Study Of Catalytic Ozonation By Iron Silicate To Remove 4-CNB In Aqueous

4-CNB is a typical refractory compounds of the concentration at ng/L to ug/L level which is detected in aqueous,and there are potential damages to water economics and humans,the removal efficiency of 4-CNB is not ideal in traditional water treatment processes,so AOPs are more often to be used for the removal of it.Here,ozone is used as a strong oxidant to degradation trace 4-CNB in aqueous,and iron silicate is syntheized as a catalyst to strengthen the ozonation process.Iron silicate is synthesized at pH= 11 to precipitate 24 h with Si/Fe atom ratio 0.5,and then filtered the precipitation baked at 350 ? for 2 h.Iron silicate and a-Fe₂O₃ was characterized with SEM,EDAX,BET,XRD,FT-IR,XPS and to be compared.Iron silicate is a amorphous micropore materials with a 1.9 nm average pore diameter,doped Si increased the BET surface area from 55.2 m2/g of a-Fe₂O₃ to 321.3 m2/g of iron silicate.The Fe-O-Si and Fe-O bonds on the surface of iron silicate significantly enhance the catalytic activity.To compare with single ozonation,iron silicate as a catalyst can remarkably enhance the remove efficiency of 4-CNB from 55.3% to 82.8%,while adsorption capacity of 4-CNB is faint.After 3 times cycle of reaction,the catalytic capacity of iron silicate is still stable and only traces Fe3+ dissolved in the solution each time.Iron silicate catalytic activity was investigated at different reaction conditions of temperature,pH,water quality,ions and HCO3-concentration,the results indicate that 4-CNB remove efficiency is higher at 35 ? than others;And remove efficiency is higher at pH= 9.0 than other pH values;The concentration of HCO3-has a negative effects of the catalystic system;Ca2+,Mg2+ can inhibit the catalytic activity of iron silicate by complexing reaction with specific groups on the surface of it.The adsorption process of ozone molecule on the surface of iron silicate is reversible.After TBA was added to the catalytic system,4-CNB remove efficiency significantly decrease from 82.8% to 18.0%,which indicate that ·OH is the main oxide species in the catalytic system.The ESR test results indicated that the presence of iron silicate significantly enhanced the relative intensity of the DMPO-OH adduct signal compared with sole ozonation.The Fe-Si binary oxide can prompt a-Fe₂O₃ to decompose the adsorbed Ozone molecular on the surface of iron silicate.