Remarkable catalytic degradation of malachite green by zinc supported on hydroxyapatite encapsulated magnesium ferrite (Zn/HAP/MgFe2O4) magnetic novel nanocomposite

The present study reports the synthesis, characterization and catalytic activity of zinc/hydroxyapatite/magnesium ferrite (Zn/HAP/MgFe2O4) as a novel nanocomposite. The nanocomposite was characterized by powder XRD, FTIR, SEM-EDX, TEM, VSM and XPS. The presence of Zn(0) and Zn(II) in the Zn/HAP/MgFe2O4 was confirmed by XPS studies. The composite was applied as a heterogeneous catalyst for the degradation of malachite green in the presence as well as in the absence of H2O2. In the presence of the oxidant H2O2, 100% degradation was achieved in just 2 min while in the absence of H2O2 it took almost 2 h for complete degradation. The enhancement in the rate of the degradation of the dye in the presence of H2O2 was due to fenton and fenton-like mechanism involving the formation of reactive oxygen species, such as hydroxyl and perhydroxyl radicals (HO center dot and HOO center dot). The Zn/HAP/MgFe2O4 showed high stability and because of its super-paramagnetic behaviour it could be easily separated by external magnet from the reaction mixture. Kinetic studies showed that the degradation of the dye follows first order.