Thorough Utilization of Rice Husk: Metabolite Extracts for Silver Nanocomposite Biosynthesis and Residues for Silica nanomaterials Fabrication
Rice husk (RH), a low-cost agricultural waste material, contains valuable minerals, compounds and molecules, such as amino acids, sugar, lignin, cellulose and silicon. There is lacking of an approach to completely use these resources. In this study, metabolites in RH was utilized to green synthesis of silver nanoparticles (AgNPs). Meanwhile, the residue was used to fabricate silicon dioxide nanomaterials (SiO2 NMs). We used gas chromatography-mass spectrometry (GC-MS) based metabolomics to elucidate the underlying mechanism for AgNPs forming. Totally 340 metabolites have been identified and quantified in RH extracts. By comparing the concentration of metabolites before and after reaction, approximately 39 metabolites responsible for the synthesis were screened out. Interestingly, six alcohol, six sugar and sugar derivatives, seven amino acids, eight organic acids, four fatty acids, and eight medicine, such as Xylitol, Sinapyl alcohol, Levoglucosan, Glucose, Carbamoyl-aspartic acid, Citrulline, Maleimide, Phytol, Acetanilide, etc. were markedly decreased or almost disappear after reaction, indicating these compounds act as reducing or capping role during the NPs forming process. The obtained AgNPs exhibited strong antioxidant capacities. The biosynthesized SiO2 NMs were used to remedy heavy metals contaminated soil, the results based on inductively coupled plasma-mass spectrometry (ICP-MS) analysis indicated that biosynthesis mesoporous SiO2 NMs by RH reduced the bioavailability of Cr, Cu and Cd significantly. The study provides a comprehensive view of how to utilize RH in a sustainable manner.