Rice HUSK silica: A review from conventional uses to new catalysts for advanced oxidation processes

The rice industry is of great importance worldwide and within the cereal industrialization process, rice husk is obtained as waste, a by-product with various alternative uses, among others, the obtaining of amorphous silica, a covalent oxide with chemical, structural and textural properties suitable for use as catalytic support. This review shows the potential of rice husk silica in the synthesis of heterogeneous catalysts with transition metals for the oxidation of different polluting molecules present in water, as well as the limitations of the catalytic system and the way to overcome them through new synthesis routes, to obtain single atom catalysts - SACs. The main preparation strategies applied for aqueous phase systems are summarized, as well as the studies of single atom catalysts in oxidation reactions of recalcitrant compounds using silica as support and, finally, the perspectives and opportunities regarding this novel topic.