Removal Of Azo Dyes And Phenolic Pollutants From Water By Magnetic Frameworks

With the rapid development of economies,the content of organic pollutants in the water environment is constantly increasing,the situation of water pollution is becoming increasingly serious,and water scarcity has become a major challenge facing the world.Wastewater reuse is one of the important means to alleviate global water resource shortage.However,wastewater typically contains a large amount of synthetic organic pollutants,such as azo dyes and phenolic pollutants.These organic pollutants are difficult to treat and can cause great harm to the ecological environment and human health.Thus,exploring efficient materials to reduce or even eliminate azo dyes and phenolic pollutants is of vital importance.Adsorption/degradation method is one of the effective methods for removing azo dyes and phenolic contaminants in water,and the key to this method is the adsorbent.Compared with traditional materials,frameworks materials have the advantages of adjustable pore structure,rich functional groups,large specific surface area and good structural stability.In this study,metal-organic frameworks materials and covalent organic framework materials were combined with ferric oxide nanoparticles to prepare novel magnetic composites Fe₃O₄@MOF-235,Fe₃O₄@COF-300 and Fe₃O₄@MOF-74 that can be rapidly separated from solution.Then the magnetic composites were used to adsorb/degrade Congo red,amino black10B,bisphenol A and ibuprofen in water.The results of the study are as follows:（1）Magnetic metal-organic framework composites Fe₃O₄@MOF-235 were prepared by solvothermal method,and applied as an adsorbent to the adsorption of azo dyes Congo red and amino black 10B in water.Adsorption isotherm and kinetics as well as effects of p H,temperature,adsorption time,and dye concentration on the dye adsorption process were investigated.The results showed that the composite presented excellent selective adsorption ability for Congo red and amino black 10B with an adsorption amount of 114.42 and 39.48 mg·g^-1,respectively,when the p H range was5–8.The adsorption of Congo red and amino black 10B by composites followed pseudo-second-order kinetic and Langmuir models（R²>0.99）,and was a spontaneous process.The Fe₃O₄@MOF-235 showed favorable stability and reusability,and the removal efficiency still maintained 91.8%for the fifth cycle.The maximum adsorption capacity for Congo red and amino black 10B in simulated water was basically unaffected.Therefore,the prepared composite Fe₃O₄@MOF-235 demonstrates high potential as an azo dye adsorbent.（2）Magnetic covalent organic framework composites Fe₃O₄@COF-300 were synthesized by hydrothermal method and used to remove bisphenol A and ibuprofen in water.The adsorption capacity of Fe₃O₄@COF-300 for bisphenol A and ibuprofen was investigated experimentally.The results showed that the removal efficiency of ibuprofen was 96.12%–98.52%in the p H range of 2–4 and that of bisphenol A was92.18%–95.62%in the p H range of 2–10.The experimental data were consistent with the results of pseudo-second-order kinetic and Langmuir models.The adsorption of Fe₃O₄@COF-300 pairs of bisphenol A and ibuprofen was a spontaneous endothermic process,and the maximum adsorption capacity was 173.31 and 303.03 mg·g^–1,respectively.Fe₃O₄@COF-300 can selectively adsorb bisphenol A and ibuprofen in the presence of coexisting compounds such as phenol,Congo red,and amino black 10B.The removal efficiency of both substances from the simulated water samples reached more than 88.30%.Fe₃O₄@COF-300 has a great regeneration performance,and the removal efficiency of bisphenol A and ibuprofen after five cycles was still more than92.15%and 89.29%,respectively.Therefore,the prepared composite Fe₃O₄@COF-300shows good performance as an adsorbent suitable for the adsorption of bisphenol A and ibuprofen in water.（3）The magnetic composites Fe₃O₄@MOF-74 were synthesized by solvothermal method and used as an activator for sodium persulfate to degrade bisphenol A and amino black 10B in water.The effects of different material,p H,catalyst concentration,oxidant concentration,pollutant concentration,and temperature on the reaction process were studied.The results showed that in the large p H range（p H=3–9）,amino black10B could be completely removed,and the removal efficiency of bisphenol A was above 95.58%.The degradation process conformed to the quasi-first-order kinetic model,and was dominated by sulfate radicals(SO₄^·–)and hydroxyl radicals（·OH）.The removal rate of both bisphenol A and amino black 10B were above 91.55%in the simulated water sample.Fe₃O₄@MOF-74 had a great regeneration performance,and the removal rate of bisphenol A and amino black 10B after five cycles was still above93.24%and 95.01%.In a word,the magnetic composite Fe₃O₄@MOF-74 is a potential catalyst,which can efficiently degrade bisphenol A and amino black 10B in water by activating sodium persulfate.