Abstract
The widely used sulfonylurea herbicides have caused negative effects on the environment and human beings. Electrochemical degradation has attracted much attention in the treatment of refractory organic compounds due to its advantage of producing no secondary pollution. Three kinds of IrO2-based dimensionally stable anodes (DSAs) were used to degrade nicosulfuron by a batch electrochemical process. The results showed that a well-distributed crack network was formed on the Ti/Ta2O5-IrO2 electrode and Ti/Ta2O5-SnO2-IrO2 electrode due to the different coefficients of thermal expansion between the Ti substrate and oxide coatings. The oxygen evolution potential (OEP) increased according to the order of Ti/RuO2-IrO2 < Ti/Ta2O5-SnO2-IrO2 < Ti/Ta2O5-IrO2. Among the three electrodes, the Ti/Ta2O5-IrO2 electrode showed the highest efficiency and was chosen as the experimental electrode. Single factor experiments were carried out to obtain the optimum electrolysis condition, shown as follows: currency intensity 0.8 A; electrode spacing 3 cm, electrolyte pH 3. Under the optimum conditions, the degradation of nicosulfuron followed first-order kinetics and was mainly due to indirect electrochemical oxidation. It was a typical diffusion-controlled electrochemical process. On the basis of the intermediate identified by high performance liquid chromatograph-mass spectrometry (HPLC-MS), two possible degradation routes were proposed.
Highlights
Sulfonylurea herbicides have been considered as “new formulation pesticides” because of their high selectivity and low persistence in the environment
On the basis of the intermediate identified by high performance liquid chromatograph-mass spectrometry (HPLC-MS), two possible degradation routes were proposed
Some of the commonly used sulfonylurea herbicides are able to remain in natural environmental medium such as soil and water [5,6]
Summary
Sulfonylurea herbicides have been considered as “new formulation pesticides” because of their high selectivity and low persistence in the environment. They have been widely used to control a variety of broad-leafed weeds and grasses [1,2]. With high toxicity and high residue herbicides fading out of the market, the production and application of sulfonylurea herbicides have been developing more rapidly. Their sales have accounted for more than 11% of the global herbicide market [3,4]. How to remove the residues of sulfonylurea herbicides has become an urgent problem in China [10]
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