Production of non-activated biochar based on Biden pilosa and its application in removing methylene blue from aqueous solutions

Biden pilosa (BP) is a type of weed commonly found in Thailand that needs to be removed from agricultural areas for protecting main crops. This research proposed a method to reduce BP by using BP as a feedstock for biochar production. Non-activated BP biochar from fresh BP was produced in pilot scale using a drum kiln with a heat-transferring duct at a pyrolysis temperature of 550 °C at a slow heating rate. The physical properties of the non-activated BP biochar were investigated using scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, and a surface area analyzer. A batch experiment was used to study the adsorption behavior of methylene blue (MB) on BP biochar. The microstructure study of the BP biochar indicated that it has a cell structure similar to that of BP, which shows the non-destructive nature of the proposed technique for BP production. Six dominant peaks at 3283, 2915, 1559, 1403, 1116, and 863/839 cm⁻1 were observed in the FTIR spectrum. The BP biochar exhibited a surface area of 5.21 m2/g and a pore size of 8 nm. The adsorption of MB on the BP biochar followed the Langmuir adsorption isotherm and pseudo-second-order kinetics. The Langmuir-based maximum adsorption capacity of MB on the BP biochar was 200 mg/g at 303 K.