Photocatalytic behaviour of Ag3PO4, Fe3O4 and Ag3PO4/Fe3O4 heterojunction towards the removal of organic pollutants and Cr(VI) from water: Efficiency and light-corrosion deactivation

• Magnetic Ag 3 PO 4 /Fe 3 O 4 heterojunction was synthesised for water purification. • Ag 3 PO 4 /Fe 3 O 4 showed enhanced photoactivity under solar light. • Photocatalytic activity was testes to remove organic pollutants and Cr(VI). • Ag 3 PO 4 /Fe 3 O 4 showed better light anti-corrosion compared to bare Ag 3 PO 4. • Z-scheme heterojunction system was built for enhanced ROSs generation. This work aims to synthesize and study the photocatalytic behaviour of Ag 3 PO 4 , Fe 3 O 4 and Ag 3 PO 4 /Fe 3 O 4 to oxidize organic pollutants (diclofenac sodium and acid green 25) and photoreduction of Cr(VI). In terms of organic pollutants oxidation, Ag 3 PO 4 /Fe 3 O 4 composite showed higher efficiency than bare Ag 3 PO 4 and Fe 3 O 4 . Based on the reactive oxygen species scavenging experiments, it was found that Ag 3 PO 4 /Fe 3 O 4 can enhance the photogeneration of − O 2 species, solving the low ability of bare Ag 3 PO 4 to reduce O 2 into − O 2 because of its lower conduction band compared to the redox potential of O 2 / − O 2 . As a result, it was claimed that the Z-scheme heterojunction is more plausible than type II heterojunction system for enhancing photoproduced charges separation and photoactivity in Ag 3 PO 4 /Fe 3 O 4 platform. In terms of photoreduction of Cr(VI), Fe 3 O 4 and Ag 3 PO 4 /Fe 3 O 4 were more effective than bare Ag 3 PO 4 under solar light. The deactivation tests carried out comparatively on Ag 3 PO 4 and Ag 3 PO 4 /Fe 3 O 4 for successive oxidation of diclofenac sodium under solar light showed that Ag 3 PO 4 /Fe 3 O 4 has better long-term use. At the same time, Ag 3 PO 4 lost its activity significantly along with a total change of its colour from green to black because of the strong light corrosion. On top of the high stability and easy magnetic recovery of Ag 3 PO 4 /Fe 3 O 4 , the coating of Ag 3 PO 4 on low-cost Fe 3 O 4 can have an economic benefit at large scale.