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1.
Zeolitization characteristics of fly ashes from wet- and dry- disposal systems
Bhagwanjee Jha, D. N. Singh, 2012, original scientific article

Abstract: The fly ash disposal at thermal power plants is either through wet- or dry-disposal systems. As these disposal practices result in different characteristics for the fly ashes, their interaction with alkalis, and hence the zeolitization potential, will be different. In order to demonstrate this, investigations were conducted to study the physical, chemical, mineralogical and morphological characteristics of the residues of the fly ashes collected from the lagoons and hoppers of the same thermal power plant, after their hydrothermal treatment. Field-emission-gun scanning electron microscopy and X-ray diffraction analysis of these residues demonstrated that the hopper ash attains an exceptionally high cation-exchange capacity and $SiO_2/Al_2O_3$ ratios (SAR), which correspond to the formation of major fly ash zeolites as compared to its counterpart. In other words, the study presented here helps to establish the superiority of hopper ash over lagoon ash for synthesizing fly ash zeolites and their enhanced quantity and quality.
Keywords: alkali activation, lagoon ash, hopper ash, fly ash zeolites
Published: 13.06.2018; Views: 269; Downloads: 52
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2.
Formation of meso- and micro-pores in fly-ash zeolites using a three-step activation
Bhagwanjee Jha, D. N. Singh, 2014, original scientific article

Abstract: Researchers have comprehensively characterized alkali- activated fly-ash (the residue) and ascertained its highly zeolitic nature. In order to evaluate its potential for application as an adsorbent for the decontamination of waste water, the decisive parameters have mostly been the cation-exchange capacity, the mineralogy and the morphology of the residue. However, a study of the pore characteristics (e.g., the size and volume) of such residues is still warranted to anticipate their contaminant transport and the diffusion phenomena as a type of geotechnical engineering material. In this situation, the present study demonstrates the evolution of pores in the fly-ash after alkali activation up to three steps, and simultaneously, its effects` on other characteristics (e.g., the specific gravity, specific surface area and the cation-exchange capacity) of three types of similarly synthesized residues (the first, produced by using a NaOH aqueous solution and the other two residues, the result of alkali activation using a NaOH spent solution, the filtrates). Based on N2 gas absorption isotherms and infrared transmittance spectra, residues obtained from the second and third steps, each involving 24 hours of treatment using filtrates of 1.5-M NaOH, are established to be significantly enriched in the finer meso- and micro-pores, respectively, in comparison with a pure and macro-porous zeolite 4A.
Keywords: fly-ash, hydrothermal treatment, three-step activation, pore characteristics
Published: 14.06.2018; Views: 205; Downloads: 38
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