Investigation of cadmium adsorption-transport coupling in soil-mineral systems: Integrating batch adsorption and...

This study systematically investigates the adsorption and transport characteristics of cadmium (Cd) in sandy soils and their mineral components, establishing quantitative relationships between single-component minerals and heterogeneous soil systems. The application of a component additivity model to integrated batch and column experiments successfully reveals a quantitative relationship between the adsorption characteristics of single minerals (illite, kaolinite, calcite, feldspar, quartz) and the heterogeneous soil system. A key novel finding is the effective prediction of composite soil adsorption behavior using data from its individual components, a principle with potential applicability to other pollutants such as heavy metals and radionuclides. Results demonstrated a consistent adsorption hierarchy: illite > kaolinite > calcite > sandy soil > feldspar > quartz. Column experiments showed 9-49 % reduced K_d values across all materials compared to batch systems, mainly due to limited contact time, decreased interfacial area, and clay mineral agglomeration. Batch experiments revealed a strong linear correlation between bulk K_d values and mineral components. This relationship confirms that single-component adsorption characteristics can effectively predict complex media adsorption behavior. The observed Cd transport behaviors introduce certain prediction uncertainties in modeling applications. However, these experimental results yield valuable insights for translating laboratory-derived adsorption data to real-world scenarios, particularly highlighting the necessity of accounting for adsorption behavior variations in environmental risk evaluations and remediation planning.