Solidification and Biotoxicity Assessment of Thermally Treated Municipal Solid Waste Incineration (MSWI) Fly Ash

Abstract

In the present work, thermal treatment was used to stabilize municipal solid waste incineration (MSWI) fly ash, which was considered hazardous waste. Toxicity characteristic leaching procedure (TCLP) results indicated that, after the thermal process, the leaching concentrations of Pb, Cu, and Zn decreased from 8.08 to 0.16 mg/L, 0.12 to 0.017 mg/L and 0.39 to 0.1 mg/L, respectively, which well met the limits in GB5085.3-2007 and GB16689-2008. Thermal treatment showed a negative effect on the leachability of Cr with concentrations increasing from 0.1 to 1.28 mg/L; nevertheless, it was still under the limitations. XRD analysis suggested that, after thermal treatments, CaO was newly generated. CaO was a main contribution to higher Cr leaching concentrations owing to the formation of Cr (VI)—compounds such as CaCrO4. SEM/EDS tests revealed that particle adhesion, agglomeration, and grain growth happened during the thermal process and thus diminished the leachability of Pb, Cu, and Zn, but these processes had no significant influence on the leaching of Cr. A microbial assay demonstrated that all thermally treated samples yet possessed strong bactericidal activity according to optical density (OD) test results. Among all samples, the OD value of raw fly ash (RFA) was lowest followed by FA700-10, FA900-10, and FA1100-10 in an increasing order, which indicated that the sequence of the biotoxicity for these samples was RFA > FA700-10 > FA900-10 > FA1100-10. This preliminary study indicated that, apart from TCLP criteria, the biotoxicity assessment was indispensable for evaluating the effect of thermal treatment for MSWI fly ash.

Mechanical Properties and Toxicity Risks of Lead-Zinc Sulfide Tailing-Based Construction Materials

“…It can also be used for the reclamation of the tailings pond, the hardening of the mining area, and the filling for mining wells in the mining area. Moreover, the values of the tested specimens were higher than that of the references [ 24 , 25 ]. After 28 days of curing, the compressive strength of the C1 specimen was about three times of that of the references.…”

Microbial induced solidification and stabilization of municipal solid waste incineration fly ash with high alkalinity and heavy metal toxicity

“…Jiang et al [44] used a chemical chelating agent to stabilize the heavy metals in MSWI fly ash, and observed that the stabilization rates of Pb, Cd, Zn and Cr reached over 85% at a chemical dosage of 0.2% by weight, and can be higher than 90% at chemical dosages of 0.4% and 0.6%. Gong et al [45] used thermal treatment to stabilize MSWI fly ash, and found the stabilization rates of Pb, Cu and Zn were 86.1%, 66.7% and 56.4%, respectively, at 700 o C treating for 10 min. It is observed that MSWI fly ash treated by MICP could achieve comparable stabilization rates for Pb, Cu and Zn, and slightly lower stabilization rates for Cd and Cr, when compared with the above solidification/stabilization methods.…”

Heavy Metals Removing from Municipal Solid Waste Incineration Fly Ashes by Electric Field-Enhanced Washing

“…Pb and Cd extracted reached 12.82 mg/L and 1.21 mg/L, which exceeded the threshold of GB 5085.3-2007 of 5 and 1 mg/L. Moreover, the leaching toxicity of Pb is more than double the standard threshold [25]. Annotation: "ND" Not detected.…”