Preparation, characterisation and adsorption performance of KOH-modified palm fibre, platanus bark and sesame stem biochar

This study systematically explored the effect of the conditions adopted for the preparation of biochar on its adsorption performance. Palm tree fibre, sesame stalk and Platanus bark were chosen as raw materials and converted to biochar using a temperature-controlled vacuum carbonization method. This was then modified using KOH across various alkali–carbon ratios, activation temperatures and activation times, and the adsorption performance of the resulting samples was analyzed. Characterization analyses based on scanning electron microscopy (SEM), Brunner Emmet Teller (BET) measurements, Energy-dispersive X-ray spectroscopy (EDX) and Fourier transform infrared spectrometry (FTIR) revealed that after KOH activation, the biochar samples exhibited numerous defects and cross-sections, huge specific surface areas and abundant pore structures, all of which serve as adsorption sites. Characteristic functional groups(For example –OH and NH–), which significantly enhance adsorption, also increased. The iodine adsorption values of all three types of biochar initially increased and then decreased with the increase in pyrolysis temperature. An orthogonal test showed that the order, based on adsorption performance, of the three types of biochar prepared and modified under optimal conditions was palm tree fibre biochar (1628.55 mg.g⁻¹) > sesame stalk biochar (1485.23 mg.g⁻¹) > Platanus bark biochar (1360.43 mg.g⁻¹). Their adsorption performances exceeded the national first-class product limit standard, implying that they exhibited good usability. This indicates that a lower alkali–carbon ratio can be used to obtain near-optimal results, thereby reducing corrosion and saving on production costs.