Abstract
The work is concerned with the photocatalytic degradation of acetamiprid, a widely used pyridine-based neonicotinoid insecticide, in UV-irradiated aqueous suspensions of O2/TiO2. The rate of degradation was studied by HPLC/DAD and UV spectrophotometry. It was found that the reaction in the investigated concentration range (0.5-2.0 mg cm-3) is of a pseudo-first order. The ¹H NMR analysis indicated that beside acetaldehyde, formic and acetic acid, pyridine-containing intermediates (e.g. 6-chloronicotinic acid) formed during the process. The HPLC/MS measurements also proved the presence of aromatic degradation intermediates. During the photocatalytic process the pH changed by even three units, from 5 to 2. In contrast to the photocatalytic results in the photolytic experimental conditions, acetamiprid appeared to be stable. To get a deeper insight into the complex photocatalytic process of acetamiprid, the photocatalytic degradation of 6-chloronicotinic acid, the detected pyridine-based degradation product, was also investigated.
Highlights
IntroductionThe removal or mineralization of different persistent organic contaminants, such as industrial chemicals (textile dyes, surfactants), pharmaceuticals (antibiotics, steroids), antifouling compounds, and crop protection agents, is an area that has received extensive attention.[1,2,3,4,5,6,7,8] Apart from the frequently used biodegradation processes for wastewater treatment, aiming at the total mineralization of organic pollutants, advanced oxidation processes (AOPs) are of special importance
The removal or mineralization of different persistent organic contaminants, such as industrial chemicals, pharmaceuticals, antifouling compounds, and crop protection agents, is an area that has received extensive attention.[1,2,3,4,5,6,7,8] Apart from the frequently used biodegradation processes for wastewater treatment, aiming at the total mineralization of organic pollutants, advanced oxidation processes (AOPs) are of special importance
To get a deeper insight into the understanding of the degradation of this insecticide, we have studied the photocatalytic degradation of 6-chloronicotinic acid, 6-CNA
Summary
The removal or mineralization of different persistent organic contaminants, such as industrial chemicals (textile dyes, surfactants), pharmaceuticals (antibiotics, steroids), antifouling compounds, and crop protection agents, is an area that has received extensive attention.[1,2,3,4,5,6,7,8] Apart from the frequently used biodegradation processes for wastewater treatment, aiming at the total mineralization of organic pollutants, advanced oxidation processes (AOPs) are of special importance. Moza et al.[21] investigated the photolytic degradation of imidacloprid and found that the irradiation at 290 nm resulted in 90%. To get a deeper insight into the understanding of the degradation of this insecticide, we have studied the photocatalytic degradation of 6-chloronicotinic acid, 6-CNA (6-chloropyridine-3-carboxilic acid, Figure 1(b), a compound with an aromatic structure similar to the investigated one, and which is known from the literature as the last stable product in the degradation chain of imidacloprid.[24]. Acetamiprid solutions for photocatalytic/photolytic investigations were prepared in D2O for 1HNMR and doubledistilled water in all other investigations and the applied concentrations covered a relatively high concentration range from 0.5 to 2.0 mg cm-3, suitable for direct 1H NMR measurements without an additional preparation of the samples.
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