**5.5 Use of modified algae (metal ion sorption by pretreated algae biomass)**

With a variety of physical and chemical methods, the strength and number of active sites of algae can be increased. Physical improvement methods such as heating, boiling, crushing, freezing, and drying usually increase biological absorption because they provide more surface area for connecting bonds, and removing cell contents increases the possibility of forming metal bonds. The most famous chemical


### **Table 3.**

*The effect of different types of chemical modifications on algae absorption.*

modifications are with formaldehyde, CaCl2, HCl, NaOH, and glutaraldehyde, whose effects can be seen in **Table 3** [12].
