Study On The Treatment Of Pharmaceutical Wastewater By Modified Attapulgite Supported Polymetallic Catalytic Photo-Fenton

In recent years,the pharmaceutical industry in China and even the world has entered the take-off stage.In this process,a large amount of pharmaceutical wastewater was produced,which has become one of the factors that endanger the water environment.Among them,the wastewater produced by chemical synthesis pharmaceutical process（referred to as chemical pharmaceutical wastewater）is highly toxic to the environment and human body due to the high difficulty of treatment,and with the expansion of industrial scale,the output of waste water has increased significantly,which has aroused people’s attention,and the ecological environment may be destroyed.In view of the current situation that it is difficult to achieve ideal results in the treatment of high concentration and low pH chemical pharmaceutical wastewater by traditional methods,this paper developed an effective process for the treatment of refractory wastewater and prepared an efficient and economical catalytic material,which is also the current research hotspot and problem in the field of heterogeneous Fenton treatment.The main research contents and results of this paper are as follows:（1）By comparing the catalytic performance of catalysts with different active centers,the new type of aeration-coprecipitation method was selected to develop Fe-Mn-Cu@ATP catalyst with modified attapulgite（ATP）as a carrier and loaded with multiple transition metals.The supporting method,mass ratio of metal carrier,molar ratio of metal and calcination temperature were optimized.The mass ratio of metal carrier was 1:1,the molar ratio of Fe/Mn/Cu was 1:1:2 and calcination was 400℃as the preparation conditions.The catalysts were characterized by XRD,SEM and FT-IR.The results showed that Fe,Mn and Cu metal elements were successfully loaded onto the surface of the support,and the presence of metal characteristic functional groups were observed.BET surface area（BET）and pore size（BJH）analysis showed that the specific surface area and pore volume of the sample decreased and the average pore size increased slightly after loading.X-ray photoelectron spectroscopy（XPS）showed that Fe,Mn and Cu elements existed on the surface of Fe-Mn-Cu@ATP as Fe（Ⅲ）,Mn（Ⅲ）and Mn（Ⅳ）and Cu（Ⅱ）,respectively.（2）The Photo-Fenton catalytic treatment system was established for the raw water of a pharmaceutical compound wastewater.It was found that the synergistic treatment effect of the pharmaceutical compound wastewater was the best under the UV/Fe-Mn-Cu@ATP/H₂O₂ system,and the COD treatment effect was improved by more than 40%compared with the single treatment method.The effect of reaction conditions on the catalytic performance of Photo-Fenton system was analyzed by single factor test method.The results showed that the initial pH of the solution was 2.0,the concentration of hydrogen peroxide was 0.5mol/L,the dosage of catalyst was 10g/L,and the ultraviolet distance was 10cm.After 180min of catalytic degradation,the removal rate of chemical oxygen demand（COD）of effluent reached 67.15%,and the biochemical ratio（BOD₅/COD）increased from 0.172 to 0.415.The catalyst cycle test proved that it has good recyclability.（3）The mechanism of catalytic degradation of compound pharmaceutical wastewater by Fe-Mn-Cu@ATP was analyzed from the aspects of gel chromatography（GPC）,gas phase chromatography-mass spectrometry（GC-MS）,three-dimensional fluorescence spectroscopy（3D-EEM）,catalytic reaction kinetics test,UV-Vis scanning（UV-vis）and reaction system free radical capture test before and after reaction.GPC and 3D-EEM analysis showed that most of the fluorescent humic acids and fulamic acids in the wastewater were degraded and eliminated,and the macromolecular substances were degraded into small molecules or even completely mineralized.The removal rates of chroma and UV₂₅₄ reached 56%and 82%,respectively.By GC-MS,the possible degradation pathway of the double bond breaking of organic compounds in the UV/Fe-Mn-Cu@ATP/H₂O₂ reaction system of the compound pharmaceutical wastewater was speculated.The mechanism of degradation of organic pollutants by UV catalyzed H₂O₂ to produce·OH was also revealed in terms of electron transfer between active metal centers and free metal ions in the Photo-Fenton system.