Arsenite–soil humic acid binding by Isothermal Titration Calorimetry: thermodynamics and MNIS model
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Date
2022
Authors
Čokeša, Đuro
Marković, Mirjana
Potkonjak, Nebojša
Kaluđerović, Branka
Radmanović, Svjetlana
Šerbula, Snežana
Journal Title
Journal ISSN
Volume Title
Publisher
University of Belgrade, Technical Faculty in Bor
Source
Proceedings - 29th International Conference Ecological Truth and Environmental Research - EcoTER'22, 21-24 June 2022, Sokobanja, Serbia, 2022, 121-126
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Issue
Abstract
Arsenite–humic acid-binding process was investigated using the Isothermal Titration Calorimetry (ITC). The ITC data were successfully (R2=0.996-0.936) interpreted by applying the MNIS model, enabling thermodynamic parameters to be determined. The MNIS model was adjusted to the arsenite–HA binding process assuming hydrogen bonding as the dominant type of interaction in the system. Negative enthalpy change values indicated the arsenite–HAs binding as an exothermic process. Negative ΔG values (-(27.85-26.83) kJ mol-1) pointed out to spontaneous binding reaction, leading to the formation of the arsenite–HA complexes. High binding constants values ((7.57-5.02)105 M-1) clearly demonstrated pronounced binding affinity. As ΔS values (0.041-0.027) kJ mol-1 K-1) were apparently positive, but close to zero, and ΔH>ΔS, the reaction could be considered enthalpy driven. Reaction heats and H values (-(18.96-15.64) kJ mol-1) confirmed hydrogen bonds as the most ascendant interaction type in the arsenite–HA complex. Thermodynamic and reaction parameters clearly indicated that arsenite–HA complexes are formed at common soil pH values, confirming the possible influence of humic acids on increased As mobility, and its reduced bioavailability.
Description
Keywords
humic acid, arsenate, enthalpy, reaction coefficient
Citation
DOI
Scopus
ISSN
ISBN
978-86-6305-123-2
License
CC-BY-NC-ND