Study of alkali fused acid leaching of malaysian monazite for recovery of rare earth element
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Date
2019-07
Authors
Wan Syakirah Binti Wan Rostan
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Abstract
Alkali fused acid leaching process of Malaysian Monazite was carried out by using an alkali fusion of monazite continued by acid leaching of alkali fused residue. The alkali fusion process conducted at the constant parameters while the acid leaching was being conducted within five parameters. Raw monazite was characterized by using a few techniques such as XRF, XRD, LOI, SEM-EDX, and Particle Size Analysis (PSA). From the XRD Analysis, the major peaks of monazite are detected with high noise and thick profile due to the sensitivity of the XRD detector and the content of other elements. Besides, XRF Analysis has shown that the monazite contains the major elements such as cerium (Ce), lanthanum (La), neodymium (Nd), thorium (Th) and phosphorus (P). The alkali fusion is conducted with one to three ratio of monazite to sodium hydroxide and fused for three hours at 350°C in the furnace. The acid leaching of monazite is conducted by manipulating several parameters such as the molar concentration of hydrogen peroxide, the concentration of hydrochloric acid, the solid to liquid ratio, monazite to hydrochloric acid, temperature of leaching, and duration of leaching. This analysis used constant particle size of monazite, which is 75μm. The solid to liquid ratio, monazite to hydrochloric acid used are 10g/1000ml, 30g/1000ml and 50g/1000ml. Furthermore, the leaching temperature is at 70 °C, 80 °C and 90 °C and conducted for two hours, four hours and six hours. Then, the concentration of hydrochloric acid used in this experiment is 3 Mol, 6 Mol and 9 Mol. The solution will be added with hydrogen peroxide improve the performance of acid leaching. The molar concentration of hydrogen peroxide that be used are 0 Mol/L, 5 Mol/L and 10 Mol/L. All of parameters are simultaneously tested by conducting Design of Experiment (DOE). The optimum alkali leaching achieved when the condition of the experiment is using 9 Mol of concentration of hydrochloric acid, 10 Mol/L of the molar concentration of hydrogen peroxide, 10g/1000 ml of solid to liquid ratio and at 70 °C for 6 hours. It gives a high recovery of rare earth elements and thorium element.