Visible LED-light driven photocatalytic degradation of organochlorine pesticides (2,4-D & 2,4-DP) by Curcuma longa mediated bismuth vanadate

Abstract

Constructing stable and effective bio-synthesized heterostructure-photocatalyst has been demanding in the advancement of the photocatalysis-field. Herein, bismuth vanadate (BiVO4) was bio-fabricated using Curcuma longa via hydrolysis route for effective charge separation due to supramolecular-organic-semiconductor system of C. longa. Transmission Electron Microscopy (TEM), High Resolution-Transmission Electron Microscopy (HR-TEM), Surface Assisted Electron Diffraction (SAED), and Electron Impedance Spectroscopy (EIS) reflected successful fabrication of heterojunction between C. longa and BiVO4. The as-fabricated nanoflowers of C. longa/BiVO4 (BVO-G) reflected highly efficient photocatalytic fragmentation of Organochlorine Pesticides (OCPs) [2,4-D (2,4-dichlorophenoxy acetic acid, 90.2%) and 2,4-DP [2-(2,4-dichlorophenoxy propionic acid, 70.52%)] on comparison with pristine BiVO4 [2,4-D (45.94%) and 2,4-DP (28.18%)] within 120 min of visible-light-irradiation and also showed much better efficiency in comparison with earlier fabricated materials. Further, optical studies including photochemical responses and radical-quenching showed that h+, ·O2− and ·OH were responsible for the fragmentation of these recalcitrant herbicides. Based on in-situ High Performance Liquid Chromatography (HPLC) and Liquid Chromatography Mass Spectroscopy (LCMS) analysis, degradation pathways were designed. This work provides an in depth understanding of bio-fabrication of photocatalyst by enhancing the active sites of the reactants and hindering the recombination of photogenerated charge carriers.