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Two-stage multi-fraction first-order kinetic modeling for soil Cd extraction by EDTA
Hang Wei1, Weihua Zhang2, Luwen Zhuang3
1School of Environmental Science and Engineering, Sun Yat-sen University, Guangzhou, 510275, China; Soil Remediation Research Center of Sun Yat-sen University and Zhisheng Environmental Protection Group Ltd., Guangzhou, 510275, China.
Chemosphere
|September 19, 2018
Summary
A new kinetic model accurately predicts cadmium (Cd) extraction from contaminated soils using ethylenediaminetetraacetic acid (EDTA). The model highlights how EDTA dosage and soil properties influence Cd removal efficiency.
Area of Science:
- Environmental Chemistry
- Soil Science
- Chemical Engineering
Background:
- Cadmium (Cd) contamination in soils poses significant environmental and health risks.
- Effective remediation strategies are crucial for mitigating Cd pollution.
- Understanding the kinetics of Cd extraction is vital for optimizing remediation processes.
Purpose of the Study:
- To develop and validate a two-stage, multi-fraction, first-order kinetic model for Cd extraction from contaminated soils.
- To investigate the influence of ethylenediaminetetraacetic acid (EDTA) dosage, Cd species distribution, and washing time on Cd extraction efficiency.
- To elucidate the distinct extraction mechanisms and behaviors of different Cd species.
Main Methods:
- Establishment of a two-stage, multi-fraction, first-order kinetic model.
- Incorporation of Cd species distribution, chelate dosage (EDTA), and washing time into the model.
- Simulation of experimental Cd extraction data from various contaminated soils.
- Validation of the model using normalized root-mean-square error, index of agreement, and modeling efficiency.
Main Results:
- The model accurately simulated experimental Cd extraction data across different soil types.
- Increased EDTA dosage generally enhanced Cd extraction efficiency and accelerated the formation of EDTA-Cd complexes.
- Cd species associated with Fe/Mn hydro(oxides) (FeMnOx) showed complex extraction behavior, influenced by EDTA dosage and dissolution rates.
- Exchangeable and carbonate-bound Cd (EXCH+CARB) removal was initially unaffected by EDTA dosage but increased significantly at extreme dosages due to the detachment of destabilized Cd species.
Conclusions:
- The developed kinetic model demonstrates excellent validity for predicting Cd extraction in various soil matrices.
- EDTA dosage is a critical factor controlling Cd extraction efficiency, with higher dosages promoting faster and more complete removal.
- Different Cd species exhibit distinct extraction dynamics, necessitating a nuanced understanding for effective soil remediation.
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