| Disposal of municipal solid wastes (MSW) is becoming a problem nationwide. Many sanitary landfills are either closing or approaching maximum capacity. With new landfills becoming difficult to site, alternative methods must be used to reduce the volume being disposed in landfills.; Incineration, through thermal destruction, reduces the volume of MSW by up to 85%. However, problems do exist with the resulting fly and bottom ashes. Metals are not destroyed by this process, but are concentrated within the ashes. A majority of the ashes fail EPA's Extraction Procedure Toxicity Test by exceeding either cadmium or lead concentration limits.; The objectives of this dissertation were threefold: (i) examine the physical and chemical properties of ashes; (ii) determine ash composition and morphology; and (iii) determine extractive behavior of cadmium, chromium and lead in an aqueous environment. Three different incinerators, from Canada, Massachusetts, and New Jersey, burning primarily residential MSW, were chosen to determine equipment and operational effects on ash composition and extractive behavior.; Supplemental combustion air provided more complete combustion. Cadmium, potassium and sodium preferentially partitioned to the fly ash with lead partitioning differently between fly and bottom ashes depending on the incinerator.; Fly ash morphology and composition did not vary significantly between incinerators. The ash matrices were composed primarily of complex, multi-substituted aluminosilicates, amorphous glass and iron oxides. CaSO{dollar}sb4{dollar}, NaCl and KCl were the predominant species. SEM micrographs showed a variety of shapes throughout the particle ranges with crystals heavily dispersed on the surfaces.; Extraction of cadmium was shown to depend on extractant pH while lead extraction varied according to the anion added to the solution. Increased lead solubility resulted from ligand formation. Extraction of both metals was approximately 80%. Chromium was not affected by either condition and approximately 15% was recovered.; The conditions developed in this dissertation can be used to develop on- or off-site processes where the metals are extracted from the ashes, thus preventing environmental contamination.; A theoretical model was developed to explain the increased solubility resulting from acidity and ligand effects. Qualitative results were obtained which correlated closely with experimental results. |
