Removal of Mixed Pesticides from Drinking Water System Using Surfactant-Assisted Nano-TiO2

The present study focused on the degradation of mixed pesticides using UV-induced photocatalytic degradation of lindane (1α,2α,3β,4α,5α,6β-hexachlorocyclohexane), methyl parathion (O,O-dimethyl-O-4-nitrophenyl phosphorothioate), and dichlorvos (2,2-dichlorovinyl-O-O-dimethyl phosphate). Different grades of TiO₂ were prepared through the acid route (AR), alcohol route (AlR), and surfactant route (SR) and their photocatalytic activity were compared with commercially available Degussa P-25 TiO₂. The rate of degradation of pesticides was high for TiO₂ prepared through the SR compared to the other three catalysts. The crystalline structure and morphology of SR TiO₂ was identified with scanning electron microscope, energy dispersive X-ray analyzer, UV, and transmission electron microscope analyses and was compared with that of Degussa P-25 TiO₂. Degradation studies of individual as well as mixed pesticides were carried out. The intermediate formed during the photodegradation of methyl parathion, lindane, and dichlorvos were identified by gas chromatography–mass spectrometry analysis.     

Site of Interaction of Copper on Bacillus Polymyxa

Copper uptake potential of different bacterial strains isolatedfrom contaminated soil was compared. The bacterial strainidentified as Bacillus polymyxa showed maximum copperuptake capacity. An attempt was made to elucidate the site ofinteraction of Cu(II) with B. polymyxa using electronparamagnetic resonance (EPR) studies. The EPR spectra showedthat accumulated copper formed complexes with oxygen andnitrogen which may be the carboxyl groups of cell-wallpeptidoglycan and nitrogen atoms of aminosugars or structuralproteins. The absence of super hyperfine splitting in theg ⊥ region of EPR spectra of treated B. polymyxa cellsafter Cu(II) uptake indicated that copper could be coordinatedwith the oxygen atoms from carboxyl groups of peptidoglycan inthe cell walls.