Synthesis of zeolites using aluminosilicate residues from the lithium extraction

Abstract

The production of lithium from spodumene ores generates huge amounts of residue mainly composed of aluminosilicate. The main objective of this study was to compare the performances of three different processes to produce zeolites from aluminosilicates residues originating from lithium extraction. Zeolites were synthesized using: i) a conventional hydrothermal process (Process_1), ii) a conventional hydrothermal process assisted by calcination (Process_2), and iii) a conventional hydrothermal process assisted by alkaline fusion (Process_3). A physico-chemical (e.g., chemical composition, sorption capacity) and mineralogical (e.g., XRD, SEM) characterization of synthesized and commercial zeolite was done to identify the most performing synthesis route. Then, the effect of operating parameters (i.e., aging time and temperature, crystallization time, solid/liquid ratio) on the physico-chemical properties of the zeolite synthesized using the most performant process route was assessed. Initial aluminosilicate residues were mainly composed of Al2O3 (24.6%) and SiO2 (74.0%), while containing low amounts of potential contaminants (< 1.6%). Based on its chemical composition, the fine fraction (< 53 µm) was identified as the most suitable fraction to produce zeolite. Physico-chemical and mineralogical characterization of produced zeolite showed that conventional hydrothermal process was the most performant route to synthesize zeolite with properties like commercial zeolite 13X. Crystallization time (from 8 to 24 h), aging temperature (from 25 to 75°C) and S/L ratio (from 10 to 30% - w/v) are the main parameters affecting the properties of synthesized zeolite (i.e., ion-exchange capacity). Finally, a zeolite type X with an ion-exchange capacity of 58 mg/g, which is close to commercial zeolites (76–77 mg/g), was synthesized from the fine fraction of aluminosilicate residue using the conventional hydrothermal process after 8 h of aging at 75°C and 16 h of crystallization at 100°C, with a solid/liquid ratio of 10% (w/v).