Preparation Of Diatomite-Supported Of Heterogeneous Fenton Catalyst And Study On Its Capability Of Degrading Dyes

According to statistics,discharging a ton of dye wastewater will lead to pollution for about 20 tons of water.The dye wastewater features refractory biodegradation and the toxicity of carcinogenicity,teratogenicity and mutagenicity,which do great harm to lakes,rivers and other water bodies.Fenton technology is one of the most concentrated and promising Advanced Oxidation Processes?AOPs?for the treatment of this kind of waste water.This method is characteristic of high degradation efficiency,friendly chemical reaction process,low cost and wide application.However,the traditional Fenton system has the disadvantages of high effluent chroma,high iron loss,and the acid reaction system.The studies found that the preparation of insoluble catalysts can improve the shortcomings of traditional Fenton.A new supported-heterogeneous catalyst was prepared based on diatomite by direct evaporating method.The preparation conditions of D-Fe₂O₃ were optimized,and the prepared D-Fe₂O₃ was characterized by SEM,XRD and so on.The catalytic degradation effects of various reaction factors were investigated.The process of oxidizing MB and the reaction kinetics of each factor were preliminarily discussed.The stability of D-Fe₂O₃ was analyzed and its practicability was evaluated by using the heterogeneous Fenton fluidized bed.The experiment results illustrated that iron ion concentration and solid-liquid ratio have an effect on the catalytic performance of D-Fe₂O₃ in the preparation process.The optimal iron concentration and solid-to-solution ratio for D-Fe₂O₃ preparation are 0.5 mol/L and 1:15,respectively.The results of SEM,EDS and XRD showed that the dense and unshaped Fe₂O₃ was supported on diatomite.A heterogeneous Fenton system?D-Fe₂O₃/H2O2?was established subsequently.Compared with traditional Fenton system,this one attains an increase of 3.5 times for MB decolorization rate in the same reaction condition.Through the orthogonal experiment,it can be learned that the influence of each factor on decoloration efficiency is different The results shows: pH>reaction temperature> D-Fe₂O₃ dosage> hydrogen peroxide dosage.,with the influence degree from large to small being pH,reaction temperature,D-Fe₂O₃ dosage,hydrogen peroxide dosage,orderly.The results of single factor experiments illustrated that the optimal degradation rate could reach over 99% within 20 minunder the reaction conditions of the D-Fe₂O₃ dosage of 12 g/L,the H2O2 concentration of 120 mmol/L,the initial pH of 3 and the reaction temperature of 55 ?.Through UV-vis analysis and literature reading,it can be learned that N,S diene ring in the chromogenic group?sulfydryl,-S-?and the benzene ringconnected to both sides of it broke down in the degradation process.Intermediate products are continuously demethylated and deaminated until they are degraded to CO2,H2 O and inorganic salt ions?Cl-,NO3-and SO42-?.Moreover,the degradation reaction conforms to the pseudo-first order kinetic model.The linear correlation was more than 0.950.The stability analysis of D-Fe₂O₃ showed that its dissolution amount of iron were receptively 5.31 mg/L and 0.05 mg/L in strong acid and alkali environments,demonstrating its good acid and alkali resistance.After 5 consecutive reuses,D-Fe₂O₃ can still maintain a decolorization rate of over 99% within 90 min.And then,D-Fe₂O₃ was used in a heterogeneous Fenton fluidized-bed for small-scale experiments.The results showed that the reactor effluent was clearand the color could reach the sewage discharge standards.The concentration of COD,decolorization rateand dissollution amount of iron in effluent of the reactor were receptively more than 50 mg/L,99% and 18 mg/L.In summary,D-Fe₂O₃ has the potential to practical application and is a promising heterogeneous Fenton catalyst.