*5.3.4 Physiochemical activation*

The physiochemical activation method is a combination of both physical and chemical activation methods, and it is considered a recent advancement in the production of activated carbon. In this method, the activated carbon precursor is first activated chemically and then subjected to thermal treatment at a high temperature ranging between 600 and 1000° C. Initially, the char was subjected to chemical impregnation and dried at 85°C. **Figure 6** shows the carbonization process was carried out in a stainless-steel vertical tubular reactor that was placed inside a tube furnace. The reactor was purged with purified nitrogen (99.995%) at a flow rate of 150 cm3 / min, and the temperature was raised to 450° C, a fixed heating rate of 10°C/min, where it was maintained for 4 hours. The resulting mixture was dehydrated by placing it in an oven overnight at 85 C and then activated by gradually raising the temperature to 850°C at the same heating rate. Once the final temperature was reached, the flow of nitrogen gas was replaced by carbon dioxide, and the activation process was allowed to continue more 3 hours. Finally, the activated carbon was cooled to room temperature under a nitrogen flow of 150 cm<sup>3</sup> /min [58]. The two-step physiochemical method for producing activated carbon is illustrated in **Figure 7**. This approach leads to the production of activated carbon with unique surface properties such as a very large surface area and high pore volume. However, this method tends to induce more mesopores, which is an important characteristic needed for liquid-phase applications. Therefore, the physiochemical activation method is currently a priority in activated carbon production technology.
