Feasible Leaching Procedure Of Toxicity Characteristic Of MSWI Fly Ash And Its Melting Residures

Fly ash is second pollutant produced from incineration of Municipal Solid Waste (MSW), Vitrification is effective technology for the solidification of fly ash. We studied the characteristic of fly ash and its melting residue, identified their hazardous characteristic, evaluated environmental risk during the course of utilization of melting residue, studied the transference law of heavy metals such as lead, chromium, zinc, copper during melting. The results showed that according to Extraction Procedure Toxicity of our country and Toxicity Characteristic Leaching Procedure of US EPA, fly ash belonged to hazardous waste, but its melting residue was not hazardous waste and didn't show current and potential threats to human health during the course of utilization. The transference law of heavy metals was represented by solidification ratio.Leaching toxicity is important hazardous characteristic of fly ash and its melting residue. From discussing the influence of pH, Liquid-to-Solid Ratio (L/S Ratio) and leaching time on leaching characteristic of heavymetals in fly ash, we understand leaching characteristic of fly ash better, and provided experimentation basis for standards of management, disposal and utilization of fly ash. The results showed that pH was a major controlling factor in metal leaching ability. The metals exhibited a marked increase in leaching ability at low and sometimes high pH values, while relatively low leaching ability of the metals was observed at neutral pH values. Total extractable metal concentration (mg/g fly ash ) increased as the L/S Ratio increased until it got the maximal leaching concentration, after that it was changeless, but concentration of heavy metals in leachate decreased because lower mass of waste in the leaching solution. The longer fly ash was in contact with the extraction solution, the more metal will leach. When use mixture of sulfuric and nitric acids as a leaching solution, heavy metals in fly ash achieved equilibrium concentration in less than 8h.On the basis of studying advanced experiences of developed countries and analyzing the results of examination, leaching procedure that was used to identify toxicity characteristic of fly ash should combine disposition means that fly ash was chosen and aim of environmental protection that was pay attention to when considered possible pollution of fly ash in disposition site. When we evaluate whether MSW fly ash can be disposed in safe landfill, leaching procedure of our country is feasible. To determine whether melting residues of fly ash can be utilized as resources, the leaching procedure that use mixture of sulfuric and nitric acids as a...