Preparation of Nanosilica Powder Using Rice Husk via Precipitation Method

Abstract

Silica in nanoscale has various superior properties which leads to a wide range of applications. Most researches used and metal alkoxides as the sources but very few researches attempted at preparing nanosilica powder from the agricultural waste which environmental friendly and inexpensive. This research is presented as the studies of optimization of parameters involved during preparation, aimed to improve the purity of silica produced. In this work, rice husk ash (RHA) precursor was subjected to precipitation method in order to produce nanosilica powder. Acid leaching and thermal treatment were done as a pre-synthesis process. The process parameters that have been studied were the refluxed NaOH concentration, heating time, and temperature, in which the properties were then evaluated during characterization process. The results from X-Ray Flourescence (XRF) confirmed that it is possible to extract 100% purity of silica from RHA treated by the combination of thermal treatment, acid leaching, refluxed with 2.5 M of NaOH and heated at 50°C for 48 hours. X-Ray Diffraction (XRD) illustrated that the produced silica is in amorphous state. Meanwhile, the mean particle size of the spherical shape of silica obtained ranging from 44.7 nm to 1.23 μm. Therefore, the best mean particle size obtained was by using the sample refluxed with 2.5 M NaOH and heated at 50°C for 48 hours, which were confirmed by Scanning Electron Microscope (SEM) and Field Emission Scanning Electron Microscope (FESEM). These findings on the optimum parameters indicate the successful production of highest purity of nanosilica powder with nanoscaled particle size.

Recovery of Chlorosilane Residual Liquid to Prepare Nano-Silica via the Reverse Micro-Emulsion Process

“…According to the above silica preparation method, the effects on the particle size, morphology, and dispersion of the prepared nano-silica were studied via varying the influencing factors such as the concentration of chlorosilane residual liquid (0.04 mol/L, 0.08 mol/L, 0.12 mol/L, 0.16 mol/L, 0.20 mol/L), the value of HLB (13.50, 11.63, 10.50, 9.75, 9.21), molar ratio of water to surfactant (ω) (9,12,16,20,32), and the concentration of ammonia (0.15 mol/L, 0.30 mol/L, 0.44 mol/L, 0.58 mol/L, 0.65 mol/L).…”

“…At present, the main methods for the preparation of nano-silica include vapor phase hydrolysis [14], chemical precipitation [15,16], solgel [17,18], and inverse micro-emulsions methods [19]. Among them, inverse micro-emulsions were usually a uniform and stable dispersion system composed of surfactant, co-surfactant, oil phase, and water phase, all of which had a translucent to transparent appearance [20].…”