Fate of iodate on adsorbed/coprecipitated ferrihydrite-organic matter complexes

IF 5 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Geochimica et Cosmochimica Acta Pub Date : 2025-09-24 DOI:10.1016/j.gca.2025.09.034

Shilin Zhao , Junxia Li , Xianjun Xie , Yanxin Wang

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引用次数: 0

Abstract

The mobility of iodate in soils and sediments is significantly related to the states of iron minerals and natural organic matter (NOM). However, the influences of associated processes (adsorption versus coprecipitation) between iron minerals and NOM on the fate of iodate remain unclear. In this study, the iodate behavior on adsorbed or coprecipitated ferrihydrite (HFO)-humic acid (HA) complexes was investigated through batch experiments under varying conditions (pH, ionic strength, and co-existing anions). Mechanisms insights were obtained using attenuated total reflectance Fourier transform infrared spectroscopy and density functional theory. The results show that compared to pure HFO, iodate adsorption decreases in the presence of adsorbed or coprecipitated HA, due to the reduced inner-sphere adsorption sites occupied by HA. The reduction degree in iodate adsorption is greater for coprecipitated HFO-HA (HFO-cHA) complexes than for adsorbed HFO-HA (HFO-aHA) complexes. The adsorbed iodate is more prone to combine with adsorbed HA to form organic iodine compared to coprecipitated HA. With increasing pH and co-existing anions, the decreasing in iodate adsorption was observed in pure HFO and HFO-aHA/HFO-cHA complexes, but interestingly, the decreased degree in iodate adsorption follows the order of HFO-cHA complexes > pure HFO > HFO-aHA complexes. The dominant outer-sphere species of iodate on the complexes leads to the more sensitive surface of HFO-cHA complexes, and as the coprecipitated HA increases, the percentage of inner-sphere species of iodate was decreasing. Compared to the coprecipitated HA, the adsorbed HA can be more easily dissolved as the pH rising or as co-existing ions replace HA on the adsorption sites. Iodate can sorb and occupy sites vacated by HA desorption. The findings of this study provide new insights to understand the mobilization of soil/sediment iodate, which plays a vital role in the cycling of iodine in nature.

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碘酸盐在吸附/共沉淀的水合铁-有机物络合物上的归宿

土壤和沉积物中碘酸盐的迁移与铁矿物和天然有机质（NOM）的状态密切相关。然而，铁矿物与NOM之间的相关过程（吸附与共沉淀）对碘酸盐命运的影响尚不清楚。在本研究中，通过批量实验研究了不同条件（pH、离子强度和共存阴离子）下，碘酸盐在吸附或共沉淀的水合铁(HFO)-腐植酸（HA）配合物上的行为。利用衰减全反射傅立叶变换红外光谱和密度泛函理论获得机理见解。结果表明，与纯HFO相比，吸附或共沉淀的HA存在时，碘酸盐的吸附减少，这是由于HA占用的球内吸附位减少。共沉淀的HFO-HA （HFO-cHA）配合物的碘酸吸附还原程度大于吸附的HFO-HA （HFO-aHA）配合物。与共沉淀的透明质酸相比，吸附的碘酸盐更容易与吸附的透明质酸结合形成有机碘。随着pH值的增加和阴离子的共存，纯HFO和HFO- aha /HFO- cha配合物对碘酸盐的吸附均呈下降趋势，但有趣的是，纯HFO和HFO- aha配合物对碘酸盐吸附的下降程度依次为：HFO- cha配合物→gt→gt→HFO- aha配合物。配合物上的优势外球种碘酸盐导致HFO-cHA配合物的表面更敏感，随着共沉淀HA的增加，内球种碘酸盐的百分比逐渐降低。与共沉淀的HA相比，吸附的HA随着pH的升高或共存离子取代吸附位点上的HA而更容易溶解。碘酸盐可以吸附并占据HA解吸空出的位置。本研究结果为了解土壤/沉积物中碘的动员提供了新的见解，这在自然界中碘的循环中起着至关重要的作用。

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来源期刊

Geochimica et Cosmochimica Acta 地学-地球化学与地球物理

CiteScore

9.60

自引率

14.00%

发文量

437

审稿时长

6 months

期刊介绍： Geochimica et Cosmochimica Acta publishes research papers in a wide range of subjects in terrestrial geochemistry, meteoritics, and planetary geochemistry. The scope of the journal includes: 1). Physical chemistry of gases, aqueous solutions, glasses, and crystalline solids 2). Igneous and metamorphic petrology 3). Chemical processes in the atmosphere, hydrosphere, biosphere, and lithosphere of the Earth 4). Organic geochemistry 5). Isotope geochemistry 6). Meteoritics and meteorite impacts 7). Lunar science; and 8). Planetary geochemistry.