New insights into the adsorption of Aurocyanide Ion on activated carbon surface: electron microscopy analysis and computational studies using fullerene-like models

Hdl Handle:
http://hdl.handle.net/10149/324202
Title:
New insights into the adsorption of Aurocyanide Ion on activated carbon surface: electron microscopy analysis and computational studies using fullerene-like models
Authors:
Yin, C. (Chun-Yang); Ng, M. (Man-Fai); Saunders, M. (Martin); Goh, B. (Bee-Min); Senanayake, G. (Gamini); Sherwood, A. (Ashley); Hampton, M. (Marc)
Affiliation:
Teesside University. Technology Futures Institute.
Citation:
Yin, C., Ng, M., Saunders, M., Goh, B., Senanayake, G., Sherwood, A., Hampton, M. (2014) 'New insights into the adsorption of Aurocyanide Ion on activated carbon surface: electron microscopy analysis and computational studies using fullerene-like models' Langmuir; 4, 30 (26):7703
Publisher:
American Chemical Society
Journal:
Langmuir
Issue Date:
Jun-2014
URI:
http://hdl.handle.net/10149/324202
DOI:
10.1021/la501191h
Additional Links:
http://pubs.acs.org/doi/abs/10.1021/la501191h
Abstract:
Despite decades of concerted experimental studies dedicated to providing fundamental insights into the adsorption of aurocyanide ion, Au(CN)2–, on activated carbon (AC) surface, such a mechanism is still poorly understood and remains a contentious issue. This adsorption process is an essential unit operation for extracting gold from ores using carbon-in-pulp (CIP) technology. We hereby attempt to shed more light on the subject by employing a range of transmission electron microscopy (TEM) associated techniques. Gold-based clusters on the AC surface are observed by Z-contrast scanning TEM imaging and energy-filtered TEM element mapping and are supported by X-ray microanalysis. Density functional theory (DFT) calculations are applied to investigate this adsorption process for the first time. Fullerene-like models incorporating convex, concave, or planar structure which mimic the eclectic porous structures on the AC surface are adopted. Pentagonal, hexagonal, and heptagonal arrangements of carbon rings are duly considered in the DFT study. By determining the favored adsorption sites in water environment, a general adsorption trend of Au(CN)2– adsorbed on AC surface is revealed whereby concave > convex ≈ planar. The results suggest a tendency for Au(CN)2– ion to adsorb on the carbon sheet defects or edges rather than on the basal plane. In addition, we show that the adsorption energy of Au(CN)2– is approximately 5 times higher than that of OH– in the alkaline environment (in negative ion form), compared to only about 2 times in acidic environment (in protonated form), indicating the Au extraction process is much favored in basic condition. The overall simulation results resolve certain ambiguities about the adsorption process for earlier studies. Our findings afford crucial information which could assist in enhancing our fundamental understanding of the CIP adsorption process.
Type:
Article
Language:
en
ISSN:
0743-7463; 1520-5827
Rights:
Subject to restrictions, author can archive post-print (ie final draft post-refereeing). For full details see http://www.sherpa.ac.uk/romeo [Accessed: 05/08/2014]

Full metadata record

DC FieldValue Language
dc.contributor.authorYin, C. (Chun-Yang)en
dc.contributor.authorNg, M. (Man-Fai)en
dc.contributor.authorSaunders, M. (Martin)en
dc.contributor.authorGoh, B. (Bee-Min)en
dc.contributor.authorSenanayake, G. (Gamini)en
dc.contributor.authorSherwood, A. (Ashley)en
dc.contributor.authorHampton, M. (Marc)en
dc.date.accessioned2014-08-05T09:30:37Z-
dc.date.available2014-08-05T09:30:37Z-
dc.date.issued2014-06-
dc.identifier.citationLangmuir; 4, 30 (26):7703en
dc.identifier.issn0743-7463-
dc.identifier.issn1520-5827-
dc.identifier.doi10.1021/la501191h-
dc.identifier.urihttp://hdl.handle.net/10149/324202-
dc.description.abstractDespite decades of concerted experimental studies dedicated to providing fundamental insights into the adsorption of aurocyanide ion, Au(CN)2–, on activated carbon (AC) surface, such a mechanism is still poorly understood and remains a contentious issue. This adsorption process is an essential unit operation for extracting gold from ores using carbon-in-pulp (CIP) technology. We hereby attempt to shed more light on the subject by employing a range of transmission electron microscopy (TEM) associated techniques. Gold-based clusters on the AC surface are observed by Z-contrast scanning TEM imaging and energy-filtered TEM element mapping and are supported by X-ray microanalysis. Density functional theory (DFT) calculations are applied to investigate this adsorption process for the first time. Fullerene-like models incorporating convex, concave, or planar structure which mimic the eclectic porous structures on the AC surface are adopted. Pentagonal, hexagonal, and heptagonal arrangements of carbon rings are duly considered in the DFT study. By determining the favored adsorption sites in water environment, a general adsorption trend of Au(CN)2– adsorbed on AC surface is revealed whereby concave > convex ≈ planar. The results suggest a tendency for Au(CN)2– ion to adsorb on the carbon sheet defects or edges rather than on the basal plane. In addition, we show that the adsorption energy of Au(CN)2– is approximately 5 times higher than that of OH– in the alkaline environment (in negative ion form), compared to only about 2 times in acidic environment (in protonated form), indicating the Au extraction process is much favored in basic condition. The overall simulation results resolve certain ambiguities about the adsorption process for earlier studies. Our findings afford crucial information which could assist in enhancing our fundamental understanding of the CIP adsorption process.en
dc.language.isoenen
dc.publisherAmerican Chemical Societyen
dc.relation.urlhttp://pubs.acs.org/doi/abs/10.1021/la501191hen
dc.rightsSubject to restrictions, author can archive post-print (ie final draft post-refereeing). For full details see http://www.sherpa.ac.uk/romeo [Accessed: 05/08/2014]en
dc.titleNew insights into the adsorption of Aurocyanide Ion on activated carbon surface: electron microscopy analysis and computational studies using fullerene-like modelsen
dc.typeArticleen
dc.contributor.departmentTeesside University. Technology Futures Institute.en
dc.identifier.journalLangmuiren
or.citation.harvardYin, C., Ng, M., Saunders, M., Goh, B., Senanayake, G., Sherwood, A., Hampton, M. (2014) 'New insights into the adsorption of Aurocyanide Ion on activated carbon surface: electron microscopy analysis and computational studies using fullerene-like models' Langmuir; 4, 30 (26):7703-
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