Phycoremediation: Algae as Eco-friendly Tools for the Removal of Heavy Metals from Wastewaters

Abstract

Phycoremediation is a potential tool to eradicate the excess toxics (heavy metal and organic contaminants) from the industrial waste stream. The algal species are a promising, eco-friendly, and sustainable move toward a possible advantage to enhance the algal cultivation which in turn magnifies the economics of algal-based value-added products. Therefore, algae have been documented as a sustainable and inexpensive vector for detoxification of noxious waste-loaded industrial waste stream. Algal species may bind up to 10% of their biomass as metals. Various physical and chemical methods used for this purpose suffer from serious limitations like high cost, high energy input, alteration of basic properties, and disturbance in native flora. In contrast, phycoremediation provides a new insight/dimension for this problem by perceiving it as cost-effective, efficient, novel, eco-friendly, and solar-driven technology with good public acceptance. The mechanism for the removal of heavy metal through alga works on the principle of adsorption onto the cell surface which is independent of cell metabolism and absorption or intracellular uptake which depends on cell metabolism. So, their ability to adsorb and metabolize is associated with their large surface/volume ratios; the presence of high-affinity, metal-binding groups on their cell surfaces; and efficient metal uptake and storage systems. Hence, the present review article deals with the basic mechanism of algal-based heavy metal removal strategies with the effect of physicochemical parameters. Use of transgenic approaches to further enhance the heavy metal specificity and binding capacity of algae with the objective of using these algae for the treatment of heavy metal-contaminated wastewater is also focused in this article.