Acceleration of photo-reduction and oxidation capabilities of Bi4O5I2/SPION@calcium alginate by metallic Ag: Wide spectral removal of nitrate and azithromycin

Abstract

Wide spectral responsive photocatalysts with improved charge separation and transfer capacity have attracted researchers for various photo-oxidative and reductive applications. This work reports Vis-NIR active photocatalyst Ag@Bi4O5I2/SPION@calcium alginate (here in designated as ABSA) prepared by hydrothermal impregnation for high performance degradation of azithromycin (AZY) and selective reduction of NO3– into N2. The composite catalyst ABSA shows 98.4% AZY degradation in 90 min with visible light. Surprisingly, the apparent rate constant for ABSA catalyst (0.08321 min−1) is ~ 8 times higher than bare Bi4O5I2. The photocatalyst is capable of selectively reducing NO3– into N2 with formic acid at a wide range of pH especially in acidic conditions with ~ 100% photo-reduction and 97.6% N2 selectivity. The high performance is manifested in the excellent photoreduction and oxidative capabilities under UV, visible, NIR and sunlight. SPIONs and Ag improve the visible activity, I3-/I- redox mediates better charge flow and Ag provides “hot electrons” via SPR effect. ●O2– radicals are the active species during AZY degradation as confirmed by ESR probe. ●CO3– plays immensely important role in selective NO3– reduction into N2. This work reports a relatively simple photocatalytic system with more bio-benevolence utilizing Bi4O5I2 and Calg and modifying with Fe3O4 and Ag as dopants for a wide spectral photo-redox capability. The hybrid wide spectrum responsive material integrates environmental friendliness, robust structure, full recycling and stability with sturdy improvement in photocatalytic efficiency.