A study on leaching behavior of rare earth elements from heavy mineral of the domestic beach sand

Abstract

Research on Leaching Rare Earth Elements in Heavy Minerals of Beach Sand in Korea. Heavy minerals of beach sand produced in Korea are used as the raw materials for leaching test and research on rare earth elements (REE). To recover effectively the REE in heavy minerals of beach sand, low-grade monazites obtained through physical concentration are used as the raw materials firstly. The monazites are crushed before test to enhance the chemical reaction efficiency, aiming to enlarge the contact area between minerals and solvents during solid-liquid reaction and carry out leaching reaction in a better and thorough way. Put the crushed minerals into the strong acid solution, compare the factors including mixing speed, solid-to-liquid ratio, time, temperature and concentration of aqua regia and study the influence on the leaching rate of REE. The results show that, the granularities of raw materials (averagely 50 microns) which go through mechano chemical treatment are effectively controlled if the crushing period is limited within 150 minutes. Afterwards, the suitable reaction conditions of leaching REE as follows: mixing speed 1000 rpm, 1:30, 100% and 90 degrees, under which the leaching effect is perfect. Except Ce, the REE including La, Pr and Nd are effectively recovered and their recovery rates are as high as 99%. The leaching rates of heavy rare earth elements (HREE) Gd and Y are 80% and 75% respectively and that of Th, a radioactive element, reaches over 99% as well. Based on the test results, a chemical kinetics analysis is carried out on the reactions of Ce, La and Gd in this solid-liquid phase. The obtained diffusion activation energy of Ce is 15.789KJ and its reaction difference (n) is 2.10. The influence on diffusion speed in different reaction layers is accordingly evaluated. The diffusion activation energy effectively reflects the reaction processes of diffusion and penetration of solution on the surface of and within the solute during the solid-liquid reaction and the reaction difference is to confirm the determination of the level of sensitivity of acid concentration reaction during surface diffusion after mechano chemical treatment.