Synthesis and Application of Fe₃O₄-Modified Nano-Perlite as a Dispersive Sorbent for Co(II) Ion Preconcentration

In this study, acid-treated lamellar perlite (ALP) and Fe₃O₄-decorated acid-treated lamellar perlite (Fe₃O₄-ALP) were synthesized and applied as sorbents for dispersive solid-phase extraction coupled with flame atomic absorption spectrometry (DSPE-FAAS) for trace Co-(II) determination. The synthesized materials were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX), and BET surface area analysis. Fe₃O₄ decoration onto the lamellar aluminosilicate framework of perlite yielded a mesoporous composite with enhanced surface heterogeneity and convenient magnetic recoverability, facilitating rapid phase separation in the DSPE workflow. Comparative experiments demonstrated that Fe₃O₄-ALP exhibited substantially higher extraction efficiency than ALP, confirming the beneficial role of Fe₃O₄ decoration on Co-(II) uptake. Under optimized analytical conditions, the DSPE-FAAS method showed a linear response for Co-(II) in the range of 5-250 ng mL^-1 with a correlation coefficient exceeding 0.999. The limits of detection and quantification were determined as 0.626 ng mL^-1 and 2.086 ng mL^-1, respectively, corresponding to a 122-fold LOD improvement factor relative to direct FAAS analysis. The method exhibited satisfactory precision, with relative standard deviations ranging from 4.4% to 8.1%. The applicability of the developed DSPE-FAAS method was validated by analyzing groundwater and rock leachate samples, which yielded recoveries in the range of 84.4-110.4%, confirming method robustness under geochemically complex matrix conditions. Overall, Fe₃O₄-ALP represents a cost-effective and analytically efficient sorbent for trace Co-(II) determination in environmental samples.