Lon adsorption behavior (in aqueous solutions) of lanthanum, cerium, and europium in organic adsorbents: review of kinetic, isothermal, and thermodynamic studies

Rare earth elements are present in a large number of raw materials for different applications in high technology, including lasers, magnets, fiber optics, X-ray machines, and lamps. Therefore, efforts have been made to find new alternatives that improve the recovery and recycling of these important elements, given that rare earth reserves worldwide are scarce and highly polluting. The aim is to counteract demand and help the environment by using alternative methods and making use of waste at the end of its useful life. Some of this waste is found in water sources from treatment plants and mining, which is significantly dangerous for nature and humans. As a viable alternative, the adsorption method has been chosen as it is an effective and low-cost process. This document aims to analyze different literature on the adsorption of lanthanum, cerium, and europium ions (in aqueous solutions) on organic adsorbents such as biomass and activated carbons, in order to verify whether the adsorption technique proves to be effective for the recovery of these elements, analyzing the kinetic, isothermal, and thermodynamic models. The results obtained confirm that the parameters that depend on adsorption are contact time, pH, and temperature, with a high capacity for removing metal ions. The isotherms most used by the different authors were Langmuir and Freundlich. For the kinetic study, a correlation was found with the activation energy taking place in chemisorption. Most of the literature studied showed that these were spontaneous and endothermic processes.