Journal
JOURNAL OF HYDROLOGY
Volume 598, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.jhydrol.2021.126228
Keywords
Hexavalent chromium; Adsorption; Model selection criteria; Non-equilibrium transport
Funding
- National Key Research and Development Program of China [2018YFC1800900]
- Program for Jilin University (JLU) Science and Technology Innovative Research Team [2019TD-35]
- National Natural Science Foundation of China [41772253, 41972249, 51774136]
- Natural Science Foundation of Hebei Province of China [D2017508099]
- Program of Education Department of Hebei Province [QN219320]
- Engineering Research Center of Geothermal Resources Development Technology and Equipment, Ministry of Education, China
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This study investigates the adsorption mechanisms of Cr(VI) in sediments with different properties and identifies grain sizes and clay mineral contents as the controlling factors for adsorption capacity. The results suggest that irreversible chemical adsorption is the dominant mechanism for Cr(VI) adsorption onto sediment samples.
Transport of hexavalent chromium, Cr (VI), in groundwater is largely influenced by adsorption and desorption processes. Sediment types can result in substantial difference in adsorption mechanisms. The goal of this work is to explore the adsorption mechanism of Cr (VI) within sediments with different properties and to identify the controlling factors. In this paper, Cr (VI) adsorption onto six different natural unconsolidated sediments (two loamy sands, two sandy loams, one loam, and one silty loam clay) collected from a typical fluvial aquifer in Qiqihar, China, was assessed with batch and column experiments. Equilibrium adsorption capacities and kinetic rates were quantified with batch experiments. Potential controlling effects of pH, solid/solution ratio, grain size, and clay mineral content on adsorption capacities were also analyzed. Adsorption kinetics was evaluated with Elovich, pseudo first- and second-order models, and equilibrium properties were assessed with Henry, Freundlich, and Langmuir isotherms. Model adequacy was discriminated with selection criteria of Akaike information criterion (AIC), modified Akaike information criterion (AICc), Bayesian information criterion (BIC), and Hannan information criterion (HIC). Adsorption and desorption of Cr (VI) onto and from the collected sediment samples under flow conditions were investigated with column experiments. Key results suggest that irreversible chemical adsorption is the dominant mechanism for Cr (VI) adsorption onto the sediment samples. Grain sizes and clay mineral contents are the controlling factors for adsorption capacity. Fine-grained sediments with high clay mineral contents present the highest Cr (VI) adsorption capacity. Chromium (VI) presents high retention on loam and silty loam clay, and high mobility on loamy sand. Results from this study may provide important insight for understanding the transport behaviors of Cr (VI) in shallow aquifers.
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