The Production of Biogenic Silica from Different South African Agricultural Residues through a Thermo-Chemical Treatment Method

Abstract

A thermo-chemical treatment method was used to produce biogenic amorphous silica from South African sugarcane and maize residues. Different fractions of South African sugarcane (leaves, pith, and fiber) were processed for silica production. The biomass samples were leached with either 7 wt% citric acid or 7 wt% sulfuric acid at 353 K for 2 h prior to being rinsed, dried and combusted using a four-step program ranging from room temperature to 873 K in a furnace. The characterization of the pre-treated biomass samples was conducted using thermogravimetric analysis (TG/DTA), X-ray fluorescence analysis (XRF) and elemental analysis (CHN), while the final products were characterized by XRF, X-ray diffraction (XRD), elemental analysis, nitrogen physisorption and scanning electron microscopy (SEM). Citric acid pre-treatment proved to be an attractive alternative to mineral acids. Amorphous biogenic silica was produced from sugarcane leaves in good quality (0.1 wt% residual carbon and up to 99.3 wt% silica content). The produced biogenic silica also had great textural properties such as a surface area of up to 323 m2 g−1, average pore diameter of 5.0 nm, and a pore volume of 0.41 cm3 g−1.

An Overview of Current and Prognostic Trends on Synthesis, Characterization, and Applications of Biobased Silica

“…Additionally, liquid is added into the quantity of solid and vice versa for the case of dispersed classes. To prepare metallic oxides of silica, nitric, hydrochloric, and sulphuric acids are widely applied [1,8].…”

“…In another way, silica is obtained from the ash of corn cob using the acid precipitation method [3]. In elsewhere, maize leaves are used for silica production using leaching method [8]. Sugarcane bagasse and leaves are another bioresource for biosilica [3,70].…”

“…Biomass can be a potential source for the extraction of synthetic silica components such as silica gel. In such a way, biomass resources ash of rice husk [5], sorghum bagasse [6], tef straw [7], maize leaves [8], rice straw [9], wheat straw [10], sugarcane bagasse [11], sugarcane leaf [12], bamboo leaf [13] corn cob [14], and palm [1] are found to be potential feedstock. Sodium silicate is used in general to extract the silica from the residual ash of the feedstock [15].…”

“…Silica gel can be produced from renewable sources of selected biomass such as palm tree [1], wheat straw [10], maize leaves [8], tef straw [7], sugarcane bagasse [11], rice husk and rice straw [5,9], sugarcane leaf [12], oat husk [54], bamboo leaf [13], and corn cob [14]. At present, agricultural residues receive signifcant attention as feedstock to produce silica gel due to sustainability, economic and environmental concern.…”

Green synthesis of silica and silicon from agricultural residue sugarcane bagasse ash – a mini review

“…Similarly, Maseko et al 40 investigated biogenic amorphous silica that was extracted from different agricultural wastes using the thermo-chemical treatment process. Biomass samples were leached using 7% CA and 7% H 2 SO 4 before thermal treatment in a furnace; CA pretreated was slightly less effective at removing inorganic impurities when compared to H 2 SO 4 pretreated SCBA (silica content of 95.4% and 99.3%, respectively).…”