Azizi Dariush, Larachi Faïçal
Department of Chemical Engineering , Université Laval , 1065 Avenue de la Médecine , Québec , Québec G1V 0A6 , Canada.
J Phys Chem A. 2019 Jan 31;123(4):889-905. doi: 10.1021/acs.jpca.8b09140. Epub 2019 Jan 22.
Aqueous mineral carbonation of brucite is an important mineralization route for carbon capture and sequestration. Prerequisite to mineral carbonation are the simultaneous CO absorption and brucite dissolution which imply, in the first place, the formation and release in the liquid phase of CO, HCO, Mg, MgOH, and MgHCO ions. To gain insights on the nature of adsorption sites and resulting surface complexes, the affinity of water and of dissolved species for pristine and partially dissolved brucite (001) cleaved surfaces in aqueous mineral carbonation has been investigated using density-functional theory (DFT) simulations. The species' affinity for uptake by the brucite (001) surface is predicted to obey the trend: Mg > MgHCO > MgOH > HCO > CO, whereas the surface acid/base behavior controls affinity following the order: dehydroxylated (001) surface > deprotonated (001) surface > neutral and protonated (001) surfaces. Covalent bonds have been predicted for the following (charge-determining) ion-(001) brucite surface sites: CO ≡ dehydroxylated site, HCO ≡ dehydroxylated site, MgOH ≡ dehydroxylated/deprotonated sites, MgHCO ≡ dehydroxylated/(de)protonated sites, and Mg ≡ neutral/(de)protonated/dehydroxylated sites. Congruent dissolution of (001) brucite surface leads to a diverse population of coordination-deficient Mg and O centers which are more active to form covalently bonded surface complexes with aqueous CO, HCO, Mg, MgOH, MgHCO as compared to the undissolved surface. However, although affinity of the altered surfaces for dissolved ions increases conspicuously, the same affinity trend is predicted for the dissolving surfaces as compared to the pristine (001) brucite surface.
水镁石的水相矿物碳酸化是碳捕获与封存的一条重要矿化途径。矿物碳酸化的前提是同时吸收二氧化碳和溶解水镁石，这首先意味着在液相中形成并释放CO、HCO、Mg、MgOH和MgHCO离子。为深入了解吸附位点的性质以及由此产生的表面络合物，利用密度泛函理论（DFT）模拟研究了水和溶解物种对水相矿物碳酸化中原生和部分溶解的水镁石（001）解理面的亲和力。预计水镁石（001）表面对各物种的吸收亲和力遵循以下趋势：Mg > MgHCO > MgOH > HCO > CO，而表面酸碱行为控制的亲和力顺序为：脱羟基（001）表面>去质子化（001）表面>中性和质子化（001）表面。已预测以下（电荷决定）离子 - （001）水镁石表面位点存在共价键：CO ≡ 脱羟基位点，HCO ≡ 脱羟基位点，MgOH ≡ 脱羟基/去质子化位点，MgHCO ≡ 脱羟基/（去）质子化位点，以及Mg ≡ 中性/（去）质子化/脱羟基位点。（001）水镁石表面的一致溶解导致形成了多种配位不足的Mg和O中心，与未溶解表面相比，这些中心更易于与水相中的CO、HCO、Mg、MgOH、MgHCO形成共价键合的表面络合物。然而，尽管改变后的表面对溶解离子的亲和力显著增加，但与原始（001）水镁石表面相比，溶解表面的亲和力趋势预计相同。
