Chapter Eight - Solidification/Stabilization Process of Fly Ash

Abstract

It is crucial to solidify/stabilize fly ash before its utilization or incorporating in landfill, owing to leaching toxicity. To date, solidification methods such as cement solidification and chemical solidification are widely used in China for their high efficiency and easy application. The chemical solidification method involves the transformation of hazardous waste into materials with low solubility, migration, and toxicity, by using the chemical reagents. Different chemicals, including gypsum, bleaching powder, sodium thiosulfate and sodium hydroxide, sodium sulfide, and organic polymer stabilizers can be utilized based on the kinds of heavy metals. Four types of chemicals were used, i.e., NaOH, ethylenediaminetetraacetic acid disodium, sodium sulfide, and thiourea, to explore the possibility of chemical stabilization for fly ash treatment. At last, a high-pressure formation method is performed to reduce landfill volume. Under a certain degree of pressure, fly ash can be shaped using a hydraulic press and specific mold, which can greatly reduce the amount of chemical agents required, as well as running costs.