Effect of inorganic ions, photosensitisers and scavengers on the photocatalytic degradation of nicosulfuron

Abstract

In the present study, the photocatalytic degradation of nicosulfuron, using TiO2 as a catalyst under UV light (315-400 nm), was studied. The optimization of the nicosulfuron photodegradation was performed. It was found that the optimal concentration of the catalyst was 1 g L-1 at concentration of nicosulfuron solution of 20 mg L-1 while the highest reaction rate was obtained using 2 g L-1. The degradation rate was the highest at pH .= 5.0. Effects of anions (Cl-, SO42- NO3- and F-) and cations (Na+, Ca2+, Al3+) were investigated. In addition, the influence of isopropanol, acetone, and hydrogen peroxide was studied. It was shown that the photocatalytic degradation is mainly due to the reaction of nicosulfuron with (OH)-O-center dot in solution. Also, liquid chromatography coupled with mass spectrometry (HPLC-MS) was used to identify intermediates during the photocatalytic degradation of nicosulfuron. the mineralization was monitored with ion chromatography (IC) and total organic carbon (TOC) analysis. Although 100% HPLC removal of nicosulfuron was achieved, only 69% TOC removal after 90 min was recorded. The results of ion chromatography showed that the mineralization resulted in ammonium and nitrate ions during the process. The phytotoxicity experiments using mung bean seeds showed a reduction in phytotoxicity.