Synthesis of silica nanoparticles from Vietnamese rice husk by sol–gel method

Van Hai Le,Huy Ha Thuc,Chi Nhan Ha Thuc

doi:10.1186/1556-276x-8-58

Abstract

Silica powder at nanoscale was obtained by heat treatment of Vietnamese rice husk following the sol–gel method. The rice husk ash (RHA) is synthesized using rice husk which was thermally treated at optimal condition at 600°C for 4 h. The silica from RHA was extracted using sodium hydroxide solution to produce a sodium silicate solution and then precipitated by adding H2SO4 at pH = 4 in the mixture of water/butanol with cationic presence. In order to identify the optimal condition for producing the homogenous silica nanoparticles, the effects of surfactant surface coverage, aging temperature, and aging time were investigated. By analysis of X-ray diffraction, scanning electron microscopy, and transmission electron microscopy, the silica product obtained was amorphous and the uniformity of the nanosized sample was observed at an average size of 3 nm, and the BET result showed that the highest specific surface of the sample was about 340 m2/g. The results obtained in the mentioned method prove that the rice husk from agricultural wastes can be used for the production of silica nanoparticles.

Highlights

Materials Rice husk from the natural rice source of Mekong Delta, Vietnam, was used
We have focused our effort on preparing stable nanosilica from sodium silicate which was synthesized from Vietnamese rice husk using the sol–gel technique
When the cetyltrimethylammonium bromide (CTAB) concentration was increased from 2.5 to 3.0 wt.% as shown in Figure 3e,f, the results show the appearance of small particles, while being distributed synchronously unclear, which tend to agglomerate, and silica nanoparticles were not distributed in the butanol solvent when the concentrations of CTAB were increased (Figure 4a)

Summary

Introduction

Materials Rice husk from the natural rice source of Mekong Delta, Vietnam, was used. Sodium hydroxide, cetyltrimethylammonium bromide (CTAB), cetyl amine (CA), polyethylene glycol (PEG, 10,000), Arkopal, cethyl ammonium chloride (CAC), Aliquat 336, alkyl dimethyl benzyl ammonium chloride (ADBAC), cetylpyridiniumbromide (CPB), and cetyltrimethylammonium chloride (CTAC) were purchased from Merck (Darmstadt, Germany) and used as surfactant agents. 20% of the rice paddy is husk, giving an annual total production of 120 million tons [1]. It is important that the silica in RHA exists in the amorphous state and has high surface area [9,10,11,12,13]. Because of these features, silica has many applications, such as sources for synthetic adsorption materials [14,15,16], carriers, medical additives, fillers in composite materials, etc. Silica has many applications, such as sources for synthetic adsorption materials [14,15,16], carriers, medical additives, fillers in composite materials, etc. [17,18], and demonstrates advantages when achieved at nanometer size

Methods

Findings

Discussion

Conclusion