Fabrication Of Iron,Zirconium,and Aluminum Based Metal Organic Frameworks For Removal And Detection Of Water Pollutants

Adsorption is a simple,low-cost,environmentally friendly wastewater treatment technology,which has been widely used in the removal of pollutants in water.Traditional adsorbents,such as biological materials,metal oxides,activated carbon,polymer,etc.,are widely used in water remediation due to their simple preparation process and excellent adsorption performance.However,the potential secondary pollution,unfavorable collection and reutilization,as well single performance dramatically restrict the practical application of these conventional adsorbents in wastewater remediation.In the past few years,a new type of metal organic framework materials(MOFs)with the superiority of large surface area,high porosity,abundant surface functional groups and exposed active sites has been expected to possess a promising prospect in wastewater treatment.In addition,the fluorescence signal can be presented through the coordination interaction between the amino functionalized MOFs and target ions,enabling dual functions of detection and removal into one-body.Importantly,the bulk composites loaded with MOFs not only have good removal ability,but also the advantages of simple operation,easy separation and recovery,ensuring their feasibility in the actual environment.An iron-based MOF(NH2-MIL-88(Fe))with octahedral structure has been successfully fabricated for the arsenic removal,achieving the goal of double functions in detection and removal.In order to solve the problems of easy aggregation and difficult recovery of powdery adsorbents,we have synthesized FeOOH/straw composite derived from Prussian blue/straw.Taking fluorine as the representative pollutant,the as-synthesized NH2-MIL-53(Al)nanosheets are utilized for the simultaneous detection and removal toward fluoride.In view of the difficulty in separation and recovering of MOFs particles,the UioO66(Zr)/CF composite is designed.As a result,the monolithic adsorbent can be easily separated and recovered.The main results are concluded as follows:(1)Amino-functionalized iron-based MOF nanooctahedra have been successfully synthesized via a facile one-step solvothermal route for the selective detection and facile removal of arsenate from polluted water.Benefiting from the unique fluorescence enhancement and high specific surface area as well as excellent stability,the resultant NHZ-MIL-88(Fe)nanooctahedra can be utilized for the quantitative assay of arsenate,accompanied by a fast response time(<1 min),broad linear range(0.1-50 mM)and high sensitivity(detection limit of as low as 4.2 ppb)along with excellent selectivity towards arsenate.More significantly,the proposed sensing system has been further exemplified for the determination of arsenate in real environmental water samples with acceptable recoveries,highlighting its feasibility in complicated environmental samples.It is noteworthy that the as-synthesized NH2-MIL-88(Fe)nanooctahedra also exhibit extraordinary sorption performance towards As(V)in terms of high saturated adsorption capacity(125 mg g-1)and fast sorption kinetics,capable of easily reducing trace amounts of As(?)to below the acceptable standard for drinking water within 60 min.(2)3D porous FeOOH/straw hybrid monolith derived from Prussian blue/straw(PB/straw)has been successfully fabricated based on a facile hydrothermal technique followed by the subsequent NaOH treatment at room temperature.Thanks to large surface area,hollow microboxes and fully exposed active sites,the obtained composite presents excellent removal performance toward arsenic,as reflected by the remarkable high adsorption capacity of 104 mg g'1 for arsenate and 59 mg g-' for arsenite,ultrafast adsorption kinetics along with exceptional sorption selectivity.Specifically,the developed adsorbent is capable of treating the wastewater containing arsenic to below the limit of drinking water.More importantly,the fabricated 3D FeOOH/straw hybrid monolith has the characteristics of simple operation,environmental friendliness,easy separation and recovery.After 4 cycles of adsorption-regeneration,the arsenic removal rates can still maintain 64%,indicating its excellent recycling characteristics.(3)Amino-functionalized MOF(NH2-MIL-53(Al))nanosheets with various sizes are successful fabricated by regulating water/DMF ratios of mixed solution via a one-step solvothermal technique.Particularly,smaller size of NH2-MIL-53(Al)features the most adsorption capacities of 202.5 mg g-1 and fast sorption kinetics performance,capable of treating wastewater containing fluoride to below the limitation for drinking water within 15 min.Based on the collective advantages of large surface area,tunable pore size and short diffusion path,the proposed NH2-MIL-53(Al)displays the selective detection based on the fluorescence enhanced performance,as reflected by a broad range(0.5-100?M)and a low detection limit(0.31 ?M).Importantly,the fluorescence sensing system has been successfully utilized in real environment water with feasible detection value,verifying the feasibility and extensive practical application.(4)A novel hybrid monolith has been successfully fabricated for highly efficient defluoridation from contaminated waters,in which the UiO-66(Zr)particles are perfectly anchored on three dimensional(3D)porous carbon foam(CF).Benefiting from fully exposed active sites,excellent pore accessibility and efficient mass transport,the integrated UiO-66(Zr)/CF hybrid monolith exhibits fast adsorption kinetics,and outstanding uptake capacity toward fluoride as high as 295 mg g-1.Furthermore,the fluoride removal efficiency of the spent monolith can reach up to 70%after four cycles,accompanied by facile separation nature and outstandin g water stability.More significantly,the resulting UiO-66(Zr)/CF packed column(0.36 g)can continuously treat 400 mL of F solution with 6.2 mg L-1 before the breakthrough point occur,highlight its potential feasibility for fluoride removal in the practical applicability.