METHODOLOGY WITH INDUSTRIAL SCALABILITY FOR OBTAINING LITHIUM HYDROXIDE AND / OR LITHIUM CARBONATE FROM MINERAL CLAYS.

Abstract

A proposal is presented for an industrial plant to process 100 tons per day of lithium-rich clays, with the capacity to produce large quantities of lithium hydroxide (LiOH) and lithium carbonate (Li₂CO₃). The purity and yield of LiOH have not been defined. The purity and yield of Li₂CO₃ are 98% or greater and range from 200 kg / day to 600 kg / day, respectively; the latter corresponding to initial lithium availability in the clays from 0.05% (500 ppm) to 0.20% (2000 ppm). The established methodology or process was developed based on systematic evidence gathered from a series of experimental procedures with clays collected from the surface in Mexico, but of uncertain origin (likely from the state of Chihuahua, Mexico). A representative set of eight samples was used, of which only half showed a lithium availability greater than 500 ppm.In the clays studied, the predominant lithium-bearing phase was zinnwaldite, comprising approximately 40-60% of the total. Lepidolite was also observed in smaller proportions. For unknown reasons, the availability of lithium in the clays studied is generally five to ten times lower than theoretically expected (see the Table of Lithium-Associated Minerals in the BACKGROUND). On the other hand, the process yield is close to 60%. In summary, the combination of these two factors suggests that the LiOH and Li₂CO₃ production capacities of the present invention are probably not sufficiently competitive globally. However, the present invention could establish a domestic or national supply (Mexico). The process yield can be improved by preparing concentrates of the lithium-rich phases (through physical separation) or by high-energy mechanical milling.While the second is considered unfeasible or impractical within an industrial context, the first could be established through the implementation of various utility models related to the present invention. Other utility models related to the present invention could include some adaptations of the proposed industrial plant to: 1) process between 10-100 and 100-1000 tons of clay daily, 2) utilize the calcium carbonate (CaCO3) available in the clay, and—most importantly—3) recycle the water used in the process. Finally, it should be mentioned that other specific aspects, such as the geometric layout of the plant and the piping to connect its components, will depend significantly on the dimensions and surface conditions of the land where the plant is to be installed.