Publication detail

Role of polar and apolar moieties in water adsorption by humic acids under arid conditions

Fashina, Bidemi Novak, Frantisek Kucerik, Jiri

Original Title

Type

journal article in Web of Science

Language

English

Original Abstract

In arid soils, humic acids (HAs) are used as amendments to improve water uptake from the atmosphere. This method of harvesting water involves several steps depending on the relative humidity (RH). At low RH, water is adsorbed solely on primary sorption sites such as polar groups. As RH increases, more water is adsorbed on polar groups forming secondary sorption sites, which grow as the RH increases. As a result, the neighboring sorption sites can connect to form water molecule bridges (WaMBs). The WaMBs are responsible for the transport of water in the form of clusters into hydrophobic pores resulting in an increase in water content in organic matter (OM), swelling of OM and formation of phase water. HA being a complex mixture complicates the understanding of the relationship between the proportion of polar groups and properties of water. The understanding of these relationships can guide the design of humic-based amendments applicable in arid systems. To address this issue, seven HAs were characterized by nuclear magnetic resonance followed by the investigation of the properties of water (water content, strength of WaMBs and strength of water binding) on the HAs. Results showed that the content of polar groups positively correlated with the amount of water adsorbed by HA and the stability of WaMBs. It was found that presumably apolar moieties such as aromatics and phenols increased the binding energy of water to HA thereby appearing to be responsible for preventing the desiccation. In addition, between 44 and 76% RH, the WaMB stability positively correlated with O-alkyl and peptides moieties. Therefore, both polar and apolar domains influence water properties depending on RH. We conclude that this synergism is an advantage in systems composed of hydrophobic and hydrophilic molecules held together by weak interactions providing high flexibility to the system under arid conditions.

Keywords

Humic acid; Hydration; Desiccation; C-13 NMR; DSC; Water molecule bridges

Authors

Fashina, Bidemi; Novak, Frantisek; Kucerik, Jiri

Released

22. 9. 2021

Publisher

SPRINGER

Location

DORDRECHT

ISBN

1388-6150

Periodical

Journal of Thermal Analysis and Calorimetry

Year of study

145

Number

State

Hungary

Pages from

3031

Pages to

3039

Pages count

URL

https://link.springer.com/article/10.1007/s10973-020-09964-6

BibTex

@article{BUT170303,
  author="Fashina, Bidemi and Novak, Frantisek and Kucerik, Jiri",
  title="Role of polar and apolar moieties in water adsorption by humic acids under arid conditions",
  journal="Journal of Thermal Analysis and Calorimetry",
  year="2021",
  volume="145",
  number="1",
  pages="3031--3039",
  doi="10.1007/s10973-020-09964-6",
  issn="1388-6150",
  url="https://link.springer.com/article/10.1007/s10973-020-09964-6"
}