Abstract
Municipal solid waste incineration bottom ash (MSWI BA) is the main output of the municipal solid waste incineration process, both in mass and volume. It contains some heavy metals that possess market value, but may also limit the utilization of the material. This study illustrates a robust and simple heap leaching method for recovering zinc and copper from MSWI BA. Moreover, the effect of autotrophic and acidophilic bioleaching microorganisms in the system was studied. Leaching yields for zinc and copper varied between 18–53% and 6–44%, respectively. For intensified copper dissolution, aeration and possibly iron oxidizing bacteria caused clear benefits. The MSWI BA was challenging to treat. The main components, iron and aluminum, dissolved easily and unwantedly, decreasing the quality of pregnant leach solution. Moreover, the physical nature and the extreme heterogeneity of the material caused operative requirements for the heap leaching. Nevertheless, with optimized parameters, heap leaching may offer a proper solution for MSWI BA treatment.
Highlights
Incineration has become the typical method for treating municipal solid waste (MSW) in EuropeanUnion, where 68 million tons of MSW was treated with incineration (MSWI) technology in 2016 [1].During incineration, the organic content of the MSW is converted to thermal energy that can be utilized in generation of heat and power with simultaneous 90 wt % and 75 vol % reduction of initial waste [2].The main residue of MSWI is bottom ash (BA), representing approximately 80% of solid incineration rejects [3]
With optimized parameters, heap leaching may offer a proper solution for Municipal solid waste incineration bottom ash (MSWI BA) treatment
The actual leaching was shown to require a much lower pH than required by the formation of hydroxides, indicating that not much metal hydroxides that refereed studies were done in agitated bottom ash slurry, where leaching may be different, as compared to heap leaching; these experiments were done in batch-wise while this study examined continuous heap leaching
Summary
Incineration has become the typical method for treating municipal solid waste (MSW) in EuropeanUnion, where 68 million tons of MSW was treated with incineration (MSWI) technology in 2016 [1].During incineration, the organic content of the MSW is converted to thermal energy that can be utilized in generation of heat and power with simultaneous 90 wt % and 75 vol % reduction of initial waste [2].The main residue of MSWI is bottom ash (BA), representing approximately 80% of solid incineration rejects [3]. Incineration has become the typical method for treating municipal solid waste (MSW) in European. The organic content of the MSW is converted to thermal energy that can be utilized in generation of heat and power with simultaneous 90 wt % and 75 vol % reduction of initial waste [2]. Residual heavy/toxic metals can cause challenges in both reuse and disposal of MSWI BA, and serve as a secondary source for valuable elements [5,6,7]. MSWI BA is an extremely heterogeneous residue stream including glass, synthetic ceramics, natural minerals, unburned organic matter and a variety of metals in different forms [3,8,9,10]. Heavy metals have been reported to concentrate on glass matrix; Cr, Zn and Mn have been incorporated into spinels, while Cu and Pb associated to Fe, Sn and Zn metallic inclusions [9,10]
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