Abstract
Sweet sorghum (Sorghum bicolor (L.) moench), a crop that is grown by subsistence farmers in Zimbabwe was used to extract silica gel in order to assess its possible use as a raw material for the production of silica-based products. The gel was prepared from sodium silicate extracted from sweet sorghum bagasse ash by sodium hydroxide leaching. Results show that maximum yield can be obtained at pH 5 and with 3 M sodium concentration. The silica gel prepared at optimum pH 5 had a bulk density of 0.5626 g/cm3 and anestimated porosity of 71.87%. Silica gel aged over 10 h had improved moisture adsorption properties. X-ray fluorescence (XRF) determinations show that the silica content in the ash is 40.1%. Characterization of sweet sorghum ash and silica gels produced at pH 5, 7 and 8.5 by Fourier Transform Infrared spectroscopy gave absorption bands similar to those reported by other researchers.Transmission electron micrographs show that silica prepared under optimum conditions is amorphous and consisted of irregular particles. Sweet sorghum proved to be a potential low cost raw material for the production of silica gel. Key words: Silica gel, sweet sorghum, extraction, ash, bagasse, X-ray powder diffraction (XRD).
Highlights
Silica gel is a non-toxic and inert inorganic polymer composed of amorphous silicon dioxide
Five grams of sweet sorghum bagasse ash was leached for 30 min in 100 ml of 1 M hydrochloric acid (HCl) solution to remove heavy metals
The effect of temperature on ash content was investigated for the temperature range 200 to 800°C
Summary
Silica gel is a non-toxic and inert inorganic polymer composed of amorphous silicon dioxide It is characterized by a large surface area of up to 800 m2/g. Research has so far focused on the preparation of silica gels of various morphology e.g. nano particles, meso, macro and microporous particles (Noushad et al, 2012; Thuadaji and Nuntiya, 2008). Another potential silica source is the sugarcane bagasse ash. Mamat (2012) reported a new approach of preparing ordered and disordered silica gel particles from bagasse ash. This research paper reports a new biobased approach of extracting silica from sweet sorghum bagasse ash. Sweet sorghum bagasse ash is renewable since is derived from plant source
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