Methylene blue removal using coconut shell biochar synthesized through microwave-assisted pyrolysis

Abstract

Indonesia is the world’s second largest producer of coconut. This at the same time resulted in huge generation of coconut shell waste that need to be properly managed to prevent environmental contamination such as water, air and soil pollution. Current techniques of physical and thermal processing are time and energy consuming. This study reports on the conversion of coconut shell biomass into biochar using microwave-assisted pyrolysis (MAP). The MAP processes were carried out at different microwave power (550-650 W) and residence time (15-25 minutes). Two of the highest biochar yields were obtained at 550 W with the residence times of 15 minutes (91.31 wt%, termed as S1) and 20 minutes (83.88 wt%, termed as S2), respectively. Both values were higher than biochar yield obtained using conventional pyrolysis process i.e. 30.10 wt%. Both S1 and S2 showed considerable capacity to remove 0.6875 mg.g-1 and 0.5165 mg.g-1 methylene blue which had the initial concentration of 25 mg.L-1. The adsorption efficiencies of S1 and S2 biochars were 55.00% and 41.32%, respectively. Results obtained from the FTIR, FESEM and BET analysis also supported the methylene blue removal properties of both S1 and S2, respectively. As a conclusion, coconut shell showed potential as a useful raw material to produce biochar that can be used for methylene blue removal from solution. Nevertheless, more investigation need to be carried out prior to commercialization venture of the coconut-shell based biochar.