched fluoride water with limited success. Briefly, both adsorption and co-precipitation generate excess sludge. The reverse osmosis methods remove ions in treated water than required. Most of the electrocoagulation (EC) methods used aluminum scarifying anode, which may pause additional threat of leaching neuro-toxic free Al3+ into the treated water stream. Therefore, we developed a novel anode composites using nano Fe and reduced graphene oxide (rGO) to be used in EC cells to regulate excess fluoride. rGO was synthesized by the modified Hummers method at ambient temperature. Natural green tea leaves polyphenols were used to reduce Fe2+/ Fe3+ into metallic Fe. The widely used NaBH4 method was also used to produce metallic Fe. The resulted composites are designated as polyphenol derived reduced graphene oxide-nano Fe (rGO–nZVI-P), and NaBH4 derived reduced graphene oxidenano Fe (rGO–nZVI-B). Before their application, conventional and spectroscopic methods extensively characterized rGO-nZVI composites. 2D Raman bands appeared at 2715 cm-1 for rGO-nZVI-P confirm the presence of multilayer structure while the bands at 2680 cm-1 for rGOnZVI-B confirm the presence of the single-layer structure of graphene. XRD diffraction peaks confirm the presence of BCC, α-phase Fe (0) in the core of both nZVI particles. Our results suggest that 1 mg/L fluoride in water can be removed within 1 hr. to 75 µg/L and 3 µg/L respectively using rGO-nZVI-P and rGO-nZVI-B composites with minimal waste generation. Following pseudo-second-order kinetics, at pH 5.6, both composite materials adsorbed over 90 % of 1 mg/L fluoride within 1 hr. The rGO-nZVI-P based EC has the potential to treat fluoriderich waters efficiently.
Investigation of fluoride adsorption capacity of characterized graphene oxide based super sand
(Research Symposium on Pure and Applied Sciences, 2018 Faculty of Science, University of Kelaniya, Sri Lanka, 2018) Perera, R. T.; Pathirannehe, P. N. S.; Weerasooriya, R.; Kumarasinghe, A. R.; Liyanage, J. A.
Sand is conventionally used in water treatment plants to control water turbidity. This research work was aimed for improving its performance using a chemical modification to remove other water contaminants as well. Thus improved substrate was designated as “Super Sand”. Super sand has proven to be a better adsorbent for the removal of fluoride from water. Fluoride is an essential constituent for human health and toxicity of the fluoride depends on the concentration of the fluoride in the drinking water source. The fluoride adsorption capacity of characterized super sand was determined. Graphene Oxide (GO) was synthesized using the modified Hummers method and then GO was coated with purified sand for the generation of super sand. Single GO coated super sand and multiple GO coated super sand were synthesized for the investigation of fluoride adsorption capacity. GO and super sand were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectrometry (EDXAS), Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction (XRD) analysis and surface titration. Surface titration curve depicted that surface charge of super sand vary with pH value of the medium. Between pH 4 to 7 it has a total positive charge and above pH 7 it has a total negative charge. In order to determine the fluoride adsorption process, isotherm studies were done for both single coated and multiple coated super sand. According to the isotherm studies, single coated super sand has the maximum fluoride adsorption capacity at 2 mg/L fluoride concentration and multiple coated one has maximum fluoride adsorption capacity at 3 mg/L fluoride concentration. Further optimization studies were also performed and finally it was proved that fluoride adsorption by the super sand follows the Langmuir isotherm model. Further, FTIR analysis of super sand and fluoride adsorbed super sand at different pH mediums depicted that adsorption process is a chemisorption process. However, FTIR peak patterns depend on the pH of the medium. Hence, it can be concluded that surface modified super sand is suitable for the fluoride removal from the fluoride contaminated drinking water.