Applications of Zinc oxide Nanoparticles as Catalyst in Dissipation Kinetics of S-Metolachlor Herbicide in Different pH waters UnderDirect sun light

Abstract

Studied the dissipation behavior of S-Metolachlor under direct sunlight using Zinc oxide nanoparticles as catalyst. Zinc oxide nanoparticles are synthesized and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscope (TEM) and Fourier transform Infrared Spectroscopy (FT- IR). The experiment was conducted by spiking in three different aqueous buffer solutions having pH 4.0, 7.0 and 9.0 to give the uniform concentrations of T0 – Untreated Control, T1 – S-Metolachlor 96% w/v @ 1 mg/L of water and T2 – S-Metolachlor 96% w/v @ 2 mg/L of water. The spiked samples were kept under sunlight. The sampling occasions were 0, 6th, 12th, 24th, 48th and 72nd hour for acidic water (pH 4.0), neutral (pH 7.0) and basic water (pH 9.0). The collected samples were quantified using a validated high performance liquid chromatography with ultra Violet detector (HPLC-UV) at a wave length of 220 nm with flow rate of 1.0 mL/min, injection volume 10 μL, column oven temperature being 30°C, with mobile phase as acetonitrile: 0.1% orthophosphoric acid (80:20 (v/v)) and Zodiac C8, 250 mm x 4.6 mm, 5μm column was used. The method has the limit of detection 0.01 mg L-1 and the limit of quantification (LOQ) 0.03 mg L-1 based on signal to noise ratio 3:1 and 10:1 respectively for all the molecules investigated. The residues of S-Metolachlor in aqueous buffer solutions dissipated to below the detectable level by 72nd hour. The DT50 (Half Life) of S-Metolachlor was calculated by regression analysis from the dissipation data.