Leaching optimization of mining wastes with lizardite and brucite contents for use in indirect mineral carbonation through the pH swing method

Abstract

This study investigated the leaching process in order to maximize Mg and Fe extraction and to produce amorphous silica (SiO 2 ) with high purity. For this, a mining waste identified as S-GO was employed; which is a serpentinite rock with high lizardite 1T and native brucite contents. A Taguchi Experiment Design was used in order to assess the parameters that influence the leaching process such as: granulometry, hydrochloric acid concentration (HCl), leaching temperature, and mass/volume ratio. Furthermore, thermogravimetric analysis (TGA) was done to understand the interrelation between the mineral structure and leaching performance. Results show that lizardite 1T-bearing serpentinite presents a low content of tetrahedral Al 3þ and high octahedral Fe 3þ contents on S-GO. Native brucite delayed the formation of a hydrated silica layer and improved dissolution of serpentines. For this, Mg and Fe extractions are efficient, reaching 88 ± 2% of Mg and Fe extracted during the first 30 min of reaction, under mild process conditions: stoichiometric mass/volume ratio, 1M HCl concentration, pressure of 1 bar, temperature of 100 C, and 300 mm particle size. On the other hand, an excess of acid improves Mg and Fe extraction by only 10 ± 5% for S-GO. Such characteristics reduce energetic penalties and costs involved on indirect mineral carbonation processes by the pH swing method.

Influence of physicochemical properties of Brazilian serpentinites on the leaching process for indirect CO2 mineral carbonation

“…A greater value would indicate more permeability at the beginning of the reaction to any fluid within the material. This is interesting because it could explain the high extraction rate reported by Arce et al (2017), in which 88 ± 2% of Mg and Fe were extracted from S-GO in the first 30 min of the reaction.…”

“…The diffractogram for R10E1 ( Fig. 2a) reveals that there is significant structural modification consistent with the production of amorphous silica which is formed after the bonds between octahedral and tetrahedral sheets are broken in the serpentines, in which siloxanes (Si -O -Si) are encapsulated and precipitated as silica (Arce et al, 2017;McCutcheon et al, 2015;Sanna et al, 2013aSanna et al, , 2013bPark and Fan, 2004). However, the diffractogram also shows that a large amount of the material has been transformed into amorphous silica, while non-reactive lizardite (L) and brucite (B) are still present.…”

“…S-GO had a high level of this ratio due to the presence of brucite (Mg(OH) 2 ). The structure of S-GO is made up of 6.1% brucite (Arce et al, 2017). Although this quantity isn't very high, this mineralogical characteristic makes S-GO more efficient at leaching than S-MG.…”

Serpentinites: Mineral Structure, Properties and Technological Applications

“…Serpentinite with high lizardite content, obtained from a mining industry residue, was used to produce amorphous silica with high purity. The influence of parameters such as granulometry, HCl concentration, temperature, and mass/volume ratio in the leaching process was evaluated by Arce et al 37 Serpentinite with relatively low Al 3+ , Fe 3+ and Fe 2+ contents reduce the formation of hydrated silica and improve the dissolution of the mineral. Results indicated that in samples larger than 300 mm, the extractions of magnesium and iron were more efficient.…”

CO2 sequestration by pH-swing mineral carbonation based on HCl/NH4OH system using iron-rich lizardite 1T

“…Sterile is a residue from a mining step related to asbestos production, normally disposed of in landfills. However, since it has low chrysotile contents, it is considered a hazardous waste and its disposal represents a challenge for environmental engineering and public health [1][2][3][4][5]. According to Valuoma et al [5], Fedoročková et al [6], and Gadikota et al [1], carbon capture and storage by mineralization (CCSM) using asbestos-containing materials is a technology that would have several environmental benefits, since it can permanently alter the asbestos fiber structure in these materials, as well as sequester carbon dioxide (CO 2 ) in a safe and permanent manner, producing materials with high aggregated value in the market.…”