Sustainable Engineering of SBA-15 Mesoporous Silica from Sugar Cane Husk Ash for Catalysis, Adsorption and Energy Applications

Abstract

Sugar cane bagasse ash (SCBA), a large amount of agro-industrial waste from sugar mills, was successfully used as a renewable silica source for the synthesis of SBA-15 mesoporous silica. The SCBA was first acid washed (1 M HCl) to remove metallic impurities and then alkaline extracted (3 M NaOH) to yield sodium silicate as the silica precursor. SBA-15 was prepared by a P123-templated sol-gel process under acidic conditions, hydrothermal ageing at 100°C for 24 h and calcination at 500°C for 2 h. The synthesised material was fully characterized by XRD, FTIR, BET, BJH, SEM, TEM, TGA and EDS. The SCBA-derived SBA-15 showed a well-ordered hexagonal mesostructure (p6mm symmetry) with three characteristic XRD reflections at 2θ = 1.02°, 1.58° and 1.74°. The BET surface area, pore volume and average pore diameter were found to be 466 m2/g, 0.14 cm3/g and 3.12 nm respectively. The material exhibited a high adsorption capacity for brilliant green dye (55.1% removal, 5.51 mg/g uptake) and exhibited a promising catalytic activity in the production of biodiesel from waste sunflower oil (yield of FAME 5.6%). Comparative analysis with material synthesized using TEOS showed that the material synthesized using SCBA has similar textural and structural properties. This work demonstrates that SCBA can be used as an alternative to synthetic silica precursors, which is both cost effective and sustainable, while also providing a route to the production of functional mesoporous materials for environmental and catalytic applications, with waste valorisation as an additional benefit.