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@ARTICLE{Konrad:1050433,
author = {Konrad, Alexander and Mulder, Ines and Hofmann, Diana and
Lang, Friederike and Stutz, Kenton P. and Siemens, Jan},
title = {{T}hermodynamics of {O}rganic {A}cid {S}orption to
{G}oethite},
journal = {European journal of soil science},
volume = {77},
number = {1},
issn = {0022-4588},
address = {Oxford [u.a.]},
publisher = {Wiley-Blackwell},
reportid = {FZJ-2026-00203},
pages = {e70278},
year = {2026},
abstract = {Adsorption to minerals is a key mechanism in stabilizing
organic carbon in soils. We used isothermal titration
calorimetry (ITC) to quantify the thermodynamics of binding
of citric acid, oxalic acid, and salicylic acid to four
goethites with different specific surface areas (SSA,
14–120 m2 g−1). Thermodynamic parameters could be
determined for sorption of citric and salicylic acids, while
flocculation of particles prevented their quantification for
sorption of oxalic acid. For citric acid adsorption, ∆H
shifted from −23.5 ± 0.57 to −27.0 ± 0.47 kJ
mol−1 and ∆S from −8.8 ± 1.54 to
−29.9 ± 0.13 J mol−1 K−1 with increasing
SSA and broader (110) diffraction peaks of goethite, thus
reducing ∆G from −20.7 ± 0.02 to
−18.0 ± 0.03 kJ mol−1. Salicylic acid adsorption
was more exothermic (∆H −40.53 ± 1.93 kJ mol−1)
and accompanied by a larger loss of entropy (∆S
−65.1 ± 1.91 J mol−1 K−1), possibly due to
chelation of its ortho hydroxyl and carboxyl groups to
single iron atoms on the mineral surface. These results
demonstrate that ITC can decipher adsorption thermodynamics
of organic ligands to mineral surfaces, but ligand-induced
flocculation can render the interpretation of results
difficult. Crystallite size and lattice defects of adsorbent
minerals influence the thermodynamics of sorption by
determining the conformation of organic molecules sorbed to
goethite surfaces.},
cin = {IBG-3},
ddc = {550},
cid = {I:(DE-Juel1)IBG-3-20101118},
pnm = {2173 - Agro-biogeosystems: controls, feedbacks and impact
(POF4-217)},
pid = {G:(DE-HGF)POF4-2173},
typ = {PUB:(DE-HGF)16},
UT = {WOS:001659114000001},
doi = {10.1111/ejss.70278},
url = {https://juser.fz-juelich.de/record/1050433},
}