Synthesis Of Micro/nanostructured Alumina Powder And Study Of Their Adsorption Performance

Hierarchical micro/nanostructured alumina powder has been widely used in the field of absorbent and catalyst because it maintained special properties of nano materials microcosmically and got over the deficiency of nano materials macroscopically.Therefore,its preparation methods attracted widespread attention of researchers.In this paper,serials of hierarchical micro/nanostructured alumina of clusters,hexagonal prism and coral shaped were prepared through the hydrothermal method and liquid precipitation method,and its application in absorption field.The main results were as follows:1.Series of hierarchical micro/nanostructured?-Al₂O₃ with enhanced adsorption performance towards CO₂ were successfully synthesized via a facilely hydrothermal method-calcination route using AlCl₃·6H₂O as aluminum source,CH₃COOK as precipitant and poly sodium 4-styrenesulfonate)?PSS?as structure directing agent,respectively.Effects of PSS concentration on the phase structure,morphologies,textural properties of the as-prepared?-Al₂O₃ and their adsorption performance towards CO₂ at 25°C were comparatively characterized by X-ray powder diffraction?XRD?,scanning electron microscopy?SEM?,N₂ adsorption-desorption techniques.It was shown that PSS plays an important role in controlling the morphologies,textural properties and adsorption performance of the?-Al₂O₃.The?-Al₂O₃ obtained without PSS shows irregular massive particles.With increasing its concentration to 2 g/L,4g/L and 6 g/L,respectively,the corresponding?-Al₂O₃ show irregular nanorods cluster-like micron particles,spherical-like cluster composed of nanorods and interwoven fibrous micron particles,respectively,and their specific surface area and pore volume gradually increase in turn.In comparsion with the?-Al₂O₃ obtained without PSS,the?-Al₂O₃ obtained with PSS show higher adsorption capacity and faster adsorption kinetics.Especially,when the PSS concentration is 6 g/L,the?-Al₂O₃ has the highest adsorption capactiy of 0.69 mmol/g,and shows stable adsorption capactiy after consecutive recycle times of 6.2.Series of hierarchical micro/nanostructured alumina powder of silkworm chrysalis and hexagonal prism shaped were successfully synthesized via a facilely hydrothermal method-calcination route using aluminium potassium sulfate as aluminum source,CH₃COOK as precipitant and one of PSS,polyethylene glycol PEG and triblock copolymer?P123?as structure directing agent,respectively.The phase structure,morphologies,textural properties of the as-prepared?-Al₂O₃ and their adsorption performance towards Congo red were comparatively characterized by XRD,SEM,N₂ adsorption-desorption techniques,FT-IR and UV.It was shown that the structure directing agent plays a key role in the formation of different morphologies of the?-Al₂O₃,and that their particle size ranged in 1-2?m long,2-3?m high.Although the specific surface area of the as-prepared samples were low,but what determined the adsorption performance towards Congo red were not specific surface area and pore size distribution.In particular,the adsorption kinetics of the as-prepared?-Al₂O₃ with any kind of structure directing agent towards Congo red were significantly accelerated.Especially when PSS was used as structure directing agent,the removal rate of corresponding product towards towards Congo red reached98.1%in 30 min,and it reached adsorption equilibrium in 60 min,but product without structure directing agent reached in 180 min.After consecutive recycle times of 4,the adsorption of product with structure directing agent towards Congo red still kept 83.5%of the first time and reached 416.1 mg/g which showed the excellent ability of cyclic regeneration capability.3.Series of hierarchical micro/nanostructured alumina powder of coral shaped were synthesized via a simple process of liquid precipitation using aluminium nitrate as aluminum source,ammonium carbonate as precipitant and PSS as structure directing agent,respectively.The phase structure,morphologies,textural properties of the as-prepared?-Al₂O₃ and their adsorption performance towards CO₂ at 25°C were comparatively characterized by XRD,SEM,N₂ adsorption-desorption techniques.It was shown that the addition of structure directing agent resulted the increase of specific surface area and pore volume as well as the change of pore structure while the as-prepared?-Al₂O₃ possessed high specific surface area of 274 m²/g and large pore volume of 1.02 cm³/g.The maximum adsorption of the as-prepared?-Al₂O₃towards CO₂ at 25°C reached 1.1 mmol/g,and after consecutive recycle times of 5,the adsorption of product still reached 0.92 mmol/g which showed that it had a excellent stability and recycle ability.