Abstract
The present study aims to prepare two new types of chitosan-metal oxide nanoparticles (Ch-MO NPs), namely, chitosan-copper oxide nanoparticles (Ch-CuO NPs) and chitosan-zinc oxide nanoparticles (Ch-ZnO NPs), using sol-gel precipitation mechanism, and test them new as adsorbent materials for extraction and clean-up of different pesticides from water. The design of core-shell was implemented by metal oxide core with chitosan as a hard shell after crosslinking mechanism by glutaraldehyde and then epichlorohydrin. The characterizations of the prepared nanoparticles were investigated using Fourier transform infrared spectrometry (FT-IR), zeta potential, scanning electron microscopy (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD). FT-IR confirmed the interaction between chitosan, metal oxide, and crosslinking mechanism. SEM and TEM explained that the nanoparticles have a spherical morphology and nanosize of 93.74 and 97.95 nm for Ch-CuO NPs and Ch-ZnO NPs, respectively. Factorial experimental design was applied to study the effect of pH, concentration of pesticide, agitation time, and temperature on the efficiency of adsorption of pesticides from water samples. The results indicated that optimum conditions were pH of 7, temperature of 25°C, and agitation time of 25 min. The SPE cartridges were then packed with Ch-MO NPs, and seven pesticides of abamectin, diazinon, fenamiphos, imidacloprid, lambda-cyhalothrin, methomyl, and thiophanate-methyl were extracted from water samples and determined by HPLC. The extraction efficiency of Ch-ZnO NPs was higher than Ch-CuO NPs, but both removed a larger amount of most of tested pesticides than the standard ODS cartridge (C18). The results showed that this method achieves rapid and simple extraction in small quantities of adsorbents (Ch-MO NPs) and solvents. In addition, the method is highly sensitive to pesticides and has a high recovery rate.
Highlights
Pesticides are widely used in agricultural production to prevent or control pests, diseases, weeds, and other plant pathogens in an effort to minimize or eliminate yield losses and maintain high quality of products [1, 2]
The results indicated that the adsorption or retention percentage increased with increasing of the pH and temperature, but the optimum adsorption percentage was observed at pH 7 and temperature of 25∘C
The factors of the pH, temperature and agitation time were studied on the efficiency of these products in adsorption or retention of imidacloprid insecticide and the results proved that the pH was the most significant factor
Summary
Pesticides are widely used in agricultural production to prevent or control pests, diseases, weeds, and other plant pathogens in an effort to minimize or eliminate yield losses and maintain high quality of products [1, 2]. The biopolymer materials have been shown to be of low cost and good efficiency in removal of various contaminants from aqueous media Among these biopolymers, chitosan (poly-β-(1→4)-2-amino-2-deoxy-D-glucose) [20, 21] has been considered to be one of the most promising and applicable materials in adsorption applications [22]. Glutaraldehyde has been used more frequently since it is less expensive, nontoxic, and highly soluble in aqueous solution It is a dialdehyde whose aldehydic groups are highly reactive and can form covalent bonds with functional groups such as primary amine by Schiff base suggesting that the conjugated aldehyde moieties in the polymers yield more stable reaction products [29,30,31]. This protocol addresses the detection of trace amounts of these pesticides in water and optimizes the conditions for SPE technique compared with the commercial SPE of Supelco Sigma product
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