*3.2.1.1 Alkaline treatment*

Alkaline treatment is a process whereby the biomass is treated with an alkali reagent to eliminate non-cellulosic components such as pectins, hemicelluloses and lignin. The filtrate is then washed with water to neutralize it and the obtained solid contains mostly cellulosic components. The common concentration of NaOH used for this treatment is 8–16% and the mixture is heated to 90–160°C for 1–2 h for the removal of hemicelluloses and some parts of lignin. Treatment is usually carried out using a strong base solution such as sodium hydroxide or potassium hydroxide with varying conditions as tabulated in **Table 3**.

Novel approaches such as steam explosion have successfully removed the lignin fraction while producing purer and structurally intact cellulose. Next, the solubilized components are eliminated by rinsing with deionized water and filtered. The conditions applied may vary depending on the fiber source and its constitution [43].
