Synthesis Of Mesopous Iron Oxide And Its Adsorption Properties

For this work,using inorganic iron salts as precursors,and different structures of surfactants are used as templating agents to replace traditional acid or base catalysts by introducing mild propylene oxide（PO）as a proton-depleting agent,five mesoporous iron oxide materials with different structural characteristics were synthesized in water or alcohol system respectively.The phase change of the mesoporous iron oxide materials in the process of calcination and template removal was characterized by XRD,N₂ adsorption,TG and SEM.At the same time,the mesoporousα-Fe₂O₃ formed after calcination was used to simulate the adsorption removal of Congo red in dye wastewater,and different models were used to simulate the adsorption kinetics,thermodynamic process and adsorption mechanism.The specific findings are as follows:1、In the FeCl₃?6H₂O-PO-EtOH system,mesoporous tetragonal fibrous iron phase（β-FeOOH）was synthesized by using neutral primary amine（dodecylamine）as template at 80℃.After calcination at 450℃,it was transformed intoα-Fe₂O₃ phase with a specific surface area of 22.12m²/g and pore volume of 0.208 cm³/g.It is used to simulate the removal of Congo red in dye wastewater.The maximum adsorption capacity can reach 134mg/g.2、In the Fe（NO₃）₃?9H₂O-PO-EtOH system,the amorphous mesoporous iron oxide material was synthesized by using cationic quaternary ammonium salts surfactant cetyltrimethylammonium bromide（CTAB）as template at 80℃.After calcination at 350℃,it was transformed into mesoporousα-Fe₂O₃ phase with a specific surface area of 117.834 m²/g and pore volume of 0.281 cm³/g.The adsorption capacity of Congo Red in simulated dye wastewater was acceptable 240 mg/g.3、In the FeCl₃?6H₂O-PO-H₂O system,mesoporous tetragonal fibrous iron phase（β-FeOOH）was synthesized by using dodecylamine as template at 80℃.The sample was calcined at 450℃and transformed into mesoporousα-Fe₂O₃ with a specific surface area of 58.429 m²/g,which was higher than that ofα-Fe₂O₃ sample synthesized under the same template condition using alcohol as solvent.The maximum absorption of Congo Red in simulated wastewater was 356 mg/g.4、In the FeCl₃?6H₂O-PO-H₂O system,mesoporous tetragonal fibrous iron phase（β-FeOOH）was synthesized using CTAB as template at 80℃.The sample was calcined at 400℃and transformed into mesoporousα-Fe₂O₃ with a specific surface area of 118.815 m²/g and a pore volume of 0.241 cm³/g.The adsorption capacity of Congo Red in simulated wastewater could reach 364 mg/g.5、In the FeCl₃?6H₂O-PO-H₂O system,mesoporous tetragonal fibrous iron phase（β-FeOOH）was also synthesized using ionic surfactant sodium dodecyl sulfate as template at 80℃.The sample was calcined at500℃and transformed into mesoporousα-Fe₂O₃,its specific surface area of the material was 102.178 m²/g,the pore volume was 0.151m³/g,and the adsorption capacity of Congo Red was as high as 368 mg/g.The results of this work show that mesoporous iron oxide can be controlled and synthesized in a milder system without the presence of acid or alkali.The temperature of transition to mesoporousα-Fe₂O₃ is different due to the different templates and solvents used.The adsorption effect of Congo red dye in simulated wastewater is also different,and is not positively related to the size of its specific surface area.This may be related to the difference in the residual amount of the templating agent and the PO ring opening product at different calcination temperatures and their presence.In addition,the room temperature photocatalytic degradation process of Congo red dye byα-Fe₂O₃ may occur in the adsorption process,and further systematic research is still in progress.And the adsorption process conforms to Langmuir’s single molecule adsorption model.The adsorption kinetics process is more in line with the pseudo-second-order kinetic model.The results of thermodynamic studies show that the adsorption process belongs to the adsorption process.In the thermal process,increasing the adsorption temperature contributes to an increase in the amount of adsorption.The results of regeneration adsorption showed that the adsorption effect remained good after three cycles,which was expected to play an active role in the treatment of dye wastewater.