Eco-friendly synthesis of nanostructured mesoporous materials from natural source rice husk silica for environmental applications

Abstract

Nanostructured mesoporous materials of MCM-41 type were synthesized using a natural, non-toxic, and cheap source of silica from rice husk. Then, this pure silica was modified with several Fe loadings by a wet impregnation method. The chemical and physic properties of MCM-41 solids obtained were similar to those of MCM-41 synthesized from commercial silica by conventional method. Thus, all catalysts exhibited good structural regularity preserving the mesoporosity after the metal incorporation. The performance of the Fe/MCM-RHA composites as photo-Fenton heterogeneous catalysts was evaluated for photocatalytic degradation of different endocrine-disrupting chemicals (EDCs), such as herbicides (atrazine), and compounds derived from the plastic industry (bisphenol A) and the pharmaceutical industry (acetaminophen). The major photo-catalytic efficiency obtained (Fe/MCM-RHA(2.5)) is consistent with the highest presence of iron species, which are finely dispersed and stabilized on the silica structure, the isolated Fe3+ ions being the accessible and active sites for the reaction. Finally, a cheaper solid arising from the valorization of residual biomass and with excellent photocatalytic performance for the degradation of EDCs (above 99%, 75%, and 60% for BPA, ATZ, and ACE respectively, in a reaction time of 240 min) was obtained.