skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Adsorption of gold(III)-chloride and gold(I)-thiosulfate anions by goethite

Abstract

Gold(III)-chloride and gold(I)-thiosulfate adsorption by goethite was investigated as a function of pH (4 to 8), Cl{sup {minus}} concentration , and ionic strength. Several observations suggest that Au(III)-chloride hydrolysis species with < 4 Cl ligands are preferentially adsorbed by goethite and that at low surface coverages these species are adsorbed in an inner-sphere, bidentate fashion. At pH 4.0 and in 0.01 M NaNO{sub 3}, adsorption isotherms have a shape and maximum adsorption densities (210 {mu}mol Au/g) similar to those previously observed for phosphate. In addition, excess Cl{sup {minus}} appears in solution after adsorption, and an ionic strength increase to 0.1 M NaNO{sub 3} has little effect on adsorbed amounts below 25% of maximum surface coverage. In 0.01 and 0.1 M NaCl, however, adsorption increases as pH increases from 4 to 7, which is opposite to typical behavior for anion adsorption onto oxide surfaces. This behavior suggest Au(I)-thiosulfate adsorption occurs primarily via a non-specific or outer-sphere mechanism. The contrast in adsorption behavior of these two gold species demonstrates the importance of steric factors to adsorption processes. Gold(III)-chloride species are square planar, and the distance along an edge of this square (3.23 {angstrom}) closely matches the distance between A-type hydroxyl groups onmore » the goethite surface (3.04 {angstrom}). Thus, these hydroxyl groups form an ideal template for bidentate coordination. Conversely, Au(S{sub 2}O{sub 3}){sub 2}{sup 3{minus}} is a large, linear anion, and consequently it is difficult for this species to coordinate specifically with goethite surface hydroxyl groups.« less

Authors:
;  [1];  [2]
  1. Pennsylvania State Univ., University Park (United States)
  2. Univ. Federal Fluminense, Rio de Janeiro (Brazil)
Publication Date:
OSTI Identifier:
5978977
Resource Type:
Journal Article
Journal Name:
Geochimica et Cosmochimica Acta; (United States)
Additional Journal Information:
Journal Volume: 55:3; Journal ID: ISSN 0016-7037
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; GOETHITE; SORPTIVE PROPERTIES; SURFACE PROPERTIES; GOLD CHLORIDES; ADSORPTION; SULFUR COMPOUNDS; GEOCHEMISTRY; GOLD IONS; IONIC COMPOSITION; PH VALUE; CHARGED PARTICLES; CHEMISTRY; CHLORIDES; CHLORINE COMPOUNDS; GOLD COMPOUNDS; HALIDES; HALOGEN COMPOUNDS; IONS; MINERALS; OXIDE MINERALS; SORPTION; TRANSITION ELEMENT COMPOUNDS; 580000* - Geosciences

Citation Formats

Machesky, M L, Rose, A W, and Andrade, W O. Adsorption of gold(III)-chloride and gold(I)-thiosulfate anions by goethite. United States: N. p., 1991. Web. doi:10.1016/0016-7037(91)90340-B.
Machesky, M L, Rose, A W, & Andrade, W O. Adsorption of gold(III)-chloride and gold(I)-thiosulfate anions by goethite. United States. doi:10.1016/0016-7037(91)90340-B.
Machesky, M L, Rose, A W, and Andrade, W O. Fri . "Adsorption of gold(III)-chloride and gold(I)-thiosulfate anions by goethite". United States. doi:10.1016/0016-7037(91)90340-B.
@article{osti_5978977,
title = {Adsorption of gold(III)-chloride and gold(I)-thiosulfate anions by goethite},
author = {Machesky, M L and Rose, A W and Andrade, W O},
abstractNote = {Gold(III)-chloride and gold(I)-thiosulfate adsorption by goethite was investigated as a function of pH (4 to 8), Cl{sup {minus}} concentration , and ionic strength. Several observations suggest that Au(III)-chloride hydrolysis species with < 4 Cl ligands are preferentially adsorbed by goethite and that at low surface coverages these species are adsorbed in an inner-sphere, bidentate fashion. At pH 4.0 and in 0.01 M NaNO{sub 3}, adsorption isotherms have a shape and maximum adsorption densities (210 {mu}mol Au/g) similar to those previously observed for phosphate. In addition, excess Cl{sup {minus}} appears in solution after adsorption, and an ionic strength increase to 0.1 M NaNO{sub 3} has little effect on adsorbed amounts below 25% of maximum surface coverage. In 0.01 and 0.1 M NaCl, however, adsorption increases as pH increases from 4 to 7, which is opposite to typical behavior for anion adsorption onto oxide surfaces. This behavior suggest Au(I)-thiosulfate adsorption occurs primarily via a non-specific or outer-sphere mechanism. The contrast in adsorption behavior of these two gold species demonstrates the importance of steric factors to adsorption processes. Gold(III)-chloride species are square planar, and the distance along an edge of this square (3.23 {angstrom}) closely matches the distance between A-type hydroxyl groups on the goethite surface (3.04 {angstrom}). Thus, these hydroxyl groups form an ideal template for bidentate coordination. Conversely, Au(S{sub 2}O{sub 3}){sub 2}{sup 3{minus}} is a large, linear anion, and consequently it is difficult for this species to coordinate specifically with goethite surface hydroxyl groups.},
doi = {10.1016/0016-7037(91)90340-B},
journal = {Geochimica et Cosmochimica Acta; (United States)},
issn = {0016-7037},
number = ,
volume = 55:3,
place = {United States},
year = {1991},
month = {3}
}