Application of algae as low cost and effective bio-adsorbent for removal of heavy metals from wastewater: a review study

ABSTRACT These days the control of pollution caused by various industries is one of the major concerns of societies. It is necessary to provide cost-effective and efficient methods, despite the economic constraints for controlling the pollution of wastewater treatment processes. Nowadays, heavy metals are one of the most important environmental pollutants. So, removal of these metals from water and wastewater, up to a permissible amount, is necessary. Adsorption is widely used due to its flexibility in design and operation, reversibility, low cost, and desirable results. However, finding suitable and environmentally friendly adsorbents for removal of these metals increasingly seems essential. In recent years, the use of algae as a bio-adsorbent has received much attention due to its especial properties such as environmentally friendly, low cost, easy access and high adsorption capacity. This study, reviews various methods of removing heavy metals and investigates the use of algae as bio-adsorbents to remove these metals and their hazards and sources. Moreover, the equilibrium, kinetic, and thermodynamic behaviours of the heavy metal ion adsorption process using Langmuir and Freundlich adsorption models, pseudo-first and second-order kinetic models, and thermodynamic parameters including enthalpy (ΔH °), entropy (ΔS °) and Gibbs free energy changes (ΔG °) are reviewed briefly. In almost all cases, the pseudo-second-order kinetic model and Langmuir and Freundlich isotherms were better matched with the experimental data. Also, the heavy metal adsorption on the algae showed exothermic process. GRAPHICAL ABSTRACT