scholarly journals Kinetics Study of Al Extraction from Desilicated Coal Fly Ash by NaOH at Atmospheric Pressure

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7700
Author(s):  
Andrei Shoppert ◽  
Irina Loginova ◽  
Dmitry Valeev
Keyword(s):  
Fly Ash ◽  
Atmospheric Pressure ◽  
Inductively Coupled Plasma ◽  
Coal Fly Ash ◽  
Acid Leaching ◽  
Emission Spectrometry ◽  
Pressure Leaching ◽  
Water Leaching ◽  
X Ray ◽  
Promising Source

The most promising source of alumina in the 21st century is the coal fly ash (CFA) waste of coal-fired thermal plants. The methods of alumina extraction from CFA are often based on the pressure alkaline or acid leaching or preliminary roasting with different additives followed by water leaching. The efficiency of the alumina extraction from CFA under atmospheric pressure leaching is low due to the high content of acid-insoluble alumina phase mullite (3Al2O3·2SiO2). This research for the first time shows the possibility of mullite leaching under atmospheric pressure after preliminary desilication using high liquid to solid ratios (L:S ratio) and Na2O concentration. The analysis of the desilicated CFA (DCFA) chemical and phase composition before and after leaching has been carried out by inductively coupled plasma optical emission spectrometry (ICP-OES) and X-ray diffraction (XRD). The morphology and elemental composition of solid product particles has been carried out by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). An automated neural network and a shrinking core model (SCM) were used to evaluate experimental data. The Al extraction efficiency from DCFA has been more than 84% at T = 120 °C, leaching time 60 min, the L/S ratio > 20, and concentration of Na2O-400 g L−1. The kinetics analysis by SCM has shown that the surface chemical reaction controls the leaching process rate at T < 110 °C, and, at T > 110 °C after 15 min of leaching, the process is limited by diffusion through the product layer, which can be represented by titanium compounds. According to the SEM-EDX analysis of the solid residue, the magnetite spheres and mullite acicular particles were the main phases that remained after NaOH leaching. The spheric agglomerates of mullite particles with non-porous surface have also been found.

scholarly journals Complete Extraction of Amorphous Aluminosilicate from Coal Fly Ash by Alkali Leaching under Atmospheric Pressure

Metals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1684
Author(s):  
Andrei Shoppert ◽  
Dmitry Valeev ◽  
Irina Loginova ◽  
Leonid Chaikin
Keyword(s):  
Fly Ash ◽  
Inductively Coupled Plasma ◽  
Coal Fly Ash ◽  
Optical Emission ◽  
Product Layer ◽  
Emission Spectrometry ◽  
Sem Images ◽  
X Ray ◽  
Before And After ◽  
Shrinking Core

One of the potential sources of alumina and mesoporous silica is the coal-fired thermal plants waste known as the coal fly ash (CFA). The studies of the alumina extraction from CFA are often focused on the preliminary desilication, but the efficiency of the alkali desilication is low due to formation of the desilication product—Na6[Al6Si6O24]·Na2X (DSP). This research is focused on the possibility of CFA desilication without formation of DSP using a leaching process with higher liquid to solid ratios (L/S) and alkali concentrations. The experimental data were analyzed using an artificial neural network (ANN) machine learning method and a shrinking core model (SCM). The investigation of the CFA morphology, chemical and phase composition before and after leaching were carried out by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), inductively coupled plasma optical emission spectrometry (ICP-OES) and X-ray diffraction (XRD). The present work shows that it is possible to avoid formation of DSP if using the L/S ratio >20 and concentration of Na2O—400 g/L during CFA leaching. The kinetics analysis by SCM showed that the process is limited by the surface chemical reaction at T <100 °C, and by diffusion through the product layer at T >100 °C, respectively. The SEM images of the solid residue after NaOH leaching under conditions that prevent the DSP formation show mullite particles with an acicular structure.

scholarly journals Distribution and Mode of Occurrence of Co, Ni, Cu, Zn, As, Ag, Cd, Sb, Pb in the Feed Coal, Fly Ash, Slag, in the Topsoil and in the Roots of Trees and Undergrowth Downwind of Three Power Stations in Poland

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 133
Author(s):  
Henryk R. Parzentny ◽  
Leokadia Róg
Keyword(s):  
Inductively Coupled Plasma ◽  
Coal Fly Ash ◽  
Atomic Emission ◽  
Emission Spectrometry ◽  
Plasma Atomic Emission Spectrometry ◽  
X Ray ◽  
Inductively Coupled ◽  
Power Stations ◽  
Mode Of Occurrence ◽  
Feed Coal

It is supposed that the determination of the content and the mode of occurrence of ecotoxic elements (EE) in feed coal play the most significant role in forecasting distribution of EE in the soil and plants in the vicinity of power stations. Hence, the aim of the work was to analyze the properties of the feed coal, the combustion residues, and the topsoil which are reached by EE together with dust from power stations. The mineral and organic phases, which are the main hosts of EE, were identified by microscopy, X-ray powder diffraction, inductively coupled plasma atomic emission spectrometry, and scanning electron microscope with an energy dispersive X-ray methods. The highest content of elements was observed in the Oi and Oe subhorizons of the topsoil. Their hosts are various types of microspheres and char, emitted by power stations. In the areas of long-term industrial activity, there are also sharp-edged grains of magnetite emitted in the past by zinc, lead, and ironworks. The enrichment of the topsoil with these elements resulted in the increase in the content of EE, by between 0.2 times for Co; and 41.0 times for Cd in the roots of Scots pine, common oak and undergrowth, especially in the rhizodermis and the primary cortex and, more seldom, in the axle roller and cortex cells.

scholarly journals Characterization of Fly Ash Generated from Matla Power Station in Mpumalanga, South Africa

2012 ◽  
Vol 9 (4) ◽  
pp. 1788-1795 ◽  
Author(s):  
Olushola S. Ayanda ◽  
Olalekan S. Fatoki ◽  
Folahan A. Adekola ◽  
Bhekumusa J. Ximba
Keyword(s):  
Fly Ash ◽  
Inductively Coupled Plasma ◽  
Coal Fly Ash ◽  
Harmful Effect ◽  
Point Of Zero Charge ◽  
X Ray Diffraction ◽  
Power Station ◽  
X Ray ◽  
Inductively Coupled ◽  
Plasma Mass Spectrometry

In this study, fly ash was obtained from Matla power station and the physicochemical properties investigated. The fly ash was characterized by x-ray fluorescence, x-ray diffraction, scanning electron microscopy, and inductively coupled plasma mass spectrometry. Surface area, particle size, ash and carbon contents, pH, and point of zero charge were also measured. The results showed that the fly ash is alkaline and consists mainly of mullite (Al6Si2O13) and quartz (SiO2). Highly toxic metals As, Sb, Cd, Cr, and Pb as well as metals that are essential to health in trace amounts were also present. The storage and disposal of coal fly ash can thus lead to the release of leached metals into soils, surface and ground waters, find way into the ecological systems and then cause harmful effect to man and its environments.

scholarly journals Alkali Fusion-Leaching Method For Comprehensive Processing Of Fly Ash

2017 ◽  
Vol 2 (2) ◽  
pp. 89 ◽  
Author(s):  
A.A. Shoppert ◽  
I.V. Loginova ◽  
L.I. Chaikin ◽  
D.A. Rogozhnikov
Keyword(s):  
Fly Ash ◽  
Power Plant ◽  
X Ray Diffraction ◽  
Water Leaching ◽  
X Ray ◽  
Comprehensive Utilization ◽  
Alkali Fusion ◽  
Wet Chemical ◽  
Promising Source ◽  
Comprehensive Processing

<p>Fly ash, composed of mullite, hematite, amorphous silica and quartz, is a promising source for the recovery of alumina and silica. Desilication with help of NaOH and alkali fusion-leaching method and utilization of alumina and silica in the fly ash for preparation of sodalite and silica white were explored in this research. The samples were characterized by using wet chemical analysis and X-ray diffraction. The optimal extraction of SiO<sub>2</sub> from Reftinskaya power plant fly ash was 46.2% with leaching at 95 <sup>o</sup>C for 3 h. Sodalite was synthesized at 200 °C for 1 h followed water leaching at 95 °C for 1 h. Silica white with specific surface area 180-220 m2/g was prepared by carbonation of the Na<sub>2</sub>SiO<sub>3</sub> solution at 40 <sup>o</sup>C for 90-120 min. The as-prepared silica has a purity of 98,8%.</p><p>The proposed method is suitable for the comprehensive utilization of the fly ash.</p>

scholarly journals Activation Pretreatment and Leaching Process of High-Alumina Coal Fly Ash to Extract Lithium and Aluminum

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 893
Author(s):  
Shenyong Li ◽  
Penghui Bo ◽  
Lianwei Kang ◽  
Haigang Guo ◽  
Wenyue Gao ◽  
...  
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Coal Fly Ash ◽  
Northern China ◽  
High Alumina ◽  
Pressure Leaching ◽  
Water Leaching ◽  
Leaching Process ◽  
Pressure Extraction ◽  
New Phase

Experiments were conducted to investigate the process of aluminum and lithium extraction from high-alumina coal fly ash (HCFA) generated from coal-fired power plants located in northern China. The presence of mullite and other aluminosilicates lead to low reactivity of coal fly ash. An activation pretreatment that destroys an inert composition of coal is necessary. The activation roasting of coal fly ash using sodium chloride and a subsequent leaching process were performed in this research. The results showed that almost no aluminum and lithium were dissolved under direct water leaching, while about 7% and 10% of those were leached into the acid solution respectively. Adding NaCl enhanced the atmospheric pressure leaching of aluminum and lithium with a leaching rate around 50%. Phase analysis and equilibrium calculations results showed that the roasting reaction between the HCFA and NaCl occurred, which led to generation of main new phase NaAlSi3O8. The pressure extraction efficiencies of aluminum and lithium were increased to about 93% and 98%, respectively. The implications of the findings provide an alternative process for recovering aluminum and lithium from readily available high-alumina coal fly ash.

scholarly journals Recovery of rare earth elements from coal fly ash through sequential chemical roasting, water leaching, and acid leaching processes

2021 ◽  
Vol 284 ◽  
pp. 124725
Author(s):  
Jinhe Pan ◽  
Behzad Vaziri Hassas ◽  
Mohammad Rezaee ◽  
Changchun Zhou ◽  
Sarma V. Pisupati
Keyword(s):  
Rare Earth ◽  
Fly Ash ◽  
Rare Earth Elements ◽  
Coal Fly Ash ◽  
Acid Leaching ◽  
Water Leaching

Recovery of Zinc from Municipal Solid Waste Incineration Fly Ash

2021 ◽  
Vol 13 (5) ◽  
pp. 956-965
Author(s):  
Chen-Piao Yen ◽  
Yun-Hwei Shen ◽  
Kai-Lun Chiu ◽  
Hsin-Hsiang Huang
Keyword(s):  
Fly Ash ◽  
Chemical Properties ◽  
Acid Leaching ◽  
Physical And Chemical Properties ◽  
Water Leaching ◽  
X Ray ◽  
Msw Incineration ◽  
Physical And Chemical ◽  
Target Metal ◽  
And Chemical Properties

In recent years, over one million tons of Municipal Solid Waste (MSW) incineration fly ash has been generated annually Taiwan. Only a small percentage of the ash was used as raw material for other utilities besides landfill. Fly ash contains many harmful heavy metals, such as Cd and Cr, among others; however, fly ash also contains many valuable metals, including as Zn, Pb, and Ga.To recover Zn from fly ash, in this work, an experiment was first designed to determine the physical and chemical properties of the fly ash. Then, treatment processes, including water leaching, acid leaching, and ion exchange were conducted.Test samples were subjected to scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence spectrometer (XRF), and atomic absorption spectroscopy (AAS) to determine their physical and chemical properties. Then, water leaching was conducted under optimal experimental conditions. Thereafter, acid leaching was performed using two different acids (hydrochloric and sulfuric) to extract the target metal ions, and finally the ion exchange process was deployed to concentrate and recover the target metal ions.Ultimately, an optimal process to recover zinc from MSW incineration fly ash was developed in this work. An aqueous solution containing approximately 1 wt% zinc was obtained by leaching with sulfuric acid. Zn was then concentrated using a chelating resin IRC-747 in column mode.

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