Method And Mechanism To Prepare Activated Carbon Rfom Coconut Shell With Pvrolysis Processing

Activated carbons have been widely used due to its advantage of well-developed porestructure, large specific surface and high adsorption properties. With the development ofsociety, the activated carbons with high adsorption property, versatility and strength have beendeveloped. The traditional preparation method of activated carbon has many problems, such ashigh chemical reagent usage, waste pollution, high energy consumption and so on, thus it isextremely urgent to find an alternative method.In the present work, the activated carbons of high adsorption properties were prepa-redfrom coconut shell by pyrolysis activating without any chemical reagents or activated gas. Theeffects of activation temperature and time, heating rate, reaction volumes and size of rawmaterials on pore structure, adsorption properties and special surface area of activated carbonswere investigated. The mechanism of pyrolysis activation was explored, which provide basicdata and the theoretical basis for the preparation process of activated carbon.The results show that the carbon prepared at the activation temperature of900℃for4hours, along with the heating rate of10℃/min has well-developed micropore with surfacearea of994m²/g, the iodine adorption of1295mg/g and methylene blue adsorption of135mg/g. The results of N₂adsorption show that the activated carbon has an average pore size ofabout2nm and total pore volume of0.5039cm³/g, of which micropore volume ratio is85.39%. The results of CO₂dynamic adsorption show that the adsorption quantity is up to56.61mg/g. The main performance of the sample is superior to that of activated carbon fromcoconut shell of commercially available.The pyrolysis activation conditions, such as activation temperature, activation time,heating rate, amount of raw materials and raw material particle size, are investigated. Theresults are suggested that with the increasing activation temperature and time, the yield ofactivated carbon decreased and methylene blue and iodine adsorption value increased. Beyond a certain value, the adsorption performance would decrease because of the pore collapsed andmergered. Under the experimental conditions, as the heating rate increased, the adsorptionperformance of activated carbon increased.Without any activation gas or chemical reagents added, the better performance ofcoconut shell activated carbon can be attributed to the following mechanism: in the pyrolysisprocess, raw material releases H₂O, CO₂and other gases and pores are formed; those gases andthe air inside the reactor will activate coconut shell, in the high temperature material notcarbonized is converted into an aromatic compound with a form of graphite crystallites,whichhave a good influence on pore structure.