An overview of microalgae for Cd²⁺ and Pb²⁺ biosorption from wastewater

Lead (Pb²⁺) and cadmium (Cd²⁺) are the most toxic heavy metals that have been discharged into the environment. There is interest in new adsorbents capable of removing heavy metals. This review focuses on the use of microalgae as an alternative for removing Pb²⁺ and Cd²⁺. It was found that microalgae biomass has a higher affinity for the biosorption of Pb²⁺. The ion exchange was a main mechanism of adsorption. The optimal pH to remove these metals was not clear, but values between 4.0 and 7.0 were the most implemented. The thermodynamics equilibrium was affected by microalgae species, heavy metal affinity, cell surface form, ionic medium complexity, and other factors. Langmuir isotherm model describe the Pb²⁺ and Cd²⁺ adsorption. Finally, carboxyl group was the most important in adsorption Pb²⁺ and Cd²⁺ heavy metals.