Preparation Of Magnetic ZIF-8 Composites And Its Application In Organic Contaminant Adsorption

Pesticides and dyes,two major organic compounds,are indispensable substances in agriculture,food industry and light industry.However,with their extensive use,they may remain in food and water sources and pose a serious threat to human health.As a result,developing rapid and efficient technologies for pesticide residue analysis and dye adsorption is particularly important.Zeolite imidazolate frameworks?ZIFs?are a subclass of metal-organic frameworks?MOFs?.They possess the periodic network structure,high specific surface area,huge porosity and designable pore structure of MOFs and meanwhile exhibit high stability of zeolites.In recent years,they have shown good application prospects in organic pollutant adsorption.However,the fabrication of ZIFs nanocomposites with good operational convenience and strong ability to capture the target molecules is still a challenge.Therefore,the preparation of multi-functional ZIFs composites is not only conducive to overcoming the intrinsic shortcomings of materials and widening its the application field,but also helpful for the development of new detection technology for organic contaminants and water remediation technology.This study focused on preparing functionalized ZIF-8 nanocomposites via different synthetic strategies.The synthesis steps were simplified and the properties of the nanocomposites were improved.Nicotine pesticides,sulfonylurea pesticides and dyes were chosen as the target organic contaminants and their adsorption performance on ZIF-8 nanocomposites was investigated.Also,the prepared nanocomposites were appled as new MSPE adsorbents for fast enrichment and detection of neonicotinoid insecticides and sulfonylurea herbicides and removal of organic dye.The results of this study are as follows:1.Fe₃O₄/ZIF-8 was synthesized via in situ method and applied as an efficient magnetic solid-phase extraction?MSPE?adsorbent for adsorption and enrichment of neonicotinoid insecticides.The results show that Fe₃O₄/ZIF-8 had higher adsorption and enrichment capacities for clothianidin,imidacloprid,acetamiprid and thiacloprid than dinotefuran.Under the optimum conditions,a MSPE-HPLC-MS/MS method for the determination of neonicotinoid insecticides in water samples was established.This developed method showed high sensitivity,satisfactory recoveries,good repeatability,simplicity and robustness.This study provides a simple preparation method for the functionalization of MOFs materials and highlights the excellent flexibility and practicability of Fe₃O₄/ZIF-8 for analyzing emerging environmental contaminants in water samples of various types.2.A“half”core-shell g-C₃N₄/Fe₃O₄@ZIF-8 nanocomposite was synthesized by in situ method.The composite had good magnetic properties,thermal stability and high specific surface area and exhibited superior adsorption capacities for sulfonylureas herbicides in comparison with pure ZIF-8 and C₃N₄.Furthermore,the obtained g-C₃N₄/Fe₃O₄@ZIF-8 nanocomposite was successfully applied as an MSPE adsorbent to establish a MSPE-HPLC-MS/MS method for simultaneous determining 15 sulfonylureas herbicides in water samples.The developed DMIP-SPE-LC-MS/MS method showed good linearity,high sensitivity,and satisfactory accuracy and precision,manifesting that the fabricated nanocomposite would be a promising materials for extraction and high-throughput analysis of various chemicals from aqueous solution.This study provides referenced experiments for separation,enrichment and trace analysis of various concerned organic contaminants.3.Three kinds of g-C₃N₄/Fe₃O₄@ZIF-8 nanocomposites were synthesized by using different amounts of g-C₃N₄ in the preparation process.The fabricated nanocomposites were applied as adsorbents for the adsorption and removal of malachite green,rhodamine B,azophloxine and metanil yellow.The characteristics of the nanocomposites were studied using FTIR,SEM,TEM,XRD,BET,TGA and UV–vis techniques.Compared with pure g-C₃N₄ and ZIF-8,only nanocomposites showed good removal efficiencies for all the four dyes.Additionally,the nanocomposite with the best adsorption properties was determined.The factors influencing the adsorption performance,adsorption thermodynamics and adsorption kinetics were further studied.Overall,the highly adsorption capacities,good stability and simple synthesis indicate the prepared nanocomposites was as promising candidates for the adsorptive removal of multiple organic contaminants.