Magnetically separable indium doped ZnS-NiFe2O4 heterostructure photocatalyst for mineralization of acid violet 7 dye

A new magnetically separable visible light active indium doped ZnS-NiFe2O4 photocatalyst is synthesized and evaluated for the photodegradation of acid violet 7 (AV-7) dye. Characterization of nanocomposite suggests that indium doped ZnS exists in hexagonal structure, while NiFe2O4 is in the cubic structure and they are found to be in a highly dispersed state. The optical property of ZnS-NiFe2O4 composite is improved after indium doping and considerable visible light absorption is observed. Magnetic study suggests that the composite is a soft magnetic material having ferrimagnetic property, which allows easy separation of catalyst from the aqueous suspension using an external magnetic field. The photodegradation study of AV-7 using indium doped composite shows better degradation kinetics than the corresponding indium doped ZnS, NiFe2O4 and ZnS-NiFe2O4. Further, total organic carbon (TOC) analysis revealed that total mineralization of AV-7 occurs within 60 min of visible light irradiation. Electrochemical results suggest better charge-storage capacitance behaviour, improved charge carrier transport and enhanced aqueous phase stability for the composite compared to NiFe2O4 and ZnS. In addition, photocurrent and life time measurements suggest considerable separation of electron-hole pair in indium doped ZnS-NiFe2O4 nanocomposite over indium doped ZnS. Current results provide new insights in developing and designing recyclable photocatalyst. The magnetic properties of this composite eliminate the risk of secondary pollution and easy recovery of the catalyst.