Research on Furfural Removal from Aqueous Solution with Modified Bio-Chars Derived from Biomass Pyrolysis

Furfural is a typical fermentation inhibitor that is simultaneously generated in biomass hydrolysates, restricting the growth of microorganisms associating with bio-ethanol production, therefore the removal of furfural has attracted increasing attentions. Bio-char derived from biomass pyrolysis has the complex surface and pore structures, which makes it possible to be used as a promising adsorbent material. Hence, the adsorptive removal of furfural from aqueous solutions onto biochar was investigated in this study. Bamboo chip was selected as the typical biomass feedstock, which was pyrolyzed in a bench-scale fluidized bed reactor under nitrogen atmosphere to obtain bamboo charcoal (bio-char). Bamboo charcoal (BC) was treated with different methods, i.e. oxidation either by KMnO₄ or HNO₃, basic treatment with NaOH, and thermal treatment. Results showed that chemical treatments increased the hydrophilicity of BC, whereas thermal treatment caused the opposite effect. Oxidation treatment caused the introduction of a significant number of oxygenated acidic surface groups on the BC surface, with HNO₃ being more effective than KMnO₄. By contrast, NaOH and thermal treatments increased the basicity of BC. Pore structures were also changed significantly after these modifications. Furfural adsorption capacity increased with increasing basic surface group content, which can be attributed to the enhancement of dispersive interactions. The samples modified by thermal treatment demonstrated the highest capacity for furfural adsorption, with removal efficiency of up to 100% at furfural concentration of 10 g/L, because of their low hydrophilicity, high basicity, and micropore volume. The results may be helpful for the development of low-cost adsorbents for furfural removal from aqueous solution.