Medical waste incinerator fly ash (MWIFA) is quite different from municipal solid waste incinerator fly ash (MSWIFA) due to its special characteristics of high levels of chlorines, dioxins, carbon constituents, and heavy metals, which may cause irreversible harm to environment and human beings if managed improperly. However, treatment of MWIFA has rarely been specifically mentioned. In this review, various treatment techniques for MSWIFA, and their merits, demerits, applicability, and limitations for MWIFA are reviewed. Natural properties of MWIFA including the high contents of chlorine and carbonaceous matter that might affect the treatment effects of MWIFA are also depicted. Finally, several commendatory and feasible technologies such as roasting, residual carbon melting, the mechanochemical technique, flotation, and microwave treatment are recommended after an overall consideration of the special characteristics of MWIFA, balancing environmental, technological, economical information.
The objective of the research was to compare the flotation performance of medical waste incinerator fly ash (MWIFA) by considering two methods: the cyclonic-static micro-bubble flotation column (FCSMC) method and conventional flotation cell (CFC) method. The results indicated that for FSCMC, the optimum parameters were kerosene = 3.5 g/kg·ash, methyl isobutyl carbinol (MIBC) = 0.2 g/kg·ash, Tween 80 = 7.5% of kerosene concentration, slurry concentration = 100 g/L, and pump speed = 380 r/min. The optimized conditions resulted in a higher dioxin removal efficiency (90.98%), carbon removal efficiency (91.88%) and lower loss on ignition (LOI) (4.96%). The data obtained from the CFC under different optimum operating conditions were 88.65%, 90.63% and 5.68%, respectively. FSCMC was proven to be more efficient for the flotation of MWIFA than CFC.
Inspired by the recent discovery that aryldiazoacetates could be excited with visible light to generate carbenes in a mild and catalyst‐free manner, we tested the possibility to induce the cyclization of fluorenes from biaryldiazoacetate precursors simply by visible light irradiation at ambient temperature. The experimental results showed that 455 nm blue light is most effective on the synthesis of a diversity of fluorenes and indenoarenes in excellent yields. Analysis of UV absorbance and electronic transition properties of biaryldiazoacetates revealed that their absorbance peaks in the blue light region are due to the n–π* transition of diazo group. Their small ϵ420 nm values well explains the fact that only when exposed to intense blue light could biaryldiazoaetates be excited to generate carbenes. Theoretical calculations and kinetic isotopic effect (KIE) study illustrated that the fluorene cyclization proceeds via the intramolecular carbene C−H insertion pathway rather than the cyclopropanation pathway. In addition, a furan ring‐opening mechanism for the unexpected formation of an indene‐based unsaturated aldehyde was also proposed based on the calculated potential energy surfaces of three plausible reaction pathways.
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