The rate-determining step in a low temperature PCDD/F formation from oxidative breakdown of native carbon in MSWI fly ash

Carbon-Fluorine (C-F) bonds are considered the most inert organic functionality and their selective transformation under mild conditions remains challenging. Herein, we report a highly active Pt-Pd nanoalloy as a robust catalyst for the transformation of C-F bonds into C-H bonds at low temperature, a reaction that often required harsh conditions. The alloying of Pt with Pd is crucial to activate C-F bond. The reaction profile kinetics revealed that the major source of hydrogen in the defluorinated product is the alcoholic proton of 2-propanol, and the rate-determining step is the reduction of the metal upon transfer of the <i>beta</i>-H from 2-propanol. DFT calculations elucidated that the key step is the selective oxidative addition of the O-H bond of 2-propanol to a Pd center prior to C-F bond activation at a Pt site, which crucially reduces the activation energy of the C-F bond. Therefore, both Pt and Pd work independently but synergistically to promote the overall reaction

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A mini-review of heavy metal recycling technologies for municipal solid waste incineration fly ash

Waste Management & Research ◽

10.1177/0734242x211003968 ◽

2021 ◽

pp. 0734242X2110039

Author(s):

Huan Wang ◽

Fenfen Zhu ◽

Xiaoyan Liu ◽

Meiling Han ◽

Rongyan Zhang

Keyword(s):

Fly Ash ◽

Municipal Solid Waste ◽

Solid Waste ◽

Waste Incineration ◽

Electrochemical Process ◽

Chemical Extraction ◽

Air Pollution Control ◽

Municipal Solid Waste Incineration ◽

Mswi Fly Ash ◽

Metal Recycling

This mini-review article summarizes the available technologies for the recycling of heavy metals (HMs) in municipal solid waste incineration (MSWI) fly ash (FA). Recovery technologies included thermal separation (TS), chemical extraction (CE), bioleaching, and electrochemical processes. The reaction conditions of various methods, the efficiency of recovering HMs from MSWI FA and the difficulties and solutions in the process of technical development were studied. Evaluation of each process has also been done to determine the best HM recycling method and future challenges. Results showed that while bioleaching had minimal environmental impact, the process was time-consuming. TS and CE were the most mature technologies, but the former process was not cost-effective. Overall, it has the greatest economic potential to recover metals by CE with scrubber liquid produced by a wet air pollution control system. An electrochemical process or solvent extraction could then be applied to recover HMs from the enriched leachate. Ongoing development of TS and bioleaching technologies could reduce the treatment cost or time.

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Effect of silica fume on the mechanical property and hydration characteristic of alkali-activated municipal solid waste incinerator (MSWI) fly ash

Journal of Cleaner Production ◽

10.1016/j.jclepro.2021.126317 ◽

2021 ◽

Vol 295 ◽

pp. 126317

Author(s):

Jun Ren ◽

Lu Hu ◽

Zhijun Dong ◽

Luping Tang ◽

Feng Xing ◽

...

Keyword(s):

Mechanical Property ◽

Fly Ash ◽

Municipal Solid Waste ◽

Silica Fume ◽

Waste Incinerator ◽

Municipal Solid Waste Incinerator ◽

Mswi Fly Ash ◽

Solid Waste Incinerator ◽

Alkali Activated ◽

Hydration Characteristic

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An Experimental Study on the Melting Solidification of Municipal Solid Waste Incineration Fly Ash

Sustainability ◽

10.3390/su13020535 ◽

2021 ◽

Vol 13 (2) ◽

pp. 535

Author(s):

Jing Gao ◽

Tao Wang ◽

Jie Zhao ◽

Xiaoying Hu ◽

Changqing Dong

Keyword(s):

Heavy Metals ◽

High Temperature ◽

Fly Ash ◽

Municipal Solid Waste ◽

Solid Waste ◽

Liquid Slag ◽

Melting Process ◽

Waste Incineration ◽

Municipal Solid Waste Incineration ◽

Mswi Fly Ash

Melting solidification experiments of municipal solid waste incineration (MSWI) fly ash were carried out in a high-temperature tube furnace device. An ash fusion temperature (AFT) test, atomic absorption spectroscopy (AAS), scanning electron microscope (SEM), and X-ray diffraction (XRD) were applied in order to gain insight into the ash fusibility, the transformation during the melting process, and the leaching behavior of heavy metals in slag. The results showed that oxide minerals transformed into gehlenite as temperature increased. When the temperature increased to 1300 °C, 89 °C higher than the flow temperature (FT), all of the crystals transformed into molten slag. When the heating temperatures were higher than the FT, the volatilization of the Pb, Cd, Zn, and Cu decreased, which may have been influenced by the formation of liquid slag. In addition, the formation of liquid slag at a high temperature also improved the stability of heavy metals in heated slag.

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