Preparation Of Cu-MCM-41and The Application In Wet Catalytic Oxidation Of Phenol Wastewater

Phenol is one of the most common toxic organics in industry wastewater, which isresistant to degradation and has negative impact for ecosystems and human life. Severaltechnologies are useful to eliminate phenol wastewater based on biological, physical andchemical treatments. Among them, catalytic wet oxidation appears to be economical and alsoefficient under mild reaction conditions. Recently, many studies have been conducted for thecatalytic wet oxidation of phenol using various heterogeneous catalysts, which avoid elevatedmetal contamination. Iron is always used as active component while it works well within onlya narrow pH range (pH3-4) and greatly limits the catalytic performance of oxidation systemsbecause most organic wastewater has pH values ranging from5to7. To tackle this problem,copper has been suggested to be the active component for its higher activities in the oxidationprocess and wider working pH value. Thus, developing a systematic research for theapplication of copper catalysts in phenol wastewater treatment is of great importance. In thispaper, the preparation and catalytic performance in phenol oxidation of CuO/MCM-41andCu-MCM-41zeolite catalysts were systematically studied; the preparation technique ofMCM-41zeolite membrane on microfibrous support was investigated preliminarily.First, MCM-41zeolite was synthesized by hydrothermal method and CuO/MCM-41zeolite was prepared by impregnation method. The properties of CuO/MCM-41zeolite werecharacterized by XRD, N2adsorption-desorption, H2-TPR and XPS. The effects of reactiontime, reaction temperature, initial solution pH value, catalyst concentration, adding acid sortand copper load on the conversion of phenol, TOC and copper leaching concentration wereexplored, respectively. The experimental results indicated that the presence of the extra-framework copper oxide in CuO/MCM-41. The phenol conversion increased as reaction time,temperature, catalyst concentration increased and kept stable as initial solution pH valuechanged. The phenol conversion reached97.93%in120min at the reaction temperature of60℃，initial solution pH value of6.5, catalyst concentration of2g/L, stirring rate of550rpm. The TOC conversion reached29.71%and wasn’t enhanced by adding acids into thesolution. The lowest copper leaching concentration was of10.69mg/L at pH=4.5. Second, Cu-MCM-41zeolite was prepared at room temperature. The properties of Cu-MCM-41zeolite were characterized by XRD, FT-IR and H2-TPR. The effects of reactiontemperature, catalyst concentration, reaction time, initial solution pH value on the conversionof phenol, TOC and copper leaching concentration were explored. The experimental resultsshowed that copper in Cu-MCM-41zeolite was partially located in the skeleton. The phenolconversion increased as reaction time, temperature increased and fluctuated as catalystconcentration and the initial solution pH value increased. The phenol conversion reached88.57%in120min at the reaction temperature of60℃，initial solution pH value of5.5,catalyst concentration of1g/L, stirring rate of550rpm and the TOC conversion reached20.5%. The lowest copper leaching concentration was of2.94mg/L at pH=6.5.Finally, the preparation of microfibrous MCM-41zeolite membrane composite wasinvestigated. The paper-like stainless steel microfibrous support was prepared by wet layuppapermaking and sintering process. The support was pre-impregnated with CTAB and TEOSrespectively after high-temperature calcinations and then the MCM-41zeolite membrane wasprepared by hydrothermal method on the surface of treated support. The structure andmorphology of MCM-41membranes were characterized by XRD and SEM. Continuous anddense zeolite membranes were successfully fabricated on the surface of stainless steelmicrofibrous by both pre-treated methods. The thicknesses of zeolite membranes fabricatedon the support pre-impregnated with CTAB and TEOS were1μm and0.8μm, respectively.