Facile synthesis of Fe3O4@pyrogallol-formaldehyde resin@Ag core-shell nanomaterials for the catalytic degradation of contaminants.

Noble metal nanoparticles (NPs) show excellent performance in catalysis, but their strong aggregation effect can lead to a decrease in or even disappearance of their catalytic activity. In this study, Fe3O4@pyrogallol-formaldehyde resin@Ag (Fe3O4@PGFR@Ag) nanomaterials were synthesized using Fe3O4 as a magnetic core and pyrogallol-formaldehyde resin (PGFR) as a shell layer. The presence of Fe3O4 ensured rapid material recovery. At the same time, the phenolic hydroxyl group in PGFR enabled the in situ reduction of Ag+ to form embedded Ag NPs, effectively avoiding the aggregation and shedding of Ag NPs. Cetyltrimethylammonium bromide (CTAB) was used to modify the surface charge of the catalyst. Results showed that negatively charged Fe3O4@PGFR@Ag exhibited high catalytic activity, with a 90% higher catalytic rate constant for cationic dye rhodamine B (RhB) compared with Fe3O4@PGFR@Ag-CTAB. Positively charged Fe3O4@PGFR@Ag-CTAB showed high catalytic activity, with a 124% higher catalytic rate constant for the anionic dye methyl orange (MO) compared with Fe3O4@PGFR@Ag. Therefore, the matching of the charges of the catalyst and contaminants, which facilitates the adsorption of the pollutants around the catalyst, has a significant impact on the catalytic performance and should be considered in the process of pollutant treatment.