Leaching Properties of Fly Ash in Strong Alkaline Solution

Abstract

Dissolution properties of fly ash in strong alkaline solution have been studied by leaching in 7.5 M potassium hydroxide solution at room temperature. The solid to liquid ratio is 40 and the leaching time is from 6 to 168 h. Results show that the mass of silica and aluminum leached out increase with time but the rate decrease. Silica and aluminum tend to leach out to alkaline solution in the same rate at the beginning and then the rate of silica change to a little higher and the silica and aluminum tend to precipitate to amorphous "gel" phase. The leaching rate of metal ions are in the order of barium > calcium > magnesium > titanium > iron. Almost all the metal ions tend to precipitate to "gel" phase at beginning of leaching which make the "gel" phase rich in iron and calcium.