Mechanistic Insights into Universal Construction of Magnetic Adsorbents via Simple Physical Comixing: Interfacial Energy Landscape and Reversible Separation

Magnetic solid-phase extraction (MSPE) has emerged as a powerful sample pretreatment technique, yet the fabrication of functional magnetic adsorbents often involves complex and time-consuming processes. While the physical comixing (PCM) method has been widely used as a simple, scalable, and cost-effective approach to prepare magnetic adsorbents for MSPE, its fundamental mechanism remains unclear. This work systematically investigates the mechanistic principles governing the PCM-based fabrication of magnetic adsorbents. Through systematic experiments and theoretical calculations, we demonstrate that the PCM-driven coretrieval is governed by a colloid coagulation mechanism rooted in Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, where van der Waals interactions dominate over electrostatic repulsion. Four types of magnetic particles (MPs) and diverse nonmagnetic adsorbents (NMAs) were investigated to validate the universality of this approach. Key factors such as MP dosage, particle size, and ionic strength were found to critically influence the retrieval efficiency. By modulating electrolyte concentrations, we achieved universal coretrieval of MPs and NMAs. Furthermore, the reversibility of coagulation was demonstrated, enabling material reuse. This work provides a generalized guideline for designing customizable magnetic adsorbents via PCM, significantly simplifying MSPE workflows while maintaining high performance, thus broadening their applicability in environmental, biomedical, and analytical chemistry.