Fe³⁺/Mn²⁺ Loaded On Sepiolite As A Heterogeneous Fenton-like Reagent And Degradation Characteristics

Fe³⁺/Mn²⁺ doped on sepiolite, a heterogeneous Fenton-like catalyst, was prepared in this paper. The catalyst was used for the degradation of bromamine acid aqueous solution and the outcome was good. The selection of preparation method and carrier, preparation conditions and characterization of the catalyst were discussed and analyzed comprehensively. Meanwhile, the degradation properties of the heterogeneous Fenton-like reagent were evaluated by the degradation of bromamine acid aqueous solution. All the work was shown as follows:(1) The addition of citric acid in the complex reaction would cause the formation of chelate complex, which would improve the dispersion of active component and the stability of the catalyst. The heterogeneous Fenton-like catalyst with a high activity was prepared with a sol-gel method by using sepiolite as a carrier. The optimal preparation conditions were determined by single factor experiments, the results were that the optimal molar ratio of Fe³⁺, Mn²⁺ and citric acid was 2:1:3 with a concentration of Fe³⁺ and Mn²⁺ of 0.050 mol/L, 0.025 mol/L respectively and the optimal pH of precursor was of 8.0. Additionally, the catalyst was calcined at 450?℃for 3 h. The catalyst was used in the degradation of bromamine acid aqueous solution with a initial concentration of 30 mg/L, and the chroma removal rate could reached up to 98 % in 30min. We could define that the existence form of Fe and Mn on the surface of sepiolite wereγ-Fe2O3 and MnO respectively by the pattern of XRD and SEM.(2) The dissolution rate of active component, the reuse of the catalyst and the effect of inorganic ions on the activity were observed,the result showed that the catalyst processed good stability. The chroma removal rate of bromamine acid aqueous solution with a concentration of 30 mg/L degraded by the catalyst was higher than the plus of that of the catalyst with only Fe³⁺ or Mn²⁺, which was illustrated the there was a synergy between Fe³⁺ and Mn²⁺.(3) The degradation properties of the heterogeneous Fenton-like reagent were determined by single factor experiments, and the optimal reaction conditions were that the dosage of the catalyst was 2.0 g/L and the dosage of H2O2 was 1.00 mL/L. After reaction for 10 min, the chroma removal rate of bromamine acid aqueous solution could reach up to 98.37 %. The similar results were obtained on the pH values ranged between 3.0 and 11.0,which widened the use scope of pH. The chroma removal rate of the other three dye aqueous solution degraded with the catalyst were also high, which was illustrated that the application of the catalyst in the degradation of dye waster had a certain extensive.(4) The effect of the reaction time on the degradation of the heterogeneous Fenton-like system was analized by a dynamic analysis. The result showed that the degradation of bromamine acid aqueous solution was in accordance with a first order kinetics and the dynamical equation between the concentration and reaction time was set up in this paper.