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

Iron oxide nanoparticles (Fe3O4 NPs) aqueous suspension was prepared as a novel liquid binding phase in 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 rely on the superior binding efficiency of Fe3O4 NPs toward phosphate. The adsorption mechanism of DRP on Fe3O4 NPs was illustrated through the FT-IR and XPS. Various factors on the Fe3O4-DGT performance for the sampling of DRP were taken into accounts, including initial concentration of phosphate, deployment time, pH value, ionic strength, interferences from major competitive ions and the aging effect of liquid binding phase. In the present study, the effective capacity of Fe3O4-DGT device toward DRP was approximately 105 μg of phosphate per device (15.4 μg P cm-2). Compared with phosphomolybdenum blue (PMB) method, successfully field deployments of Fe3O4-DGTs samplers in Nanfei River indicated that basic Fe3O4-DGT coupled with ICP-OES method was suitable for long-term monitoring of the DRP concentration in situ.