Research Of Activated Alumina/Activated Carbon Composite Materials

In this paper, activated alumina/activated carbon composite materials wereprepared by using a certain way to fix activated carbon powder onto activated alumina.The raw materials used were from different sources, i.e., aluminums hydroxide wasself made, waste aluminum slag, activated carbon and HNO3(as binder) werecommercially available. This new composite materials can overcome the difficultshaping shortcomings of activated carbon and it possess different pore sizes, highspecific surface area and superior absorption performance.The influences of formula, HNO3concentration, calcining temperature, heatingrate, holding time on properties such as iodine absorption and compressive strengthwere tested, thus the preparing conditions were decided. SEM, BET, XRD and otheranalytical methods were used to investigate the microstructures of composite materials.The bulk density, water absorption and porosity of the samples prepared under optimalconditions were determined, and the benzene and formaldehyde absorption of thesamples were also tested and reported.The optimal processes of activated alumina/activated carbon compositematerials by using aluminium hydroxide as raw material were as follows: firstly, theratio of aluminium hydroxide to activated carbon was controlled to be3to1, HNO3with a concentration of13%was used as binder. The mixture was then shaped intopallets after mixed thoroughly. Secondly, the resulting pallets were calcined at450℃for2hours with a heating speed of200℃/h after drying and then cooled downnaturally to get the final products. The corresponding properties of the materials arelisted below: the average compressive strength of pallets is44N, iodine value is441.40mg/g; carbon content is38.42%; specific surface area is360.07m2/g, averagepore size is2.906nm, pore volume is0.2616m3/g; bulk density is0.933g/cm3, waterabsorption is66.70%and the porosity is62.20%. The optimal processes of activatedalumina/activated carbon composite materials by using waste aluminum slag as rawmaterial were as follows: firstly, the ratio of waste aluminum slag to activated carbon was controlled to be3to1, HNO3with the same concentration (13%) with aluminiumhydroxide as binder, then shaping the mixture into pallets and calcining them at550℃for3hours with a heating speed of200℃/h after drying to get the composite materials.The average compressive strength of the resultant materials is32N, iodine value is381.97mg/g; carbon content is24.70%; specific surface area is261.95m2/g, averagepore size is3.886nm, pore volume is0.2545m3/g; bulk density is1.007g/cm3, waterabsorption is59.40%and the porosity is59.90%.The benzene adsorption experiment shows that, the benzene adsorption of the twosamples after saturated for12-24hours at30℃have the maximum absorption capacityof225.23mg/g,241.02mg/g. The benzene adsorption can be influenced by the ambienttemperatures considerably. The absorption mechanism belongs to physical adsorptionunder40℃and then changes to chemical adsorption dominant after that.The formaldehyde absorption experiment shows that, at30℃of ambienttemperature, the benzene adsorption of the two samples are saturated after48-72hoursand have maximum absorption capacity of284.19mg/g,268.50mg/g, and themaximum absorption capacity is at40℃.BET pore size distribution shows that mesopores and millipores are both existedin the composite materials and the average pore size of mesoporous is about3.0to8.0nm, meanwhile and the average pore size of millipore is about0.6to1.7nm.