| Water pollution problem increasingly prominent has become a big problem which human need to face nowadays.In order to monitor the presence of pollutants,we must conduct water sample analysis.Because of the complexity of the matrix and the trace level of the environmental pollutants in water,it is necessary to develop effective pretreatment procedures for enrichment and purification of the analytes prior to sensitive GC/MS or UPLC-MS/MS detection.However,the traditional SPE method generally consumes a large volume of sample and organic reagent and encounters serious matrix effect;the adsorbents have shortcomings in the aspect of low adsorption capacity and selectivity.Accordingly,developing a highly efficient,selective sorbent material and new type of solid-phase extraction method with environmentally friendly property and good purification effect is an effective way to accurately detect trace concentrations of residual organic pollutants in water.Metal-organic frameworks(MOFs)are a kind of recently identified porous nanometer materials.They have gained considerable attention in the field of analytical chemistry science due to its ultrahigh porosity,tunable pore and crystal size and modifiable framework with chemical groups,enormous internal surface areas.This dissertation focuses on the utilization of MOFs and magnetic composite as the adsorbent for the new solid-phase-extraction of organic pollutants.In addition,the further investigation of MOFs and magnetic composite materials on the adsorption mechanism,adsorption property and removal performance for organic pollutants is performed to provide the basis for the trace pollutants removal.The main contents are summarized as follows:The instability of most types of MOFs in water restricted the applications for the adsorption and the separation in liquid phase.Only a few types of MOFs were proved to be stable in water.MIL-101(Cr)(Material Institute Lavoisier,MIL)is one of the most prominent sorbents among thousands of MOFs in virtue of such attractive features as large surface area,high porosity,numerous unsaturated metal sites and excellent chemical stability.They have gained excellent potential application value in the adsorption field due to these characteristics.Two MOFs,MIL-101(Cr)and MIL-100(Fe)were synthesized by hydrothermal methods and the characterization was completed by means of SEM,XRD,and so on.To resolve the separation question between liquid and solid of nanometer MIL-101(Cr),we have designed strong magnetic,large surface areas Fe3O4/MIL-101(Cr)compound by using MIL-101(Cr)as template and Fe3O4 particles partially filled the pores of the parent material by in-situ reduction-precipitation method.To achieve the effective and low cost adsorbent,the novel synthesis method that exhibited the privilege of short-time reaction and controllable synthesis conditions was investigated.The method was simple and easily to be repeated,effectively enhanced the mechanical strength of the material,avoided the phenomenon of reunion.Fe3O4/MIL-101(Cr)would readily disperse in water and effectively extract the pollutants in water due to its magnetic strength and large surface area complexes.MIL-101(Cr),used as the sorbent in the porous membrane-protected micro-solid-phase extraction(?-SPE)device for the pre-concentration of organic pollutants,has not been reported so far.So attractive MIL-101(Cr)material was synthesized and applied as the sorbent in the porous membrane-protected ?-SPE device for the pre-concentration of phthalate esters(PAEs)in drinking water samples for the first time.The ananlytes included dimethyl phthalate(DMP),diethyl phthalate(DEP),dibutyl phthalate(DBP),benzyl butyl phthalate(BBP),di-(2-ethylhexyl)phthalate(DEHP)and di-n-octyl phthalate(DNOP).Parameters influencing the extraction efficiency,such as selection of sorbent materials,pH adjustment,effect of salt,magnetic-stirring extraction time,desorption solvent and desorption time,were investigated.Under the optimum conditions,the limits of detection from gas chromatography-mass spectrometric analysis for PAEs varied from 0.004 to 0.02 ?g·L-1.The linear ranges were from 0.1 to 50?g·L-1 or from 0.2 to 50?g·L-1 for the analytes with the relative standard deviations fluctuating from 0.8 to 10.9%(n=5).The enrichment factors(EFs)for the target PAEs were varied from 143 to 187.MIL-101(Cr)exhibited remarkable advantages compared to activated carbon and MIL-100(Fe).On the other hand,computational method was first used to predict the adsorption of MIL-101(Cr)towards PAEs.The molecular interactions and the free binding energies between MIL-101(Cr)and PAEs were observed and calculated in terms of molecular modeling method.MIL-101(Cr)showed high potential in the analysis of PAEs at trace level in drinking water.The computational result was consistent with the detected enrichment factors.The computational modeling accurately predicted the extraction efficiency of MOFs-based material towards the target analytes.Therefore,the combination of experimental and computational study provided a new strategy on the trace contaminant analysis.Next,a novel magnetic solid phase extraction combined with UPLC-MS/MS was developed and validated for the pretreatment and the determination of eight non-steroidal anti-inflammatory drugs(NSAIDs)in water samples.The analytes included piroxicam,ketoprofen,meloxicam,naproxen,diclofenac,indometacin,mefenamic acid and tolfenamic acid.High selective material Fe3O4/MIL-101(Cr)was used as the novel sorbent in the magnetic solid phase extraction and UPLC-MS/MS was employed for the detection of residual drugs in real water samples.The proposed method would significantly reduce the matrix effect and enhance the sensitivity.The experimental conditions affecting the extraction efficiencies for the analytes,such as amount of adsorbent,pH value,salt concentration,extraction time,desorption solvent and desorption time,were investigated.As results,the linearities of the target analytes were in the range of 0.1(0.2,0.05,0.02)to 500.0 ?g·L-1.The detection limits ranged from 0.03?g·L-1 to 0.06 ?g·L-1.The recoveries were in the range of 76.5%?95.5%with relative standard deviations of 0.9%?6.1%.The enrichment factors for the target analytes ranged from 191 to 240.Comparing with the other pretreatment methods for the extraction of NSAIDs,the developed method was simple,rapid,sensitive,and accurate.It would be applied for the analysis of NSAIDs in water samples,The developed magnetic composite material was successfully applied for the trace analysis of organic pollutants.At last,we try to apply it for the treatment of the typical NSAIDs diclofenac sodiumand acid dyes in water.Using diclofenac sodium(DCF)and acid red 1(AR1)and orange G(OG)as models,their adsorption in aqueous solution onto the Fe3O4/MIL-101(Cr)composite weas studied in view of the adsorption behavior and the adsorption performance.The experimental conditions affecting adsorption performance for the adsorbates,such as amount of adsorbent,pH value,salt concentration,adsorption time,experiment temperature and initial concetration were investigated.The results showed that Fe3O4/MIL-101(Cr)had good adsorption capacity for DCF,AR1 and OG.The adsorption isotherm,the adsorption kinetics and the thermodynamics demonstrated that both of chemical and physical adsorption existed at the same time in the adsorption of the adsorbates.And the n values of DCF,AR1 and OG were 2.854,1.538 and 2.019 obtained in Frendlich model,representing that the adsorption process is a favorable adsorption.The maximum adsorption capacities were calculated as 119,142.9 and 200 mg·g-1 by Langmuir equations for DCF,AR1 and OG.The adsorption kinetics of the adsorbate was in line with pseudo-second order kinetic model.And the adsorption thermodynamics showed that the adsorption of the adsorbate was spontaneous exothermic process.The results indicated that the electrostatic interactions between the adsorbate and the adsorbent might be critical to the adsorption mechanism.In addition,hydrophobic effects,?-? interactions,hydrogen bonds effect,coordination bonds effects were also predicted.Saturated Fe3O4/MIL-101(Cr)would be desorbed using 0.01 mol·L-1 NaOH solution.After adsorbent recycling six times,the removal rate still reached above 98%.The material has good stability in solvent,making its great potential applications in the related fields of adsorption.In conclusion,by utilizing various professional knowledge and techniques such as materials science,analytical chemistry,physical chemistry,and computer science,the attractive material Fe3O4/MIL-101(Cr)was synthesized by a simple reduction-precipitation.The new analytical methods using metal-organic frameworks MIL-101(Cr)and high performance magnetic MIL-101(Cr)composite were employed as the sorbent in the micro solid phase extraction and the magnetic solid phase extraction coupled with GC-MS and UPLC-MS/MS were developed and to be applied for the separation,the enrichment and the detection of phthalate esters and non-steroidal anti-inflammatory drugs in water sample.On the other hand,a combination strategy of experimental and computational study to explore the adsorption mechanism of MIL-101(Cr)and PAEs was performed.The adsorption ability of Fe3O4/MIL-101(Cr)toward typical NSAIDs diclofenac sodium and acid dyes was also explored by the adsorption experiment.All of the achieved results in the thesis would provide the scientific basis for the detection,the removal and the health risk assessment of trace organic pollutans in water sample. |
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