Use of the Wise method as a pretreatment for the selective removal of lignin when preparing bamboo-activated carbon

The Wise method, which is known in wood science as a technique for the quantitative analysis of holocellulose, was applied as a pre-treatment to prepare a porous precursor for activated carbon. The precursor has a specific pore size structure derived from the organizational architecture of the natural plant. The lignin in the plant tissue of the bamboo was successfully removed in a stepwise fashion by the Wise method treatment. All the N₂ adsorption isotherms at 77 K for the carbonized samples, including the samples treated by the Wise method, were similar in shape. Specifically, they were type I as classified by IUPAC with low-pressure hysteresis, and there was no specific effect of the selective removal of lignin from the carbonized sample. However, after CO₂ activation for more than 2 h, samples treated with the Wise method had slit pores, which is type H4 as classified by IUPAC. The slit width calculated by the INNES method, which is the theory for slit-type mesopores, was ca. 2.5 nm. When samples delignified by more than 60% were activated by CO₂ for 3 h, the percentage of the micropores in the total pores was ca. 40%. Samples treated by the Wise method for the stepwise selective removal of lignin, should enable pore structure derived from plant tissue to be controlled in the activated carbon.