crystal thickness using supercooling temperature.
The flyash was obtained from Gladstone coal fire plant in Queensland, Australia. The ASTM D1505-03, 10 min melt flow index
In this study the process of hydration of fly ash, produced by a municipal solid waste (MSW) incinerator, is examined in water
and in a solution enriched with Ca(OH)2. The examined fly ash samples are characterized by a high content of alkaline chlorides and anhydrite and by remarkable amounts
of heavy metals. Investigations using differential thermal analysis/thermogravimetry (DTA/TG) and X-ray diffractometry (XRD)show
particular kinetics of the formation of the ettringite phase. The development of such a hydrated phase is much more intense
in the presence of an excess of Ca(OH)2so as to consume the ‘free’ sulphate in the case of the more reactive fly ash. Experimental results from thermal analysis
and X-ray diffractometry show the presence of different hydrated phases during the interaction between fly ash and aqueous
solution. The analytical determinations, related to the aqueous solution, point out an interesting decrease in concentration
of metals Pb, Zn and Cr(VI), relating to the middle period of the interaction.
Coal fly ash, a waste generated at the Figueira coal-fired electric power plant located in Brazil, was used to synthesize
zeolite by hydrothermal treatment with NaOH solution at 100 °C for 24 h. The fly ash (FA) and this synthesized zeolite (ZM)
that was characterized predominantly as hydroxy-sodalite were used as adsorbents for anionic dye indigo carmine from aqueous
solutions. The samples were analyzed by instrumental neutron activation analysis (INAA) for the determination of As, Co, Fe,
La, Mo, Na, Sb, Sc, Sm, Th, U and Zn. Effects of contact time and initial dye concentration were evaluated in the adsorption
processes. The kinetics studies indicated that the adsorption followed the pseudo-second order kinetics and that surface adsorption
and intraparticle diffusion were involved in the adsorption mechanism for both the adsorbents. The Langmuir isotherm model
provided the best correlation of the experimental data. The maximum adsorption capacity was found to be 1.48 mg L−1 for FA and 1.23 mg L−1 for ZM. Laboratory leaching and solubilization tests conducted to classify this ZM as if was a waste residue according to
the Brazilian regulation classified it as a residue non-hazardous and non-inert.
Cementitious mixtures with so-called high calcium
fly ash show better strength parameters as compared to the ones with conventional
siliceous fly ash. This practical feature is the consequence of improved hydraulic
activity. Differential thermal analysis and thermogravimetry were used, together
with the other methods, to evaluate the reactivity of high calcium fly ash
in mixtures with cements. This type of fly ash exhibits hydraulic properties
(setting and hardening on hydration) and durability, after hardening, in the
presence of water. The so-called pozzolanic activity is the feature of high
active silica containing fly ash while the hydraulic activity is related to
the high calcium ones. However, the chemical and phase composition is variable
and related to the particle size. The hydraulic/ pozzolanic properties are
strongly improved by additional grinding (specific surface increase).
Sequestration of radioactive nickel (63Ni2+) in fly ash coming from hospital wastes incineration plant by incorporating nano-goethite as a function of pH, particle size
and the ratio of solid and liquid was investigated under the batch leaching experiments. The synthetic nanogoethite was characterized
by X-ray diffraction (XRD), transmission electron microscopy (TEM) and specific surface area (SSA). The admired needle nanogoethite
was obtained in terms of XRD, TEM and SSA analysis. Approximate 5% of 63Ni2+ was desorbed from the nanogoethite/fly ash composite under the circum natural pH conditions. The ratio of solid to liquid
has little effect on desorption of 63Ni2+ from nanogoethite/fly ash composite. These results indicate that the radioactive nickel in fly ash can be sequestrated by
incorporating nanogoethite. The results may play significantly a role in immobilization in situ of trace radionuclides in
the natural environment.
In this study a calorimeter was applied to investigate the hydration of cements with fly ash (pulverised fuel ash – PFA) admixture.
Four cements were used to produce the binders containing from 5 to 60% fly ash. The process of hydration in cementitious systems
with fly ashes is slower than in reference pastes without admixtures. However, the calorimetric calculations and the shape
of heat evolution curves seem to indicate a complex interaction between the components of cement and ash resulting in the
increasing total heat evolved values per unit of cement. At higher fly ash content the accelerating effect of alkalis and
alumina should be taken into account and discussed in terms of the composition of initial cement. The modifications of hydration
kinetics and mechanism in this case is very well visualised by means of calorimetry.
pesticide is challenging for present generations. Coal FlyAsh (FA) is an eco-friendly and promising sustainable mineral fertilizer and pesticide [ 14 , 17 ]. Globally, 53% of electricity is generated by lignite coal at present. In India, coal-fired plants
The present research is concerning the characterization of FDR (fuel derived from residues) fly ash and mixtures with lime/brick
hydraulic binder by DTA/TG/DTG thermo-analysis, X-ray diffractometry and chemical analysis. The use of hydraulic binder obtained
from building brick rejects, which is less expensive than the usual solidifiers such as cementitious binder and silicates,
allows us to reutilize, in the meantime, this wreckage material, to the advantage of environmental sustainability. Fly ash
samples investigated in the present study were separated in a thermo-incineration plant. Mineralogical DTA/TG/DTG and XRD
investigations reveal the presence of different phases as well as chemical analysis shows a moderate concentration of heavy
metals and high content of chloride and sulphate. Results obtained from leaching tests with water carried out on hardened
pastes containing fly ash lead to interesting results, which highlight behaviour to the release of contaminants. The whole
of the results obtained in the present study make it possible to regard the objective of disposing such hardened materials
in inert waste landfill sites as achievable.