Limitation of K2CO3 as a Chemical Agent for Upgrading Activated Carbon

Processes

Jung-Eun Park¹  Gibbum Lee¹  Seok-Hwi Kim¹  Ji-Hyun Kim² 

[1] Center for Bio-Resource Recycling, Institute for Advanced Engineering, Yongin 11780, Gyeonggi, Korea;Convergence Research Division, Korea Carbon Industry Promotion Agency, Jeonju 54853, Jeonbuk, Korea;

关键词: activated carbon;    chemical activation;    KOH;    K₂CO₃;    impregnation;    recycling;   

DOI  :  10.3390/pr9061000

来源: DOAJ

【 摘 要 】

The chemical activation of a carbon precursor with KOH generally results in an activated carbon (AC) with a high specific surface area. However, this process generates a large volume of wastewater that includes dissolved alkali metals, existing mainly as K₂CO₃. Thus, wastewaters with a high concentration of dissolved K₂CO₃ can potentially be used in place of KOH as a chemical agent. In the present study, to reduce the thermal stability of K₂CO₃, which decomposes at temperatures greater than 891 °C, K₂CO₃ was chemically impregnated into carbon precursors prior to activation of the precursors. The thermochemical properties and activation efficiency of the carbon precursors treated with K₂CO₃ were compared with those of carbon precursors treated with KOH. Analysis by XPS indicated that C–O–K complexes formed on the surface of the carbon precursors; in addition, their peak intensities were approximately the same irrespective of the chemical agent used. However, the specific surface area of the K₂CO₃-impregnated AC was 2162 m²/g, which was ~70% of that of the KOH-impregnated AC (3047 m²/g) prepared using the same K/C molar ratio of 0.5. XRD results confirmed that both K₂CO₃ and KOH transformed into KHCO₃ and K₄H₂(CO₃)₃·1.5H₂O during the impregnation. The peak intensities of these compounds in the XRD pattern of the K₂CO₃-impregnated carbon precursors were two times greater than those in the pattern of the KOH-impregnated carbon precursors. These compounds eventually transformed into K₂CO₃, which hardly participated as a chemical agent at the temperature used in the present study (850 °C). Therefore, recrystallisation of K₂CO₃, even during the impregnation, appeared to adversely affect the degree of activation. Nevertheless, the specific surface area of the K₂CO₃-activated AC was still ~1.6 times greater than that of the untreated carbon precursor (1378 m²/g), suggesting that the use of wastewater as a chemical agent is feasible for resource recycling.

【 授权许可】

Unknown