Bertoli Alexandre C, Novaes Pedro A A, Costa Luciano T, De Almeida Wagner B, Duarte Hélio A
Departamento de Química Inorgânica, Universidade Federal do Rio de Janeiro - UFRJ, Centro de Tecnologia - Cidade Universitária, Rio de Janeiro, RJ, 21941-909, Brazil.
Instituto de Química, Universidade Federal Fluminense - UFF, Outeiro de São João Batista S/N, Campus Do Valonguinho, Centro, Niterói, Rio de Janeiro, RJ, 24020-141, Brazil.
J Mol Model. 2024 Nov 23;30(12):412. doi: 10.1007/s00894-024-06213-7.
Rare earth elements (REE) are indispensable in numerous green technologies owing to their exceptional physical and chemical attributes. Separating REE is a pivotal process to meet the increasing demands of the high-tech industry. Understanding the hydrolysis of REE in aqueous environments marks the initial stride in comprehending their separation mechanisms. Sulfate commonly coexists in high-concentration solutions alongside REE, stemming from mineral processing. We analyzed the hydrolysis of REE and their complexes with sulfate using DFT methods. We present and discuss on the structural characteristics of hydrolysis species and sulfate complexes in alignment with existing experimental data. Estimates of Gibbs free energies for hydrolysis and sulfate complex formation were compared against literature values. REE pose challenges owing to the labile nature of aqua complexes and the pivotal role of system dynamics. We showed that hydrolysis reactions could be suitably modeled, yielding an error margin of approximately 5 kcal mol concerning experimental values, employing the M06 exchange-correlation functional with the SMD implicit solvation model. However, sulfate chemical species proved to be more challenging, exhibiting larger error margins with substantial variations across the REE series. The Raman spectrum analysis of lanthanum sulfate complexes demonstrated excellent agreement with experimental values.
We applied the M06, PBE, and PBE0 exchange-correlation functionals combined with def2-TZVP basis sets and SMD to obtain the Gibbs free energies of hydrolysis and sulfate complexation with lanthanides in aqueous solution. The calculations were performed using the ORCA program.
由于其独特的物理和化学特性，稀土元素在众多绿色技术中不可或缺。分离稀土元素是满足高科技产业不断增长需求的关键过程。了解稀土元素在水环境中的水解是理解其分离机制的第一步。在矿物加工过程中，硫酸盐通常与稀土元素共存于高浓度溶液中。我们使用密度泛函理论（DFT）方法分析了稀土元素及其与硫酸盐的络合物的水解情况。我们结合现有实验数据，展示并讨论了水解物种和硫酸盐络合物的结构特征。将水解和硫酸盐络合物形成的吉布斯自由能估计值与文献值进行了比较。由于水合络合物的不稳定性质和系统动力学的关键作用，稀土元素带来了挑战。我们表明，使用M06交换相关泛函和SMD隐式溶剂化模型，可以对水解反应进行适当建模，与实验值相比，误差幅度约为5千卡/摩尔。然而，硫酸盐化学物种被证明更具挑战性，误差幅度更大，且在整个稀土系列中存在显著差异。硫酸镧络合物的拉曼光谱分析与实验值显示出极好的一致性。
我们应用M06、PBE和PBE0交换相关泛函，结合def2-TZVP基组和SMD，以获得镧系元素在水溶液中的水解和硫酸盐络合的吉布斯自由能。计算使用ORCA程序进行。
