Insight into the mechanism of phosphate and cadmium co-transport in natural soils

Phosphate is ubiquitous in the environment and can affect the transport of heavy metals in the subsurface systems. In this study, column experiments were conducted to systematically evaluate the effects of phosphate on the transport of Cd in natural soils (RS, BS) under different ionic strength (IS)...

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Bibliographic Details
Published in:Journal of hazardous materials 2022-08, Vol.435, p.129095-129095, Article 129095
Main Authors: Wu, Xiaoli, Gao, Bin, Lyu, Xueyan, Zeng, Xiankui, Wu, Jichun, Sun, Yuanyuan
Format: Article
Language:English
Subjects:
Phosphate
Soil properties
Transport
XANES
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Summary:Phosphate is ubiquitous in the environment and can affect the transport of heavy metals in the subsurface systems. In this study, column experiments were conducted to systematically evaluate the effects of phosphate on the transport of Cd in natural soils (RS, BS) under different ionic strength (IS) conditions. The presence of phosphate significantly retarded the transport of Cd in the soils. The extent of retardation was closely associated with phosphate concentrations, IS and soil properties. Increasing phosphate adsorption induced more negative surface charges on soils, thereby contributing to greater retention of Cd through electrostatic attraction. In contrast, higher IS not only promoted mobility of Cd, but also reduced the retardation effect of phosphate on Cd transport in soils. Moreover, higher Fe/Al oxides contents in RS exhibited a more pronounced effect of phosphate on Cd retardation. Our results indicated that electrostatic interaction was the predominant mechanism controlling co-transport of Cd with phosphate, but no ternary surface complexes was observed in the Cd LIII-edge XANES spectra. Our findings highlight the critical role of phosphate in retarding Cd transport in natural soils, which should be considered in assessing environmental risks of heavy metals in the subsurface. [Display omitted] •Phosphate significantly inhibited the transport of Cd in natural soils.•Phosphate inhibition effect was more pronounced at higher Fe/Al oxides contents.•Electrostatic interaction dominated the co-transport of Cd with phosphate.•Ternary surface complexes were not observed during co-transport by XANES spectra.
ISSN:0304-3894
1873-3336
DOI:10.1016/j.jhazmat.2022.129095