A direct Z-scheme heterojunction g-C3N4/α-Fe2O3 nanocomposite for enhanced polymer-containing oilfield sewage degradation under visible light

The massive discharge of polymer-containing sewage has caused more and more serious consequences to the petroleum production industry and ecological environment. To solve the above problem, constructing a Z-scheme heterojunction with effective charge transfer within the photocatalyst structure is critical in improving the performance of the catalytic reaction. A series of Z-scheme photocatalysts combining g-C3N4 and alpha-Fe2O3 were synthesized, and they exhibited high photocatalytic degradation HPAM efficiencies (up to 90%) without additional photosensitizers and sacrificial agents. The experiments have confirmed an efficient alpha-Fe2O3 to g-C3N4 electron transfer via strong electrostatic interaction, resulting in electron accumulation in g-C3N4 for H2O reduction to generate the active species OH and holes in alpha-Fe2O3 for O-2 oxidation to generate the active species O-2(-); thus, OH and O-2(-) synergistically catalyse HPAM degradation by mimicking natural photosynthesis. This study provides theoretical guidance for the efficient treatment of oilfield sewage using the photocatalytic technology.