Application of Metal-organic Framework in Pesticide Residue Analysis and Adsorptive Removal
Supervisor:zhao jin hao dong xiao wu
At present,excessive and unreasonable use of pesticides is common in agricultural production all over the world,resulting in excessive pesticide residues,which not only directly pollutes water and environment,but also seriously endangers human health.Therefore,it is crucial to evaluate and remove pesticide residues in the environment to ensure public safety.However,in the field of pesticide residue analysis,chromatography(such as HPLC)have been extensively used.Nevertheless,these methods require expensive equipment with low sensitivity.In the field of pesticide adsorptive removal,adsorbents have weak adsorption capacity.As a new type of material,MOFs with large specific surface,high porosity and strong functionality have become an effective way to solve these problems.Taking MOFs as the research object,by nanotechnology,in situ polymerization,post-synthetic modification(PSM)and other advanced means,we developed a new type of MOFs immune sensor for simultaneous detection of a variety of pesticides with high sensibility,and a variety of novel MOFs adsorbents for the efficiency removing pesticides from water.The main works were displayed as follows:(1)A novel electrochemical immunosensor based on amino-functionalized nano-MOFs(UiO-66-NH2)was developed for simultaneous detection of triazophos and thiacloprid.UiO-66-NH2 with an average particle size of 83.6 nm was prepared by solvent thermal method.It has a large specific surface(1018 m2·g1)and can adsorb large amounts of Cd2+(230.1 mg g-1)and Pb2+(270.8 mg g-1).The MOFs were first bound to the antigen as signal probes,then recognized by antibodies immobilized on the magnetic beads,magnetically separated,and analyzed by square wave voltammetry(SWV)to give signals for Cd2+ and Pb2+ at-0.82 V and-0.56 V(vs.Ag/AgCI)for triazophos and thiacloprid,respectively.Under optimized conditions,the method has a wide linear range(0.2-750 ng-mL-1)and low detection limits(0.07 ng-mL-1 and 0.1 ng-mL-1 at a S/N of 3 for triazophos and thiacloprid,respectively).This method is successfully used for the detection of rice samples.By changing the types of metal ions and antibodies,the immunosensor will provide a potential way for simultaneous detection of other pesticides or other small organic pollutants.(2)The linear polymer/Cr-MIL-101 composites were developed through doping functionalized materials by in-situ polymerization for aqueous-phase herbicide adsorption.The benzenesulfonic acid(BSA)and methylamino-pyridine(MAP)vinyl derivative monomers with the active sites were immersed in the pore of Cr-MIL-101s.PBSA/Cr-MIL-101 and PMAP/Cr-MIL-101 were prepared as adsorbents by in-situ polymerization.The effects of adsorption time,solution pH and adsorbent dosage on herbicide removal ability from water were investigated.The structure of the adsorbent was characterized by means of 1H-NMR.LC-MS.PXRD.FT-IR and SEM.The results showed that PBSA and PMAP were successfully entangled in the pores of the MOFs.Among them,the content of BSA active site is 1.01 mmol·g-,which provided π-π and acid-base sites,and significantly improved the adsorption capacity of Cr-MIL-101 for alachlor,acetochlor,and gramoxone(the adsorption capacity was increased by 1.4,0.9 and 1.8 times.respectively);the content of MAP active site was 0.55 mmol·g-1,which provided π-π and hydrogen bonding sites,and significantly improved the adsorption capacity of Cr-MIL-101 for alachlor,acetochlor,chipton(the adsorption capacity ofacetochlor,acetochlor,and chipton increased by 1.1,0.8 and 1.6 times,respectively).Moreover,these two MOFs composites have excellent water stability and regeneration capacity,demonstrating their potential application in the field of adsorbent.(3)A series of furan/thiophene-derived Cr-MIL-101s were obtained via visible-light-inediated post-synthetic modification(PSM)for aqueous-phase herbicide adsorption.The guest trapping process was achieved under very mild and metal-free condition.affording newly functionalized MOFs(Cr-MIL-101-C1-C5)with more π-π stacking,hydrogen bonding properties and excellent adsorption capacity in removing herbicides from aquatic environments.The HPLC yield was up to 94%.The post-modified MOFs were used as adsorbents,and the effects of adsorption time,solution pH and adsorbent dosage on herbicide removal from water were investigated.It was characterized by NMR,HRMS,SEM and PXRD.The results showed that the introduced furan/thiophene and their derivatives could increase the π-π and hydrogen bonding sites of Cr-MIL-101,significantly improved the adsorption capacity of Cr-MIL-101 for diuron,alachlor,tebuthiuron and gramoxone(the adsorption amount increased by 1.2 to 2.8 times),and the removal percentage was as high as 96.9%in the herbicide aqueous solution with low concentration(30 mg·L-1).Further mechanistic studies(XPS analysis and adsorption competition experiments)confirmed that n-,n and hydrogen bonding played an important role.In summary,the synthesis methods of several new functionalized MOFs in this paper are relatively fast,economical,and relatively green.In the field of pesticide residues analysis,a highly sensitive electrochemical immunosensor,which can simultaneously quantitative analyze two pesticides,was prepared for the first time by using nano-MOFs.In the field of pesticide adsorptive removal,a variety of adsorbents were prepared by in situ polymerization and visible-light-mediated PSM with high adsorption capacity for herbicides in water.By synthesizing a series of functionalized MOFs with high abilities,we successfully broadened the application of MOFs in pesticide residue analysis and adsorptive removal.