Studies On The Removal Of Phenols With The δ-MnO₂ And MnO₂-TiO₂

In recent years,studies on the utilization of metal oxides to remove and control the pollutants in the water have become the focuses in the native environmental realm.These metal oxides with changeable valences such as TiO₂,Fe₂O₃,MnO₂ etc. were used as new environmental materials.Hydro-xybenzene is plasmatic poison.It has high virulence.People pay more attention to disposing the hydroxybenzene in the wastewater.In this paper,hydroxybenzene was the disposing object.The efficiency of removing hydroxybenzene from simulative wastewater by some synthetic MnO₂ and MnO₂-TiO₂ was determined.The main conclusions are summarized below:1.Synthesis and its efficiency determination of phenol by some MnO₂Twelve kinds of manganese dioxide were synthesized.Their efficiency of removing phenol was determined and the results were as follows:the samples of MnO₂ gained through the reaction with NaClO₃ as oxidant had neutral sorption.The samples of MnO₂ gained by sintering with high temperatrue had the lowest adsorption.2.The remoal of phenol by theδ-MnO₂The sample of MnO₂ in suspension gained through the reaction of MnSO₄ with KMnO₄ wasδ-MnO₂.Its characteristics and the efficiency of remobing phenol were studied in detail.The conclusions were as follows:(1)The MnO₂ wasδ-MnO₂,with quasi-spherical shape,mean size 250nm,surface area 94.18m2/g and its surface had two hydroxyl.(2)Theδ-MnO₂ had high adsorption of phenol.The pH value of MnO₂ in suspension before adsorption was the key factor.And low pH value was benefit to the adsorption of phenol.Under the room temperature,pH=2.0,the dosage ofδ-MnO₂ were 500mg/L,the initial concentration of phenol was 100mg/L and adsorption time was 60min,the removal percentage was up to 80%.(3)The procession of adsorption of phenol on theδ-MnO₂ was very fast.In the first 10 minutes,the rate of the adsorption increased rapidly.Then it increased slowly and after 60 minutes it reached the equilibium state.(4)When the dosage aboutδ-MnO₂ was 500mg/L ,the adsorption isotherm which was the phenol at the surface ofδ-MnO₂ obeyed to the law of Langmuir.Increasing the temperature,the adsorption isotherm mobed down and the adsorption became difficult.To some extent,larger dosage ofδ-MnO₂ had bigger removal percentage of phenol.(5)The removal percentage reduced with the appending of Cl^-,NO₃^- and PO₄^3- in the solution.It also decreased with the appending of Ca²⁺,Al³⁺ in the solution when pH was in the range from 2 to 9.But it decreased when Fe³⁺ was appended in the condition of pH>4.(6)In the process of the adsorbing phenol from the aqueous solution byδ-MnO₂,traces of manganese oxide dissolved inti the solution under low pH values.But under high pH values,manganese oxide had not dissoved.It indicated that the removal of phenol byδ-MnO₂ was mainly caused by sorption.3. The removal of phenol by the mixed MnO₂-TiO₂ powderThe sample of the mixed MnO₂-TiO₂ powder were prepared by the reaction of TiCl4 with KMnO₄.Its characteristics and the efficiency of removing phenol were studied in detail.The conclusions were as follows:(1)The MnO₂-TiO₂ powder were amorphous MnO₂ and anatase or rutile TiO₂. Under the wallop condition, the surface area of the mixed MnO₂-TiO₂ powder was prepared by the reaction of TiCl4 with KMnO₄ were 741.078m2/g .(2)The MnO₂-TiO₂ powder had high adsorption effect of phenol.The pH value of MnO₂ in suspension before adsorption was the key factor.And low pH value was benefit to the adsorption of phenol.(3)The procession of adsorption of phenol on the MnO₂-TiO₂ was very fast.In the first 5 minutes,the rate of the adsorption increased rapidly, then it increased slowly and after 120 minutes they reached the equilibium state.(4)The adsorption isotherm kept to the law of Langmuir when the MnO₂-TiO₂ dosage were 500mg/L.Increasing the temperature,the adsorption isotherm mobed up and the adsorption became easy.In certain range,larger dosage of MnO₂-TiO₂ had bigger removal percentage of phenol.(5)Photocatalytic activity of the mixed MnO₂-TiO₂ powder had been studied by degrading the solution of phenol in different conditions. The results show: The photocatalytic capability of MnO₂-TiO₂ had close correlation with the crystal form, catalysis time, sintering temperature and pH value.