The Prospective Approach for the Reduction of Fluoride Ions Mobility in Industrial Waste by Creating Products of Commercial Value

In this work, we present the possibility to reduce the amount of fluoride ions in silica gel waste by using different techniques or to immobilize these ions by creating products of commercial value. The leaching of fluoride ions from silica gel waste to the liquid medium was done under static and dynamic conditions. It was determined that the removal of fluoride ions from this compound depends on various factors, such as dissociation, solubility, the w/s ratio, reaction temperature, leaching conditions, the adsorption properties of silica gel waste, and others. The obtained results showed that, by applying different techniques, the quantity of fluoride ions can be reduced by 60%, while obtained water was neutralized by calcium hydroxide. Additionally, it was determined that silica gel waste is a promising raw material for the hydrothermal synthesis of a stable compound containing fluoride ions–cuspidine.