Leaching Characteristics of Heavy Metals and Dioxins from Fly Ash Using Batch and Dynamic Leaching Procedures

• Main Authors: Sin-yu Chen, 陳信彧
• Other Authors: Moo-been Chang
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/49125581222596611089

碩士 === 國立中央大學 === 環境工程研究所 === 100 === The MSWI fly ash which contains high concentrations of heavy metals and dioxins has been classified as hazardous waste. In this study, batch and dynamic leaching procedures were used to explore the leaching behaviors of heavy metals and dioxins in the fly ash generated from MSWI. Heavy metals and dioxins leached from different solutions are assessed, and different chelating agents are tested for higher stability of MSWI fly ash. The results of batch leaching procedure indicate that the leached Pb concentrations of the plant A were 21.6, 19.3, 16.7 and 16.0 mg/L for HAc, acid rain, humic acid and SDBS as solvents, respectively. These concentrations all exceeded the regulated standard (5 mg/L). The leached Pb, Cu and Cd concentrations of the plant B exceeded the regulated limit, but only occurred in HAc solution. Highly chlorinated PCDD/Fs were observed in the leachates of fly ash, accounting for more than 80% of PCDD/Fs. In addtion, 3,3’,4,4’-TCB, 2,3’,4,4’,5-PeCB and 2,3,3’,4,4’-PeCB were also observed in the leachates of the fly ash. The results of dynamic leaching procedure indicated that the leached Pb concentrations of the plant A was the highest, followed by Zn, Cu, and Cr, whereas Cd was the lowest. In the SDBS solution, the leached Cd concentrations was the highest. On the other hand, the leached Zn, Pb, Cu and Cr concentrations were the highest in HAc solution. The structures of fly ash were destroyrd due to the long-term washing (13 days) of fly ash were washed by HAc solution, resulting in the increase of PCDD/Fs concentrations leached from the fly ash. 3,3’,4,4’,5-PeCB, 2,3,3’,4,4’,5-HxCB and 2,3,3’,4,4’,5,5’-HpCB were also observed in the leachates of the fly ash, compared with the results of batch leaching. Adding inorganic sulfide (A plant) or phosphate (B plant) along with cement results in the best stabilization effect in treating the fly ash. We also found there was some stabilization effect for dioxins of fly ash.