Graphene oxide wrapped magnetic nanoparticle composites induced by SiO_(2) coating with excellent regenerability

Graphene oxide(GO)wrapped Fe_(3)O_(4) nanoparticles(NPs)were prepared by coating the Fe_(3)O_(4) NPs with a SiO_(2) layer,and then modifying by amino groups,which interact with the GO nanosheets to form covalent bonding.The SiO_(2) coating layer plays a key role in integrating the magnetic nanoparticles with the GO nanosheets.The effect of the amount of SiO_(2) on the morphology,structure,adsorption,and regenerability of the composites was studied in detail.An appropriate SiO_(2) layer can effectively induce the GO nanosheets to completely wrap the Fe_(3)O_(4) NPs,forming a core-shell Fe_(3)O_(4)@SiO_(2)@GO composite where Fe_(3)O_(4)@SiO_(2) NPs are firmly encapsulated by GO nanosheets.The optimized Fe_(3)O_(4)@SiO_(2)@GO sample exhibits a high saturated adsorption capacity of 253 mg·g^(-1) Pb(Ⅱ)cations from wastewater,and the adsorption process is well fitted by Langmuir adsorption model.Notably,the composite displays excellent regeneration,maintaining a~90%adsorption capacity for five cycles,while other samples decrease their adsorption capacity rapidly.This work provides a theoretical guidance to improve the regeneration of the GO-based adsorbents.