**5. Preparing biomass-based activated carbon**

The production process of biomass-based activated carbons typically consists of two stages: activation of the carbonized material, as depicted in **Figure 4**. The ultimate physical and chemical characteristics of the activated carbons, including pore volume, pore size distribution, type of surface functional groups, and surface area, are heavily influenced by factors such as the chemical composition of the biomass precursor materials, the techniques used for carbonization and activation, and the respective conditions employed.

#### **5.1 Pretreatment of biomass precursor**

Prior to the carbonization of biomass materials, it is crucial to remove any impurities such as soil by washing the materials with hot or cold deionized water, acid, or base. The materials should then be dried at a temperature between 65 and 105°C. To ensure a uniform and efficient carbonization process, the particle size of the dried biomass should be reduced through milling, as discussed in a study by Ahmed et al. [13].

#### **Figure 4.**

*The schematic production process of activated carbons, from biomass and char, by physical or chemical activation [38].*
