Sugarcane Bagasse Ash as an Alternative Source of Silicon Dioxide in Sodium Silicate Synthesis

Abstract

To reduce the environmental impacts from sodium silicate synthesis, a ceramic method was suggested, with sugarcane bagasse ash (SCBA) as the source of silicon dioxide and sodium carbonate. Although the production of sodium silicate is carried out on a large scale, it should be noted that its process requires temperatures above 1000 °C; it also requires the use of highly corrosive agents such as sodium hydroxide and chlorine gas to neutralize the remaining sodium hydroxide. In the present study, the synthesis temperatures were reduced to 800 °C with a reaction time of 3 h by pressing equimolar mixtures of previously purified SCBA and sodium carbonate; then, heat treatment was carried out under the indicated conditions. The resulting materials were analyzed with Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Among the crystalline phases, calcium disodium silicate was identified, in addition to sodium silicate; thus, it was inferred that the other components of the ash can interfere with the synthesis of silicate. Therefore, in order to obtain the highest composition of sodium silicate, a leaching treatment of the SCBA is required.

The Use of Solid Sodium Silicate as Activator for an Amorphous Wollastonitic Hydraulic Binder

“…A. Broad band between 2500 and 3800 cm −1 associated with O-H stretching vibration [24,25]; B. CO3 2− characteristic bands at 1450 cm −1 attributed to asymmetric stretching mode [25]; C. Bands 1050-1100 cm −1 characteristic of stretching Si-O-Si bond [20,24,26]; D. Band at 973 cm −1 attributed to the Si-O symmetric stretching [25]; E. Band associated with Si-O-Si asymmetric stretching vibration, specifically Q 0 and Q 1 at ∼850, ∼900 cm −1 [14,27]; F. CO3 2− characteristic bands at 712 cm −1 caused by the in-plane bending modes [28][29][30].…”

“…The strip highlighted as (D) reveals that all spectra exhibit a band at 950 cm −1 , indicating the presence of the Na-O-Si bond [20], hence suggesting an effective reaction [20]. In the diatomite-based sample, the band is broader, possibly due to the higher amount of Si-O-T (T = Si, Al) structures (946 cm −1 ) [32].…”

“…In Figure 3, the XRDs of the lab-made activators are compared with those of the commercially available EastChem sodium silicate powder. All samples displayed a crystalline structure, and the following nomenclature was given to the identified peaks: 1-Na 6 Si 2 O 7 [23], 2-Na 2 SiO 3 [20], 3-CaAl 2 O 4 [23], 4-CaAl 2 O 4 [23] and 5-Na 2 CO 3 [33]. The samples produced with sand and diatomite presented a peak at 26.6 • (2θ) (Q), which is indicative of the presence of unreacted silica [16].…”

“…Several studies have focused on the synthesis of this activator [13,14] using different silica-rich sources as raw materials. These sources include low-value, silicate-rich wastes [15][16][17][18], and bio-derived materials [19,20]. There are two main routes of synthesis that can be applied [21], a thermochemical method and a hydrothermal method.…”