Effects of Experimental Parameters on the Extraction of Silica and Carbonation of Blast Furnace Slag at Atmospheric Pressure in Low-Concentration Acetic Acid

Abstract

Blast furnace slag (BFS), a calcium-rich industrial byproduct, has been utilized since 2005 as a mineral carbonation feedstock for CO 2 sequestration, producing calcium carbonate precipitates. In this study, the conditions for the dissolution of Ca and Si in acetic acid, and subsequent carbonation, were elaborated. For this purpose, the retardation of the polymerization of silicon was attempted by varying the concentration of acetic acid, temperature, and leaching time. An inductively coupled plasma (ICP) analysis revealed that both the Ca and Si dissolved completely within 30 min in 5% acetic acid at room temperature. This high dissolution value can be attributed to the fact that Ca was bound to O rather than to Si, as determined by X-ray photoelectron spectroscopy (XPS). The use of CO 2 -absorbed monoethanolamine enabled the complete carbonation of BFS at ambient conditions without the need for a pH swing. The presence of dissolved silica was found to affect the polymorphs of the precipitated CaCO 3 . We believe that this process offers a simple method for manipulating the composites of products obtained by mineral carbonation diminishing the leaching residues.

Preparation of Silica-Alumina Nanoparticles via Blast-Furnace Slag Dissolution in Low-Concentration Acetic Acid for Carbonation

“…Granulated BFS was obtained from a steel making company in Pohang, Korea [17]. The sample was crushed and powdered to obtain particles ranging from 75 to 300 µm in size.…”

“…Our previous study demonstrated that carbonation could be performed via two methods using the extracted solution: One was to carbonate after separating the silica-rich gel, while the other was to carbonate all the leachates [17]. In this study, during the former process, impurities containing dissolved divalent cations such as Ca and Mg were elaborated to remain as much as possible in solution for the preparation of pure Si-Al nanoparticles.…”

“…Fortunately, our recent study revealed that the Si-Al gel precursor can be separated from the impurities by exploiting an extracted solution containing hydrated Si and Al ions [17]. The dissolved hydrated Si and Al ions were then precipitated to form pure Si-Al nanoparticles through a sol-gel route.…”

“…In this study, during the former process, impurities containing dissolved divalent cations such as Ca and Mg were elaborated to remain as much as possible in solution for the preparation of pure Si-Al nanoparticles. A more detailed carbonation conditions are described in our previous work [17].…”

“…For silica-alumina nanoparticles, tetraethoxysilane (TEOS, Si(OC 2 H 5 ) 4 ) or tetramethoxysilane (TMOS, Si(OCH 3 ) 4 ), and aluminum-tri-sec-butoxide (ATSB, Al(C 2 H 5 CH(CH 3 )O 3 ) are generally used as precursors for silica and boehmite sol, respectively [16]. Previously, we demonstrated that Si-Al oxide composites could be prepared from BFS despite the use of uncontrolled coarse granules embedded with Fe(III) as a minor impurity [17]. It is possible to retard the formation of silica gel by manipulating the experimental parameters (i.e., acetic acid concentration, extracting temperature, and extracting time) during dissolution prior to the BFS carbonation process.…”