Sustainable methods for the recovery of silica from coal fly ash for industrial applications

This review examines the conversion of coal fly ash (CFA), a waste byproduct of coal-fired power plants, into high-purity silica with promising industrial applications, including adsorption and CO2 capture. It focuses on alkali-dissolution and alkali-fusion as the primary extraction methods, demonstrating their ability in producing valuable silica. However, persistent challenges such as the removal of residual metals and salts, as well as the environmental impact of using strong alkalis and acids, hinder progress. Overcoming these obstacles is critical to improving the efficiency and sustainability of the process. A newly discovered template-free synthesis method is highlighted, which produces silica with exceptionally high purity (up to 99.1%) and large surface area, surpassing conventional techniques. Future research should aim to develop more eco-friendly and efficient extraction techniques by integrating advanced tools for optimizing process parameters and assessing economic viability. This will help bridge the gap between laboratory findings and industrial applications, minimizing chemical usage and environmental impact. By refining extraction methods and enhancing process sustainability, CFA-derived silica can become a vital industrial resource, contributing to greener waste management practices and environmentally responsible manufacturing. Unlocking this potential will transform CFA from a problematic waste into a valuable material for the future.