Morphology, Extraction Yield, and Properties of Biogenic Silica Nanoparticles from Indonesian Rice Husk as Influenced by Solvent Type and Aging Time

Abstract

Rice husk is a rich source of biogenic silica nanoparticles (SNPs) having excellent physico-chemical properties and numerous potential applications. Extraction yield of the biogenic SNPs may be influenced by many factors. In this study, morphology and the influence of solvent type (sodium hydroxide/NaOH, potassium hydroxide/KOH) and aging time (0, 6, 12, 18, 24h) on extraction yield and properties of selected biogenic SNPs from Indonesian rice husk were investigated. The biogenic SNPs were produced by a simple sol-gel method. The presence of biogenic SNP aggregates in the rice husk tissues was successfully identified by SEM-EDX micrographs. NaOH produced better SNPs extraction results than KOH. Aging time for 6h was the optimum condition for production of SNPs. The TEM image showed that SNPs from the best treatment were approximately spheroidal with particle sizes in the range of 20–50nm. The XRD patterns revealed the amorphous nature of the SNPs. Nitrogen adsorption–desorption analysis showed that the SNPs had BET surface area of 235,78m2/g, total pore volume of 0.58cc/g, and average pore radius of 4.91nm. The SNPs exhibited a type IV isotherm and H1 hysteresis loop indicating a characteristic of mesoporous materials. The results suggest that the sol-gel method developed could provide a simple and relatively fast extraction technique producing biogenic amorphous mesoporous SNPs that could extend their potential applications and increase the economic benefits of utilizing rice husk.

Effects of nanobiosilica from rice husk ash application on rice growth, productivity, and milling quality

“…Rice husks were collected from a rice milling plant in Karawang District. Analytical grade NaOH and HCl for production of nanobiosilica [2] were purchased from PT Merck Chemicals and Life Sciences. Rice seeds (Oryza sativa) cv.…”

“…Rice husk contains 15-20% silicon dioxide (SiO 2 ) or silica [3], a beneficial element used widely for various applications, including sustainable rice production [4]. Our study showed that appropriate extraction of rice husk ash could produce biogenic silica nanoparticles powder, which is called nanobiosilica, with individual particle sizes of 20-50 nm [2]. SiO 2 is a chemically bonded compound of silicon (Si) commonly found in nature.…”

“…Rice husk ash (RHA) used for the field experiment was prepared using a direct combustion method equipped with a specifically designed instrument that condensed the smoke produced. Extraction of solid nanobiosilica (powder) from rice husk was conducted by the sol-gel method using NaOH solution as reported in the previous study [2]. Chemical composition of RHA and nanobiosilica was analyzed by an X-Ray Fluorescence (XRF) Spectrometer (Malvern Panalytical Axios mAX WDXRF).…”

“…This was confirmed by the lower concentrations of other constituents in nanobiosilica than those in RHA, except for Na 2 O and Cl. During production of nanobiosilica from rice husk using the sol-gel method, several washing/leaching steps were conducted in the beginning of rice husk handling and following gel formation process [2]. The washing/leaching steps could remove water soluble constituents and hence decreased their concentrations in nanobiosilica produced.…”

“…Indonesia, the world's third-largest rice producer [1], is estimated to produce more than 10 million tons of rice husk (RH), a rice milling by-product, annually [2]. RH has a low economic value, and it is difficult to decompose naturally.…”