Study On Preparation And Catalytic Ozonation Performance Of Fe-Functionalized 4A Zeolite

In recent years,the pollution of water resources in our country is becoming more and more serious,among which the main pollution comes from industrial wastewater and domestic sewage.The traditional water treatment technology can no longer meet the needs of people for healthy use of water.Because refractory organic matter has the characteristics of strong persistence in the environment,dispersibility,and multi-pathage into the water body,it has caused great danger to human health.Therefore,it has become a top priority to study the advanced treatment technology for refractory organic matter.As a typical advanced oxidation technology,heterogeneous catalytic ozone oxidation technology has the characteristics of strong removal ability,high ozone utilization rate,wide application range and green pollution-free in the advanced treatment of organic materials,and is widely used in practical engineering.Previous studies have focused on the removal of a refractory organic matter by a catalytic system in a heterogeneous catalytic system,but there are few studies on the comprehensive evaluation of hydroxyl radical?HO·?pathways in the catalytic process.In this paper,the Fe-4A nanocatalyst was first synthesized by impregnating and roasting iron into the nanopores of4A molecular sieve,and combined with ozone oxidation technology to establish a heterogeneous catalytic system.A series of experiments were designed to evaluate the activity of the catalyst and to confirm the presence of the HO?signal in the catalytic system,including the free radical probe reaction with p-CBA as the probe compound,advanced oxidation treatment with ATZ as a toxicity model compound and a free radical induced mineralization reaction with OA as an oxidation intermediate.In addition,the exposure of HO·was calculated quantitatively by establishing a model,and the possible paths in the catalytic process were discussed in depth.The structural and surface properties of the catalyst were characterized by SEM,BET,XRD and FTIR.The material was found to be a microporous structure with a pore size of about1 nm.The surface morphology was discontinuous and formed by metallic micro-clusters.X-ray diffraction was found to have the appearance of iron-based feature bands,and the FT-IR spectra clearly observed the formation of related functional groups at 2339 cm^-1.NH₃-TPD characterization of the Fe-4A showed that Fe³⁺in the catalyst increased the acidity of the catalyst as the Lewis acid center.By comparing the degradation effect of ATZ,the catalyst with higher activity?4%-Fe-4A?was selected,and the order of activity of the catalyst was from low to high:bare 4A(0.017min^-1)<0.5%-Fe-4A(0.019min^-1)<8%-Fe-4A(0.028min^-1)<2%-Fe-4A(0.031min^-1)<4%-Fe-4A(0.037min^-1)?R²>0.996?.ATZ was used as a model compound to investigate the effects of different process conditions on the degradation of substrates and the key factors in the reaction process.The results show that the catalytic system Fe-4A/O₃ is increased by 2.176 times compared with the ordinary single ozone system,and the ozone dosage,the pH in the solution and the increase of the catalyst dose can effectively increase the catalytic reaction rate;Through the free radical probe reaction?using p-CBA as the HO?probe substrate?and the free radical-induced mineralization reaction?using OA as the oxidation intermediate?,the signal strength of HO?and mineralization efficiency of refractory substance in the catalytic oxidation process was investigated.The results show that the degradation of organic matter in Fe-4A/O₃ system mainly follows the mechanism of hydroxyl radicals,and the mineralization efficiency of OA is significantly higher than that of single ozone oxidation process.In addition,the reproducibility and stability of the catalyst Fe-4A were examined.In addition,the effect of repeated catalysts on the degradation of ATZ and the leaching of iron ions in the catalytic ozonation process was investigated,the results show that Fe-4A is a highly active and stable regenerable catalyst.Combined with the characterization of the surface acidity of the catalyst material,the possible path of HO?in the Fe-4A/O₃ catalytic system was studied.It was found that the Lewis acid site provided by the Fe³⁺active center on the surface of Fe-4A material played an active role in the catalytic oxidation process.The kinetic model was first proposed and the R_CTT parameters were calculated to quantitatively describe the total exposure of HO?to ozone in the solution during catalytic ozonation as an indicator for evaluating the catalytic activity of the ozone catalyst.The R_CT value of the 4%-Fe-4A/O₃ system is 5.18×10^-8,which is almost six times that of the single ozone system(8.9×10^-9).