Preparation Of Hollow Mesoporous Silica Nanoparticles And Its Adsorption Of Heavy Metal Ions

Hollow mesoporous nano/microspheres have become an international research hotspot due to their large surface area,adjustable pore structure and size,diversity of components,good stability and biocompatibility,which make them having great potential applications in the areas of molecular adsorption and separation,catalysis,and biomedicine,et al.At present,the construction of hollow mesoporous nano/microspheres is generally based on the concept of template method and self-sacrificing template method,both of which require the participation of template particles.And the process of removing the template is complex and high energy consumption.Therefore,it is very imperative to develop some simple,efficient and controllable methods for the preparation of hollow mesoporous nanoparticles.In this paper,we choose two commonly used silane coupling agent,by introduceing a new strategy of the pre-hydrolysis of the silane coupling agents in the mixture solution of ethanol and acetic acid,the hollow mesoporous silica nanoparticles were directly obtained by microemulsion method.On this basis,we further generally synthesized hollow mesoporous silica nanoparticles with adjustable pore sizes by using different kinds of expanding agents.And the adsorption behavior of heavy metal ions onto the hollow mesoporous silica nanoparticles was further studied.The main research content and results are summarized as follows:?1?Controllable preparation of hollow mesoporous silica nanoparticlesUsing 1,2-bis?triethoxysilyl?ethane?BTEE?and tetraethyl orthosilicate?TEOS?as the silane coupling agent precursors and pre-hydrolyzed in the mixture solution of ethanol and acetic acid,then adding to the alkaline reaction solution containing surfactant hexadecyl trimethyl ammonium bromide?CTAB?and poly?ethylene glycol?-block-poly?propylene glycol?-block-poly?ethylene glycol??P123?,hollow mesoporous silica nanoparticles?HMSs?were controllably prepared by the oil-in-water?W/O?microemulsion method.By changing the proportion of BTEE/TEOS,BTEE/TEOS overall dosage,the dosage of triethylamine,hydrolysis time and the dosage proportion of the CTAB/P123,the particle size,shell thickness,pore size,yield and component of the hollow mesoporous silica nanoparticles can be regulated.And the formation mechanism of the hollow structure based on assembly micelles and precursors of co-emulsification formation of O/W microemulsion system was proposed.?2?Universal preparation of hollow mesoporous silica nanoparticles with adjustable pore sizeBased on the research the W/O microemulsion preparation of the hollow mesoporous silica nanoparticles,hollow mesoporous silica nanoparticles were generally prepared by introducing different kinds of expanding agents,including block copolymers?P123,F127?and organic hydrophobic expanding agents?cyclohexane,1,3,5-trimethylbenzene?.By changing the amount of expanding agents,the pore size of hollow mesoporous silica nanoparticles could be regulated,and the mesoporous size can be enlarged from 2.5 nm to 4.2 nm.The possible mechanism of expansion of mesoporous size of the hollow mesoporous silica nanospheres was proposed.?3?Study the adsorption behavior of heavy metal Cu²⁺onto hollow mesoporous silica nanoparticles.Hollow mesoporous silica nanoparticles were used as adsorbents to study the adsorption behavior of heavy metal Cu²⁺.The adsorption of Cu²⁺onto hollow mesoporous silica nanoparticles is greatly affected by the pH of the solution.When the pH of the solution was 6.0,the adsorption effect is the best.The adsorption amount reaches 50 mg/g with the removal rate of 91%.The adsorption isotherm curve of Cu²⁺onto hollow mesoporous silica nanoparticles is in accordance with the Langmuir model,which belongs to single-layer adsorption.The adsorption kinetics of Cu²⁺onto hollow mesoporous silica nanoparticles is in accordance with the pseudo-second-order model.And the intraparticle diffusion model further showed that the Cu²⁺adsorption rate was controlled by internal diffusion and surface adsorption.XPS analysis showed that-OH groups on the surface of hollow mesoporous silica nanoparticles were coordinated with Cu²⁺.The nanoparticles of adsorbed Cu²⁺were eluted by hydrochloric acid solution.After five adsorption-desorption cycles,the hollow spherical shape still remained good with the removal of 83%,indicating that hollow mesoporous silica nanoparticles had good recycling properties.