Development Of Magnetic SiO 2 Mesoporous Materials And Application Of Wastewater Purification

In recent years,due to the development of printing industry,dye wastewater pollution is increasing.Different technologies have been developed for wastewater purification.Compared with other technologies,the adsorption method is simple,low cost,safe,and efficient.The treatment of dye wastewater by adsorption avoids the highly toxic intermediate metabolites production due to incomplete degradation for the dyes.So it becomes very important to develop an economic adsorbent for adsorption technology.Mesoporous silica materials have become the focus of attention because of their regular pore structure,high specific surface area and adjustable pore size.But these kinds of materials are severely limited its application because of difficult separation from the water.In this paper,composite materials composed of magnetic spinel zinc ferrite and mesoporous silica were synthesized,which show mesoporous pore structure,high specific surface area and magnetic response ability.In addition,the adsorption mechanism of these adsorbents was systematically studied,which may provide the basis for the development of dye treatment technology in water environment.The obtained results are listed in the following:1.An adsorption technology is thought as one of the most extensive application for removal organic dyes from wastewater.In additional to surface area of the adsorbent,the adsorption properties of the adsorbent can be affected by the pore size and the electrostatic interaction between the charged surface of the adsorbent and the charged dye molecule,which is rarely studied.In the present study,hierarchical guest-host composites(Zn0.2Fe2 8O4@SBA-15)with the magnetic Zn0.2Fe2.8O4 nanoparticles embedded in the SBA-15 silica were synthesized through a solvothermal method.Stoichiometric amounts of zinc and iron ions were incorporated into the SBA-15 cavities,which induced the Zn0.2Fe2.8O4 nanobeads formation with about a diameter of 8.4 nm.The mesoporous pore size of the SBA-15 was expanded from 5.2 to 11.4 nm,which has not been reported as far as we know.The composite shows higher surface potential than the SBA-15.The lowest molar ratio of the Zn0.2Fe2.8O4 to the SBA-15 was calculated to be 0.12±0.02,which can be conveniently separated from a solution by an external magnetic field.Experimental results indicated that the composite showed excellent adsorption capacity for methylene blue(206 mg/g)from an aqueous solution.We believe this encapsulation route may pave a way for directly introducing magnetic metal oxide into mesoporous silica matrix for adsorption or other fields.2.Hollow mesoporous silica spheres(HMSS)were facilely synthesized by the Stober method,in which decane was first used to form the hollow structure.The pore diameter of the mesoporous shell and the porous volume of the HMSS become higher with addition of decane.The average diameter of the HMSS is about 1100 nm,the thickness of the shell is about 190 nm.The mesoporous channels are perpendicular throughout the shell to the center of the HMSS.The HMSS shows an excellent adsorption property for cationic organic dye(methylene blue,MB)from aqueous solutions,such as higher adsorption rate and capacity than those reported.Furthermore,we also demonstrate that this facile method can be used to prepare yolk-shell structures with magnetic core and radially oriented mesoporous shell.3.A solvothermal method was used to prepare magnetic HMSS,which HMSS was synthesized as the above.The HMSS shell was converted into nanosized SiO2 sheets with open mesopores.Magnetic Zn0.2Fe2.8O4 nanoparticles were synthesized on these SiO2 sheets.The composites show excellent adsorption properties for methylene blue(MB),which can reach equilibrium in less than 1 min and the maximum adsorption capacity is 495.05 mg/g.We further found that the composites showed a high selectivity for adsorption of methylene blue.The experimental results are fitted Langmuir isothermal adsorption model,and the adsorption process is exothermic and spontaneous by thermodynamic analysis.Thus,as a promising adsorbent,Mag-glass can quickly and selectively remove MB from aqueous solutions and is easy to recycle and reuse.