The reuse of waste materials helps to alleviate the pressure on sustainable economic development caused by the rapid consumption of natural resources. In this paper, a new process for the recovery of Li and Mn from spent LiMn₂O₄ cathode materials was studied. LiMn₂O₄ was mixed with NaHSO₄·H₂O according to a certain mass ratio and roasted, and then the roasted products were leached with deionized water. The chemical changes during roasting were studied by thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. After roasting, Li exists in the form of LiNaSO₄, while the form of Mn is affected by the content of NaHSO₄·H₂O in the mixture. Within the corresponding temperature range, the chemical reaction between LiMn₂O₄ and NaHSO₄·H₂O can proceed spontaneously. During the reaction, the following reactions will occur in the II and IV stages: NaHSO₄⋅H₂O → NaHSO₄ + H₂O(g), Na₂S₂O₇ → Na₂SO₄ + SO₃(g) and reaction of different metal oxides with SO₃, and their average activation energies are 153.07 kJ/mol and 533.81 kJ/mol, respectively, and the restrictive link is three-dimensional diffusion. The roasted products were leached with deionized water, the extraction rate of Li and Mn elements increases with the decrease of mixing mass ratio, when the mass ratio of LiMn₂O₄ to NaHSO₄·H₂O is 1:1.07, the roasting temperature is 873 K, the roasting time is 0.5 h, under the condition of water leaching temperature of 333 K, the extraction rates of Li and Mn were 96.6% and 9.7%, respectively.

Graphical Abstract

中文翻译：

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基于 NaHSO4·H2O 硫酸化焙烧和水浸出的废 LiMn2O4 阴极材料的金属回收

废弃物的再利用有助于缓解自然资源快速消耗对经济可持续发展的压力。本文研究了一种从废LiMn ₂ O ₄正极材料中回收Li和Mn的新工艺。将LiMn ₂ O ₄与NaHSO ₄ ·H ₂ O按一定质量比混合并焙烧，焙烧产物用去离子水浸出。通过热重分析、差示扫描量热法、X射线衍射、X射线光电子能谱和扫描电子显微镜研究了焙烧过程中的化学变化。焙烧后，Li以LiNaSO _{4的形式存在}，而Mn的形态受混合物中NaHSO ₄ ·H _{2 O含量的影响。}在相应的温度范围内，LiMn ₂ O ₄与NaHSO ₄ ·H ₂ O之间的化学反应可以自发进行。在反应过程中，在II和IV阶段会发生以下反应：NaHSO ₄ ⋅H ₂ O → NaHSO ₄  + H ₂ O(g)，Na ₂ S ₂ O ₇  → Na ₂ SO ₄  + SO ₃ (g)以及不同金属氧化物与 SO _3的反应，它们的平均活化能分别为153.07 kJ/mol和533.81 kJ/mol，限制环节为三维扩散。焙烧产物用去离子水浸出，Li、Mn元素的提取率随着混合质量比的降低而增加，当LiMn ₂ O ₄与NaHSO ₄ ·H ₂ O的质量比为1:1.07时，焙烧温度为873 K，焙烧时间为0.5 h，在水浸温度333 K的条件下，Li和Mn的提取率分别为96.6%和9.7%。

图形概要