Ce and Nd Extraction by Cationic Exchange, Using Bentonite, Diatomite, and Eggshell—Preliminary Study

China, Vietnam, Brazil, and Russia have the largest deposits of rare earths. However, in recent works, the occurrence of light rare earth elements has been demonstrated in an exhalative sedimentary type mineral (SEDEX) in Mexico, with adequate Ce and Nd contents. Additionally, it is this mineral that has been used to study the cation exchange capacity of non-metallic minerals and organic materials, such as bentonite, diatomite, and eggshell. To carry out this work, the crushed and ground SEDEX ore was leached using HCl, H2SO4, and HNO3. Subsequently, the liquid containing the Ce and Nd ions extracted from the mineral was put in contact with the respective ion exchangers, evaluating the effect of temperature and pH to determine the cation exchange efficiency of each exchanger tried. It was found that the best leaching results were achieved with the H2SO4, obtaining an extraction of Ce and Nd of 97.6% and 95.7%, respectively. On the other hand, in the case of cation exchange, the best results found for the extraction of Ce and Nd were using diatomite at a temperature of 323 K and a pH of 3, obtaining an extraction of 99.06% Ce and 99.07% Nd.