An Efficient Approach for Lithium and Aluminum Recovery from Coal Fly Ash by Pre-Desilication and Intensified Acid Leaching Processes

Abstract

A novel technique was developed for the recovery of lithium and aluminum from coal fly ash using a combination of pre-desilication and an intensified acid leaching process. The main components of the high-aluminum fly ash were found to be Al 2 O 3 and SiO 2 , and the Al/Si ratio increased from 1.0 to 1.5 after desiliconization. The lithium content of the coal fly ash met national recycling standards. The optimal acid leaching conditions, under which the leaching efficiencies of lithium and aluminum were 82.23% and 76.72%, respectively, were as follows: 6 mol/L HCl, 1:20 solid to liquid ratio, 120 • C and 4 h. During the hydrochloric acid pressure leaching process, spherical particles of desilicated fly ash were decomposed into flakes. Part of the mullite phase was dissolved, and most of the glass phase leached into the liquor. The generation of the silicates hindered lithium transport, which decreased the leaching rate of lithium. This work suggests that the preprocessing is a promising option for effective recovery of high-aluminum and fly ash-associated lithium.

Influence of Na2CO3 and K2CO3 Addition on Iron Grain Growth during Carbothermic Reduction of Red Mud

“…After the separation of metallic iron, the tailings were proposed to be leached by hydrochloric acid for Al, Ca, and Sc dissolution and subsequent extraction. Previous research has shown the best efficiency of hydrochloric acid compared to sulfuric and nitric acid for leaching of aluminosilicate minerals [59]. It is then possible to recover selectively scandium from the chloride solutions by resins or extraction methods [60][61][62].…”

Kinetics of Iron Extraction from Coal Fly Ash by Hydrochloric Acid Leaching

“…There are a number of studies on preliminary processing of bauxite by low concentration hydrochloric acid for removal of unintended impurities: iron oxides, and carbonates of calcium and magnesium [24][25][26][27][28][29]. This approach is very promising in relation to coal fly ash, since the main alumina mineral, mullite, has low solubility in HCl, and losses of aluminum in this process will be minimum [30]. An aqueous solution of FeCl 3 can be recycled by spray pyrolysis at 600 • C. Spheres of α-Fe 2 O 3 received by this method, can be used as pigments [31][32][33][34].…”

Valuable Metal Recycling

“…Zhao et al [6] investigated leaching kinetics of zinc from hemimorphite in an ammonium chloride solution and reported on how pregrinding may significantly enhance the leaching efficiency of Zn. Li et al [7] developed an efficient method to recover Li and Al from coal fly ash by intensified acid leaching after predesilication. Zhou et al [8] recovered iron and rare earth from tailings by means of water leaching following roasting processes.…”

“…Zhou et al [8] recovered iron and rare earth from tailings by means of water leaching following roasting processes. These studies [6][7][8] revealed that pretreatment is important for leaching of valuable metals from refractory materials. Kim et al [9] reported on the preconcentration of copper from glass in automobile shredder residue by means of an electrostatic separation process.…”