A facile method for production of high-purity silica xerogels from bagasse ash

In this paper, we systematically report the synthesis of mesoporous silica xerogels in high purity from bagasse ash. The bagasse ash was chosen as the raw material due to its availability and low-price, and environmental considerations also were important. Silica was extracted as sodium silicate from bagasse ash using NaOH solution. The sodium silicate was then reacted with HCl to produce silica gel. To produce high-purity silica xerogels, three different purification methods were investigated, i.e., acid treatment, ion exchange treatment, and washing with de-mineralized water. We were able to produce high-purity silica (>99 wt.%) by washing the produced gels with either de-mineralized water or with ion exchange resin. The specific surface area of the prepared silica xerogels ranged from 69 to 152 m2 g−1 and the pore volume ranged from 0.059 to 0.137 cm3 g−1. The pore radii were 3.2–3.4 nm, which indicated that the silica xerogels was mesoporous. From the adsorption characterization, it was obvious that adsorptive capacity was better for high-purity silica xerogels compared with low-purity. The maximum adsorption capacity by high-purity silica xerogel was 0.18 g-H2O/g-SiO2. Finally, we demonstrate the potential of bagasse ash for mesoporous silica production with its excellent adsorptive capacity that makes it beneficial as an environmental solution.