Study On Adsorption Of Bimetallic Organic Frameworks And Its Composite Materials For Reactive Black 5 And Phosphate

Metal organic frameworks(MOFs)are a kind of nanoporous materials.Due to their large specific surface area,high porosity and adjustable three-dimensional structure,they have great application potential in the fields of adsorption and catalysis.The typical azo dye Reactive Black five(RB5)was in the printing and dyeing industry.The excessive discharge of phosphate in the tail water seriously harmed water resources and ecology.It was urgent to develop new adsorbents to remove RB5and phosphate.In this paper,MOFs and their composite materials are prepared to adsorb RB5 and phosphorus.The main research contents included:(1)The preparation of Fe-Al-MOF and its adsorption and regeneration of RB5.The Fe-Al-MOF was prepared by hydrothermal synthesis.Fe-Al-MOF was used for the study of RB5 adsorption.There are a lot of influencing factors,such as the molar ratio of iron and aluminum,the dosage of adsorbent,the initial solution p H,time and temperature.Three different materials were prepared according to n(Fe):n(Al)=3:1?1:1?1:3.Among them,Fe-Al-MOF(1)prepared when n(Fe):n(Al)=1:1 had the best adsorption effect on RB5.The optimal adsorption conditions for Fe-Al-MOF(1)on RB5 were:when the initial RB5 concentration was 100 mg/L,the optimal Fe-Al-MOF(1)dosage was 0.02 g,the adsorption equilibrium time was 40 min,the optimal p H range of the reaction was 3-11 and the maximum adsorption capacity for RB5 was 256.88 mg/g;this adsorption process had a higher degree of fit with Langmuir and pseudo-second-order kinetic models,indicating that chemical adsorption occured during the adsorption process.The adsorption process of Fe-Al-MOF(1)on RB5 was spontaneous and exothermic.In the coexistence of Reactive Black Five(RB5)and Crystal Violet(CV),Fe-Al-MOF(1)adsorbed RB5with high selectivity.In the process of Fe-Al-MOF(1)adsorption and regeneration,the adsorption efficiency of RB5 was still about 80%after 3 cycles.(2)Preparation and adsorption experiment of Fe-Al-MOF/chitosan composite membrane(Fe-Al-MOF/CS).Because Fe-Al-MOF(1)was in powder form and was difficult to recycle,the iron-aluminum metal organic framework/chitosan composite material(Fe-Al-MOF/CS film)was prepared according to the solution mixing method.The film was used for RB5 adsorption.Five materials were prepared according to m(Fe-Al-MOF(1)):m(CS)=1:4,2:4,4:4,8:4,16:4.Among them,the Fe-Al-MOF/CS(8:4)prepared when m(Fe-Al-MOF(1)):m(CS)=8:4 had the best removal effect on RB5.In50 m L of 100 mg/L RB5 solution,0.05 g Fe-Al-MOF/CS(8:4)achieved the best adsorption capacity;the equilibrium time for Fe-Al-MOF/CS(8:4)to adsorb RB5 was450 min,it was more conducive to the occurrence of adsorption under acidic conditions;the correlation coefficient can be obtained by model fitting and this process was suitable for Langmuir and pseudo-second-order kinetic models.In the five adsorption-desorption process of Fe-Al-MOF/CS(8:4),the adsorption rate was still greater than 70%.(3)Preparation of magnetic carbon nanofiber material and its adsorption and regeneration of phosphate.The magnetic carbon nanofiber materials(Fe₃O₄-CNFs)were prepared by the co-precipitation method.Four materials were prepared according to m(Fe₃O₄):m(CNFs)=0.5:1,1:1,2:1,5:1.Among them,Fe₃O₄-CNFs₂had the best adsorption effect on phosphate.Fe₃O₄-CNFs₂ had fast adsorption kinetics and strong anti-interference.The maximum adsorption capacity was 7.26 mg P/g and the best initial p H was 3-6.In addition,Fe₃O₄-CNFs₂ exhibited good adsorption performance in secondary wastewater(SW).0.5 g/L Fe₃O₄-CNFs₂ can reduce the concentration of phosphate from 0.95 mg P/L to 0.05 mg P/L.In addition,after 5consecutive regeneration cycles,the removal rate of phosphate can still exceed 80%,indicating that Fe₃O₄-CNFs₂ has excellent regeneration performance.According to the material characterization,it can be speculated that the adsorption mechanism of Fe₃O₄-CNFs₂ involved surface precipitation and electrostatic attraction.(4)Preparation and adsorption of iron-aluminum metal organic framework/carbon fiber composite materials(Fe-Al-MOF/CFs).The iron-aluminum metal organic framework/carbon fiber composite material(Fe-Al-MOF/CFs)was prepared by solvothermal method and the adsorption experiment of phosphate was carried out.Four materials were prepared according to the addition amount of carbon fiber(CFs)of 10,20,40,and 120 mg.When the addition amount of CFs was 40 mg,the Fe-Al-MOF/CFs(40)had the best adsorption effect on phosphate.In 50 m L of 50mg/L phosphate solution,the optimal use amount of Fe-Al-MOF/CFs(40)was 0.05 g.When the initial p H was 6-8,Fe-Al-MOF/CFs(40)had a good adsorption effect on phosphate and its maximum adsorption capacity for phosphate was 67.38 mg/g.The adsorption process conformed to pseudo-second-order kinetics,intra-particle diffusion and Langmuir model.Surface precipitation and intra-particle diffusion dominated the phosphate adsorption.After 4 adsorption cycles,the adsorption efficiency of Fe-Al-MOF/CFs(40)on phosphate was above 75%,which had the characteristics of regeneration effect and easy removal from water.This research provided new insights for the removal of Reactive Black five and phosphate.Meanwhile,it provided an experimental theoretical basis for its application in actual wastewater treatment.