The solid residue of Japanese citron after its compression to obtain juice and then the extraction of oil was used as the raw material of activated carbon in order to substantiate the cascading use of Citrease for several high value products. Most of the inorganic compounds in the carbonized samples were K4H2(CO3)3·1.5 H2O and CaCO3. Although the amount of these inorganic compounds was independent of the carbonization temperature, most of these inorganic compounds were removed by the KOH activation process. The BET specific surface area of the sample after the KOH activation increased with the increasing amount of KOH added for activation, and the value was greater than 1900 m2 g−1 when the amount of KOH was greater than 67 wt%. The pore sizes and pore volumes were calculated by several methods, such as the Langmuir, t method, αs method, MP method, BJH method, and INNES method, in order to analyze in detail the surface condition related to the pores. The capacitance value of the sample activated at KOH 75 wt% was 157 F g−1 at 1 mV s−1.
Biochar KOH activation Activated carbon Japanese citron Cascading use
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This study was supported by JSPS KAKENHI Grant Number JP 17K06031. The authors are grateful for JSPS. The raw material used in this study was supported by the Kanematsu Engineering Co., Ltd. The authors are grateful for the Kanematsu Engineering Co., Ltd.