Effective stabilization of antimony in Waste-to-Energy fly ash with recycled laboratory iron–rich residuals

Recycling of iron-bearing waste for stabilizing antimony (Sb) in Waste-to-Energy (WtE) fly ash is a low-cost and sustainable approach. In this work, two laboratory iron–rich residuals (LIR–1 and LIR–2) were collected and their effectiveness for stabilizing Sb in WtE fly ash were evaluated by toxicity characteristic leaching procedure (TCLP) and continuous acid leaching tests. The results of TCLP tests showed that addition of 1.75% LIR–1 and LIR–2 decreased the Sb leaching concentration from 2.04 ± 0.064 mg/L to 0.17 ± 0.004 and 0.15 ± 0.035 mg/L, respectively, which were below the limit value in the standard of 40 CRF 268.40 (1.15 mg/L). Continuous acid leaching tests indicated that the leaching of Sb was pH-dependent, and the dissolution of metal oxides (Fe, Mn and Al) played an important role in controlling the release of Sb from raw WtE fly ash. After LIR treatment, the leaching of Sb was significantly decreased than that from raw fly ash, which was mainly ascribed to the formation of tripuhyite precipitation. These results indicated that LIR could be recycled as stabilizers to immobilize Sb in WtE fly ash, which provided an alternative way for realizing of cleaner production of LIR. Copyright © 2019 Elsevier Ltd. All rights reserved.