The aggregate structure of iron nanoparticles is susceptible to environmental condition, such as the periodically drying-rewetting alternation in paddy soil. Understanding the influence of ferrihydrite aggregate state on the sorption behavior of phosphorus is immense importance for efficient P-management. In this study, phytate (IHP) and phosphate (Pi) sorption on ferrihydrite with two aggregation states (loose aggregate, fresh ferrihydrite, FHFO; dense aggregate, HFO) were investigated by batch experiments, synchrotron-based X-ray diffraction (XRD) and P K-edge X-ray adsorption near edge structure (XANES). The results show that both IHP and Pi have a higher sorption amount on FHFO than on HFO, and the ratio of Pi sorbed to IHP-Pi sorbed (calculated as Pi) is 0.6 on FHFO, while that is 3.27 on HFO. Due to the dense aggregate structure and the small pore structure for HFO, IHP with big molecule structure is more difficult to diffuse into the pore structure than Pi. Thus, the sorption amount of Pi on HFO is higher than that of IHP-Pi. The XRD pattern and P K-edge XANES results show that both IHP and Pi form surface precipitates on FHFO and the proportion of precipitates is 79.5±4.4% and 71.3±2.4% for IHP and Pi, respectively. In contrast, the sorption amount of Pi and IHP on HFO is lower due to its dense aggregate structure so that some sites in the pore cannot be used, and the proportion of precipitates is 38.4±1.0% for Pi and 0±1.3% for IHP. Simulation experiments with paddy soil show that under flooded conditions, the amount of short-range-ordered iron oxide increases and the ratio of Pi sorbed to IHP-Pi sorbed decreases when compared with the dry soil and re-drying soil. These are comparable to the sorption behavior of Pi and IHP on FHFO and HFO. This study indicates that drying-rewetting alternation in paddy soil changes the aggregation state of ferrihydrite, impacting the sorption behavior of organic phosphorus and inorganic phosphorus, thus causing organic phosphorus and inorganic phosphorus to have different environmental loss risks.

Phytate and phosphate sorption behavior on ferrihydrite with different aggregation states: To simulate the drying-rewetting alternation of soils

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.