Surface complexation of sulfate by hematite surfaces: FTIR and STM observations

Sulfate adsorbed to hematite surfaces from aqueous solution is examined using Fourier transform infrared (FTIR) spectroscopy and scanning tunneling microscopy (STM). FTIR was carried out using an Attenuated Total Reflectance (ATR) element coated with a fixed layer of hematite particles; this configu...

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Autores principales: Eggleston, C.M., Hug, S., Stumm, W., Sulzberger, B., Afonso, M.D.S.
Formato: JOUR
Materias:
adsorption
FTIR
haematite
STM
sulphate
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00167037_v62_n4_p585_Eggleston
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_00167037_v62_n4_p585_Eggleston2023-10-03T14:14:37Z Surface complexation of sulfate by hematite surfaces: FTIR and STM observations Eggleston, C.M. Hug, S. Stumm, W. Sulzberger, B. Afonso, M.D.S. adsorption FTIR haematite STM sulphate Sulfate adsorbed to hematite surfaces from aqueous solution is examined using Fourier transform infrared (FTIR) spectroscopy and scanning tunneling microscopy (STM). FTIR was carried out using an Attenuated Total Reflectance (ATR) element coated with a fixed layer of hematite particles; this configuration allowed in situ variation of pH and sulfate concentration. The FTIR results are consistent with an inner-sphere monodentate surface complex. On dried samples, sulfate may form bidentate or possibly monodentate bisulfate complexes. STM was applied to samples that were removed from solution and imaged in air, conditions corresponding to those of the dried samples in FTIR. The images show mobile adsorbates whose lifetimes were greater than 5 ms and less than 240 ms, times that bracket the average lifetimes of aqueous FeSO+ 4 complexes (∼50 ms). In addition, the images show pairs of bumps, in agreement with STM images of bisulfate adsorbed on Pt(111) electrode surfaces (Funtikov et al., 1995). Although the STM images do not provide chemical identification, they are consistent with imaging of adsorbed inner-sphere sulfate (STM is incapable of seeing outer-sphere adsorbates). Our results suggest that categorization of adsorbates into inner-sphere and outer-sphere on the basis of macroscopic adsorption information is perhaps oversimplistic. Instead, a spectrum of intermediate behaviors is likely. Adsorbates classed (macroscopically) as outer-sphere may be those for which a relatively small proportion of adsorbates are in inner-sphere complexes at any given time. Copyright © 1998 Elsevier Science Ltd. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00167037_v62_n4_p585_Eggleston
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic adsorption
FTIR
haematite
STM
sulphate
spellingShingle adsorption
FTIR
haematite
STM
sulphate
Eggleston, C.M.
Hug, S.
Stumm, W.
Sulzberger, B.
Afonso, M.D.S.
Surface complexation of sulfate by hematite surfaces: FTIR and STM observations
topic_facet adsorption
FTIR
haematite
STM
sulphate
description Sulfate adsorbed to hematite surfaces from aqueous solution is examined using Fourier transform infrared (FTIR) spectroscopy and scanning tunneling microscopy (STM). FTIR was carried out using an Attenuated Total Reflectance (ATR) element coated with a fixed layer of hematite particles; this configuration allowed in situ variation of pH and sulfate concentration. The FTIR results are consistent with an inner-sphere monodentate surface complex. On dried samples, sulfate may form bidentate or possibly monodentate bisulfate complexes. STM was applied to samples that were removed from solution and imaged in air, conditions corresponding to those of the dried samples in FTIR. The images show mobile adsorbates whose lifetimes were greater than 5 ms and less than 240 ms, times that bracket the average lifetimes of aqueous FeSO+ 4 complexes (∼50 ms). In addition, the images show pairs of bumps, in agreement with STM images of bisulfate adsorbed on Pt(111) electrode surfaces (Funtikov et al., 1995). Although the STM images do not provide chemical identification, they are consistent with imaging of adsorbed inner-sphere sulfate (STM is incapable of seeing outer-sphere adsorbates). Our results suggest that categorization of adsorbates into inner-sphere and outer-sphere on the basis of macroscopic adsorption information is perhaps oversimplistic. Instead, a spectrum of intermediate behaviors is likely. Adsorbates classed (macroscopically) as outer-sphere may be those for which a relatively small proportion of adsorbates are in inner-sphere complexes at any given time. Copyright © 1998 Elsevier Science Ltd.
format JOUR
author Eggleston, C.M.
Hug, S.
Stumm, W.
Sulzberger, B.
Afonso, M.D.S.
author_facet Eggleston, C.M.
Hug, S.
Stumm, W.
Sulzberger, B.
Afonso, M.D.S.
author_sort Eggleston, C.M.
title Surface complexation of sulfate by hematite surfaces: FTIR and STM observations
title_short Surface complexation of sulfate by hematite surfaces: FTIR and STM observations
title_full Surface complexation of sulfate by hematite surfaces: FTIR and STM observations
title_fullStr Surface complexation of sulfate by hematite surfaces: FTIR and STM observations
title_full_unstemmed Surface complexation of sulfate by hematite surfaces: FTIR and STM observations
title_sort surface complexation of sulfate by hematite surfaces: ftir and stm observations
url http://hdl.handle.net/20.500.12110/paper_00167037_v62_n4_p585_Eggleston
work_keys_str_mv AT egglestoncm surfacecomplexationofsulfatebyhematitesurfacesftirandstmobservations
AT hugs surfacecomplexationofsulfatebyhematitesurfacesftirandstmobservations
AT stummw surfacecomplexationofsulfatebyhematitesurfacesftirandstmobservations
AT sulzbergerb surfacecomplexationofsulfatebyhematitesurfacesftirandstmobservations
AT afonsomds surfacecomplexationofsulfatebyhematitesurfacesftirandstmobservations
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