Three-dimensional Composite Aerogels Decorated With MIL-88B(Fe) For Activation Persulfate Removal Of Norfloxacin From Water

Antibiotics,widely used in aquaculture,livestock and poultry breeding,and other industries,have received tremendous concern due to environmental problems.Norfloxacin（NOR）,a common class of quinolone antibiotics,was frequently detected in drinking water and surface water.NOR remaining in the environment would not only affect the water quality,but also caused human health risks through accumulation in the food chain.Therefore,it is of great practical significance to establish a method to effectively remove NOR from water.Among the numerous water treatment technologies,advanced oxidation technologies（AOPs）based on persulfate have attracted extensive attention due to their strong oxidizing ability and simple operation.The key to improving the catalytic performance of persulfate lies in the choice of catalyst.The iron-based metal-organic frameworks（Fe-MOFs）exhibited great potential in activating persulfate because of their good water stability and non-toxicity.The application of traditional powder catalysts is limited by particle agglomeration and difficult recovery.To address above the defects,an effective way is to fix MOFs on suitable carriers.Aerogel,a kind of three-dimensional（3D）macroscopical material that integrates low-density,high-elasticity and compressible,which properly meets the above demand as s carrier,is a promising emerging material for supporting MOFs.Therefore,in this study,a 3D porous aerogel catalyst for organic pollutants degradation in water by activating peroxydisulfate（PDS）was successfully synthesized,which was obtained via directly mixing of MIL-88B（Fe）with sol precursors followed by vacuum freeze-drying and low-temperature calcination.The morphology,structure and functional groups of the composite aerogels were analyzed by corresponding characterization tests.The effects of different reaction conditions on the degradation of norfloxacin were systematically investigated.The degradation mechanism and pathway of NOR by activated PDS of the composite aerogel were discussed,and the practical application potential of MGA-150 was evaluated.The main research contents and conclusions are as follows:（1）The direct mixing method was used to synthesize MGA composite aerogels.By optimizing the composite aerogels prepared under different synthesis conditions,MGA-150with an amount of MIL-88B（Fe）of 0.15 g and a calcination temperature of 150°C was finally determined as the best catalyst.The MGA-150/PDS system can remove 98.7%of NOR within90 min,and its pseudo-first-order kinetic constant is 23.2 times higher than that of the gelatin aerogel/PDS（GA/PDS）system.（2）The SEM,XRD,XPS,N₂ adsorption-desorption and FT-IR characterization results of MGA-150 showed that chemical bonds and hydrogen bonds were formed between the aerogel and MIL-88B（Fe）,which revealed the immobilization of MIL-88B（Fe）on gelatin aerogel.According to TG and DTG analysis,the loading capacity of MIL-88B（Fe）in the MGA-150mixed aerogel was as high as 36.3?wt%.（3）The effects of different PDS doses,NOR concentrations,initial p H and reaction temperature on the removal efficiency of NOR were investigated.The effects of common anions(Cl^-,SO₄^2-,HCO₃^-,HPO₄^2-)and humic acid（HA）on the degradation efficiency of NOR were studied.The results showed that ions and organic matter in the solution had no significant effect on the degradation of NOR.（4）The active species of the MGA-150/PDS system were determined by quenching experiment,electron paramagnetic resonance（EPR）test and linear scanning voltammetry（LSV）.The study found that free radicals(SO₄^·-,·OH),Both non-radical（¹O₂）oxidation and direct electron transfer are involved in the degradation of NOR,among which·OH is dominant.The intermediate products in the NOR degradation process were detected by high performance liquid chromatography-mass spectrometry（LC-MS）.Furthermore,we proposed the possible degradation paths of NOR in the MGA-150/PDS system.（5）The MGA-150 had excellent stable cycling performance and the degradation efficiency of NOR over 90.0%could still be maintained after 10 cycles.The catalytic performance of different Fe-MOFs/gelatin aerogels was compared,and various pollutant degradation experiments were carried out.When the MGA-150/PDS system was applied to NOR solutions in different water bodies（tap water,Peach Lake water,Xiangjiang water,medical wastewater）,the degradation effect of nearly 100%could still be achieved.The fixed bed-column dynamic experiment continued to run for 286 min,the average flow rate of the pump was 2.86?m L/min,and the degradation rate of NOR remained at 87.3%.