Design,Preparation And Adsorption Properties Of Functional Silica Mesoporous Materials

With the continuous development of modern industrial process,a large amount of waste water containing lead ions（II）is discharged into the environment,which not only affects the living environment of animals and plants in the water,but also threatens the health of human beings and causes great harm.Adsorption method is a common method for treating heavy metal ions in water because of its relatively low cost and simple operation.MCM-41molecular sieve is a kind of mesoporous silica material,which has the advantages of large specific surface area,regular pore structure,excellent chemical stability and thermal stability.Therefore,MCM-41 mesoporous molecular sieve can be used as an adsorbent for Pb²⁺adsorption in water,but pure silicon MCM-41 has a weak ability to adsorb Pb²⁺in water.The surface modification of MCM-41 can improve the adsorption performance of MCM-41mesoporous molecular sieve for Pb²⁺,which has become a research hotspot.MCM-41 mesoporous molecular sieve is prepare by sol-gel method in this paper,and then through grafting treatment,after the preparation of（3-Aminopropyl）trimethoxysilane（APTMS）functional base MCM-41 mesoporous molecular sieve（N-MCM-41）,and on this basis,through the reaction of the schiff base received surface adjacent hydroxy benzaldehyde branches with NH₂ MCM-41 mesoporous molecular sieve（N-MCM-41）,get the adjacent hydroxy benzaldehyde functional resorcinarene MCM-41 mesoporous molecular sieve（F-MCM-41）,and then through grafting treatment,after the preparation of（3-Aminopropyl）trimethoxysilane（APTMS）functional base MCM-41 mesoporous molecular sieve（N-MCM-41）,and on this basis,through the reaction of the schiff base received surface adjacent hydroxy benzaldehyde branches with NH₂ MCM-41 mesoporous molecular sieve（N-MCM-41）,get the adjacent hydroxy benzaldehyde functional resorcinarene MCM-41mesoporous molecular sieve（F-MCM-41）.The modified MCM-41 mesoporous molecular sieves were characterized by SEM,TEM,XRD,FT-IR,TGA,XPS and N₂ adsorption and desorption.The adsorption performance of the modified MCM-41 mesoporous molecular sieve for Pb²⁺was investigated under different initial concentration,adsorption time,adsorption temperature and p H values.The adsorption kinetics and thermodynamics of the mesoporous molecular sieve were analyzed,and the corresponding adsorption model was established.The adsorption mechanism of Pb²⁺on F-MCM-41 mesoporous molecular sieve was determined by XPS characterization.The continuous adsorption experiments of F-MCM-41 on adsorption columns were carried out to study the breakout curves at different bed heights,flow rates and initial concentrations,and the corresponding model fitting was carried out.The results showed that:（1）The surface morphology and structure of MCM-41mesoporous molecular sieve were not significantly changed after the modification of APTMS and o-hydroxybenzaldehyde,but the specific surface area and pore size decreased accordingly.Adsorption experiments showed that the adsorption capacity of the modified MCM-41mesoporous molecular sieve for Pb²⁺was significantly higher than that of MCM-41,and the adsorption capacity of N-MCM-41 and F-MCM-41 for Pb²⁺reached 71.3 mg/g and 115.8mg/g,respectively.（2）The Langmuir model can describe the adsorption characteristics of N-MCM-41 and F-MCM-41 for Pb²⁺by isotherm simulation.The adsorption kinetics analysis showed that the adsorption process of N-MCM-41 and F-MCM-41 conformed to pseudo second-order kinetic model and belonged to chemical adsorption.The adsorption process of Pb²⁺was mainly through the chelation of functional groups on the surface of MCM-41.Thermodynamic analysis shows that the adsorption of Pb²⁺by N-MCM-41 and F-MCM-41 is a spontaneous process.（3）The effects of bed height,initial concentration and flow rate on the adsorption of Pb²⁺by F-MCM-41 were investigated.The adsorption data were fitted by Adam Bohart,Yoon Nelson and Thomas models.The above results fully show that F-MCM-41 has a certain application value in the removal of Pb²⁺from aqueous solution.