Modification of pore structure and functionalization in MSU-X silica and application in adsorption of gold thiosulfate

Abstract

Mesoporous silica ceramics have found widespread applications in industry as well as energy and environment, and since their advent in early 1990s they have been the focus of many studies regarding their structural and functional properties. Mesoporous silicas and in particular the MSU group of these materials have several advantages in their preparations and properties as well as in applications such as adsorption from solutions. Toward this end, synthesis and processing of different members of MSU-X silica and functionalization of them with different simple ligands was followed in this research. Recovering gold thiosulfate from simulated leach solutions was considered as the main application of the mesoporous organosilicas because the material had previously shown strong affinity for such gold compound. While comparison of the materials’ structures and functionalization revealed the differences due to the synthesis and post-synthesis processing conditions, it also showed some minor or major differences in the adsorption behaviors. For the smaller-pore-sized MSU-2 and MSU-4, the inherently high specific surface area was found to be more of a controlling factor on gold adsorption capacities. On the other hand, in larger-pore-sized MSU-3 and MSU-F with similar functionalizations, the mesopore properties such as pore order, pore size distribution and mesopore geometry were considered as the main influential factors controlling both the material structure and performance in gold adsorption. The latter properties could be controlled by synthesis parameters such as co-condensation at different temperatures and post-synthesis hydrothermal treatment so that the gold adsorption capacity of the hybrid material would further be enhanced.