Alkali activation of recovered fuel–biofuel fly ash from fluidised-bed combustion: Stabilisation/solidification of heavy metals

This paper regards the possibility of using geopolymer matrix to immobilize heavy metals present in ash and slag from combustion of medical waste. In the related research one used the fly ash from coal combustion in one Polish CHP plant and the waste from two Polish incineration plants. It was studied if the above-named waste materials are useful in the process of alkali-activation. Therefore, two sets of geopolymer mixtures were prepared containing 60 and 50% of ash and slag from the combustion of medical waste. The remaining content was fly ash from coal combustion. The alkali-activation was conducted by means of 14M solution of NaOH and sodium water glass. The samples, whose dimensions were in accordance with the EN 206-1 norm, were subjected to 75°C for 24 h. According to the results, the geopolymer matrix is able to immobilize heavy metals and retain compressive strength resembling that of C8/10 type concrete.

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The Leachability of Heavy Metals from Alkali-Activated Fly Ash and Blast Furnace Slag Matrices

Materials Science Forum ◽

10.4028/www.scientific.net/msf.851.141 ◽

2016 ◽

Vol 851 ◽

pp. 141-146

Author(s):

Jan Koplík ◽

Miroslava Smolková ◽

Jakub Tkacz

Keyword(s):

Mechanical Properties ◽

Heavy Metals ◽

Blast Furnace ◽

Fly Ash ◽

Blast Furnace Slag ◽

Inductively Coupled Plasma ◽

Emission Spectrometry ◽

Alkali Activation ◽

Furnace Slag ◽

Alkali Activated

The ability of alkali-activated materials (AAMs) to fix and immobilize heavy metals was investigated. Two raw materials were used to prepare alkali-activated matrices – high-temperature fly ash and blast furnace slag (BFS). NaOH served as an alkaline activator. Two heavy metals (Mn, Ni) were added in different amounts to find out the influence of dosage of heavy metal on the mechanical properties of the matrices and the leachability. Leachability was measured as concentration of heavy metals in leachates (ČSN EN 12457-4) by inductively coupled plasma/optical emission spectrometry (ICP/OES). Structure of prepared matrices was characterized by scanning electron microscopy (SEM). Increasing of addition of heavy metals led to decrease of mechanical properties of matrices. The leaching tests showed, that both matrices can immobilize Mn and Ni in dosages of 0.1 – 2,5%. Higher dosages caused deterioration of the matrices and increased the leachability. After alkali activation both heavy metals were transformed into the form of insoluble salts.

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The Evaluation of the Heavy Metal Leaching Behavior of MSWI-FA Added Alkali-Activated Materials Bricks by Using Different Leaching Test Methods

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph16071151 ◽

2019 ◽

Vol 16 (7) ◽

pp. 1151 ◽

Cited By ~ 1

Author(s):

Peng Xu ◽

Qingliang Zhao ◽

Wei Qiu ◽

Yan Xue

Keyword(s):

Heavy Metals ◽

Heavy Metal ◽

Fly Ash ◽

Metal Leaching ◽

Alkali Activation ◽

Leaching Tests ◽

Leaching Behavior ◽

Heavy Metal Leaching ◽

Environmental Compatibility ◽

Alkali Activated

Alkali-activated materials (AAMs) not only have the potential to replace cement applications in architecture and civil engineering, but also have an excellent effect on the stabilization solidification of hazardous industrial wastes. This study used two types of municipal solid waste incineration fly ash (MSWI-FA)—grate firing fly ash (GFFA) and fluidized bed fly ash (FBFA)—as AAMs brick raw materials. It is discovered from this study that AAMs bricks with different weight ratios of GFFA and FBFA can both meet the required standard of GB21144-2007 (Solid concrete brick). From the results obtained from the four leaching tests, the equilibrium pH of the leachate varies, resulting in significant differences in the leaching of heavy metals in Raw GFFA, Raw FBFA, and AAMs bricks with GFFA and FBFA. The AAMs brick with the addition of GFFA and FBFA has an alkali activation system to encapsulate heavy metals. By comparing the results obtained from the CEN/TS 14429 leaching behavior test and the four batch leaching tests, it was found that the most influential factors for the heavy metal leaching concentration are whether the heavy metal has been solidified/stabilized in the samples. GFFA and FBFA tend to have consistent characteristics after being activated by alkali to form AAMs bricks. This can be confirmed by the acid neutralization ability concentrated on a specific pH range. The results obtained from CEN/TS14429 verified that the AAMs bricks with the addition of GFFA and FBFA have excellent environmental compatibility and that it provides a comprehensive evaluation on the environmental compatibility of the test materials and products. This demonstrated that the MSWI-FA is suitable for used as alkali-activated materials and its products have the potential to be commercially used in the future.

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Conditioning of oily sludges with municipal solid wastes incinerator fly ash

Water Science & Technology ◽

10.2166/wst.1997.0318 ◽

1997 ◽

Vol 35 (8) ◽

pp. 231-238 ◽

Cited By ~ 7

Author(s):

Tay Joo Hwa ◽

S. Jeyaseelan

Keyword(s):

Heavy Metals ◽

Fly Ash ◽

Specific Resistance ◽

Sewage Treatment ◽

Sewage Treatment Plant ◽

Treatment Plant ◽

Solid Wastes ◽

Municipal Solid Wastes ◽

Capillary Suction ◽

Optimum Dosage

Conditioning of sludges improves dewatering characteristics and reduces the quantity of sludge to be handled. Anaerobic digested sludge collected from a sewage treatment plant contained 1.8% to 8% oil. The increase of specific resistance and capillary suction time (CST) with increasing oil content observed in these samples indicates the interference of oil in dewatering. It has been found that addition of municipal solid wastes incinerator fly ash decreases the specific resistances and capillary suction times of oily sludges rapidly up to 3% dosage. Beyond 3% fly ash, the decrease is less significant and the solids content in the sludge cake increases. This optimum dosage remains the same for sludges with varying oil contents from 1.8% to 12%. The total suspended solids of filtrate decreases with fly ash dosage but the toxic concentrations of heavy metals increases considerably. However at the optimum dosage of 3%, concentrations of heavy metals are within the limits for discharging into the sewers. The correlations of CST with the dewatering characteristics such as specific resistance, filter yield and corrected filter yield are established. These correlations can be used to obtain a quick prediction on dewaterability.

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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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Recovery of Cenospheres and Fine Fraction from Coal Fly Ash by a Novel Dry Separation Method

Energies ◽

10.3390/en13143576 ◽

2020 ◽

Vol 13 (14) ◽

pp. 3576

Author(s):

Jan Wrona ◽

Witold Żukowski ◽

Dariusz Bradło ◽

Piotr Czupryński

Keyword(s):

Fly Ash ◽

Coal Fly Ash ◽

Fine Fraction ◽

Free Fall ◽

Raw Material ◽

Fluidised Bed ◽

Air Chamber ◽

Pneumatic Separation ◽

Bed Separation ◽

Separation Product

Aluminosilicate microspheres are a valuable fraction of coal fly ash with diverse applications due to their low density. Currently, there is no efficient and ecologically rational method of cenosphere recovery from fly ash. A combination of dry methods for the recovery of both fine ash particles and aluminosilicate microspheres from coal fly ash is presented. It is comprised of fluidised bed separation followed by screening and pneumatic separation in a free-fall air chamber. Fluidised bed separation was assisted by a mechanical activator to prevent agglomeration. This step reduced the portion of material that required further treatment by 52–55 wt.%, with the recovery of microspheres exceeding 97%. Then, the concentrates were individually subjected to pneumatic separation. The final separation product for the fly ash containing 0.64 wt.% cenospheres was a cenosphere concentrate that constituted about 17 wt.% of the initial fly ash. The recovery of cenospheres was around 81%. Usage of a combination of dry methods allowed for maintaining almost 83 wt.% of the raw material in its dry form. Furthermore, the produced fly ash grain fractions could be used for different industrial purposes.

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