Atomistic insights into the carbonation behavior of olivine minerals: Role of metal cation composition

Abstract

Olivine minerals possess significant potential for CO₂ sequestration through carbonation reactions, with their reactivity highly influenced by cation composition. This study employs first-principles calculations to systematically investigate the impact of metal cations (Mg²⁺, Ca²⁺, Mn²⁺, Fe²⁺, Co²⁺) on the carbonation behavior of five olivine structures: forsterite (Mg₂SiO₄), calcio-olivine (γ-Ca₂SiO₄), tephroite (α-Mn₂SiO₄), fayalite (α-Fe₂SiO₄), and Co-olivine. Analyses of bond characteristics, total bond order density, and local density of states reveal fundamental differences between alkaline earth and transition metal olivines. We have found that in alkaline earth (AE) olivines, carbonation primarily involves an electrophilic attack of O²⁻ by H⁺ and a nucleophilic attack of metal cations by HCO₃⁻/CO₃²⁻ species. Calcio-olivine exhibits higher reactivity than forsterite due to enhanced Ca²⁺ nucleophilicity. Conversely, transition metal (TM) olivine reactivity is governed by the multivalent cations, contributing significantly to both electrophilic and nucleophilic pathways. Considering both mineral reserves and carbonation reaction mechanisms, calcio-olivine is determined to be the most advantageous among the five olivine minerals in terms of carbonation reactivity. This atomic-scale understanding guides the development of olivine-based materials with improved carbonation performance for efficient CO₂ sequestration and utilization in carbon capture, utilization, and storage technologies.