Green synthesis and characterization of Khat stem activated carbon supported CaO nanoparticles using Senna siamea leaf extract

Abstract

In this study, Khat stem (KS) activated carbon (AC) supported CaO nanoparticle using Senna siamea leaves extract (SS) as a reducing agent was synthesized. Prior to synthesis of KSAC, proximate analysis of KS was investigated. To synthesis of KSAC, H 3 PO 4 was used as activating agent with impregnation ratio of H 3 PO 4 to KS at a ratio of 2:1, 1:1 and 1:2 and its thermal activation was performed with activation temperatures range of 550–650 ℃ for activation times from 2 to 4 h. Then, CaO nanoparticles was synthesized using SS as reducing agent using mixing ratio of the leaves extract to CaCl 2 ·H 2 O solution of 1:5, 1:2 and 1:1 at a thermal activation temperature of 550, 600 and 650 ℃ for 2, 3 and 4 h. Then, supported CaO particles were synthesized using 2–8 g of KSAC in the prepared mixing ratio of SS to CaCl 2 ·H 2 O solution and then calcinated at the same activation temperature and time using sol-gel techniques. The synthesized unsupported CaO nanoparticles have high basicity and low BET surface area compared with KSAC supported CaO nanoparticles. The crystallinity size of synthesized KSAC, CaO nanoparticles and KSAC-SS-CaO nanoparticles was found to be 27.3 nm, 33.8 nm and 36.11 nm, respectively. These findings demonstrated that KSAC serves as an effective support for synthesis of SS-CaO nanoparticles by improving their surface characteristics while maintaining strong catalytic basicity. This study provides a renewable and low-cost approach for biomass-based wastes into potential alternative heterogeneous catalysts, highlighting their potential application for the production of biodiesel.