Study On Preparation Of Controllable Size Spherical Silica By Chlorosilane Residue Liquid

With the continuous depletion of natural resources,such as oil and coal,the new energy,such as solar energy and fuel cells,using polysilicon as raw material,is becoming more and more popular.Thus,the polysilicon industry has been developed rapidly,and the more chlorosilane residue liquid,which is of high utilization value,is also more and more.Chlorosilane residue liquid has strong corrosion and toxicity.If it is discharged directly,it will not only cause great harm to the human body and the environment,but also lead to the great waste of effective resources.Through the comparison and analysis of various methods for treating chlorosilane residue liquid,it is found that the preparation of silica by hydrolysis of chlorosilane although has some shortcomings and defects,but it can achieve the maximum recovery and utilization from its economic and technical perspective.But using the general hydrolysis process,the size of the silica particles is larger,the dispersion is poor and the agglomeration will appear.The preparation of nano-particles using microemulsion method has the advantages of narrow particle size distribution and easy to control,and the particles are not easy to agglomerate and have good dispersibility.Therefore,in this paper,the controllable particle size and morphology of nanosilica were prepared by microemulsion method using chlorosilane residue liquid as raw material.In this paper,the phase behavior of the microemulsion system composed of three kinds of surfactant,TX-100,CTAB and SDS respectively with n-hexanol,cyclohexane and ammonia,were studied.And the particle size and morphology of silica prepared using chlorosilane residue liquid as raw material were compared by different microemulsion systems.The results show that the microemulsion system composed of TX-100 as the surfactant has a larger W/O microemulsion area than the microemulsion system composed of CTAB and SDS as the surfactant;in addition,the SiO₂ particles prepared by the microemulsion system composed of TX-100 as the surfactant have smaller particle diameter and more uniform distribution,and the dispersity of particles was relatively good;but,the size and distribution of SiO₂particles prepared by microemulsion system composed of CTAB and SDS as surfactants are large and uneven,and agglomeration phenomenon also occurred.Therefore,the microemulsion system composed of TX-100 as a surfactant is more suitable for the preparation of silica using chlorosilane residue liquid as a raw materialThe nanosilica was prepared using the chlorosilane residual liquid as a raw material by single microemulsion and double microemulsion method using a microemulsion system composed of TX-100/cyclohexane/n-hexanol/ammonia,and the results showed that both methods can nanometer silica was prepared,but the SiO₂particles prepared by the single microemulsion method had larger particle size,poorer dispersion,and serious agglomeration,while the SiO₂ particles prepared by the double microemulsion method had smaller particle size,dispersibility is also good.Therefore,when nanosilica particles were prepared from chlorosilane residue liquid by double microemulsion method,we studied the effects of aging?reaction?time,reaction temperature,the amount of chlorosilane residue liquid,the amount of co-surfactant,the molar ratio of water and surfactant,the amount of ammonia on the size,morphology and dispersibility of nanosilica.The results show that when the aging time is 24h,the reaction temperature is 30,and the HLB value is 10.50,the size of the silica particles is smaller and the dispersion is better.With the increase of?in the system,the particle size of prepared nanosilica becomes larger;in addition,the amount of the suitable chlorosilane residual liquid and ammonia is favorable for the contact reaction,nucleation and growth of the nanosilica particles during the reaction,and it make the size of the silica prepared smaller and dispersivity better.The prepared nanosilica particles were characterized by X-ray diffraction,BET specific surface area analysis,infrared spectroscopy and thermogravimetric analysis.The results showed that the nanosilica particles prepared by microemulsion method were amorphous mesoporous silica with the specific surface area of 455.277m²/g;there is a TX-100 group in the prepared nanosilica,which does not completely remove the surfactants group after calcining at 600?,nor does it change the physical properties of its silica,but a part of the Si-OH bond is dehydrated and condensed to synthesize the Si-O-Si bond.In addition,it was found in the thermal stability analysis that it had a total weight loss rate of 22.4%in the temperature range of 0 to 1400?,and when the temperature exceeded 1135°C,a phase change of silica from amorphous to crystalline will been occur.This study focused on the problems of the large particle size and poor dispersibility of chlorosilanes in the acidic hydrolysis process.And the advantage of the microemulsion method for preparation of nanoparticles was adopted.The microemulsion method was used to treat the chlorosilane residue liquid and the controllable particle size and morphology of nanosilica were prepared,thus achieving high value-added resource utilization of chlorosilane residue liquid,provides a new idea for the treatment of chlorosilane residue liquid.