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Transport of Cd²⁺ through saturated porous media : Insight into the effects of low-molecular-weight organic acids

Title data

Zhang, Haojing ; Lu, Taotao ; Shang, Zhongbo ; Li, Yanxiang ; He, Jianying ; Liu, Shanhu ; Li, Deliang ; Zhou, Yanmei ; Qi, Zhichong:
Transport of Cd²⁺ through saturated porous media : Insight into the effects of low-molecular-weight organic acids.
In: Water Research. Vol. 168 (2020) . - No. 115182.
ISSN 0043-1354
DOI: https://doi.org/10.1016/j.watres.2019.115182

Abstract in another language

Low-molecular-weight organic acids (LMWOAs) are ubiquitous in the aquatic environment and consequently may affect the heavy metal transport in aquifer systems. In this study, the influences of LMWOAs on the transport of Cd2+ under different pH conditions in saturated porous media were evaluated. For this, three LMWOAs such as acetic acid, tartaric acid, and citric acid were employed. A two-site nonequilibrium transport model was applied to simulate the transport data. Under acidic conditions (pH 5.0), the results indicated that LMWOAs inhibited the transport of Cd2+ even at the low concentrations of organic acids (i.e., 0.05 and 0.1 mM). The inhibition effects might be attributed to the complexation role of the sand surface-bound organic acids and also electrostatic interaction. Meanwhile, the inhibition effects of LMWOAs on Cd2+ transport in the following order of citric acid > tartaric acid > acetic acid, which was also in agreement with the decreasing complex stability constants between Cd2+ and LMWOAs. This order may be dependent on their molecular structures (i.e., amount and type of functional groups) and complexing strength. Interestingly, when the LMWOA concentrations 0.5 mM, tartaric acid and citric acid still inhibited Cd2+ transport, while acetic acid slightly enhanced the Cd2+ mobility due to its weaker complexing strength. However, under neutral conditions (pH 7.0), LMWOAs generally enhanced the transport of Cd2+. The transport-enhancement of LMWOAs was ascribed to the formation of stable aqueous non-adsorbing Cd–organic acid complexes. In addition, citric acid could obviously inhibit the transport of Cd2+ under competitive transport conditions (i.e., with competing cations), which is mainly due to different complex affinities of citric acid to Pb2+ and Cd2+. These findings demonstrate that LMWOAs may inhibit or facilitate Cd2+ transport under different environmental conditions. Thus, environmental assessment concerning the transport of heavy metals should consider the roles of organic acids.

Further data

Item Type: Article in a journal
Refereed: Yes
Keywords: Cd2+; LMWOAs; Transport model; Porous media
Institutions of the University: Research Institutions
Research Institutions > Research Centres
Research Institutions > Research Centres > Bayreuth Center of Ecology and Environmental Research- BayCEER
Graduate Schools
Graduate Schools > Bayreuth Graduate School of Mathematical and Natural Sciences (BayNAT)
Result of work at the UBT: Yes
DDC Subjects: 500 Science > 550 Earth sciences, geology
Date Deposited: 13 Jan 2022 13:23
Last Modified: 13 Jan 2022 13:23
URI: https://eref.uni-bayreuth.de/id/eprint/68358