**Abstract**

The development of industrial activities has caused an increase in the production of various water pollutants, of which heavy metals are among the most important due to their toxicity and harmful environmental effects. Bioabsorption is a promising and environmentally friendly technology, which has been widely used in various wastewater treatment applications in recent years. Among the bioabsorbents, algae are particularly important due to their high absorption efficiency, availability, and cost-effectiveness. In this chapter, the advantages of using algae and their use as biosorbents for removing heavy metals such as copper, aluminum, cadmium, zinc, mercury, chromium, nickel, and lead from aqueous solutions have been investigated. The effect of various factors, including factors related to biomass and process conditions (solution pH, adsorbent dosage, contact time, temperature, and initial concentration of heavy metal ions) has been evaluated. Also, the mechanisms of biological absorption of heavy metal ions in algae have been analyzed. Numerous studies show that algae are effective and economic bioabsorbents for the removal of heavy metals from industrial wastewater, and due to their predictability with simple equilibrium and kinetic mathematical equations, they are suitable for large-scale applications in continuous processes.

**Keywords:** wastewater treatment, removal of heavy metals, biological treatment, microalgae, absorbing heavy metals
