Bisphosphonate modified mesoporous silicon for scandium adsorption

Scandium has several applications in advanced technology, but its wider utilization is restricted by the limited supply. Scandium exists in low concentration in ores and, therefore, the conventional extraction methods are difficult, uneconomical, and often hazardous to the environment. Adsorption is more sustainable method to extract scandium, because of low energy consumption and scalability. However, selectivity and stability of adsorbents are often inadequate. The present paper introduces a novel hybrid material as a robust adsorbent for efficient extraction of scandium. The material comprises of bisphosphonate molecules grafted on thermally carbonized surfaces of mesoporous silicon. The mesoporous framework was utilized to make the material water permeable to be used in a flow-through system, and the surface modifications made the material exceptionally stable even in harsh conditions. The material exhibited a remarkable selectivity towards scandium with a separation factor of 13, which is 3-fold higher compared with the commercial ion exchange resin Dowex 50WX8. Crucially, the hybrid material proved to be highly stable and reusable up to 50 adsorption/desorption cycles of scandium.