Effects of the type of sintering atmosphere on the chromium leachability of thermal-treated municipal solid waste incinerator fly ash

The sintering process offers an opportunity to combine detoxification and r esource recovery for the treatment of municipal solid waste (MSW) incinerat or fly ash. However, the chromium (Cr) in the sintered fly ash becomes more readily leachable with increasing sintering time and temperature, thus pos ing severe threats to the environment and human health when the sintered as h is recycled or reused. This study investigated the enhanced leachability of fly ash containing Cr, by heating the chromium (III) oxide (Cr2O3)-spike d fly ash to 800 degreesC in atmospheres containing air, nitrogen gas (N-2) , and 5% H-2+95% N-2, respectively. The results indicated that trivalent ch romium was converted to its soluble hexavalent form during sintering in the air atmosphere; whereas sintering in a nitrogen atmosphere significantly r educed the leachability of Cr due to lack of oxygen (O-2) to oxidize. The e ffects of the sintering temperature on the total chromium content and the l eaching concentration in the toxicity characteristic leaching procedure (TC LP) extract are also discussed. (C) 2000 Elsevier Science Ltd. All rights r eserved.