Surfactant modified ZnO–Bi2O3 nanocomposite for degradation of lambda- cyhalothrin pesticide in visible light: A study of reaction kinetics and intermediates

Abstract

Coupling of semiconductor photocatalyst attracted more attention in the area of heterogeneous photocatalytic process. Herein we developed a low-cost visible light responsive coupled ZnO–Bi2O3 semiconductor with a molar ratio of 1:4, 1:2, and 3:4 by facile one-step hydrothermal method using a surfactant. The influences of Bi2O3 content on coupled catalyst were investigated. The synthesized catalysts were characterized by X-Ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectrum (FT-IR), UV–Vis diffuse reflectance (UV-DRS). Photocatalytic performance of ZnO–Bi2O3 was investigated using Lambda-Cyhalothrin (L-CHT), a pyrethroid pesticide that is harmful to human beings and animals under visible light irradiation. Kinetic study of the degradation of L-CHT reveals that there is a shift in the reaction order from first-order to second-order. The photocatalytic degradation of L-CHT using ZnO–Bi2O3 is found to be more efficient since the separation of photogenerated holes and electrons are improved by coupling of ZnO with Bi2O3. When compared to bare ZnO the degradation percentage of 85.7% was achieved within 120 min of the photocatalytic process using the catalyst dosage of 1.2 gm/L in 50 mg/L of L-CHT solution with formation of Phthalic acid, butyl 2-ethyl butyl ester and Diethyl phthalate as intermediates. No other hazardous intermediates are formed and a scheme for photodegradation pathway was proposed.