Supramolecular Gold Stripping from Activated Carbon Using α-Cyclodextrin
Supramolecular Gold Stripping from Activated Carbon Using α-Cyclodextrin
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DOI：
10.1021/jacs.0c11769
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发表时间：
2021-02-03
影响因子：
15
通讯作者：
Stoddart, J. Fraser
中科院分区：
文献类型：
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作者：
Liu, Wenqi;Jones, Leighton O.;Stoddart, J. Fraser
我们报告了Au(CN)(2)（-）阴离子的分子识别，这是当今黄金开采行业的重要中间体，由α -环糊精。3 x射线单晶superstructures-KAu (CN)(2)的子集alpha-cyclodextrin,考(CN)(2)的子集(alpha-cyclodextrin)(2),和KAg (CN)(2)的子集(alpha-cyclodextrin)(2)展示的绑定腔alpha-cyclodextrin适合metal-coordination复合物,如非盟(CN)(2)(-)和Ag (CN)(2)(-)与线性几何图形,而K +离子实现连接的角色alpha-cyclodextrin tori一起由于[K +中心导中心导中心点O] ion-dipole交互。在水溶液中Au(CN)(2)（-）与α -环糊精呈1:1的结合化学计量，通过H-1核磁共振滴定得到的结合常数为10(4)M-1。等温量热滴定表明，这种分子识别是由有利的焓变克服了小的熵罚驱动的。环糊精KAu(CN)(2)亚群在水溶液中的加合物形成除了疏水作用外，还受到多重[C-H中心点中心点中心点中心点π]和[C-H中心点中心点中心阴离子]相互作用的维持。分子识别也通过DFT计算进行了研究，结果表明，在乙醇存在下，α -环糊精和Au(CN)（2-）之间的2:1结合化学计量更有利。我们已经证明，α -环糊精和KAu(CN)(2)之间的分子识别过程可以应用于室温下从活性炭表面剥离金。此外，在Ag(CN)(2)（-）存在的情况下，该剥离过程对Au(CN)(2)（-）具有选择性，Ag(CN)(2)（-）对α -环糊精的结合亲和力较低。原则上，这种分子识别过程可以整合到商业金矿开采协议中，并显著降低成本、能源消耗和环境影响。
We report the molecular recognition of the Au(CN)(2)(-) anion, a crucial intermediate in today's gold mining industry, by alpha-cyclodextrin. Three X-ray single-crystal superstructures-KAu(CN)(2)subset of alpha-cyclodextrin, KAu(CN)(2)subset of(alpha-cyclodextrin)(2), and KAg(CN)(2)subset of(alpha-cyclodextrin)(2)-demonstrate that the binding cavity of alpha-cyclodextrin is a good fit for metal-coordination complexes, such as Au(CN)(2)(-) and Ag(CN)(2)(-) with linear geometries, while the K+ ions fulfill the role of linking alpha-cyclodextrin tori together as a result of [K+center dot center dot center dot O] ion-dipole interactions. A 1:1 binding stoichiometry between Au(CN)(2)(-) and alpha-cyclodextrin in aqueous solution, revealed by H-1 NMR titrations, has produced binding constants in the order of 10(4) M-1. Isothermal calorimetry titrations indicate that this molecular recognition is driven by a favorable enthalpy change overcoming a small entropic penalty. The adduct formation of KAu(CN)(2)subset of alpha-cyclodextrin in aqueous solution is sustained by multiple [C-H center dot center dot center dot pi] and [C-H center dot center dot center dot anion] interactions in addition to hydrophobic effects. The molecular recognition has also been investigated by DFT calculations, which suggest that the 2:1 binding stoichiometry between alpha-cyclodextrin and Au(CN)(2-) is favored in the presence of ethanol. We have demonstrated that this molecular recognition process between alpha-cyclodextrin and KAu(CN)(2) can be applied to the stripping of gold from the surface of activated carbon at room temperature. Moreover, this stripping process is selective for Au(CN)(2)(-) in the presence of Ag(CN)(2)(-), which has a lower binding affinity toward alpha-cyclodextrin. This molecular recognition process could, in principle, be integrated into commercial gold-mining protocols and lead to significantly reduced costs, energy consumption, and environmental impact.