Photocatalytic Degradation of Paraquat Herbicide and Printing Tie Dye under UV/Sunlight by Graphene Oxide TiO2 Nanocomposites

Abstract

Graphene oxide was prepared by hummer’s method through oxidation of graphite. Graphene was used in combination with TiO2 because of non- toxic, large surface area and excellent conductivity for the preparation of graphene oxide (GO)-TiO2 nanocomposite. Surface modification with GO enhances photocatalytic activity of TiO2. The prepared nanocomposite was then characterized by XRD, SEM, and FTIR. Herbicides are used to destroy or inhibit the growth of unwanted vegetation such as weed killers. GO-TiO2 was used for the degradation of herbicide paraquat (1, 1`-dimethyl-4, 4`-bipyridinium dichloride) and cotton tie dye in the presence of UV and Sunlight irradiation. Degradation at different time intervals was measured by UV absorption at λmax 257 nm for paraquat. While tie dye was studied at λmax 400 nm. Graphene loaded TiO2 shows best catalytic activity for the degradation of paraquat herbicide and cotton tie dye. Almost complete degradation of paraquat herbicide was achieved as absorbance decreased from 1.509-0.314 a.u after 90 minutes under UV light irradiation. Similarly, very fast degradation of the tie dye was obtained, absorbance decreased from 0.998-0.298 a.u under sunlight irradiation of 120 minutes. The degradation speeded up because graphene prevents the recombination of electron-hole pair. Due to this GO-TiO2 shows better catalytic activity as compare to TiO2 both in UV irradiation and Sunlight. It was seen to follows zero order kinetics. k- 36*10-4Ms-1 for paraquat herbicide and k- 61*10-2Ms-2 was achieved. High photocatalytic activity for the degradation of paraquat (79 %) and cotton tie dye (86%) was obtained.