Preparation Of Metal Organic Framework Materials And Study On Removal Of Contaminants In Water

Water is the lifeline of human civilization.However,the contradiction between resource shortage and serious pollution faced by water resources has become one of the focuses of global attention in the 21st century.Therefore,how to purify and reuse polluted water is the primary task to solve this problem.Among the many technical means for removing water pollutants,the adsorption method has become one of the most effective technical means due to its high efficiency,low consumption and simplicity.Therefore,the development of economic,efficient,environmentally friendly new adsorbents is of great significance to science and technology and practical applications.Metal-Organic Frameworks?MOFs?are a new class of porous materials that have emerged in recent years.Its high specific surface area and porosity,adjustable pore size,good thermochemical stability,diverse topological structure and easy functionalization make MOFs show excellent application prospects in the field of environmental pollutant removal and repair.On this basis,two binary bimetallic MOFs composites were synthesized in this paper,and their adsorption properties and possible adsorption mechanisms for metal arsenic and bisphenols in water were studied.The specific research contents and results are as follows:A series of binary MOF-74 with different Fe/Co molar ratios were prepared by solvothermal method and used for the removal of As?III?and As?V?in water.The adsorption results show that the removal efficiency of arsenic is best when the Fe/Co molar ratio was 2:1.Further,the morphology,pore structure,elemental analysis and functional group composition of Fe₂Co₁ MOF-74 were characterized by SEM,TEM,XRD,FT-IR,XPS and N₂ adsorption-desorption isotherm tests.The removal performance of arsenic was further studied by using Fe₂Co₁ MOF-74 as adsorbent.The results show that Fe₂Co₁ MOF-74 exhibits efficient and stable removal performance for both As?III?and As?V?.The adsorption kinetics and isotherm data accorded with the pseudo-second-order kinetic model and the Langmuir model,indicating that the adsorption of arsenic on Fe₂Co₁ MOF-74 was a single-layer adsorption process dominated by chemisorption.At pH=4.3,the maximum adsorption capacities of Fe₂Co₁ MOF-74 for As?III?and As?V?were 266.52 mg/g and 292.29 mg/g,respectively,which were much higher than most of the previously reported adsorbents.Coexisting ions(except PO₄^3-)and humic acid?HA?did not show a significant effect on the removal of arsenic.Meanwhile,the results of five adsorption-desorption cycles showed that the adsorbent could be regenerated in the NaOH solution and still maintain high removal efficiency.Furthermore,FT-IR analysis showed that-C-OH,-M-O and-M-OH played a major role in the adsorption process.Fe₃O₄@Co/Ni-LDH with magnetic hollow core-shell structure was prepared by synthesizing magnetic Fe₃O₄@ZIF-67 micron particles.Furthermore,the morphology,pore structure,elemental analysis and functional group composition of Fe₃O₄@Co/Ni-LDH were characterized by SEM,TEM,XRD,FT-IR,XPS and N₂adsorption-desorption isotherm tests.The adsorption properties and possible adsorption mechanisms of four kinds of BPs?BPA,BPF,BPAF and BPS?in water were studied by using Fe₃O₄@Co/Ni-LDH as adsorbent.The results show that the adsorption kinetics of BPs on Fe₃O₄@Co/Ni-LDH accords with the pseudo-second-order kinetics model,indicating that the adsorption was mainly chemical adsorption.FT-IR analysis showed that the hydrogen bonding interaction between Fe₃O₄@Co/Ni-LDH and BPs was the main adsorption mechanism.The adsorption isotherm satisfies the Langmuir model,indicating that the adsorption process was single-layer adsorption.The maximum adsorption capacities of Fe₃O₄@Co/Ni-LDH for BPA,BPF,BPAF and BPS calculated by Langmuir model were 238.96,177.09,320.56 and 345.84 mg/g,respectively.The results of other adsorption parameters showed that the effect of humic acid?HA?and actual water on BPs removal was not significant,but high pH and ionic strength were not conducive to BPs removal to some extent.The adsorbent can be quickly separated from the aqueous solution within 2 min and regenerated in a methanol solution.After 5adsorption-desorption experiments,the adsorbent still had high removal efficiency for BPs.