Purpose

The main aim of this work was to determine the efficiency and mechanism of iron (Fe)-modified calcite (FMCA) capping for preventing the release of phosphorus (P) from sediments.

Methods

The performance of phosphate removal by FMCAs with different iron loading amounts was investigated using batch experiments, the mechanism for the phosphate removal by FMCA was explored by X-ray photoelectron spectroscopy, and the effect of FMCA capping on P mobilization in sediments at various depths was studied using high-resolution dialysis and diffusive gradient in thin films (DGT).

Results

FMCA possessed better phosphate adsorption ability for aqueous phosphate than raw calcite, and the phosphate removal efficiency of FMCA increased with its loading amount of Fe. The replacement of Fe-bound hydroxyl groups with phosphate anions to the inner-sphere surface complexes and the precipitation of calcium phosphate were vital to the sorption of phosphate onto FMCA. FMCA capping could effectively inhibit the release of soluble reactive P (SRP) and labile P monitored by DGT (DGT-P) from sediment to the overlying water. The decrease of DGT-P and pore water SRP in the top sediment layer is very important for the control of sediment-P release into the overlying water. FMCA capping caused reductions of the concentrations of Fe²⁺ and labile Fe monitored by DGT in the overlying water and the top sediment, suggesting a low risk of Fe releasing from the FMCA capping layer.

Conclusion

Iron-modified calcite has the potential to be an active capping material to suppress sedimentary P release.

中文翻译：

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铁改性方解石封盖拦截沉积磷释放

目的

这项工作的主要目的是确定铁（Fe）改性方解石（FMCA）封盖的效率和机理，以防止磷（P）从沉积物中释放出来。

方法

通过分批实验研究了不同铁负载量的FMCA去除磷酸盐的性能，通过X射线光电子能谱研究了FMCA去除磷酸盐的机理，FMCA封顶对不同深度沉积物中P迁移的影响是使用高分辨率透析和扩散梯度薄膜（DGT）进行了研究。

结果

FMCA对磷酸盐水溶液的磷酸盐吸附能力要比粗方解石好，FMCA的磷酸盐去除效率随Fe的添加量而增加。Fe-结合的羟基被磷酸根阴离子置换为内球表面配合物，磷酸钙的沉淀对于将磷酸根吸附到FMCA上至关重要。FMCA封顶可以有效抑制DGT（DGT-P）从沉积物到上层水的可溶性反应性P（SRP）和不稳定P的释放。沉积物上层中DGT-P和孔隙水SRP的减少对于控制沉积物中P释放到上层水中非常重要。FMCA封顶导致Fe ²⁺浓度降低 DGT监测上覆水和顶部沉积物中不稳定的铁，表明从FMCA覆盖层释放铁的风险较低。

结论

铁改性的方解石有可能成为抑制磷释放的有效覆盖材料。