Full-components utilization: Study on simultaneous preparation of sodalite and separation of yttrium from coal gangue by chlorination roasting process

Abstract

Kaolinite-type coal gangue is a solid waste from coal mining that contains valuable rare earth elements (REE) and kaolinite. The simultaneous recovery of REE and synthesis of functional materials utilizing kaolinite from coal gangue presents an opportunity for full utilization. This study introduces synchronous chlorination volatilization of REE and preparation of sodalite from coal gangue. Thermodynamic analysis revealed xenotime reacts directly with NaCl to produce YCl3 for volatilization with the presence of O2. The effects of various factors on yttrium recovery and sodalite synthesis, including temperature, time, additives, and NaCl dosage, were investigated. Optimal conditions were identified as roasting coal gangue with 13.3 wt% NaCl and 41.7 wt% Na2CO3 at 1000 ℃, resulting in 93.4% yttrium volatilization and a 100% conversion efficiency of sodalite. The addition of Na2CO3 was found to accelerate the transition from aluminosilicate minerals to sodalite, thus achieving an outstanding sodalite conversion efficiency. This approach offers a theoretical and practical foundation for the efficient utilization of solid waste.