A novel tertiary magnetic ZnFe2O4/BiOBr/rGO nanocomposite catalyst for photodegrading organic contaminants by visible light

A novel tertiary magnetic ZnFe2O4/BiOBr/rGO visible light-driven photocatalytic system was successfully synthesized from graphite, bismuth nitrate pentahydrate, iron (III) nitrate, and zinc nitrate precursors. The produced materials were characterized regarding micro-structure, chemical composition and functional groups, surface charge properties, photocatalytic characteristics such as band gap energy (Eg), recombination rate of charge carriers, and magnetic properties. ZnFe2O4/BiOBr/rGO heterojunction photocatalyst exhibited a saturation magnetization of 7.5 emu/g, and a visible light response (Eg = 2.08 eV). Thus, under visible light, these materials could generate effective charge carriers responsible for forming free hydroxyl radicals (HO & BULL;) for degrading organic pollutants. ZnFe2O4/BiOBr/rGO also exhibited the lowest charge carriers recombination rate compared to all individual components. The construction of ZnFe2O4/BiOBr/rGO system resulted in 1.35 to 2.55 times higher in photocatalytic degradation of DB 71 compared to individual components. At the optimal conditions (0.5 g/L catalyst load and pH 7.0), the ZnFe2O4/BiOBr/rGO system could completely degrade 30 mg/L DB 71 after 100 min. DB 71 degradation process was best described by the pseudo-first-order model, with the coefficient of determination within the range of 0.9043-0.9946 for all conditions. HO & BULL; radicals were mainly responsible for degrading the pollutant. The photocatalytic system could be effortlessly regenerated, very stable, which showed an efficiency of >80.0 % after 5 repetitive runs regarding the DB 71 photodegradation. The photocatalyst was easily recovered by a magnet. This research provides a novel approach for producing an effective and practical photocatalyst that can be applied in real organic pollutants-containing waste water treatment systems.

Automated summary

A novel tertiary magnetic ZnFe2O4/BiOBr/rGO photocatalytic system was synthesized and characterized. This system exhibited a visible light response, high magnetization, and low charge carrier recombination rate, resulting in enhanced photocatalytic degradation of DB 71. The system could be effortlessly regenerated and showed high stability for organic pollutants-containing waste water treatment.