The Preparation And Application Of Mesoporous MCM-48 Composites

In this research work,the fly-ash treated by acid and alkali solution are prepared to the mesoporous molecular sieve MCM-48.The MCM-48 based on fly-ash is modified with organic and inorganic materials,respectively.Firstly,the polymer-based adsorbent modified by polyaniline（PANI）is used to remove the heavy metal ions.Secondly,the composite photocatalyst which compounded by the MCM48,ZnFe₂O₄ and BiOBr is used to degrade the organic pollutants The research results are as follows:（1）The impurities in fly ash are removed to extract silicon liquid by 3 mol/L HCland 3-6 mol/L NaOH solution.The desilication rate was evaluated from three variables:desilication time,desilication temperature and alkali concentration.It is concluded that the desilication rate of 5 moL/L NaOH solution is as high as 82.16%at 110℃ for 90 min after hydrothermal reaction.The mesoporous molecular sieve MCM-48 prepared by the desilication solution has good morphology and crystallinity.Its specific surface area,average pore size and volume are 823.7 m²/g,3.17 nm,and 0.65 cm³/g,respectively.（2）The composite materials of MCM-48/0.5PAN1,MCM-48/1PANI,and MCM-48/1.5PANI with different proportions modified by Polyaniline are synthesized.The best morphology and adsorption performance belongs to MCM-48/1 PANI,and the specific surface area,average pore size and volume of MCM-48/1PANI are 87.2 m²/g,3.91 nm,and 0.08 cm³/g,respectively.In heavy metal ions solution,the removal rates of Cd²⁺,Co²⁺ and Cu²⁺ by MCM-48/1PANI are 96.88%,90.82%and 81.73%.It has excellent adsorption capacity for Cd²⁺.The kinetic model of MCM-48 and MCM-48/1PANI adsorbents is according with the pseudo-second-order kinetic equation.Chemical adsorption is carried out between the adsorbent and metal ions through electron interaction.The adsorption isotherm model conforms to the Langmuir adsorption model and is monolayer adsorption on uniform surface.The selectivity of adsorption is Cd²⁺>Co²⁺>Cu²⁺ in the adsorption experiment of coexisting ions.Finally,the MCM-48/1PANI composite adsorbent still has excellent adsorption performance after 5 cycles.（3）The MCM-48/ZnFe₂O₄ and MCM-48/ZnFe₂O₄/BiOBr composite semiconductor are prepared by hydrothermal method and labeled as 0.5 MZBB,0.75 MZBB,1 MZBB.The 0.75 MZBB is a n-type semiconductor wihch has the best morphology and crystallinity by the characterization of XRD,SEM,FT-IR and XPS.In addition,the negative conduction band,valence band,visible light responsiveness and photoelectron-hole separation efficiency of 0.75 MZBB are optimal.（4）In the study of photocatalytic activity,the order of degradation efficiency is:0.75 MZBB>0.5 MZBB>1 MZBB>MCM-48/ZnFe₂O₄>BiOBr,where the mixture of 30 mg catalyst and 40 mg/LRhB is illuminated for 60 min.And so is the mineralization effect.The influence of initial solution concentration and pH value on RhB degradation are explored,using the 0.75 MZBB.It is found that the degradation effect of RhB solution increasing first and then decreasing with rising concentration and pH value.The degradation effect reached 99.05%,when the pH is 6 and solution concentration is 40mg/L,almost degraded and colorless completely.The active group capture experiment confirmes that the action of free radicals is-OH>·O2->h+.The degradation efficiency of 0.75 MZBB decreased from 99.23%to 91.43%after 5 cycles,which is with superior performance.