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 |
Funding
This work made use of the EPIC facility of the NUANCE Center at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205); the MRSEC program (NSF DMR-1121262) at the Materials Research Center; the International Institute for Nanotechnology (IIN); and the State of Illinois, through the IIN.
ASJC Scopus subject areas
- General Chemistry
- 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
Dataset
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CCDC 1479842: 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.cc1lnwvz, http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.5517/ccdc.csd.cc1lnwvz&sid=DataCite
Dataset
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CCDC 1479848: 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.cc1lnx16, http://www.ccdc.cam.ac.uk/services/structure_request?id=doi:10.5517/ccdc.csd.cc1lnx16&sid=DataCite
Dataset