*2.3. Delignification Pretreatments*

HS and AS were subjected to different delignification treatments. All experiments were performed at a LSR of 8 g/g, under the following conditions:


Table 1 sumarizes the different delignification experiments performed in this work.

The solid and liquid phases from treatments were separated by vacuum filtration. The treated solids were washed first with solutions of the same composition as the ones used in the respective pretreatments, and then with distilled water. The solid phases from treatments were assayed for composition and solid yield. From the experimental data, the percentages of delignification, cellulose removal and hemicellulose removal were calculated as follows:

$$\% \text{Solid Yield} \left( \text{SY} \right) = 100 \times \frac{\text{DS}\_{AD}}{\text{DS}\_{BD}} \tag{1}$$

where DS*AD* and DS*BD* are the dry weights of the solid before and after delignification, respectively;

$$\% \text{ désignification } = 100 \times \frac{\text{TL}\_{BD} - \text{TL}\_{AD} \times \frac{\text{SY}}{100}}{\text{TL}\_{BD}} \tag{2}$$

where TL*BD* and TL*AD* are the percentages of total lignin present in the solids before and after delignification, respectively;

$$\% \text{ cellulose removal} = 100 \times \frac{\text{C}\_{\text{BD}} - \text{C}\_{\text{AD}} \times \frac{\text{SY}}{100}}{\text{C}\_{\text{BD}}} \tag{3}$$

where C*BD* and C*AD* are the percentages of cellulose present in the solids before and after delignification, respectively;

$$\% \text{ hemicelluloses removal} = 100 \times \frac{\text{H}\_{\text{BD}} - \text{H}\_{\text{AD}} \times \frac{\text{SY}}{100}}{\text{H}\_{\text{BD}}} \tag{4}$$

where H*BD* and H*AD* are the percentages of hemicelluloses (measured as the overall contributions of xylan, arabinan and acetyl groups) present in the solids before and after delignification, respectively.

The lignin present in the liquid phases from treatments performed under selected conditions was precipitated by adding HCl 5M to pH = 2, kept overnight at 4 ◦C, recovered by filtration, and dried in a vacuum oven at 40 ◦C. Aliquots of the liquid phases from treatments were analyzed for hemicellulose-derived compounds (oligosaccharides, monosaccharides, acetic acid, and furans) following the methods listed in Section 2.5.


**Table 1.** Set of experiments performed in this work for the delignification of HS and AS (LSR = 8 g/g).
