Metal encapsulation of waste foundry sand stabilized with alkali-activated binder: Batch and column leaching tests

Waste stabilization processes are important to add value and reduce environmental risks related to metal contamination of soils and groundwater. This study evaluated the metal encapsulation of: (i) waste foundry sand (WFS) stabilized with an alkali-activated binder (AAB), compared to (ii) WFS-Portland cement (PC) mixture. The AAB was composed by sugar cane bagasse ash (SCBA), hydrated eggshell lime, and sodium hydroxide solution. The metal leaching behavior from WFS-AAB and WFS-PC was investigated through batch and column tests according to NBR 10005 and ASTM D4874 methods, respectively. All WFS-AAB and WFS-PC mixtures showed no metal toxicity. WFS-AAB matrices encapsulated the heavy metals Cd, Cr, and Pb from WFS and SCBA. Leaching results from NBR 10005 method were more favorable than ASTM D4874 for water quality limits (CONAMA 460, Dutch List, and EPA). Binder type, metals leaching patterns, and leaching test procedures were key factors in understanding the environmental performance of cemented WFS.