Facile synthesis of novel hierarchical core@shell structural magnetic nanovehicle Fe3O4@ZnAlCe-MoO4-LDHs for carbon steel protection

A novel dual-stimuli-responsive inhibitor nanovehicle Fe3O4@ZnAlCe-MoO4-LDHs was synthesized via a facile double-drop co-precipitation method. The obtained Fe3O4@ZnAlCe-MoO4-LDHs presents well-defined hierarchical core-shell structure with MoO42- corrosion inhibitor intercalated lamellar ZnAlCe-LDHs nanocrystals of similar to 30 nm assembling closely to Fe3O4 microspheres surface, possessing moderate inhibitor loading of 9.72% and strong superparamagnetism. The release results reveal that in the same NaCl solution, the rel(eq) (equilibrium release amount, 49.1%) and t(0.5) (the time for release fraction of 50%, 4.5 h) were delayed much by magnetic field relative to non-magnetic field case (51.6%, 2.5 h). And the releq decreased with magnetic field strength, accompanied by the prolongation of t(0.5), up to 6 h under a 1350 Gs magnet. Similarly, with keeping the magnetic field unvaried, the decline of NaCl solution concentration led to lower rel(eq) and longer t(0.5). The kinetic fittings displayed that for all cases, the release process is inclusive of interlayer diffusion between LDHs layers (path I), interparticle diffusion among stacked LDHs crystals (path II) and diffusion between magnetic nanoparticles (path III). Compared to non-magnetic field, diffusion difficulties of path III was greatly enhanced under magnetic field. While for low-Cl- concentration system, the path I were limited effectively. Thus these two stimulus response factors can be used to regulate release behavior. Meanwhile, the protection efficiency of the nanovehicle for Q235 steel is higher than 88% because of the formation of inhibition film (ferrous or iron molybdate and hydroxide of zinc and cerium) on Q235 surface and the reduction of Cl- concentration in the solution via ion exchange. Moreover, the nanovehicle, presenting outstanding structural and magnetic stabilities, can be regenerated by a series of experiments, owning appreciable recycling performance and good anticorrosion activity in six recycles.