Synthesis,Characterization And Properties Of MeAPSO-34 Molecular Sieve And Supported Ferric Silicate Based On Bauxite

Bauxite is a general designation for the ores composed of gibbsite,boehmite,diasporic bauxite.The main chemical components of bauxite include Al₂O₃,SiO₂,Fe₂O₃,together with a small amount of TiO₂,CaO and MgO etc.The bauxite resources are relatively abundant in China.However,because the diaspore-type ore as a main component of bauxite is difficult for aluminum smelt,the exploitable proportion in natural bauxite is small.Considering the main chemicals in bauxite such as aluminum,silicon,titanium and iron,converting the non-renewable bauxite into high-value inorganic functional materials in situ is a significant work to achieve the appreciable social and economic benefits.Two title materials prepared from bauxite are studied in this thesis.First,MeAPSO-34 with iron and titanium dopant ions,which is a multistage porous molecular sieve,was synthesized using a clean and efficient way.Second,bauxite supported silicate ferric salt,which has superior specific surface area and adsorption ability for organic pollutant,as a kind of Fenton catalysis was prepared through activating the iron component in bauxite.The harmless treatment for biodegradable organic pollutant of high concentration was performed as an application of the bauxite supported silicate ferric salt.The bauxite in this work was purchased from Fujian Zhangpu Lianfa according to the high ratio of silicon and iron in their product.The chapters in this thesis are introduced briefly as below:In the first chapter,based on the physical and chemical analysis of the components in bauxite,the activation process of bauxite and the subsequent MeAPSO-34 synthesis by solid phase method have been optimized to achieve the desirable crystal phase and superior specific surface area.The optimal activation procedure of bauxite:The raw material?i.e.bauxite?was calcined at 550?for 4 h,then refluxed at 95?for 3 h in 1.67mol·L^-11 oxalic acid solution.Subsequently,direct drying,then calcined at 350?for 2 h to remove the residual oxalic acid in the solid material.Using the activated bauxite as mentioned above,the multi-stage MeAPSO-34 molecular sieve was successfully prepared by solid phase method.The synthesis conditions were described as follows:According to the aluminum content in the bauxite sample,the mole ratio of Al₂O₃:P₂O₅:SiO₂:TEA:TEAOH:H₂O:Fe:Ti is 1.0:1.0:0.6:2.6087:0.3802:30.37:0.31:0.03 with n_water-in/n_water-out=0.35.The mixture was kept at 200?for 48h.After cooling to the room temperature,the crystalline MeAPSO-34 micro-mesoporous molecular sieve was successfully prepared with a specific surface area of 492 m²/g.The purpose of this study is to take the abundant and cheap Fujian Zhangpu Lianfa bauxite as the raw material,and according to its characteristics of high aluminum,high silicon and high iron content,first of all,to explore a clean and efficient way to prepare MeAPSO-34 multistage porous molecular sieve doped with iron and titanium.Secondly,design the experiment to activate the iron component of bauxite,at the same time,make full use of the bauxite matrix of the larger specific surface area,strong adsorption ability of excellent vehicle features,a new material of the bauxite-based supported silicate ferric salt heterogeneous Fenton catalysis was prepared,which accumulated data for the harmless treatment of high concentration biodegradable organic wastewater.In the first chapter,based on the composition and physical and chemical analysis of bauxite,the activation process of bauxite is studied,and the factors influencing the synthesis of multi-pore MeAPSO-34 molecular sieve by solid phase method,such as roasting process,are studied.The influence of the crystal phase and specific surface area synthesized on the molecular sieve.such as the baking process route and oxalic acid reflux treatment method,etc.,on the crystal phase and specific surface area of the synthesis of molecular sieve.The results showed that the optimal activation conditions of bauxite are:bauxite was calcined at 550?for 4 h,then refluxed at 95?for 3 h in 1.67mol·L^-11 oxalic acid solution,dried,and then calcined at the last 350?for 2 h to remove oxalic acid.On the basis of the above activation,the multi-stage MeAPSO-34 molecular sieve was successfully prepared by solid phase method.The synthesis conditions were as follows:according to the content of aluminum in the bauxite sample,the mole ratio of Al₂O₃:P₂O₅:SiO₂:TEA:TEAOH:H₂O:Fe:Ti=1.0:1.0:0.6:2.6087:0.3802:30.37:0.31:0.03rele ase,n_water-in/n_water-out=0.35,200?for 48h,successfully prepared a molecular sieve of MeAPSO-34crystal phase with a specific surface area of 492 m²/g with micro-mesopores.In the second chapter,on the basis of the successful synthesis of molecular sieve in chapter one,we have investigated the various characters of MeAPSO-34 synthesized under different conditions including Si/Al molar ratio,silicon source type,internal and external water volume,crystallization temperature,crystallization time and material stirring method.PXRD,physical absorption and stripping of nitrogen,FT-IR,SEM-EDS,the UV-Vis DRS,TG were used to characterize the final products under different synthesis conditions.The optimized procedure for MeSAPO-34 synthesis with the superior performance were described as below:On the basis of alumina content under the optimal activated process,the optimal mole ratio of Al₂O₃:P₂O₅:SiO₂:TEA:TEAOH:H₂O:Fe:Ti is 1.0:1.0:0.6:2.6087:0.3802:30.37:0.31:0.03.The mixture was kept at 180?for 16h.The micro-mesoporous molecular sieve MeSAPO-34 with the best specific surface area of 653m²/g was achieved.The third chapter of the thesis is about two types of bauxite supported silicate ferric salts using solid-phase ball milling and hydrothermal methods,that is Fe₂?SiO₃?₃/bauxite-ss and Fe₂?SiO₃?₃/bauxite-sr,respectively.Physical and chemical characterization methods including XRD,FT-IR and SEM-EDS were carried out on the two title catalysts.Methylene blue and reactive brilliant red were used as molecular probes to evaluate the catalytic performance.Both of them have high catalytic activity in heterogeneous Fenton reactions.In comparison,the performance of Fe₂?SiO₃?₃/bauxite-sr is much better,which can keep catalytic activity under wide pH range,low reaction temperature,minor consumption of H₂O₂ and catalyst.