Transformation of Small Pore Sized Zeolite from Universal Silicates and its Potential for Lithium Extraction

To broaden the disposal strategy of silicate wastes, a hydrothermal method inspired by previous work on the extraction of potassium from K-feldspar was proposed in this work to handle the representative silicates of feldspars, pyrophyllite, coal gangue, coal fly ash, and as a result, two typical small zeolites of analcime and hydroxycancrinite were obtained. Systematic ion exchange experiments under the existences of Li + , Na + , K + , Ca 2+ , Mg 2+ in different conditions were conducted to evaluate their cation selectivity and capability. Results showed that Li + was the only cation having positive feedback on the zeolite structure, in mixed-ion system solutions, it achieved efficient lithium silicate immobilization with a Li 2 O content of 4.50 wt. %, while in a single-ion system (LiCl solution), the Li 2 O content reached 9.40 wt. %. The immobilization capacities in both systems surpassed those of high-grade granitic pegmatite-type lithium ores (1.5–4 wt. %). The structure of hydroxycancrinite is always the same before and after ion exchange, and all of them are shelf silicate structures. The Spectral analysis identified the formation of Li-zeolite from hydroxycancrinite with the successful trapping of Li + inside. The overall handling process provided a new way for the process of universal silicate wastes with further combination of lithium extraction from mixed cation solution system.