International Symposium on Earth Resources Management and Environment

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Browsing International Symposium on Earth Resources Management and Environment by Subject "Acid leaching"

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    Extraction of rare earths from monazite in Pulmoddai deposit
    (Department of Earth Resources Engineering, University of Moratuwa, 2021-12) Witharana, WPWS; Prabath, DHL; Madushanka, RS; Rohitha, LPS; Dissanayake, DMDOK; Dissanayake, DMDOK; Jayawardena, CL
    Rear earth elements (REEs) have considerable demand in the world and higher market value due to various applications, emerging economies, and continuous depletion of rare earth (RE) metals. Monazite is a perfect source for REEs (61%) and consists of RE and Thorium Phosphate. The Phosphate component was removed by alkaline leaching using NaOH (80 W/V%) at 1800° C for 4 hours at 500 rpm. Thorium was removed by acid leaching using (60 W/V%) HCl at 90° C for 1hour at 500 rpm and 15% pulp density. The solvent extraction method was carried out to separate and purify RE-Oxides from other impurities. 50% Tributyl phosphate (TBP) in kerosene was used as an organic phase with available facilities, and an experiment was done for phase ratio 1 and phase ratio 2, for 3, 6, and 12 minutes of contact time. Inductively coupled plasma mass spectrometry (ICP-MS) analysis was done for elemental analysis. Most abundant REEs in Monazite were Cerium (39%), Lanthanum (20%), Neodymium (12%) and Praseodymium (4%). The main objective of this research was to identify an industrial-level efficient method for separating and purifying RE from Monazite. Economically viable industrial level extraction of REEs was obtained when the phase ratio equals one and 3 minutes contact time.
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    Feasibility of extraction of cerium dioxide (CeO2) from monazite at Pulmoddai
    (Department of Earth Resources Engineering, University of Moratuwa, 2020-12) Rasanjalee, PHAU; Delaksana, S; Sampath, MD; Dushyantha, NP; Batapola, NM; Dissanayake, DMDOK; Rohitha, LPS; Dissanayake, DMDOK; Dassanayake, ABN
    Monazite concentration in Pulmoddai mineral sand deposit in Sri Lanka is 1.38%. Its Rare Earth Elements (REE) composition is about 61%. Currently, only heavy minerals are separated and cerium rich monazite is discarded. Therefore, the study is focused on finding feasibility of extraction of CeO2 from Pulmoddai monazite. The research was conducted under four stages, removal of phosphate ions, removal of radioactive elements, purified Rare Earth oxide (REO) preparation and selective separation of CeO2. The optimum concentration of NaOH solution is found as 80% (w/v)/ 20M. Alkaline digestion was done for 4hrs at 150oC by adding 25 ml of NaOH to 25 g of monazite, followed by acid leaching with 50 ml of 60%(w/v) HCl at 90°C for 1hr. Concentration of 20 g/L (0.22M) oxalic acid should be added to the RE chloride mixture until the complete precipitation of RE oxalates. Purified REO was obtained by calcination at 900°C for 2hrs using RE oxalate precipitated. Purified REO was used to recover CeO2 by subjecting to selective precipitation. Selective precipitation of CeO2 was carried out using solid form of KMnO4 and (15wt%) Na2CO3 solution with maintaining average pH value 4 by manual addition of Na2CO3 solution ([15 g /100 L]/0.001M).
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    Hydrometallurgical approach to investigate the recovery potential of gold available in waste PCBS
    (2021-12) Munagamage, SP; Wickramasinghe, BGWMDHK; Asvini, I; Dissanayake, DMDOK; Rohitha, LPS; Dushyantha, NP; Dissanayake, DMDOK; Jayawardena, CL
    Gold is one of the highly demanded precious metals which have applications in jewellery, investment, electronic and medical industries due to its unique chemical and physical characteristics. Although the demand for gold is continuously increasing, gold producers have failed to meet the existing demand for gold through gold mining. Therefore, seeking out secondary sources of gold is vital. Since gold is one of the major metals used in the electronic industry, e-waste has enormous potential as a secondary source of gold. This study outlines the recovery potential of gold and several other valuable metals quantitatively in Printed Circuit Board (PCB) components of end-of-life computers, namely, microprocessors and Integrated Circuits (ICs), plated connectors in network cards, and plated metallic pins. The research workflow consists of a sample pre-processing and an acid leaching (digestion) process followed by a sample analysis process using an Inductively Coupled Plasma - Mass Spectrometer (ICP-MS). According to the results, the recovery potential of gold is significant in every e-waste component tested under this study.
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    Selective precipitation of lanthanum and neodymium oxides from pulmoddai monazite, sri lanka
    (Department of Earth Resources Engineering, University of Moratuwa, 2020-12) Udayakantha, KGI; Chameera, SADK; Kulogin, S; Rohitha, LPS; Dissanayake, DMDOK; Dissanayake, DMDOK; Dassanayake, ABN
    Pulmoddai is the largest known deposit of heavy mineral sand in Sri Lanka. Because of the high concentration of Rare earth elements (REEs), Pulmoddai deposit’s value is considered to be economically enhanced by extracting REEs. Lanka mineral sand produces 100-120 tons of monazite per year and is currently treated as a waste. This crude monazite consists of Light rare earth elements and the radioactive element of Thorium (Th) and Uranium (U). The objective of this work was to develop a systematic scientific process to separate phosphate ion, radioactive elements and Neodymium and Lanthanum oxides from this monazite. In today's age, many extraction methods are used to extract the REEs. But it does have some limitations in Sri Lankan context. Hence, this study was carried out using a process of selective precipitation. Dephosphorization was carried out in alkaline media with different Sodium hydroxide concentrations of 50, 60, 70, 80% (w/v) at temperature 150 0C for 4 hours at 1atm. The optimum dephosphorization was observed in 80% (w/v) of NaOH concentration. Digested rare earth hydroxides were neutralized by using 60% (w/v) of hydrochloric acid at temperature 90 0C for 1 hour at 1atm. 2% (w/v) of oxalic acid was used in the rare earth chloride solution for removing impurities. Rare earth oxides (REOs) were obtained at 900 0C using calcination of rare earth oxalates. RE oxides were dissolved using 80% (w/v) HCL. In selective precipitation, 15% (w/v) NH4OH with KMnO4 were added to isolate Lanthanum and Neodymium hydroxides from RE chloride solution at controlled pH 4. Once again, 15% (w/v) NH4OH with KMnO4 at regulated pH 8.5 was applied to separate Lanthanum and Neodymium hydroxides. To obtain their oxide forms, these two hydroxides were calcinated at 900 0C.