HIGH SURFACE OF ACTIVATED CARBON DERIVED FROM WASTE COFFEE SLUDGE BY HYDROTHERMAL PROCESS AT LOW TEMPERATURE

Circular economy is a sustainable model to replace the linear economic model which has limitations that affect the environment. In this study, coffee sludge by-product was used to produce activated carbon with high specific surface area through low-temperature hydrothermal carbonization and KOH activation, as a form of circular economy model application. The influence of temperature, time, KOH concentration and raw material ratio on the carbonization and activation process was investigated. Besides, the physicochemical properties of the material were also evaluated through FT-IR, XRD, microscope, SEM and BET analysis. The results showed that the specific surface area of coffee sludge reached 23.06 m^2g^-1 after hydrothermal process at 80% humidity, 240 °C for 5 h. The obtained activated carbon with a high surface area of 976.34 m^2 g^-1 was produced from hydrochar of coffee sludge, recorded at 5 M KOH concentration, HC/KOH ratio of 1:1.5 w/w, 650 °C for 2 h. The FT-IR results showed the decomposition of organic components in coffee sludge. In addition, XRD and SEM analysis also showed the amorphous structure and macroporous surface of the material. These results highlighted the potential of coffee sludge by-product in activated carbon production, towards sustainable development trend.