Photocatalytic mineralization of glyphosate in a small-scale plug flow simulation reactor by UV/TiO₂

Abstract

The present work involves the photocatalytic mineralization of glyphosate on a plug flow reactor by UV/TiO₂. The effect of catalyst loading shows an optimal value (0.4 g L⁻¹) which is necessary to mineralize glyphosate. The kinetic rate of glyphosate mineralization decreases with the increasing initial concentration of glyphosate, and the data can be described using the first-order model. An alkaline environment is conducive to glyphosate mineralization. The mineralization efficiency increases with elevated flow rate to 114 mL min⁻¹, which is followed by a decrease with a further increase in flow rate due to the reduction of the residence time. The presence of external oxidants (K₂S₂O₈, H₂O₂ and KBrO₃) and photosencitizer (humic acid) can significantly enhance glyphosate mineralization. Photocatalysis oxidation ability of the three studied oxidants decrease in the order of: S₂O₈ ²⁻ > BrO₃ ⁻ > H₂O₂. Finally, the Langmuir–Hinshelwood (L-H) model was used to rationalize the mechanisms of reactions occurring on TiO₂ surfaces and L-H model constants were also determined.

Keywords:

• Photocatalytic mineralization
• glyphosate
• UV/TiO₂
• plug flow reactor
• operating parameters

Acknowledgments

National Special Purpose on Public Welfare of Environmental Protection Foundation (200809016), Jiangsu Key Lab.of Environmental Engineering Open Foundation (KF2009008).