Synthesis Of Ordered Mesoporous Materials With Coal Fly Ash And Silica Fume,and Its Application For Removal Of Organic Dye

With the continuous production of dye wastewater during the dye synthesis and printing,the amount and the types of dyes entering the environment are increasing,so that the environmental pollution caused by dyes is becoming more and more serious.Due to the large specific surface area and rich surface functional groups,mesoporous silica is considered the best choice for adsorbent and catalyst carrier.However,the high price of silicon source make it impossible to produce in large scale.It is now indisputable that the rapid increase in consumption of mesoporous materials calls for further work seeking cheaper raw materials for their synthesis.And the cheap mesoporous silica materials will have a broad market in industrial wastewater treatment.On the other hand,coal fly ash and silica fume as industrial waste,have caused serious environmental pollution due to long-term unreasonable and effective use,direct discharge or accumulation.In this paper,synthesize the background of mesoporous silica materials and cool fly ash,silica fume,combined with the current situation of serious pollution of China's dye wastewater,it will be a good way to synthsis mesoporous molecular by using coal fly ash and silica fume as raw materials.In this paper,spherical aluminum-containing mesoporous material Al-MCM-41 was synthesized under the catalysis of ethyl acetate by one-step method from coal fly ash;three mesoporous silica were prepared rapidly from silica fume by using a new equipment.The effects of other components,reaction temperature and reaction time on the morphology of mesoporous materials were investigated.In this paper,methylene blue dyes were used as adsorbents,and the adsorption properties of the mesoporous materials were studied.The synthetic spherical silica fume-based mesoporous silica was used as a catalyst carrier,bimetallic oxides were loaded on the suaface to obtain two heterogeneous Fenton catalysts.The effects of initial pH value,catalyst dosage,H2O2 dosage and initial concentration of the MB dye on the degradation of dye wastewater were investigated.The innovations of this paper are shown as follow:(1)Synthesis of mesoporous molecular sieves Al-MCM-41 from industrial solid waste coal fly ash by one-step method,making it possible to produce mesoporous molecular sieves in large scale.The prepared mesoporous molecular sieves exhibit high adsorption capacity for cationic dye wastewater,pioneering the new direction of cheap mesoporous molecular sieves in the field of dyestuff wastewater treatment.(2)Rapid synthesis of three kinds of mesoporous silica with different morphologies from industrial by-product silica fume by controlling the amount of ethyl acetate used as the catalyst.The size of synthesized mesoporous silica particles are at the micron level and adjustable.(3)The spherical mesoporous silica SF-S-MCM is chosen as a carrier due to the light weight,porous structure,strong adsorption capacity and large specific surface area.Two novel heterogeneous Fenton(Fenton-like)catalytic materials were developed by loading iron-copper bimetallic oxide or manganese-copper bimetallic oxide onto the surface of mesoporous silica.According to the structure and properties of the prepared catalyst and the degradation experiment,the catalytic mechanism was discussed,providing new ideas for treatment of dye wastewater by heterogeneous Fenton technique.The main research results of this paper are shown as follow:(1)The spherical mesoporous molecular sieve Al-MCM-41 was synthesized from coal fly ash by using CTAB as the template,ethyl acetate as the catalyst,by a hydrothermal method.The single-factor experiments showed that the particle size of spherical mesoporous molecular sieve Al-MCM-41 decreased with the increase of ethyl acetate.In addition,the crystallization temperature and time affect the dispersion of particles and roundness in a certain extent.The optimum conditions for the preparation of spherical mesoporous adsorbents were as follows: the addition amount of ethyl acetate was 10 m L,the crystallization temperature was 60 ° C and the crystallization time was 12 h.(2)Rapid synthesis of three kinds of mesoporous silica with different morphologies from industrial by-product silica fume by controlling the amount of ethyl acetate used in the catalyst.The results showed that the addition of ethyl acetate in the catalyst not only affected the mophology the product but also influenced the order of the mesoporous materials.The effects of silica/CTAB molar ratio,water content,crystallization temperature,crystallization time and inorganic salt on the morphology were also studied,the morphology and size of mesoporous silica particle could be adjusted by the above conditions.(3)The effects of the initial pH value,the adsorption time,and the initial concentration of the MB solution and adsorption temperature were discussed by series of adsorption experiment.The results show that the increase of the pH value of the solution is beneficial to the adsorption of methylene blue on the four mesoporous silica materials and reached the maximum adsorption value at pH=10.0.At the same concentration,the three silica fume-based mesoporous silica materials reached the adsorption equilibrium in 30 min,faster than Al-MCM-41 adsorbent(120 min).The adsorption capacity of the four adsorbents on the methylene blue increases with the initial concentration of the solution until the saturation adsorption capacity is reached.The results of kinetics,isotherms and thermodynamics model analysis show that the adsorption process is in accordance with pseudo-second order kinetics model for all the four kinds of adsorbents.According to the isothermal model,the adsorption data for methylene blue by all the four kinds of adsorbents are consistent with the Langmuir isothermal adsorption model at three different temperatures,mainly adsorbed with monolayer.Thermodynamics research results show that the adsorption process is a spontaneous irreversible,exothermic process and suitable for low temperature and is a process of entropy reduction.(4)The catalysts were synthesized by loading the iron-copper bimetallic oxide or manganese-copper bimetallic oxide on the surface of silica fume-based spherical mesoporous silica.The XRD pattern and BET analysis showed that the loading process of the two novel catalysts did not change the pore structure,and they all retained the MCM-41 mesostructure.The results of XPS analysis showed that the valence of Fe was +3 in the form of Fe2O3,and the the valence of Cu was +2 in the form of CuO in FeCu/SFS-MCM sample;the valence of Mn was +3 and the valence of Cu was +2 in the form of CuMn2O4.The effect of molar ratio of Fe/Cu and Mn/Cu on the degradation of methylene blue by FeCu/SF-S-MCM and MnCu/SF-S-MCM composite was investigated.The optimum conditions for the preparation of FeCu/SF-S-MCM composite catalyst were as follows: the concentration of Fe3+ and Cu2+ were 0.01 mol/L and 0.02 mol/L,respectively.While the optimum concentration for the preparation of MnCu/SF-S-MCM composite catalyst were 0.01 mol/L for Mn2+ and 0.005 mol/L for Cu2+.(5)The effects of different reaction systems on the degradation of methylene blue were discussed.The results showed that the degradation rate of MB could be reach to 98.38% after 45 min reaction under the UV irradiation in the FeCu/SF-S-MCM/ H2O2 system.While for the MnCu/SF-S-MCM catalyst,the degradation rate of MB could also be 96.51%.At the same time,the same experiment was done on SF-S-MCM for comparison,the degradation rate of methylene blue was only about 50%,which indicated that the metal oxides loaded on the SF-S-MCM have a very important effect on the degradation of methylene blue.The degradation effect of methylene blue is mainly due to the synergistic effect of catalyst,H2O2 and UV light irradiation.(6)The effects of initial reaction conditions on the degradation of methylene blue were studied.The optimal reaction conditions for the degradation of methylene blue by FeCu/SF-S-MCM catalyst was as follows: the degradation rate of MB was 99.31% by using FeCu/SF-S-MCM catalyst when the initial concentration of methylene blue was 250.0 mg/L,the dosage of catalyst was 0.50 g/L,and the dosage of H2O2 was 0.3 m L.What's more,FeCu/SF-S-MCM catalystexhibits excellent catalytic performance in the pH range of 5.0-9.0.As for MnCu/SF-S-MCM catalyst,the optimal reaction conditions were as follows: the degradation rate of MB was 98.22% by using Mn Cu/SF-S-MCM catalyst when the initial concentration of methylene blue was 250.0 mg/L,the dosage of catalyst was 0.50 g/L,and the dosage of H2O2 was 0.5 mL.MnCu/SF-S-MCM catalysts exhibit outstanding catalytic performance in the pH range of 3.0-9.0,greatly broadening the pH range.