Preparation Of Tunable Cage-like Zeolitic Imidazolate Framework Composites And Application For Adsorption And Removal Of Exogenous Contaminants

Exogenous organic contaminants would threaten public health.A high sensitivity and rapid separation enrichment method and the effective removal and degradation techniques are required for a strict control of these compounds at MRPLs(minimum required performance limits).Recently,zeolitic imidazolate nanoparticles are tunable cage-like metal-organic framework material with large specific surface area and excellent stability,which provide new ideas for the rapid separation enrichment and efficient removal of exogenous contaminants in food and environmental water.In this paper,zeolitic imidazolate framework-8 composites was prepared with tunable cage-like and applicated for adsorption and removal of exogenous contaminants.(1)A novel magnetic hollow bimetallic zinc/cobalt-based zeolitic imidazolate framework(MHB-Zn/Co-ZIF-8)was prepared via a microwave-assisted chemical etching method and then it employed as an effective sorbent.Then the MHB-Zn/Co-ZIF-8-based magetic-solid phase extraction was coupled with ultra-high-performance liquid chromatography combined with ion-trap multi-stage tandem mass spectrometry(UHPLC-IT-MSn)to establish an analysis platform.This platform can be used for the sensitive quantification and identification of multiple aflatoxins(AFB1,AFB2,AFG1 and AFG2)in fruit juice and fruit.The limits of quantification(LOQ)of the analysis platform for the four aflatoxins were in the range of 0.18-1.50 ng·mL-1.The average recoveries of the four aflatoxins spiked in fruit juice ranged from 75.13%to 102.38%,with relative standard deviations less than 13.6%.In addition,the cavity cage-like structure of MHB-Zn/Co-ZIF-8 provided a large internal surface area of 804.30 m2·g-1 and abundant metal ion active sites(Zn2+and Co2+).The efficient adsorption of aflatoxin onto the MHB-Zn/Co-ZIF-8 can be mainly explained by the strong coordination between the oxygen atoms of the ?-dicarbonyl group in aflatoxin molecules and the Zn2-and Co2-ions within the hollow cages structure.This work was achieved for the first time for aflatoxins in fruit juice and fruit with the help of MHB-Zn/Co-ZIF-8 and proves the feasibility of MSPE-UHPLC-IT-MSn method for analysis of trace aflatoxins in complex fruit matrices.(2)MHB-Zn/Co-ZIF-8 was used as an adsorbent for specific mycotoxins(aflatoxins).The application of MHB-Zn/Co-ZIF-8 as a novel adsorbent for fast removal of aflatoxins in the simulated aqueous solution,the maximum adsorption capacity,adsorption kinetics,adsorption isotherms and thermodynamics were investigated in detail.The adsorption for AFB1,AFB2,AFG1 and AFG2 followed pseudo-second-order kinetics with the simultaneously adsorption capacity of AFB1(40.02 mg·g-1),AFB2(41.09 mg·g-1),AFG1(37.72 mg·g-1)and AFG2(38.26 mg·g-1).The adsorption for AFB1,AFB2,AFG1 and AFG2 fitted the Freundlich adsorption model.In thermodynamic studies,it is shown that the adsorption process is spontaneous and it is not conducive to the adsorption with increasing temperature.The development of MHB-Zn/Co-ZIF-8 as a new adsorbent to detoxify for specific mycotoxins will solve the mycotoxin pollution in common livestock production.(3)Water-resistant magnetic graphene-anchored zeolite imidazolate(Fe3O4/ZIF-8-G)composite materials with the largest surface area are formed by directly growing a hydrophobic ZIF-8 skeleton onto a graphene support through self-assembly in methanol.Fe3O4/ZIF-8-G hybrid composite is used as an effective adsorbent for adsorption and removal of residual tetracycline in wastewater.The maximum adsorption capacity,adsorption kinetics,adsorption isotherm,and adsorption thermodynamic behavior were thoroughly and systematically studied in the actual spiked wastewater.The results indicated that the adsorption for tetracycline(TC),oxytetracycline(OTC)and chlortetracycline(CTC)followed pseudo-second-order kinetics and fitted the Freundlich adsorption model with the simultaneously adsorption capacity of TC(382.58 mg·g-1),OTC(565.94 mg·g-1)and CTC(608.06 mg·g-1).The used Fe3O4/ZIF-8-G could be effectively reused and recycled at least five times without significant loss of adsorption capacity.The development of ZIF-8-based magnetic graphene hybrid composite adsorbent provides a scientific basis for the removal of residual tetracycline in the current sewage treatment system.(4)The as-prepared ZnO nanosheet was used as a zinc source to grow ZIF-8 with highly dispersed and uniform size using a mild solution method in methanol solution.Then ZnO/ZIF-8 heterojunction photocatalyst with high porosity was prepared after the calcination.The morphologies,structure and photocatalytic performance of ZnO/ZIF-8 were characterized using FT-IR,XRD,SEM,TEM,N2 adsorption and UV-Vis.The resuts show that the synergistic effect of ZIF-8 and ZnO greatly enhances the catalytic ability of the hybrid composite photocatalyst and selectively degrade sulfamethoxazole and sulfachloropyridazine in simulated aqueous solutions under visible radiation.ZnO/ZIF-8 exhibits excellent ability to catalytically degrade sulfonamide antibiotics in environmental water.