Ferrihydrite-organo composites are a suitable analog for predicting Cd(II)-As(V) coexistence behaviors at the soil solid-liquid interfaces

Huihui Du; Ning Nie; Wenkai Rao; Lei Lu; Ming Lei; Boqing Tie

doi:10.1016/j.envpol.2021.118040

Ferrihydrite-organo composites are a suitable analog for predicting Cd(II)-As(V) coexistence behaviors at the soil solid-liquid interfaces

Environ Pollut. 2021 Dec 1:290:118040. doi: 10.1016/j.envpol.2021.118040. Epub 2021 Aug 24.

Authors

Huihui Du¹, Ning Nie², Wenkai Rao², Lei Lu², Ming Lei², Boqing Tie²

Affiliations

¹ College of Resources and Environment, Hunan Agricultural University, Changsha, 410128, People's Republic of China. Electronic address: duhuihui@hunau.edu.cn.
² College of Resources and Environment, Hunan Agricultural University, Changsha, 410128, People's Republic of China.

PMID: 34454194
DOI: 10.1016/j.envpol.2021.118040

Abstract

Organomineral assemblages are building units of soil micro-aggregates and exert their essential roles in immobilizing toxic elements. Currently, our knowledge of the adsorption and partitioning behaviors of coexisting Cd-As onto organomineral composites is limited. Herein, we carefully studied Cd-As cosorption onto ferrihydrite organomineral composites made with either living or non-living organics, i.e., bacteria (Delftia sp.) or humic acid (HA), using batch adsorption and various spectroscopies. Batch results show that As(V) only enhances Cd(II) sorption on pure Fh at pH < 6 but cannot promote Cd(II) sorption to Fh-organo composites. However, Cd(II) noticeably promotes As(V) sorption at pH>~5-6. Synchrotron micro X-ray fluorescence indicates that Cd(II) adsorbs predominately to the bacterial fraction (Cd versus P, r = 0.924), whereas As(V) binds mainly to the Fh fraction (As versus Fe, r = 0.844) of the Fh-bacteria composite. On Fh-HA composite, however, Cd(II) and As(V) are both primarily sorbed by the Fh fraction (Cd/As versus P, r > 0.8), based on the scanning transmission electron microscopy-energy disperse spectroscopy analyses. Elemental distribution characterization also manifests the co-localization of Cd(II) and As(V) within the organomineral composite, particular in Fh-HA composite (Cd versus As, r = 0.8), which is further identified as the Fh-As-Cd ternary complex based on the observations (higher frequencies at ~753-761 cm^-1) of attenuated total reflection Fourier-transform infrared spectroscopy. Moreover, this ternary interaction is more pronounced in Fh-HA than in Fh-bacteria. In summary, our results suggest that Cd-As coadsorption behaviors on Fh-organo composites are different from those on pure minerals, and the presence of bacteria/HA can significantly affect metal (loid)s speciation, distribution, and ternary interaction. Therefore organomineral composites are a more suitable analog than pure mineral phases to predict the mobility and fate of Cd-As in natural environments.

Keywords: Arsenic; Bacteria; Cadmium; Coadsorption; Ferrihydrite; Humic acid.

MeSH terms

Adsorption
Cadmium*
Ferric Compounds
Humic Substances
Soil*

Substances

Ferric Compounds
Humic Substances
Soil
Cadmium
ferric oxyhydroxide