Browsing by Author "Ratnayake, A.S."

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item: Conference-Abstract
Comparison of critical metal potential in beach and offshore sediments of Pulmoddai, Sri Lanka
(Division of Sustainable Resources Engineering, Hokkaido University, Japan, 2024) Nanayakkara, C.J.; Ratnayake, N.P.; Premasiri, H.M.R.; Abeysinghe, A.M.K.B.; Ratnayake, A.S.; Dushyantha, N.P.; Batapola, N.M.; Dilshara, R.M.P.; Iresha, H; Elakneswaran, Y; Dassanayake, A; Jayawardena, C
The global transition towards renewable energy resources for power generation has increased the demand for critical metals (CMs), including rare earth elements (REEs). This rapid growth of demand coupled with geological scarcity and geo-political concerns has posed great challenges in securing the supply chain of CMs. Therefore, prospecting new CM sources worldwide is of timely importance. In this context, the Pulmoddai coastal stretch in Sri Lanka has been recognized as a dynamic deposit with established potential for REEs and other critical metal resources, currently undergoing beach face mining operations. The focus of this study is to compare the critical metal potential in the beach and offshore sediments in Pulmoddai, Sri Lanka, crucial for determining the origin and delineating the extent of this deposit. Twelve onshore and nineteen offshore samples were collected and analyzed for CMs (V, Cr, Co, Ni, Cu, Zn, Ga, As, Rb, Sr, and Cs) and REEs. Based on the results, light REE content (LREE), heavy REE content (HREE), and total REE content (TREE) were computed for both onshore and offshore locations. For onshore sites, LREE, HREE, and TREE ranged respectively from 43.27 to 244.09 ppm, 19.62 to 92.29 ppm, and 62.92 to 336.39 ppm. Conversely, offshore locations exhibited higher concentrations with the corresponding values ranging from 116.12 to 363.62 ppm, 8.57 to 120.93 ppm, and 167.93 to 484.55 ppm. Sr, Ni, and Cr were determined as the most abundant CMs for both onshore and offshore locations. Sr, Ni, and Cr concentrations ranged from 227.17 to 674.58 ppm, 116.17 to 675.88 ppm, and 43.55 to 112.87 ppm respectively for the onshore locations. The corresponding ranges for offshore sites were determined as 370.86-754.30 ppm, 235.43-721.44 ppm, and 32.51-172.62 ppm. The higher CM content in offshore regions suggests an offshore origin to this dynamic deposit, which is enriched by the offshore sediments transported onshore and deposited on a long-term basis. Therefore, regulatory authorities overseeing the mining operations of Pulmoddai deposit should accurately delineate its extent, integrating both onshore and offshore regions as a unified system, rather than solely focusing on prospecting the longshore areas.
item: Article-Full-text
Leaching of rare earth elements (REEs) from lake sediments around Eppawala phosphate deposit, Sri Lanka: A secondary source for REEs
(Elsevier, 2021) Dushyantha, N.P.; Ratnayake, N.P.; Premasiri, H.M.R; Ilankoon, I.M.S.K; Hemalal, P.V.A.; Jayawardena, C.L.; Chandrajith, Rohana; Rohitha, L.P.S.; Abeysinghe, A.M.K.B.; Dissanayake, D.M.D.O.K.; Dharmaratne, P.G.R.; Ratnayake, A.S.; Batapola, N.M.
Rare earth elements (REEs) are widely employed in a spectrum of high-tech applications. Since primary REE resources are limited, secondary REE sources will be crucial to reduce future supply chain gap between REE demand and supply, which is currently about 3000 t per year. In this context, lake sediments around Eppawala Phosphate Deposit (EPD) in Sri Lanka could be considered as a potential secondary REE source since a man-made water canal running across the EPD transports REE-rich materials to the lake sediments. The average total REE (ΣREE) concentration of the downstream surface lake sediments was 804 mg/kg. The REEs were present in lake sediments as 3 fractions, namely, ion-adsorbed, colloidal, and mineral bound fractions. Ion-adsorbed fraction was assessed using less expensive, easy, and environmentally friendly ion-exchangeable leaching by a solution of (NH4)2SO4 under optimum conditions. Experimental results revealed that 34% of ΣREE was leached as ion-adsorbed fraction. In addition, the maximum leachable REE content (i.e. ion-adsorbed and colloidal fractions) was determined as 78% of ΣREE through HCl leaching under optimum conditions. Therefore, acid leaching was proven to be the best leaching process and the results in this preliminary study could be useful to assess low-grade geological resources, especially sediments and soils around major phosphate deposits with similar geological settings.