Iron-Tuned Depth-Dependent P Transformation on Calcium Carbonate Coprecipitates: The Impact of Fe and P Loadings

作者：Jin Liu, Junfeng Zhou, Meili Sun, Mengqiang Zhu, Yuhang Zhao, Jun Xu, Tianwen Chen, Mohsen Shakouri, Lei Zheng, Peng Sui, Yuanquan Chen, Jianjun Yang · 发表于：Environmental Science & Technology · 年份：2025 · DOI：10.1021/acs.est.5c01977 · 被引用次数：6 · 研究领域：Iron oxide chemistry and applications、Radioactive element chemistry and processing、Chemical Synthesis and Characterization

The incorporation of iron (Fe) into calcium carbonate coprecipitates (CCCs) to form Fe-incorporated CCC (CCCFe) widely occurred in CCC-enriched soils and sediments. However, the molecular mechanism of phosphate (P) immobilization on CCCFe remains largely unknown. In this study, batch experiments were conducted to investigate the immobilization mechanisms of P on CCCFe with low and high Fe loadings (CCCFe l vs CCCFe h ) using P K-edge X-ray absorption near-edge structure (XANES) spectroscopy with surface-sensitive total electron yield (P-XANES TEY ) and bulk-sensitive fluorescence yield (P-XANES FLY ) modes. Results indicated that the high Fe loading inhibited calcite formation but favored vaterite production in the CCC and enhanced its P retention capacity. Hydroxyapatite (HAP) dominated over ferrihydrite-associated P (Fe–P) in the bulk of P sorbed on the CCCFe h, but amorphous calcium phosphate (ACP) dominated over HAP for the CCC, suggesting Fe-induced transformation of the ACP to the HAP. Furthermore, the P-XANES TEY analysis indicated brushite primarily formed on the surface of the P sorbed on the CCCFe h at high P loading. Consistently, the spherical aberration-corrected scanning transmission electron microscopy analysis directly revealed ferrihydrite coating on the CCC and the presence of Ca–P and Fe–P associations. This study provides new molecular-level insights into Fe-tuned depth-dependent transformation of P on the CCC, thus benefiting P management in the CCC-enric...