Advances in Methods for Recovery of Ferrous, Alumina, and Silica Nanoparticles from Fly Ash Waste

Abstract

Fly ash or coal fly ash causes major global pollution in the form of solid waste and is classified as a “hazardous waste”, which is a by-product of thermal power plants produced during electricity production. Si, Al, Fe Ca, and Mg alone form more than 85% of the chemical compounds and glasses of most fly ashes. Fly ash has a chemical composition of 70–90%, as well as glasses of ferrous, alumina, silica, and CaO. Therefore, fly ash could act as a reliable and alternative source for ferrous, alumina, and silica. The ferrous fractions can be recovered by a simple magnetic separation method, while alumina and silica can be extracted by chemical or biological approaches. Alumina extraction is possible using both alkali- and acid-based methods, while silica is extracted by strong alkali, such as NaOH. Chemical extraction has a higher yield than the biological approaches, but the bio-based approaches are more environmentally friendly. Fly ash can also be used for the synthesis of zeolites by NaOH treatment of variable types, as fly ash is rich in alumino-silicates. The present review work deals with the recent advances in the field of the recovery and synthesis of ferrous, alumina, and silica micro and nanoparticles from fly ash.

Synthesis and Characterization of Mullites From Silicoaluminous Fly Ash Waste

“…Fly ash are multifaceted material consisted of alumina, silica and iron, in the forms of mullite, quartz, magnetite, hematite, cristabolite etc. (Yadav & Fulekar, 2020). XRD have 2θ peaks at 26.27, and 41.12 with d-spacing at 3.328 Å and 2.19 Å were apparent in the graphs confirming the crystalline phase of fly ash.…”

“…sintering of raw materials of Al, and Si carbide, organic precursors, a sol-gel technique (Jurado, Arévalo Hernández, & Rocha-Rangel, 2013;Won & Siffert, 1998), and chemical vapor deposition (Mulpuri & Sarin, 2011). But, as all the approaches require expensive instruments and high amount of energy due to which they are not cost-effective, there is a demand of an economical, reliable source of aluminosilicate (Yadav & Fulekar, 2020) rich minerals suitable for mullite synthesis. One such material is fly ash which is rich in aluminosilicates, that comprises of lesser amount of ferrous and other alkali metal oxides (Prochon et al, 2020).…”

Recent Advances on Properties and Utility of Nanomaterials Generated from Industrial and Biological Activities

“…The nature of such fullerenes are impure which could be processed further to obtain highly pure fullerene. Yadav and Fulekar also reported the presence and recovery of fullerenes from the fly ash [12].…”

“…These fly ashes act as a rich source of carbon materials like fullerene, CNTs, graphene etc. Such carbon nanomaterials are formed from the organic content of the coal and incomplete combustion of coal, soots, and charcoal combustion end products [12,121]. The unburned carbon could be either directly reused in the TPPs furnace as a fuel or it could be processed further for the synthesis of fullerenes.…”

“…Nanomaterials can be produced in a variety of methods like chemical, physical and biological with different classes such as carbon-based nanomaterials: carbon-based nanomaterials [6,7], nanocomposites [8], metals, alloys, nanopolymers [9,10], nanoglassses [11], and nanoceramics [9,12]. Nanomaterials can be either synthesized in [11], and nanoceramics [9,12]. Nanomaterials can be either synthesized in the laboratory or could be derived from the natural resources [13].…”