KOH 활성화법에 의한 폐감귤박으로부터 활성탄 제조에 관한 연구

Abstract

As the method to reuse the waste citrus peel (which is a biomass resource and is discarded in large amounts in Jeju Island) efficiently, activated carbon was prepared by the carbonization process, followed by the chemical activation process with KOH. The characteristics of the products prepared at each process were analyzed, from which the optimum condition at each process was evaluated. The results obtained were as follows:

1. The waste citrus peel was composed of natural materials and it was observed that the waste citrus peel was pyrolyzed by three steps: the first step which water and a little volatile materials within it were evaporated (up to about 120℃), the second step which its weight loss ratio was great (in the range of about 120 ～350℃), and the third step which its pyrolysis came to an end slowly (above about 350℃).

2. The optimal condition of carbonization was at 300℃ for 1.5 hr and at this condition, the iodine adsorptivity of carbonized sample was 646 mg/g.

3. The activated carbon prepared with carbonized samples prepared at optimal carbonization condition, showed the highest iodine adsorptivity of 1,246 mg/g at the activation condition of 300% KOH ratio and 900℃ for 1.5 hr.

4. Comparing the composition of C, H, N and ash for activated carbon with that for waste citrus peel or carbonized sample, the content of C was increased greatly, but the contents of H and N were decreasd greatly. For ash, the composition of CaO was decreased, but K2O was increased greatly with above 60% of total composition.

5. SEM photography showed that the carbonized sample had the surface with the pores of regular shapes at carbonization temp. of 300℃, but with broken ones at higher carbonization temp., and the activated carbon had the more active surface with the production of many micropores by chemical activation, compared with that of the former.

6. With increasing KOH ratio from 100% to 300% for activated carbon, the micropores of surface were well-developed relatively, specific surface area and total pore volume were increased from 1,134 mg/g to 1,527 mg/g, from 0.662 cm3/g to 1.004 cm3/g, respectively, but average pore diameter was decreased from 24.2Å to 20.7Å. All the activated carbons prepared with different KOH ratio showed Type 1 adsorption isotherms for the adsorption of nitrogen gas.