Optimizing Metal Leaching from Porous Igneous Basaltic Powder Using Chelating Agents: A Pathway Toward Effective CO2 Mineralization

Abstract

Storage of CO2 in basaltic rocks is a long-term and safe source of carbon sequestration, but silicate dissolution kinetics are usually too slow and silicate metals are not always well-positioned to form carbonates. This paper examines how ethylenediaminetetraacetic acid (EDTA) and L-glutamic acid N, N-diacetic acid (GLDA) can be used to promote CO2 mineralization and leaching of metal in basaltic powder of the Harrat Lunayyir volcanic field, Saudi Arabia. Three months of experiments were done under conditions relevant to reservoirs (1200 psi, 50 ℃). In the case of the experiment 5% and 10% solutions of Chelating solutions in synthetic seawater were prepared and reacted with basalt and under supercritical CO2 conditions. The total inorganic carbon (TIC) analysis and thermogravimetric analysis (TGA) were used to measure the carbon partitioning between aqueous and solid phases, respectively. Findings have shown that the EDTA does drastically raise the dissolved inorganic carbon content of the aqueous phase, with TIC reading more than 10 g/L at the higher concentrations being an indication of strong and sustained complexation of metals. But high levels of EDTA inhibit the formation of solid-phase carbonates, implying that the precipitation of the minerals may be slowed down by severe chelation. Conversely, GLDA has intermediate metal complexation which favours a more balanced dissolution precipitation mechanism and sequential development of carbonate as evidenced by increasing thermal decomposition fingerprints in TGA. The results prove that the type of chelating agent and concentration plays a critical role in determining carbon distribution and efficiency of the mineralization process. EDTA has been shown to prefer improved metal mobilization and longer aqueous carbon retention, and GLDA to have favourable solid-phase carbonation. The two main agents can be further differentiated based on which objective of operation one desires to achieve, i.e. either dissolution enhancement or faster CO2 immobilization. This paper presents a mechanistic model of optimization of chemically assisted in-situ CO2 mineralization in basaltic deposits.