hr Effect of surface impregnation of Gd3+ over Bi2O3 for the degradation of bisphenol A and chlorophenoxy herbicides in natural sunlight exposure

In order to address the issues of the short life span of excitons, the limited generation of reactive oxygen species due to the unsuitable conduction band edge, and inadequate photocatalytic activity, the surface of Bi2O3 was altered by the surface impregnation of Gd3+ that converted to Gd2O3 by air calcination. The FESEM and XRD analysis revealed the uniform distribution of 50-80 nm Gd2O3 particles at the surface of Bi2O3 without affecting the skeletal arrangement. The improved absorption in the visible region and the red shift in the band gap values identified the lowering of the conduction band edge formed by the merger of Bi3+ (6p) and Gd3+ (4 f) orbitals. The supporting role of Gd3+ entities in prolonging the life span of the excitons was revealed by the sequentially decreasing intensity with the enhanced surface loading in the PL analysis. The retention of the oxidation states was assessed by XPS analysis. As compared to Bi2O3, the as-synthesized materials exhibited significantly enhanced photocatalytic activity in natural sunlight exposure for the removal/mineralization of potential organic contaminants i.e., Bisphenol A (BPA), and chlorophenoxy herbicides (2,4-dichlorophenoxyacetic acid (2,4-D), and 4-methyl, 2-chlorophenoxyacetic acid (MCPA)). The synthesized 2 % Gd3+ impregnated Bi2O3 photocatalyst showed remarkable photocatalytic activity of -98 %, -91 %, and -86 % for the degradation of 2,4-D, MCPA, and BPA, respectively, in 360 min of sunlight exposure. Total organic carbon (TOC) measurements were used to estimate the mineralization efficiency of impregnated materials and the observed percentage mineralization efficiency was -76 %, -74 %, and -70 % for 2,4-D, MCPA, and BPA pollutants, correspondingly. The data extracted from the analytical tools deliver deep insight into the supporting role of rare earth metals in the field of photocatalytic water decontamination.