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Pre-treatment process carried out on raw municipal solid waste incineration (MSWI) fly ash (FA) sample that did not comply
initially with the USEPA method 1311 toxicity characteristic leaching procedure (TCLP) regulatory limits of 2011 reduced its
chloride and heavy metal content appreciably, thereby making it compliant with the aforementioned regulatory requirement. More
than 98% of each heavy metal was successfully removed. The process was excellent in removing cadmium (Cd) (99.99%) and very
good at removing the rest. About 99.96% of Cu was eliminated, 99.96% of cobalt (Co), 99.95% of Zn, 98.61% of Cr, and 98.12%
of nickel (Ni). Also, the leachate resulting from these pre-treatment steps met the China (GB 16889-2008) and USEPA method
1311 regulatory standards for safe discharge. The density and compressive strength of all the samples prepared increased as the FA
content decreased. The compressive strength of all the samples passed the 1989 USEPA-recommended value of 0.34 MPa (50 psi),
thereby making them suitable for industrial application. The sample that attained the highest compressive strength (2.08 MPa) after
28 days of curing incorporated 55% fly ash (FACS55), while the one with the least compressive strength (0.65 MPa) after the same
period was made from only fly ash (FACS100). Moreover, the concentration of heavy metals in all the samples generally decreased
with the FA content. Chromium was not detected in all the samples, thereby making this an excellent method for its immobilization.
From the leachability test results, all the samples prepared met the USEPA method 1311 TCLP regulatory limits |
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