Coupled Kinetics of Ferrihydrite Transformation and As(V) Sequestration under the Effect of Humic Acids: A Mechanistic and Quantitative Study

Journal Article · Tue Oct 16 00:00:00 EDT 2018 · Environmental Science & Technology

DOI:https://doi.org/10.1021/acs.est.8b03492· OSTI ID:1513256

Hu, Shiwen ^[1]; Lu, Yang ^[1]; Peng, Lanfang ^[1]; Wang, Pei ^[1]; Zhu, Mengqiang ^[2]; Dohnalkova, Alice ^[3]; Chen, Hong ^[4]; Lin, Zhang ^[1]; Shi, Zhenqing ^[1]

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1. South China University of Technology
2. VISITORS
3. BATTELLE (PACIFIC NW LAB)
4. SLAC National Accelerator Laboratory

In natural environments, kinetics of As(V) sequestration/release is usually coupled with the dynamic iron mineral transformation, which is further influenced by the presence of the natural organic matter (NOM). However, both quantitative and mechanistic understanding of this process is still lacking. In this study, we investigated the effect of humic acids (HA), a major component of NOM, on the coupled kinetics of ferrihydrite transformation into hematite/goethite and sequestration of As(V) in iron minerals. Time-resolved As(V) and HA interactions with iron minerals were studied in stirred-flow kinetic experiments, using aberration-corrected scanning transmission electron microscopy (STEM), and X-ray adsorption spectroscopy. Based on the experimental results, we developed a mechanistic kinetics model for As(V) reactions with iron minerals with varying iron mineral compositions and solution chemistry. Our results showed that HA slowed ferrihydrite transformation and the rates of As(V) speciation changes within iron minerals, while HA did not incorporate into iron minerals. Our kinetics model is able to account for the variations of iron mineral compositions, solution chemistry, and As(V) speciation, which has significant environmental implications on predicting the As(V) behavior in the environment.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1513256
• Report Number(s): PNNL-SA-138364
• Journal Information: Environmental Science & Technology, Vol. 52, Issue 20
• Country of Publication: United States
• Language: English

Related Subjects

ferrihydrite
humic acid