Activated Carbon from Prickly Pear Seeds: Optimization of Preparation Conditions and Cadmium Removal Using Experimental Design Approach

In this study, activated carbon was produced from the residue of prickly pear seeds after oil extraction by chemical activation. The effects of four factors controlling the activation process such as carbonization temperature (500 or 600° C), activation temperature (400 or 500° C), activation time (1 or 2 h), and impregnation ratio (g H₃PO₄/g activated carbon) (1:1 or 2:1) were established. Moreover, a full factorial experimental design at two levels (2⁴) was carried out in order to accomplish concurrently optimal preparation conditions and high removal efficiency of cadmium ions from aqueous solutions. The experimental results showed that carbonization temperature is the most influential factor on the iodine number and cadmium ions removal. For methylene blue index, the most influential factor is the impregnation ratio with a negative impact.