Preparation And Performance Of Spherical Alumina-based Adsorbent Materials

Molecular sieve and manganese dioxide are two kinds of common usedadsorbent materials. The former has been widely employed in the separationprocess of mixed xylene isomers and the latter has been used to treat wastewater containing azo and phenolic. In present, both adsorbents are mostly inthe shape of lump, rod-like or sphere made by the rotation molding method,which are unfavorable for industry applications. To further overcome theshortcomings and expand the application fields, it is an important andnecessary issue to develop novel methods to shape these adsorbent materials.Spherical alumina prepared from alumina sol by the oil-drop method has highsphericity, smooth surface, uniform particle size, nice pore structure and highmechanical strength. Therefore, it has important significance in the value oftheory and industrial applications to shape molecular sieve and manganesedioxide using alumina sol as a adhesive by the oil-drop method.A series of spherical MnO₂-AL_O3was prepared using oil-drop method by adjusting the different ratios of alumina sol and MnO₂powder and optimisingthe operation parameters. The prepared spherical MnO₂-AL_O3were analyzedby XRD, FT-IR, BET, etc. The results show that the crystal structure of MnO₂remains and the spherical products have smooth surface, high sphericity,narrow size distribution and mesoporous structure. The amout of the adhesiveis controlled at least15wt%（calculated as the ratio of alumina in the product）.To some extent, it is effective to control the morphology and the porestructure.On the basis of adjusting the amount of alumina sol, the diameter and thepore structure of spherical MnO₂-AL_O3were further improved by addingorganic pore-forming agents such as acetone and acrylamide. The obtainedproducts were characterized by XRD, BET, etc. The results show that withincrease of the ratios of acetone and acrylamide, the diameter of the product isdecreased and the surface area and pore volume are increased. The surfacearea of modified spherical MnO₂-AL_O3can reach212.80m2/g, which is threetimes than that of the unmodified products.A series of micro-spherical13X zeolite-AL_O3were prepared withmicrofluidic injection molding technique using alumina sol as the adhensiveby oil-drop method. The products were analyzed by XRD, BET, etc. Theresults show that the addition of alumina sol does not affect the crystalstructure of the products and the spherical products have smooth surface, highsphericity and narrow size distribution. The amout of the adhesive is controlled at least5wt%（calculated as the ratio of alumina in the product）.With increase of alumina sol, the surface area and bulk density is decreasedand pore volume is increased.The decolorization of methyl orange as an probe reaction is used to studythe adsorption capacity of spherical MnO₂-AL_O3. The test results show thatthe spherical MnO₂-AL_O3has comparable adsorption capacity withmanganese dioxide powder. Comparing with the powder, sphericalMnO₂-AL_O3much simplied the operation process which can favor theindustry applications.