Thermochemical processing of a South African ultrafine coal fly ash using ammonium sulphate as extracting agent for aluminium extraction

Doucet, Frédéric J.; Mohamed, Sameera; Neyt, Nicole C.; Castleman, Barbara A.; Merwe, Elizabet M. van der

doi:10.1016/j.hydromet.2016.07.017

Cited by 42 publications

(22 citation statements)

References 36 publications

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“…Characterization of all CFA tct and CFA res samples was performed by XRD and FE-SEM in order to better understand the effect of the ammonium salts on CFA. Previous work (Doucet et al, 2016) reported that the surface topography of untreated CFA spheres was relatively smooth at the scale of observation allowed by the FE-SEM, regardless of the particle size, and that CFA tct generated using (NH 4 ) 2 SO 4 consisted of spherical particles surrounded by newly-formed, sub-10 µm hexagonal structures that were mostly interlocked to form clusters of varying sizes. We have now observed that the hexagonal structures which formed when using ABS as extracting agent were substantially smaller (sub-µm) than those formed when AS was used (results not shown).…”

Section: Structural Changes Following Thermochemical Treatment and Sumentioning

confidence: 95%

“…the mass fraction of elements extracted as sulphates into the aqueous solution, was compared to the mass of these elements initially present in untreated CFA (determined by XRF). The procedures followed for dissolution experiments and solid residue characterisation were described previously (Doucet et al, 2016).…”

Section: Thermochemical Processing and Aqueous Dissolutionmentioning

confidence: 99%

“…Our recent study indicated that thermochemical treatment using ammonium sulphate ((NH 4 ) 2 SO 4 ) may represent a promising technology for extracting Al from fly ash (Doucet et al, 2016). One of the advantages of this process resides in the fact that (NH 4 ) 2 SO 4 is widely available at low cost and can be easily recycled 3 (Highfield et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

“…One of the advantages of this process resides in the fact that (NH 4 ) 2 SO 4 is widely available at low cost and can be easily recycled 3 (Highfield et al, 2012). The most promising processing conditions were determined to be a temperature of 500 °C and a fly ash to (NH 4 ) 2 SO 4 weight ratio of 2:6 when a reaction time of 1h was used (Doucet et al, 2016). It was also found that water leaching of the reaction products obtained under these conditions resulted in the selective recovery of 95.0% Al from the amorphous phase, with < 0.6% Si extracted.…”

Section: Introductionmentioning

confidence: 99%

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Ammonium sulphate and/or ammonium bisulphate as extracting agents for the recovery of aluminium from ultrafine coal fly ash

et al. 2017

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Highlights Aluminium was extracted from an ultrafine coal fly ash  Ammonium sulphate and ammonium bisulphate were used as extracting agents  A process of thermochemical treatment followed by aqueous leaching was employed  A maximum non-selective recovery of 46.6% aluminium was obtained  Selective extraction of aluminium (37.3%) over silicon and iron was achieved AbstractWe recently showed that the selective extraction of aluminium from the amorphous phase of a South African ultrafine coal fly ash can be achieved via thermochemical treatment with ammonium sulphate for 1h followed by aqueous dissolution, as an alternative to conventional hydrometallurgical processes. In this study, insight gained from the previous work was applied to investigate and compare total vs selective aluminium extraction efficiencies using ammonium sulphate or ammonium bisulphate either on its own, or as a mixture of the two salts as extracting agents during a 2h thermal treatment process. The effects of (i) ash-to-extractant mass ratio and (ii) temperature during thermal treatment on extraction efficiency was investigated. While a maximum, but non-selective, recovery of 46.6% total aluminium was achieved using ammonium bisulphate at 400 °C, the most technically appropriate results for selective recovery yielded 37.3% aluminium, with only 0.3% silicon, 0.1% titanium and 3.9% iron having been co-extracted when using ammonium sulphate at a processing temperature of 600°C. Extraction of most of the calcium and magnesium could not be prevented. Using mixtures of ammonium salts as extracting agents during 2 thermochemical treatment may however introduce technical difficulties on large scale. Our results indicate that any of the two ammonium salts could be used on their own during thermochemical treatment.Thermochemical treatment of coal fly ash using ammonium salts may therefore represent a promising technology for extracting aluminium from South African coal fly ash.

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Section: Structural Changes Following Thermochemical Treatment and Sumentioning

confidence: 95%

Section: Thermochemical Processing and Aqueous Dissolutionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ammonium sulphate and/or ammonium bisulphate as extracting agents for the recovery of aluminium from ultrafine coal fly ash

et al. 2017

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“…Antioxidant enzymes increased in leaves reflecting stress and the extenuation of reactive oxygen species. Doucet et al (2016) used ammonium sulphate to recover aluminium from a South African ultrafine coal fly ash through thermochemical treatment. The optimal processing conditions included a fly ash to ammonium sulphate weight ratio of 2:6, a reaction time of 1 h, and a temperature of 500°C.…”

Section: Fly Ash Reuse and Disposalmentioning

confidence: 99%

Power Production Waste

Ye¹,

Zhu²,

Zhang³

et al. 2017

Water Environment Research

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This review focuses on the research literature published in 2016 relating to power production waste that results from fossil fuel and nuclear power plants. It elaborates the characterization, reuse and disposal of power production wastes. The wastes from fossil fuel power plants have been divided into fly ash, flue gas desulfurization gypsum and waste catalyst. The environmental issues, associated with nuclear power plants and waste production are also reviewed.

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Studies on Extraction of Heavy Metal (s) from Fly Ash through Hydroprocessing Approach

Behera

Hansdah

Das³

et al. 2021

Clean Coal Technologies

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Thermochemical processing of a South African ultrafine coal fly ash using ammonium sulphate as extracting agent for aluminium extraction

Abstract: Highlights  Aluminium was extracted from an ultrafine coal fly ash  Extraction was achieved via thermochemical treatment followed by aqueous leaching  The process used ammonium sulphate, a low-cost, recyclable extracting agent  Extraction efficiencies amounted to 95.

Cited by 42 publications

References 36 publications

Ammonium sulphate and/or ammonium bisulphate as extracting agents for the recovery of aluminium from ultrafine coal fly ash

Ammonium sulphate and/or ammonium bisulphate as extracting agents for the recovery of aluminium from ultrafine coal fly ash

Power Production Waste

Studies on Extraction of Heavy Metal (s) from Fly Ash through Hydroprocessing Approach

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