シミュレーションにより、豊富な鉱石中の重要元素の分布が明らかになる(Simulations Identify How Critical Elements Distribute in Abundant Mineral Ores)

2024-08-14

2024-08-13 パシフィック・ノースウェスト国立研究所(PNNL)

ニッケル（Ni）とコバルト（Co）は現代技術に不可欠ですが、高品位の鉱石が減少しています。そこで、低品位で豊富な苦鉄質および超苦鉄質鉱床が注目されていますが、これらからのNiとCoの抽出を経済的に実現する新しい方法が必要です。研究者たちは、フォルステライト（Mg2SiO4）にNiとCoがどのように取り込まれるかを分子動力学シミュレーションで調査し、M1サイトへの取り込みが優先されることを確認しました。これにより、炭酸化反応を通じて低品位鉱石からの抽出コストを削減し、鉱業のCO2削減に貢献できる可能性が示唆されました。

＜関連情報＞

フォルステライトにおけるNiとCoの取り込み：ハバード補正を用いた密度汎関数理論による研究 Ni and Co Incorporation in Forsterite: A Density Functional Theory Study with Hubbard Correction

Michel Sassi,and Sebastien N. Kerisit
ACS Earth & Space Chemistry Published::April 17, 2024
DOI:https://doi.org/10.1021/acsearthspacechem.3c00370

Abstract

Ni and Co are critical elements for the world economy and modern technologies. Mafic and ultramafic deposits represent low-grade yet abundant alternatives to traditional Ni and Co ores. In this work, density functional theory (DFT) with the Hubbard U correction (DFT+U) was used to simulate the incorporation of Ni and Co in forsterite (Mg₂SiO₄), the Mg endmember of olivine, a common mineral in mafic and ultramafic rocks. Hubbard U terms for Ni and Co were parametrized using a series of oxide, hydroxide, carbonate, silicate, and sulfide minerals relevant to extraction and recovery of Ni and Co from mafic and ultramafic deposits. Electronic, energetic, magnetic, and structural properties were considered in the parametrization. For each of Ni and Co, an effective Hubbard correction (U_eff) value that optimized agreement with either experimental data or a hybrid exchange-correlation functional for all of the minerals considered is reported. DFT+U ab initio molecular dynamics (AIMD) simulations of Ni and Co incorporated into the M1 and M2 octahedral sites of forsterite were then performed. Ni and Co substitution in the M1 site was more energetically favorable than substitution in the M2 site, in agreement with published partition coefficients. AIMD trajectories were used to compute extended X-ray absorption fine structure (EXAFS) spectra of Ni in the M1 and M2 sites for direct fitting to a published experimental spectrum of Ni in a natural San Carlos olivine sample. The results of the fit indicated that ordering of Ni in the M1 site was not as strong at the low Ni concentrations relevant to mafic and ultramafic silicate minerals as that at the higher concentrations of the Ni-Mg olivine solid solutions studied to date.