The adsorption of arsenate and phosphate onto natural or synthetic layered double hydroxides (LDHs) has emerged as a promising solution to minimize the environmental effects of these compounds in soils and waters. In the present work, the adsorption of these oxyanions onto Mg-Fe LDHs in both single-ion and competitive systems was studied through wet chemistry experiments, solid-state analyses, and advanced surface complexation modeling (SCM). The Mg-Fe LDH showed a good efficiency to remove both As and P, being the pH of the system a major driver for the adsorption levels observed. Adsorption results for competitive systems showed a decrease for both oxyanions compared to the single-ion adsorption systems. The adsorption behavior is mechanistically described using two types of SCM, namely the diffusion layer model (DLM) and the charge-distribution multisite complexation model (CD-MUSIC). The later model captures better the influence of pH and ionic strength on the adsorption of arsenate and phosphate onto LDH in both single-ion and multicomponent systems. The best description of the experimental results was obtained when combining two types of surface complexes, namely monodentate inner-sphere complex at lower pH values and monodentate outer-sphere complex at higher pH values. This model approach provides more detailed information about the surface properties of LDHs, which may be beneficial for future studies dealing with LDHs as reactive phases influencing metal(loid) mobility in water or soil systems.

将砷酸盐和磷酸盐吸附到天然或合成的层状双氢氧化物（LDH）上已成为一种有前途的解决方案，可以最大限度地减少这些化合物对土壤和水中的环境影响。在目前的工作中，通过湿化学实验、固态分析和先进的表面络合模型（SCM）研究了单离子和竞争系统中这些氧阴离子在 Mg-Fe LDH 上的吸附。Mg-Fe LDH 显示出良好的去除 As 和 P 的效率，因为系统的 pH 值是观察到的吸附水平的主要驱动因素。竞争系统的吸附结果显示，与单离子吸附系统相比，两种氧阴离子均有所减少。吸附行为使用两种类型的 SCM 进行机械描述，即扩散层模型 (DLM) 和电荷分布多位点络合模型 (CD-MUSIC)。后一个模型更好地捕捉了单离子和多组分系统中 pH 值和离子强度对 LDH 吸附砷酸盐和磷酸盐的影响。当结合两种类型的表面复合物时获得了对实验结果的最好描述，即较低pH值下的单齿内球复合物和较高pH值下的单齿外球复合物。该模型方法提供了有关 LDH 表面特性的更详细信息，这可能有利于未来研究将 LDH 作为影响水或土壤系统中金属（类）迁移性的反应相。