Heterogeneous Fenton Of Fe(?) Loaded Resins As Catalysts Degrading Phenol And P-Chlorophenol

In order to solve the defects of Fenton reaction,such as large iron mud yield,narrow application scope of pH,and the inhibition by chloride ion,the Fe(?)loaded resins were prepared as heterogeneous Fenton catalysts.Their catalytic activity and stability in catalizing phenol and P-chlorophenol degradation were discussed.Five kinds of pariculate ion-exchange resins were tested as heterogeneous Fenton catalyst carriers.The macroporous chelating styrene cation-exchange resin D401 was selected.Static impregnation method was used to prepare D401 supported Fe(?)catalyst,and the load was 28.2 mg/g(dry mass)under initial Fe(?)concentration 15.0 g/L.Under initial pH=3.0,7.5 mL/L loaded D401 catalyzed 100%phenol removal within 40 min,and the total iron dissolution concentration is 6.7 mg/L.Drying,dissoved oxygen and alkaline conversion can reduce the catalytic activity of D401 supported Fe(?)catalyst.For Nafion N-117,the load reached 47.9±0.6 mg/g(dry mass)under optimal loading condition of 1.0g Fe(?)/L,initial pH=4.0.N-117 supported Fe(?)catalyst performed as an active and stable heterogeneous Fenton catalyst under strong acid condition:phenol degradation rate reached 99.6%within 50 min,and the dissolved total iron concentration was only 3.4 mg/L.The catalytic activity of the loaded N-117 can be slightly reduced by storage in high oxygen content in water.Fe(?)loaded D401 and N-117 can both broaden the pH range of Fenton reaction,with low dissolved iron concentration.Under increased initial pH,D401 supported Fe(?)catalyzed rapid and complete decomposition of hydrogen peroxide,while phenol degradation rate was significantly decreased.The amount of iron dissolution was less than 7.1%.When catalyzed by N-117 supported Fe(?)catalyst,the speed of hydrogen peroxide decomposition and phenol degradation decreased significantly,but phenol was completely removed in 300 min,with 0.42%of loaded iron dissolved.Hydrogen peroxide decomposition catalyzed by two catalysts have different mechanisms.Hydrogen peroxide decomposition catalyzed by Fe(?)loaded D401 conformed to first order kinetic equations,while that by Fe(?)loaded N-117 conformed to second order equations.Phenol degradation catalyzed by Fe(?)loaded D401 mainly resulted from homogeneous Fenton reaction catalyzed by dissolved iron.For Fe(?)loaded N-117 catalyst,homogeneous reaction contributed to 62%of phenol removal at most under strong acidic condition.Under neutral condition,heterogeneous Fenton reaction was the main contributor for phenol removal.The Fe(?)loaded N-117 can effectively catalyze P-chlorophenol degradation in the initial pH range of 3.0?9.0,and reduce the inhibition of chloride ion.With initial 100 mg/L H2O2,initial pH of 3.0,95.6%P-chlorophenol was removed in 60 min.At initial pH of 9.0,over 87.3%P-chlorophenol was removed in 300 min.As chloride ion concentration increased from 0 mg/L to 500 mg/L,P-chlorophenol catalytic degradation rate remained no less than 87.0%,but the speed of P-chlorophenol degradation rate decreased.When humic acid concentration increased from 0 mg/L to 25 mg/L,P-chlorophenol degradation remained no less than 90.2%.Total iron dissolution increased from 0.67 mg/L to 7.5 mg/L.In continuous tests,the increase in iron load,increase in initial H2O2 concentration,and decrease in flow rate prolonged life of Fe(?)loaded D401)catalyst in continuous phenol degradation.After optimization,Fe(?)loaded D401 catalyzed 100%phenol removal within 50.4 times resin bed.Sodium ion significantly reduced phenol degradation rate catalyzted by Fe(?)loaded N-117 catalyst,while the influence of increased hydrogen peroxide concentration was negligible.Under initial H2O2 concentration of 100 mg/L and no sodium ion,phenol degradation rate remained 81.6%after 300 min continuous operation.The average total iron dissolving concentration was 0.78 mg/L.Fe(?)loaded N-117 had longer life.In recycle tests,both D401 and N-117 remained stable as heterogeneous catalyst carrier.Within 4 recycle circles,catalytic acticity and dissolved iron concentration of Fe(?)loaded D401 were slightly reduced.For Fe(?)loaded N-117,iron loads and the phenol removal speeds increased with recycling circles,and then remained stable.Compared with the Fe(?)loaded D401 catalyst,Fe(?)loaded N-117 catalyst has better catalytic performance with higher heterogeneous contribution,lower dissolved iron concentration,longer life and better continuous operation stability.