Visible-light-driven Z-scheme La-MOF/BiOBr heterojunction for the efficient removal of rhodamine B and hexavalent chromium from wastewater

Addressing the formidable challenge of treating significant quantities of organic dyes and heavy metal chromium in tannery wastewater, this study synthesized a novel Z-scheme La-MOF/BiOBr composite heterojunction photocatalyst via the hydrothermal method and established an efficient visible-light photocatalytic system. To comprehensively evaluate the photocatalytic redox activity, rhodamine B (RhB) and heavy metal Cr(VI) were selected as target pollutants. Kinetic analysis revealed that the optimal LM-BB-50 catalyst achieved over 99 % degradation of RhB and Cr(VI) within 15 min illumination, indicating the remarkable enhancement of Z-scheme heterojunction in photocatalytic oxidation and reduction efficiency. Based on various photoelectric analysis techniques, it was elucidated that the superior activity of the Z-scheme heterojunction originated from the modulation of the band structure upon La-MOF and BiOBr integration, significantly improving visible light absorption, electron-hole pair separation efficiency, and endowing the energy band with robust redox capabilities. Free radical capture and quenching experiments confirmed that photogenerated holes and superoxide radicals played a crucial role in RhB oxidation , while photogenerated electrons were the primary active species for Cr(VI) reduction.