Novel Fe3O4 nanoparticles-based DGT device for dissolved reactive phosphate measurement

Abstract

An aqueous suspension of iron oxide nanoparticles (Fe₃O₄ NPs) was prepared as a novel liquid binding phase in a diffusive gradients in thin-films (DGT) device (Fe₃O₄-DGT) combined with inductively coupled plasma optical emission spectrophotometry (ICP-OES) for the sampling measurement of dissolved reactive phosphate (DRP) in water. The DGT uptake of DRP increased linearly with deployment time, relying on the superior binding efficiency of Fe₃O₄ NPs toward phosphate. The adsorption mechanism of DRP on Fe₃O₄ NPs was illustrated through FT-IR and XPS. Various factors in the Fe₃O₄-DGT performance for the sampling of DRP were taken into account, including the initial concentration of phosphate, deployment time, pH value, ionic strength, interference from major competitor ions and the aging effect of the liquid binding phase. In the present study, the effective capacity of the Fe₃O₄-DGT device toward DRP was approximately 105 μg of phosphate per device (15.4 μg P cm⁻²). Compared with the phosphomolybdenum blue (PMB) method, successful field deployments of Fe₃O₄-DGTs samplers in the Nanfei River indicated that a basic Fe₃O₄-DGT coupled with the ICP-OES method was suitable for long-term monitoring of the DRP concentration in situ.