The photocatalytic degradation of carbofuran and Furadan 35-ST: the influence of inert ingredients

Abstract

A comparative study on photocatalytic degradation of the pesticide carbofuran and its commercial product Furadan 35-ST in an aqueous suspension of ZnO, irradiated by long-wave light (315-400 nm), is presented in this study. In order to assess the effects of inert ingredients present in the commercial product Furadan 35-ST, non-competitive and competitive adsorption and kinetic studies of carbofuran degradation processes were conducted. A higher photochemical degradation rate was found for pure carbofuran in comparison to a two-component system, carbofuran and single addition of ingredients at appropriate concentrations, and the commercial product Furadan 35-ST. The overall effect of inert ingredients was evaluated from a competitive study using the model system of Furadan 35-ST. The results of a mineralization study, obtained by ion chromatography (IC) and total organic carbon (TOC) analyses, revealed the formation of acetate, oxalate, and formate ions. Photodegradation products of carbofuran, three of them detected for the first time, were identified based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) results, and their photodegradation pathways were proposed.

A study of photocatalytic degradation of methomyl and its commercial product Lannate-90

“…Also, the maximum effectiveness of degradation occurred at pH 3.0. It had been found earlier that photodegradation with ZnO was more effective in acidic than in alkaline media [23] due to a greater electrostatic attraction between methomyl molecules and ZnO surface. Also, the degradation of Lannate was more pronounced than the degradation of pure methomyl in acidic media.…”

“…The UV spectra of both pure methomyl and Lannate-90 were recorded on a LabTOC 2100 instrument was used in a total organic carbon (TOC) analysis. HPLC-6 MS/MS analysis was conducted as before [23] using a Thermo Fisher Scientific (Waltham, MA, USA) apparatus (for details see Supplementary material).…”

“…Photodegradation of pesticides in aqueous solution is known to be affected by pH, and the generation of hydroxyl radicals depends on pH; also, the catalyst surface properties and behavior of a pollutant and its transformation products depend on pH [1,2,5,23,[35][36][37][38][39].…”

“…Inert ingredients may have different degrees of influence on the photodegradation reaction of active ingredients, either increasing or retarding its rate [23]. The differences in photodegradation rates between pure methomyl and the commercial product Lannate-90 could be attributed to the fact that methomyl, which has good solubility in water (57.9 g L -1 , 25 o C), is formulated as a soluble powder (SP).…”

“…Although photodegradation of pure active ingredients of pesticides has been the subject of many published papers [1,2,4,5,[18][19][20][21], only several papers focused on degradation of commercial pesticide products [3,[22][23][24][25]. The objective of our investigation was to study and compare the rates of photochemical degradation of the pesticide active ingredient methomyl and its commercial product Lannate-90 (soluble powder-SP).…”