Green Synthesis of Crystalline Silica from Sugarcane Bagasse Ash: Physico-Chemical Properties

Nanomaterials (Basel). 2022 Jun 25;12(13):2184. doi: 10.3390/nano12132184.


Sugarcane bagasse South Africa is an agricultural waste that poses many environmental and human health problems. Sugarcane bagasse dumps attract many insects that harm the health of the population and cause many diseases. Sugarcane ash is a naturally renewable source of silica. This study presents for the first time the extraction of nanosilica from sugar cane bagasse ash using L-cysteine hydrochloride monohydrate acid and Tetrapropylammonium Hydroxide. The structural, morphological, and chemical properties of the extracted silica nanoparticles was cross examined using XRD, FTIR, SEM, and TGA. SEM analysis presents agglomerates of irregular sizes. It is possible to observe the structure of nanosilica formed by the presence of agglomerates of irregular shapes, as well as the presence of some spherical particles distributed in the structure. XRD analysis has revealed 2θ angles at 20, 26, 36, 39, 50, and 59 which shows that each peak on the xrd pattern is indicative of certain crystalline cubic phases of nanosilica, similar to results reported in the literature by Jagadesh et al. in 2015. The crystallite size estimated by the Scherrer equation based on the aforementioned peaks for ca-silica and L-cys-silica for the extracted particles had an average diameter of 26 nm and 29 nm, respectively. Furthermore, it showed a specific surface area of 21.6511 m2/g and 116.005 m2/g for ca-silica and L-cys silica, respectively. The Infrared (IR) spectra showed peaks at 461.231 cm-1, 787.381 cm-1 and 1045.99 cm-1 which corresponds to the Si~O~Si bending vibration, the Si~O~Si stretch vibration, and the Si~O~Si stretching vibration, respectively. This confirms the successful extraction of nanosilica from sugar cane bagasse ash. TGA analysis has revealed that the as received sugarcane bagasse has high loss on ignition (LOI) of 18%, corresponding to the presence of the unburnt or partial burnt particles, similar to results reported by Yadav et al. This study has shown that sugar cane bagasse ash is a natural resource of silica which should be harnessed for industrial purposes in south Africa.

Keywords: L-cysteine hydrochloride monohydrate; citric acid; green synthesis; silica; sugarcane bagasse ash; tetrapropylammonium hydroxide.