Effect of freezing-thrawing on physico-chemical properties and pollutants releasing from the zinc extraction residue and its stabilized/solidified products

Heavy metal containing wastes are generally considered hazardous wastes due to their toxicity. Therefore, arbitrary discharges and irregular storages are prohibited by regulations. They are usually stabilized/solidified by appropriate methods and then disposed of. In stabilization/solidification (S/S); soluble components of the wastes are converted into their insoluble compounds, toxic components into their non-toxic forms, and a monolithic solid waste is generated using suitable binders. The stabilized/solidified products are first subjected to structural stability and leaching tests, and then those that comply with the regulations are discharged to landfills. However, both wastes and stabilized/solidified products can be broken up by being exposed to freezing-thawing during their storage and eventually changes in some physico-chemical properties may occur. In this case, hazardous components may tend to re-dissolve due to growths in its surface area. Freezing-thawing has been studied in detail since it poses a great risk on building materials. But, its effect on solid wastes and stabilized/solidified products has not been examined up to now. In this thesis; effect of freezing-thawing events on S/S products of zinc extraction residue, which is classified as hazardous waste due to its heavy metal content, stabilized/solidified with cement, fly ash and alkaline phosphate and their mixtures was investigated. Changes in stabilization were examined by TCLP, EC/2003 and Eluat tests, and changes in solidification were examined by compressive strength test. The results obtained revealed that freezing-thawing events increased pollutants dissolution, and they broken up the monotithic solid, and that the deteriorations varied depending on the type of S/S reagent used.