Study On The Perparation And Catalytic Activity Of SBA-15 Immobilized With Schiff Base Cu Complexes

With the development of industry,water pollution becomes more and more serious.Dyes are toxic and are stable to light,heat and oxidizing agents.The dyes are resistant to aerobic digestion.The dye wastewater is harmful to the environment and human health from dye production industry,printing and dyeing industry.Treatment of the dye waste water is becoming a headache.Studies show that the dye-containing waste water could be treated by using transition metal organic complexes as model compounds of metal enzymes.However,there are exit disadvantages,loss of active center,structural instability,and so on.Some reports on the SBA-15 immobilized enzymes and complexes show that the stability was improved.In this paper,SBA-15-supported Schiff base copper complexes were prepared and used as a catalyst for degradation of dye wastewater.The main contents and results are as follows:1)Schiffbase1-4 @ SBA-15 were prepared from SBA-15,aminopropyltriethoxysilane and aromatic aldehydes.Schiffbase5-9@SBA-15 were prepared from SBA-15,chloropropyltriethoxysilane,diamine compounds and aromatic aldehydes.The Cu-Schiffbase1-9@SBA-15 was prepared from Schiffbase1-9@SBA-15 and CuCl₂.The materials were characterized by FT-IR,solid diffuse reflectance,Cu determination,TG analysis,XRD（wide angle,small angle）,TEM,SEM and XPS.And found that Cu-Schiffbase was successfully immobilized on SBA-15,and the structure of SBA-15 was not destroyed.2)The dye removal and the effect of dye degradation from the waste water containing methyl orange concentration with 30mg/L,were investigated in the presence of Cu-Schiffbase@SBA-15 with 4mg/L,with the change oxygen,dosage of H₂O₂,the pH value,temperature,salt and dosage of salt.The results show that H₂O₂ is effective.The catalytic activity of the Cu-Schiff base@SBA-15 is better with higher pH value.The degradation rate could be improved while raising temperature.The dye degradation rate is only 80% in presence of-2-rNOB 、,and is100% in presence of- 3-24-l 、、NOSOC.The optimum conditions for the degradation of the dye were H₂O₂ as oxygen source,n（H₂O₂）: n（dye）= 400: 1,pH = 9.1,T = 40 C.3)The degradation of seven dyes（methyl orange,rhodamine B,alizarin red,R,E,O,）was investigated by using Cu-Schiffbase@SBA-15 as catalysts,under the optimum conditions.It wasfound rhodamine B was degraded completely in 1.5 h,and the degradation rate was 100%.Found that dyes R,E,O and B containing2-r-NOB 、 could not be degraded completely till 48 h,and the degradation rate was 80%.All these show that there exits certain substrate selectivity for Cu-Schiffbase@SBA-15.4)The structure-activity relationship of Cu-Schiffbase@SBA-15 was investigated.It was found that the catalytic activity is better with the longer flexible chain.Found that the catalytic activity is worse while more rigid group.Found that with electron donating group would be benefit to the catalytic activity.5)The stability of Cu-Schiffbase@SBA-15 was investigated in HCl,NaOH,pH=9.0 with stir.Found that the catalytic activity disappeared in presence of HCl,but resumed while the base added.It is found that the catalytic activity disappeared in presence of NaOH,but not resumed while the acid added.The catalysts,Cu-Schiff base@SBA-15 are stable in the presence of the buffer,they have been repeatedly used up to 5-6 cycle runs without loss in activity.6)The degradation products were determined by UV-vis,HPLC and CO₂ absorption experiments.The COD was measured by Mn method.It was found that the aromatic ring of the dye molecules were obviously weakened or disappeared.Maleic acid,oxalic acid and carbon dioxide were detected.COD range from 3 to 6.5 mg/L after degradation.All these indicate that the removal of the dyes was not only decolorization,but also degradation and mineralization.7)The kinetic progress was carried out by Graph Pad Prism 5 software.It was found that Cu-Schiffbase has enzymatic activity after loaded to SBA-15 too.The degradation progress is accord with enzymatic kinetics,Michaelis-Menten kinetic model.8)The degradation mechanism was investigated by free radical trapping inhibition experiment.It was found that 2,5-dihydroxybenzoic acid was obtained from salicylic acid and hydroxyl group.The dye degradation could be inhibited.The results show that the dye degradation is free radical progress.The degradation mechanism was deduced.