Abstract
Fly ash (FA) is produced from coal power plants’ combustion. FA is used in the concrete industry, as an ingredient in the brick and paving. Knowledge of the chemical composition and toxic metal content in FA is essential for evaluating its environmental risks. This study aimed to assess FA purification effect on its antibacterial activity against Escherichia coli and Bacillus cereus, by calculating percent bacterial reduction. Moreover, centrifugation time effect on the purification process was evaluated. Chemical composition and properties of purified FA were determined and compared with raw FA, using Fourier transform Infrared (FTIR); X-ray diffraction (XRD); X-ray photoelectron spectroscopy (XPS); energy-dispersive X-ray (EDXA); carbon, hydrogen, nitrogen, and sulfur (CHNS) elemental analysis; moisture content; and loss-of-ignition. Particle size was predicted by using dynamic laser scattering, BET and scanning electron microscopy (SEM). The CHNS results showed that purified FA contains the highest carbon content (88.9%), as compared to raw FA (82.1%). The particle size distribution (PSD) of FA microspheres ranges from 48.53 ± 17.9 to 52.98 ± 19.4 µm by using SEM. PSD, using dynamic laser scattering, showed polydispersed and non-uniform size in raw FA, ranging in size from 107.1 to 1027 nm, while purified FA manifests a monodispersed size from 103.3 to 127.3 nm. FA showed the least bacterial growth reduction %, while the purified fly ash (FA2) showed the highest bacterial growth reduction %, as compared to the control bacterial broth culture without fly ash.
Highlights
Fly ash (FA), the main waste product arising from the combustion of solid fuels, is a powdery, black, solid and fine material that flies up from the combustion chamber; it is captured and removed by emission-control methods, such as scrubbers, and baghouse [1,2,3]
Diverse environmental problems were caused by the landfill of fly ash such as leaching of heavy metals, pollution of the soil with organic compounds, and secondary dust generation
FA obtained from power plant combustion in Saudi Arabia was purified by removing metals and other minerals, to increase carbon content, which is an expensive source for activated carbon, using a simple density gradient centrifugation
Summary
Fly ash (FA), the main waste product arising from the combustion of solid fuels, is a powdery, black, solid and fine material that flies up from the combustion chamber; it is captured and removed by emission-control methods, such as scrubbers, and baghouse [1,2,3]. Discharging fly ash into the atmosphere with the flue gas is avoided due to environmental concerns [4,5] According to the GlobeNewswire report on August 2019, the global FA market was valued at $4.13 billion in 2018 and is expected to reach up to $6.86 billion by 2026 [6]. FA is near enough in its composition as pozzolanic to volcanic ash. It is mainly consisting of metal oxides, non-combustible inorganic materials, and unburned carbon (UC) [7,8,9,10,11]. UC content indicates inefficiency in combustion and may represent a barrier to the beneficial use of FA or ash products in a variety of applications [2]. The characteristics of the coal-derived UC are functions for the rank, type of the coal, size of the feed coal, and combustion
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