Photocatalytic degradation of the herbicide pendimethalin using nanoparticles of BaTiO₃/TiO₂ prepared by gel to crystalline conversion method: A kinetic approach

Abstract

Photocatalytic degradation of the herbicide, pendimethalin (PM) was investigated with BaTiO3/TiO2 UV light system in the presence of peroxide and persulphate species in aqueous medium. The nanoparticles of BaTiO3 and TiO2 were obtained by gel to crystallite conversion method. These photo catalysts are characterized by energy dispersive x-ray analysis (EDX), scanning electron microscope (SEM), x-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) adsorption isotherm and reflectance spectral studies. The quantum yields for TiO2 and BaTiO3 for the degradation reactions are 3.166 Einstein m(-2) s(-1) and 2.729 Einstein m(-2) s(-1) and catalytic efficiencies are 6.0444 x 10(-7) mg(-2)h(-1)L2 and 5.403 x 10(-7) mg(-2)h(-1)L2, respectively as calculated from experimental results. BaTiO3 exhibited comparable photocatalytic efficiency in the degradation of pendimethalin as the most widely used TiO2 photocatalyst. The persulphate played an important role in enhancing the rate of degradation of pendimethalin when compared to hydrogen peroxide. The degradation process of pendimethalin followed the first-order kinetics and it is in agreement with Langmuir-Hinshelwood model of surface mechanism. The reason for high stability of pendimethalin for UV-degradation even in the presence of catalyst and oxidizing agents were explored. The higher rate of degradation was observed in alkaline medium at pH 11. The degradation process was monitored by spectroscopic techniques such as ultra violet-visible (UV-Vis), infrared (IR) and gas chromatography mass spectroscopy (GC-MS). The major intermediate products identified were: N-propyl-2-nitro-6-amino-3, 4-xylidine, (2, 3-dimethyl-5-nitro-6-hydroxy amine) phenol and N-Propyl-3, 4-dimethyl-2, 6-dinitroaniline by GC-MS analysis and the probable reaction mechanism has been proposed based on these products.

TiO2- and BaTiO3-Assisted Photocatalytic Degradation of Selected Chloroorganic Compounds in Aqueous Medium: Correlation of Reactivity/Orientation Effects of Substituent Groups of the Pollutant Molecule on the Degradation Rate

“…Because the rate of degradation is found to depend on the substrate concentration ( C sub ), the first-order photodegradation reaction can fit to the Langmuir−Hinshelwood (L−H) kinetic model ,,, for the above chloroorganic compounds and is represented by the following equation v LH = − d C d t = k obsd K app C sub 1 + K app C sub where v LH is the L−H kinetic rate, K app is the apparent adsorption equilibrium constants, and k obsd is the observed rate constant.…”

“…The above powders were characterized by X-ray diffraction studies . The diffractograms were obtained using Phillips PW 1050/70/76 X-ray diffractometer.…”

“…There are only a few studies on these compounds in this regard . The use of BaTiO 3 as photocatalyst for the mineralization of chloroorganic compounds and the influence of substituents is less attempted. , Therefore, this kind of study may gain separate scope in photocatalysis.…”

Synthesis and study of physicochemical, sorption, and photocatalytic properties of barium titanate-modified titania powder

“…Crystals of BaTiO 3 possess semiconducting properties and have a bandgap of about 3 eV. The salt was also shown to exhibit pho tocatalytic properties [7][8][9][10][11][12].…”

Effects of the Herbicide Pendimethalin on Hormone Receptor Expressions and Dorsal Fin Biometrics in Thai Medaka, <I>Oryzias Minutillus</I> (Actinopterygii: Beloniformes: Adrianichthyidae)

“…This herbicide has been considered to be a moderately persistent, bioaccumulative toxic compound (Roca et al 2008), and it has a half-life of approximately 32 days in soil and is broken down by microbial or photocatalytic degradation (Lakshmipathi et al 2008, Alister et al 2009, Pinto et al 2012. After widespread use, pendimethalin was detected as a contaminant in ground water with 0.1 to 6 µg · L -1 and in agricultural soil at approximately 13 mg · kg -1 (Barbash andResek 1996, Strandberg andScott-Fordsmand 2004).…”