Fly ash zeolites for water treatment applications

•Conventional and novel applications of fly ash zeolites for water treatment.•Fly ash zeolites have been used for removal of heavy metals and ionic species.•Treatment of industrial sludges, acid mine drainage and domestic wastewater.

In the last few decades, fly ash, a coal combustion residue, has been used as a raw material for synthesis of microporous aluminosiliceous minerals known as zeolites. Due to their excellent ion exchange capacity, high surface area and unique pore characteristics, zeolites have been used for removal of heavy metals (viz., As, Cd, Cr, Cs, Cu, Fe, Hg, Mn, Ni, Pb, Sr, W and Zn) and ionic species (viz., ammonium, chloride, fluoride, nitrate, phosphate and sulphate) from industrial sludges, acid mine drainage and wastewater from domestic and industrial sources. In addition, fly ash zeolites find their application as sorbent medium in permeable reactive barriers and contaminant barrier liners for immobilizing the contaminant plume in soil. This paper reviews the applications of fly ash zeolites in various water treatment studies and other related environmental cleanup projects, viz., depuration of wastewater containing industrial dyes and hazardous ions and leachate treatment. Furthermore, novel applications in the use of fly ash zeolites as permeable reactive barriers and contaminant barrier liners as well as the future scope of research for environmental cleanup are also discussed.