Controllable Synthesis, Modification Of Spherical Mesoporous Silica And Adsorption Performance Study Of Heavy Metal Ions

With the rapid development of industry and agriculture,a large number of pollutants are produced,such as heavy metals?nickel,lead,mercury,chromium,etc.?and organic pollutants?such as dyes?.The phenomenon of heavy metal pollution in water is getting worse,heavy metal wastewater,emissions directly or indirectly to the natural environment,has become the most serious and urgent to solve in the world of one of the important environmental problems.In various processing techniques of wast water Adsorption method become the most popular treatment technology due to its simple operation,high removal efficiency,recycling of renewable and low cost,and the most important part is the preparation of adsorption material.Mesoporous silica nano-materials because of its unique properties,good biocompatibility,good thermal stability and chemical properties,high adsorption ability and the use of the advantages of easy recycling is one of the most development potential of adsorption material at home and abroad.According to the characteristics and the developmental current situation of this kind of material structure,many problems need to be studied and solved.Such as:on the one hand,the mesoporous silica material itself has no active site,limitted the application range of the material;On the other hand,the surface modification of the material should be selected,whether it has high selective adsorption capacity,regeneration and reusability;Moreover,that's the study of adsorption mechanism.Using the sol-gel method,this paper explores the proportion of compound surfactant influence on material structural properties,by SEM,TEM,XRD,N₂ adsorption/desorption,FTIR and TG/DSC characterization methods processing analysis of materials,explored the formation mechanism of the material.We obtained the adsorption materials and investigated to the adsorption of methylene blue,choosed the optimal performance material.By the functional surface modification of material,we getted amino and carboxyl functional materials,functional materials were applied the material effective adsorption heavy metal Ni?II?in the water.By changing the experimental conditions to study the adsorption kinetics,isothermal adsorption equilibrium,adsorption thermodynamics and adsorption materials regeneration recycling,etc.,for the practical application of this kind of multi-functional material to lay the solid the development of the tomb.The main specific research contents are as follows:?1?Using the sol-gel method,with hexadecyl trimethyl ammonium bromide?CTAB?as template agent,gelatin?GE?as complex template agent,under the condition of alkali catalysis,ethyl silicate as silicon source,adding 1,3,5-trimethyltoluene?TMB?as the expanding agent synthesized with different structural characteristics of the spherical mesoporous silica materials?MSS?.The influence of the adding amount of the common template agent for the particle size,pore diameter,specific surface area and pore volume were investigated.With the increase of amount of gelatin,material particle size gradually decreases,and the pore volume as well as the specific surface area increase gradually before slowly decreases,and when CTAB/GE=3/2,the specific surface area and pore volume were the largest,respectively is 759.1534 m²/g and 1.1282 cm³/g,the pore size of 4.1 nm.?2?In order to explore the adsorption characteristics of MSS-x?x represents the addition of gelatin in 0,0.2,0.4,0.6g?,the adsorption experiment of methylene blue was carried out by using the material,and the optimum synthesis conditions were selected.Through the analysis of dynamics analysis and adsorption isotherm adsorption,MSS-x has good adsorption effect to methylene blue,using the Langmuir isotherm equation simulation to get the adsorption capacity of?Qm,mg/g?:MSS-0.4?119.60?>MSS-0.6?119.33?>MSS-0.2?119.21?>MSS?119.14?.When CTAB/GB=3/2,the adsorption effect of MSS-0.4 to methylene blue was 98.72%.Moreover,the quasi-secondary model is better able to simulate the adsorption behavior of MSS-x on methylene blue?R²=0.999?.However,the Langmuir adsorption isotherm model can better describe the sample MSS-0.4 and MSS-0.6,which belongs to the chemical adsorption process.The Freundlich model should describe the adsorption behavior of MSS and MSS-0.2 for methylene blue,which is not restricted by the adsorption of monolayer.That result in the optimal condition:at 65?,V_water/V_isopropanol=3,CTAB/GB=3/2,0.3g KCL,10 ml ammonia,1.7 mlTMB.?3?Using the surface chemical grafting method.Functional modification of MSS-0.4 of the optimal material was performed by using polyamine silane coupling agent 3-[2-?2-amino ethyl amino?ethyl amino]propyl-triethoxy silane?NQ-62?and 2-cyanoethylated triethoxy silane?CTES?as modifying agent.First,dry toluene as solvent,amino cyano functional for the MSS-0.4.And then 50%sulfuric acid solution hydrolysis cyano obtained-COOH,the resulting amino carboxylic functional materials MSS@NH₂@COOH,used rich characterization of technical analysis of the modified materials,the specific surface area from 759.1534 m²/g reduce to 113.8859 m²/g,pore volume from 1.1282 cm³/g reduce to 0.2526 cm³/g.The amino and carboxyl groups have been successfully grafted on MSS-0.4by FTIR and TG/DSC.MSS@NH₂@COOH and MSS-0.4 was applied to the removal of Ni?II?of heavy metals in water,the adsorption process can be very good with the Freundlich model describes,through linear fitting of Ni?II?the maximum adsorption capacity were 113.71 mg/g?MSS-0.4?and0.4 mg/g?MSS@NH₂@COOH?group.Explain modification increased the adsorption capacity and selectivity of materials.The adsorption kinetics conforms to the quasi-second-order kinetics model,indicating that the adsorption is chemical adsorption process.Adsorption thermodynamic analysis shows that the adsorption process is spontaneous and is the exothermic process.After repeated use 3times,the removal rate of Ni?II?was still high.