Insight into the interaction mechanism of iron ions with soil humic acids. The effect of the pH and chemical properties of humic acids
PBN-AR
Instytucja
Instytut Agrofizyki im. Bohdana Dobrzańskiego Polskiej Akademii Nauk
Informacje podstawowe
Główny język publikacji
angielski
Czasopismo
JOURNAL OF ENVIRONMENTAL MANAGEMENT
ISSN
0301-4797
EISSN
Wydawca
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI
URL
Rok publikacji
2019
Numer zeszytu
Strony od-do
367-374
Numer tomu
245
Identyfikator DOI
Liczba arkuszy
Autorzy
Pozostali autorzy
+ 2
Autorzy przekładu
(liczba autorów przekładu: 0)
Słowa kluczowe
angielski
Iron complexation
Complexes of humic acids
Fluorescence spectroscopy
Coagulation of humic acids
Soluble complexes of humic acids
Streszczenia
Język
angielski
Treść
The main aim of this work was to study the mechanisms of interaction between iron(II) ions and humic acids as a function of pH, iron concentration and various humic acids chemical properties, including the degree of humification, elemental composition, aromaticity and content of acidic functional groups. The results indicated that iron was bound by humic acids at pH 7 in amounts ∼2 times higher than at pH 5 (averaged capacities: 117 and 57 cmol/kg, respectively). Iron binding at pH 7 increased with increasing the total carboxylic and phenolic groups content and the degree of humification of humic acids (R-coefficients: 0.99 and 0.95, respectively). The stability of humic acid-iron complexes at pH 7 were only slightly lower than at pH 5 due to iron hydroxides formed at pH > 5 (averaged stability constants: 5.18 and 5.26, respectively). Iron coordination mode varied depending on pH: at pH 5, the bidentate (chelate) mode dominated, whereas at pH 7 the bridging mode appeared prevalent. The total amount of bound iron was much smaller than the content of the carboxylic and phenolic groups in humic acids, on average by ∼80 (pH 7) and ∼90.1% (pH 5) indicating the occurrence of steric effects in humic acid structure i.e. the reduction of the complexation capacity of free functional groups by adjacent groups occupied by iron and/or the formation of intramolecular aggregates with iron hindering the access of further metal ions. At pH 5 the complexes were soluble in the iron concentration range positively correlated to carboxylic and phenolic groups content, showing the protective nature of negatively charged functional groups on the stability of the solution. At this pH, the destabilization of the system was governed by the neutralization of humic acid charged structures by metal cations and the compression of the double electric layer. At pH 7 the stability of the humic acid-iron solution was largely determined by the form of iron, mainly by the precipitation of metal hydroxides acting as a flocculant destabilizing the solution by co-precipitation of humic acid-iron complexes.
Inne
System-identifier
PX-5cf4f79cd5debaf09943f351
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