Abstract
Herein, we report an alkali metal cation-dependent approach to gold recovery, facilitated by second-sphere coordination with eco-friendly α-cyclodextrin (α-CD). Upon mixing eight salts composed of Na+, K+, Rb+, or Cs+ cations and [AuX4]- (X = Cl/Br) anions with α-, β-, or γ-CD in water, co-precipitates form selectively from the three (out of 24) aqueous solutions containing α-CD with KAuBr4, RbAuBr4, and CsAuBr4, from which the combination of α-CD and KAuBr4 affords the highest yield. Single-crystal X-ray analyses reveal that in 20 of the 24 adducts CD and [AuX4]- anions form 2:1 sandwich-type second-sphere adducts driven partially by [C-H···X-Au] interactions between [AuX4]- anions and the primary faces of two neighboring CDs. In the adduct formed between α-CD and KAuBr4, a [K(OH2)6]+ cation is encapsulated inside the cavity between the secondary faces of two α-CDs, leading to highly efficient precipitation owing to the formation of a cation/anion alternating ion wire residing inside a continuous α-CD nanotube. By contrast, in the other 19 adducts, the cations are coordinated by OH groups and glucopyranosyl ring O atoms in CDs. The strong coordination of Rb+ and Cs+ cations by these ligands, in conjunction with the stereoelectronically favorable binding of [AuBr4]- anions with two α-CDs, facilitates the co-precipitation of the two adducts formed between α-CD with RbAuBr4 and CsAuBr4. In order to develop an efficient process for green gold recovery, the co-precipitation yield of α-CD and KAuBr4 has been optimized regarding both the temperature and the molar ratio of α-CD to KAuBr4.
Original language | English (US) |
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Pages (from-to) | 11643-11653 |
Number of pages | 11 |
Journal | Journal of the American Chemical Society |
Volume | 138 |
Issue number | 36 |
DOIs | |
State | Published - Sep 14 2016 |
ASJC Scopus subject areas
- Chemistry(all)
- Biochemistry
- Catalysis
- Colloid and Surface Chemistry
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CCDC 1479841: Experimental Crystal Structure Determination
Liu, Z. (Creator), Samanta, A. (Creator), Lei, J. (Creator), Sun, J. (Creator), Wang, Y. (Creator) & Stoddart, J. F. (Creator), Cambridge Crystallographic Data Centre, 2016
DOI: 10.5517/ccdc.csd.cc1lnwty, http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.5517/ccdc.csd.cc1lnwty&sid=DataCite
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CCDC 1479843: Experimental Crystal Structure Determination
Liu, Z. (Creator), Samanta, A. (Creator), Lei, J. (Creator), Sun, J. (Creator), Wang, Y. (Creator) & Stoddart, J. F. (Creator), Cambridge Crystallographic Data Centre, 2016
DOI: 10.5517/ccdc.csd.cc1lnww0, http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.5517/ccdc.csd.cc1lnww0&sid=DataCite
Dataset
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CCDC 1479836: Experimental Crystal Structure Determination
Liu, Z. (Creator), Samanta, A. (Creator), Lei, J. (Creator), Sun, J. (Creator), Wang, Y. (Creator) & Stoddart, J. F. (Creator), Cambridge Crystallographic Data Centre, 2016
DOI: 10.5517/ccdc.csd.cc1lnwns, http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.5517/ccdc.csd.cc1lnwns&sid=DataCite
Dataset