Release of elements from municipal solid waste incineration fly ash

The element-release behavior of municipal solid waste incineration fly ash was explored through leaching test with continuous set-point pH(pH_(stat) test)and serial single reaction cell(SSRC)tests.First,the relationship between element release and acid neutralizing capacity(ANC)consumption was examined with a pHstat test.Four types of release behaviors were identified which are characteristic for different elements:(1)release curves that were almost linear with ANC consumption(Ca,Zn,and Cd);(2)release that was significantly faster than ANC(Na,K,and Cl);(3)curves that featured a strong increase with ANC consumption,after a transient release,followed by an almost equal decrease(Si and S);and(4)release that is strongly retarded compared with ANC consumption(Cr,Cu,and Pb).In the SSRC system,it the existence of a pH front and a wash-out phenomenon is demonstrated.Combining the results from the SSRC test with the kinetic analysis of the ANC system in the pH_(stat) test,it was inferred that less than one-third of the ANC measured from a batch pH titration plays a neutralization role in a field situation.The methodologies described may provide a powerful set of tools for systematic evaluation of element release from solid wastes.