Mechanochemical Degradation of OCDD/OCDF in Fly Ash from Medical Waste Incinerators

Applying mechanochemical (MC) method to treat waste containing dioxins is our research area. Two fly ash samples are collected from baghouse filters cleaning the effluent of a rotary kiln pyrolysis+ fluidized bed post-combustor and of a simple fixed bed medical waste incinerator (MWI). Dioxins and other organics in fly ash are removed, octa-cholrinated dibenzo-p-dioxin and -furan (OCDD/OCDF) are used to dope the fly ash before their MC treatment in a laboratory developed planetary ball mill. In the case of fly ash from a simple fixed bed MWI, the contents of OCDD and OCDF are decreased by 64.7% and 63.6% respectively and the degree of chlorination decreases from 6.86 to 5.53. The treated fly ash is characterized by a more homogeneous distribution, a significant decrease in overall particle size as well as great enlargement in surface area and significant reduction of the original CaCO3 content. The experimental results show that the MC degradation of dioxins is significant and certain compounds (CaCO3 et al.) in fly ash may act as dechlorinating reductant (e.g. CaO) in the process. The experiment may be practically helpful for removal of dioxin-like POPs in medical waste incineration fly ash.