Preparation And Application Of Magnesium Cement Based Photocatalytic Materials

Indoor air purification has become an important field of the current application of photocatalysis technology,developing cement based photocatalytic materials to solve the problem of indoor air purification possess great advantage because of cement based materials'characteristics of high usage,large exposed surface and low cost.Assuring the stability of cooperation between photocatalyst and carrier,and maintaining the efficient photocatalytic performance under the indoor environment of low light are essential research focuses.In this paper,Magnesium Cement Based Photocatalytic Materials?MCBPM?were prepared by cement matrix?Basic Magnesium Chloride Whisker,BMCW?,matrix modifier?SiO₂?and photocatalyst?TiO₂?,Photocatalytic Functional Wall Coatings?PFWC?were prepared by combining MCBPM with cement based putty powder.And after Ag modification,Visible Photocatalytic Functional Wall Coatings?VPFWC?were also prepared.The main research contents and results are as follows:Based on the analysis of the relationship among the raw materials composition,the crystal growth and the physical properties of BMCW,the optimal synthesis method of TiO₂ load matrix was determined.Through studying on the synthesis of SiO₂ doped modification effect on BMCW surface by different concentration of TEOs,we found that the orientation of SiO₂ synthesized on the surface of BMCW is consistent with that of BMCW in the growth direction,which means that modified basic magnesium chloride matrix?BMCW/SiO₂?exhibits good physical stability.Over high TEOs concentration results in over large particle size of SiO₂.On the contrary,the surface coverage of SiO₂ on BMCW is not enough.Therefore,when the mass ratio of SiO₂ and?BMCW+SiO₂?is 40%,the prepared BMCW/SiO₂-40%is the best TiO₂ load substrate.On the basis of the synthesis of BMCW/SiO₂-40%matrix,the MCBPM were prepared by the TiO₂ hydrosol loading and in-situ synthesis loading methods.During the preparation of hydrosol load process,because of the different corresponding pH of the isoelectric point of TiO₂ and SiO₂,mixing liquid's pH=6.20⁶.55 is the most suitable pH for the TiO₂ load.Within this pH range,increasing the concentration of TiO₂ graduallywill increase the degree of surface accumulation of TiO₂,thus forming a surface structure containing 4⁹ nm holes.MCBPM-5%were prepared at the 5%TiO₂ loading concentration,and the photocatalytic degradation rate of gas phase toluene was 55%under UV after 3 hours.In the in-situ synthesis loading process,the calcination process make MCBPM lose crystal water and become unstable.When the loading concentration of TiO₂ is 5%,the degradation rate of MCBPM-5 is up to 27%,and with the increase of TiO₂ loading concentration,TiO₂crystal particles increase rapidly,which leads to the reduced photocatalytic activity.The results of systematic analysis show that the technical route of VPFWC prepared by hydrosol-loaded MCBPM is the best choice.To increase the utilization of TiO₂,MCBPM-5%with excellent photocatalytic stability was used as the additive to prepare PFWC/VPFWC.With the increase of the MCBPM-5%introduction,photocatalytic activity of PFWC is also increased,PFWC-439 prepared with an introduction amount of 439g/m² was selected as Ag deposition modified material.Ag/AgCl was uniformly loaded onto the surface of PFWC-439 after self-assembly-light induction.With the increase of the Ag amount,the Ag/AgCl particles increase gradually,the distribution is denser,and the absorption intensity is stronger in the ultraviolet and visible regions.However,when excessive Ag sourceis introduced,too much anhydrous ethanol solution is introduced,which makes the putty powder"secondary hydration",and MCBPM-5%will be encapsulated in the hydration product and lead to reduce the photocatalytic activity.Therefore,VPFWC-16.62?prepared with the Ag deposition amount of16.62g/m²?delivers the highest photocatalytic degradation rate of toluene under visible and ultraviolet after 3 hours?28%and 73%,respectively?,and also exhibits excellent photocatalytic stability.