Solidification/stabilization of hazardous wastes by alkali activation

Typical aluminosilicate precursors for alkali-activated materials or geopolymers (GPs) are metakaolin, coal fly ash (FA), and blast furnace slag, which have an increasing demand in other fields. Expanding the range of precursors to include hazardous wastes is very important in reducing their environmental impact and reinforcing efforts on sustainability. The hazardous wastes that will be covered in this chapter are municipal solid waste incineration FA, sewage sludge incineration residue, mine tailings, metallurgical slags, electroplating and tannery sludge and other wastes such as contaminated soil and electronic waste. The following aspects of wastes were considered: their Si, Al, Ca, and Fe content, reactivity toward highly alkaline solutions, and the maximum amount of waste that can be stabilized in the GP matrix. The efficiency of stabilization was evaluated in terms of the compressive strength of product and the leachable amounts of heavy metals compared to untreated waste and regulatory limits.