Effect of Zn, Cd compounds on formation of dioxins in model fly ash

Catalyst is the key factor for formation of dioxins i.e. PCDD/Fs, for which there is not enough study currently. In this paper, the effect of different metal catalyst contained in model fly ash (MFA) on both PCDD/Fs concentration and distribution is studied under laboratory conditions. The results show that ZnO can inhibit the formation of PCDD/Fs. The catalytic effect of ZnCl2 on PCDD/Fs is far more obvious than that of CdCl2 and the concentrations of PCDD/Fs obtained are 341.78 and 16.32 ng·g?1, respectively. PCDD/Fs formed by ZnCl2 promotion is 338 times as many as that of ZnO, while the concentration of PCDD/Fs catalyzed by CdCl2 is twice more than that of CdO. Principal component analysis (PCA) is used to research the effect of catalyst on PCDD/Fs distribution. It is observed that the change of distribution for 17 toxic PCDD/Fs catalyzed by different metal catalyst is significant. Meanwhile, the PCDD/Fs concentration rises with increase of O2 content, but for PCDD/Fs distribution it has only limit influence.