Characterization of Modified Biochars Derived from Bamboo Pyrolysis and Their Utilization for Target Component (Furfural) Adsorption

Biochar (BC) derived from bamboo pyrolysis and its modified forms were treated with chemical methods (oxidation either by KMnO4 or HNO3 and base treatment with NaOH) and heat method. BC and modified BCs were investigated as adsorbents for target component (furfural) removal from aqueous solution. The samples were characterized to assess the effects of different treatments on structure and surface chemistry of BCs. The results show that chemical treatments increase the hydrophilicity of BC, whereas heat treatment causes the opposite effect. Oxidation treatment leads to the introduction of a large number of acidic functional groups on the BC surface, with HNO3 being more effective than KMnO4. In contrast, NaOH treatment and heat treatment increase the basicity of BC. Pore structures of BCs are also significantly changed after these modifications. Furfural adsorption capacity of BCs increases with the increase of basic surface group content, which can be attributed to the enhancement of dispersion interactions. The higher hydrophilicity of BC is, the lower the furfural uptake capacity is. The heat-treated samples demonstrate the highest capacity for furfural adsorption, with a removal efficiency of up to 100% at a furfural concentration of 10 g/L. However, all chemical treatments reduce furfural removal capacity. The Ho's pseudosecond-order model, intraparticle diffusion model, and Langmuir isotherm fit the adsorption data well.